jet report
TRANSCRIPT
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H O S T E D B Y
ORGINAL ARTICLE
Optimization of gas turbines for sustainable
turbojet propulsion
Yousef SH Najjarn Ibrahim AI Balawneh
Mechanical Engineering Department Jordan University of Science and Technology Irbid Jordan
Received 17 March 2014 accepted 14 January 2015
Available online 25 June 2015
KEYWORDS
Optimization
Green technology
Sustainable turbojet
engines
Performance carpets
Abstract Gas-turbines are widely used to power aero planes because they are light compact
with a high power-to-weight ratio In the turbo jet engine the main operating variables are
compressor pressure ratio r p and turbine inlet temperature (TIT ) These variables affect the
speci1047297c thrust and speci1047297c fuel consumption (SFC ) which represent the main performance
parameters In addition to the analytical work a computer program of the General Algebraic
Modeling System (GAMS) was used for analysis and optimization The analysis shows that the
speci1047297c thrust strongly depends on turbine inlet temperature (TIT ) where a 10 decrease in TIT
results in 67 decrease in speci1047297
c thrust and 68 decrease in SFC Furthermore the value of optimum pressure ratio r f for maximum speci1047297c thrust increases with TIT A 10 decrease from
design TIT results in 1143 decrease in r f The value of optimum pressure ratio for the turbojet
engine operating at Ma frac14 08 and altitude Alt frac14 13000 m and TIT frac14 1700 K was found to be 14
amp 2015 National Laboratory for Aeronautics and Astronautics Production and hosting by Elsevier BV
This is an open access article under the CC BY-NC-ND license
(httpcreativecommonsorglicensesby-nc-nd40 )
1 Introduction
Energy ef 1047297ciency could be obtained by different meth-
ods among which is waste-heat recovery [1] combinedcycles [2] using energy storage for peak shaving and load
leveling [3] and in the limit widening the range of fuel
speci1047297cations to improve thermo economics [4]
With turbojet engines air as the working 1047298uid is used to
produce thrust based on the variation of kinetic energy of
burnt gases after combustion [56] Performance typically
focuses on use of cycle ef 1047297
ciency speci1047297
c thrust and spe-ci1047297c fuel consumption [78]
Early studies handled the model of the turbojet to
evaluate performance parameters [9] Further investiga-
tions were carried out using variable cycles of turbojet
engine at supersonic speeds [10] In the last few years
many papers presented thermodynamic and aerodynamic
analyses of the behavior of a turbojet operating with and
without afterburners [11]
httppprbuaaeducn
wwwsciencedirectcom
Propulsion and Power Research
2212-540X amp 2015 National Laboratory for Aeronautics and Astronautics Production and hosting by Elsevier BV This is an open access article under the
CC BY-NC-ND license (httpcreativecommonsorglicensesby-nc-nd40 )
httpdxdoiorg101016jjppr201505004
nCorresponding author Tel thorn00962 785793463
E-mail address ysnajjarjustedujo (Yousef SH Najjar)
Peer review under responsibility of National Laboratory for Aeronautics
and Astronautics China
Propulsion and Power Research 20154(2)114ndash121
8172019 Jet Report
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Theoretical and practical engineering developments were
necessary for the design building and testing of an engine
with an afterburner [12] Other research works studied the
effects compressor pressure ratio on thrust and other perfor-
mance parameters [13] In military applications there were
special studies on the factors which determine the proper choice
of engine cycle for a combat aircraft to suit the requirements of the designed mission [14] Some researchers used energy and
exergy analyses with a turbojet engine over 1047298ight altitudes
ranging from sea level to 15000 m to determine the relative
effects of operating variables [15]
The main objective of this work is carrying out energy
analysis for the different components of the turbo jet engine
[16] Consequently optimum performance including maximum
speci1047297c thrust and minimum speci1047297c fuel consumption are
obtained [17] This will be done through an analytical method
using Excel and a speci1047297ed software using the language of the
General Algebraic Modeling System (GAMS) for comparison
[1819]
2 Theoretical analysis
A schematic diagram of the turbojet engine and the
relevant T -s diagram are shown in Figures 1 and 2
21 Overall performance
The heating value of the fuel is H vfrac14 43100 kJkg The
thrust of turbojet engine is produced from summation of
momentum and pressure components
F frac14 m C 5 C aeth THORN thorn A5 P5 Paeth THORN eth1THORN
To get the speci1047297c thrust (F s) divide Eq (1) by mass 1047298ow
Figure 1 Turbojet engine Figure 2 T-s diagram
Nomenclature
A area (unit m 2)
a speed of sound (unit ms)
Alt altitude (unit m)
C a inlet air velocity (unit ms)
C 5 exit air velocity (unit ms)
C p constant pressure speci1047297c heat (unit kJ(kg∙K))
F thrust (unit N)
F s speci1047297c thrust (unit (N∙s)kg)
f ac actual fuel air ratio
f th theoretical fuel air ratio
H v heating value (unit kJkg)
h enthalpy (unit kJkg)
Ma Mach number
m mass 1047298ow rate (unit kgs)
ORL optimum running line
P pressure (unit bar)
P x pressure at some point x (unit bar)
R ideal gas constant (unit J(kg∙K))
r f optimum compressor pressure ratior p compressor pressure ratio
SFC speci1047297c fuel consumption (unit kg(N∙s))
T temperature (unit K)
T x temperature at some point x (unit K)
TIT turbine inlet temperature (unit K)
wc compressor work (unit kJkg)
wtc turbine work needed for driving the compressor
(unit kJkg)
Greek letters
γ ration of speci1047297c heats
η isentropic ef 1047297ciency
ρ 1047298uids density (unit kgm 3
)
Subscripts
a air
c compressor
cc combustion chamber
d diffuser
g gas
j nozzle
m mechanical
pr propulsive
t turbine
Optimization of gas turbines for sustainable turbojet propulsion 115
8172019 Jet Report
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rate
F s frac14 C 5 C aeth THORN thorn A5=m
P5 Paeth THORN eth2THORN
Hence the speci1047297c fuel consumption related to the propul-
sive ef 1047297ciency of the turbojet engine is shown as
SFC frac14 f ac=F s eth3THORN
η pr frac14 2= 1 thorn C 5=C a
eth4THORN
Diffuser (a-1)
T 1 frac14 T a thorn C 2a=2C pa eth5THORN
P1=Pa
frac14 T 1s=T a
ethγ a=ethγ a 1THORNTHORNeth6THORN
ηd frac14 T 1s T aeth THORN= T 1 T aeth THORN eth7THORN
Hence
P1 frac14 Pa 1 thorn ηd C 2a=2C pT a ethγ a=ethγ a 1THORNTHORN
eth8THORN
Compressor (1 ndash 2)
P2=P1
frac14 T 2s=T 1
ethγ a=ethγ a 1THORNTHORNeth9THORN
ηd frac14 T 2s T 1eth THORN= T 2 T 1eth THORN eth10THORN
Hence
T 2 frac14 T 1 thorn T 1=ηc
P2=P1
ethethγ a 1THORN=γ aTHORN 1
h i eth11THORN
Combustor (2 ndash 3)
From energy balance equation
eth1 thorn f THORNC pg T 3 298eth THORN thorn f H v thorn C pa 298ndashT 2eth THORN frac14 0 eth12THORN
f th frac14 C pg T 3 298eth THORN thorn C pa 298 T 2eth THORN
= H v thorn C pg 298 T 3eth THORN
eth13THORN
ηcc frac14 f th= f ac eth14THORN
P3 frac14 P2 1 ΔΡcc=P2 eth15THORN
Turbine (3 ndash
4)wtc frac14 wc=ηm eth16THORN
C pg T 3ndashT 4eth THORN frac14 C pa T 2ndashT 1eth THORN=ηm eth17THORN
T 4 frac14 T 3ndash C pa T 2ndashT 1eth THORN=ηmC pg
eth18THORN
From the isentropic relations
ηt frac14 T 3ndashT 4eth THORN= T 3 T 4seth THORN eth19THORN
Hence
T s4 frac14 T 3ndash T 3ndashT 4eth THORN=ηt eth20THORN
P4 frac14 P3 T s4=T 3 ethγ g=ethγ g 1THORNTHORN
eth21THORN
Nozzle (4 ndash
5)
T c frac14 T 4 2= γ g thorn 1
eth22THORN
Pc frac14 P4 1 1=η j
γ g 1
= γ g thorn 1 ethγ g=ethγ g 1THORNTHORN
eth23THORN
The nozzle is choking if (P4 Pa)4(P4 Pc)
Then
P5frac14Pc T 5frac14 T c
C 5 frac14 γ g RT 5 05
eth24THORN
ρ frac14 P5= RT 5eth THORN eth25THORN
Table 1 The range of operating conditions for the turbojet
engine
r p 9 11 13 DP 16
15
TIT K 1400 1500 1600 1700 1800
Ma 05 06 07 08 09
Alt m 6000 8000 1000 13000 15000
Yousef SH Najjar Ibrahim AI Balawneh116
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A5=m
frac14 1= ρC 5eth THORN eth26THORN3 Discussion of results
The speci1047297c thrust (F s) and speci1047297c fuel consumption
(SFC ) are calculated at design point and other off-design
conditions and shown as in Table 1
Carrying out the variation of compressor pressure ratio
r p while keeping the other variables namely TIT Ma and
altitude the same at the design point results in Figure 3
The optimum r p for maximum speci1047297c thrust (F s) is 14 The
Figure 3 Relation of F s with SFC at design point but variable r p
Figure 4 Relation of F s with SFC at design point with variable TIT
Figure 6 Relation of F s with SFC at design point with variable
altitude
Figure 7 Performance carpet at Alt frac14 13000 m and Ma frac1408
Figure 8 Performance carpet at Alt frac14 8000 m and Ma frac1408Figure 5 Relation of F s with SFC at design point with variable Ma
Optimization of gas turbines for sustainable turbojet propulsion 117
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in1047298ection at this point is expected to be due to the effect of
the relative increase of (compressorturbine) work ratio
Carrying out the variation of turbine inlet temperature
(TIT ) while keeping the other variables namely r p Ma and
altitude at the design point results in Figure 4 Increasing
TIT increases F s and SFC but this is limited of course by
the metallurgical limit of the turbine blades From sensitiv-
ity analysis reducing turbine inlet temperature TIT by 10from the design point the SFC decreases by 68 and F sby 67
Carrying out the variation of Ma while keeping the other
variables namely r p TIT and altitude the same as at the
design point results in Figure 5 Increasing of madecreases
the F s and increases SFC because the engine drag increases
with aircraft speed From sensitivity analysis reducing Ma
by 10 from the design point the SFC decreases by 146
and F s increases by 235
Carrying out the variation of altitude while keeping the
other variables namely r p TIT and Ma the same as at the
design point results in Figure 6 After 11500 m the F s and
SFC remain constant because ambient temperature
andspeed of sound remains constant
A carpet of performance is produced as shown inFigure 7 This depicts the relation between F s and SFC
over wide range of operating conditions including r p and
TIT while keeping Ma and altitude at design conditions
Figure 8 is drawn similarly but at Alt frac14 8000 m whereas
Figure 9 at Mafrac1406
Figure 9 Performance carpet at Alt frac14 13000 m and Ma frac1406
Table 2 Relative effect of 10 reduction in operating variables
from design point on performance
Variable F s (N∙skg) SFC (kg(h∙N))
r p 00217 thorn134
TIT K 67 68
Ma thorn235 146
Alt m No effect No effect
Figure 10 Optimum values of (r f ) and (TIT ) that give maximum (F s)
and minimum (SFC ) at Alt frac1413000 m and Ma frac1408
Figure 11 The optimum running line (ORL ) superimposed on the
performance carpet
Table 3 Relative effect of 10 reduction in TIT on performance
along the ORL
Variable Effect
r f 1143
F s 121
SFC 46
Figure 12 Comparing points on the ORL using the analytical model
of this work with that from GAMS
Yousef SH Najjar Ibrahim AI Balawneh118
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Carrying out the sensitivity analysis it was possible to
calculate the relative effects of 10 drop of operating
variables from the design point on performance as depicted
in Table 2
4 Optimization
When considering the design of a turbojet the basic
thermodynamic variables at the disposal of the designer are
the TIT and r p which are used to get the optimum
performance of a turbojet Performance optimization is
intended to 1047297nd the maximum F s and minimum SFC of
the engine [20]
The method of optimization utilized here searches for the
optimum compressor pressure ratio r f at certain TIT for
which the turbojet engine has optimum performance that
gives maximum F s and minimum SFC
For each TIT there is r f that gives maximum F s hence
the optimum running line (ORL ) was formed over wide
range of operating conditions using the analytical model
with excel
A computer program called GAMS was used to solve the
optimization problem for comparison GAM was originally
developed to provide a high-level language for the compact
representation of large and complex models (Appendix A)
The optimum running points at different combinations of
operating conditions are plotted in Figure 10 The locus of
these points forms the optimum running line (ORL ) reco-
mmended for the engine to follow This line is super imp-
osed on the carpet of performance as shown in Figure 11
to show how the optimum performance is achieved over
wide range of operating conditionsCarrying out sensitivity analysis for the effect of TIT on
performance it was possible to obtain the corresponding
variation in r f F s and SFC as shown in Table 3
Its obvious from Figure 12 that there is difference in r f values between GAMS and the analytical model but in
some cases the values are very close The difference bet-
ween GAMS and the analytical method is due to the nesting
steps carried out by the GAMS leading to F s as function of
r p because the equation has one independent variable But
in the analytical method the problem is dealt with in
consecutive detailed steps using excel
5 Conclusions
a) Sensitivity analysis shows that reducing turbine inlet
temperature TIT of the turbojet engine by 10 results
in 68 increase in SFC and 67 in F s
b) On the other hand reducing the pressure ratio r p by
10 results in 134 increase in SFC and 0022
decrease in F s
c) After altitude of 11500 m there is no effect for
increasing altitude on F s and SFC This is due to the
ambient temperature and hence the speed of sound
which remaining constant after this altitude
d) Reducing Ma by 10 results in 146 decrease in SFC
and 235 increase in F s
e) The value of optimum pressure ratio r f for maximum
speci1047297c thrust increased as the turbine inlet tempera-
ture TIT increased A 10 decrease in TIT results in
1143 decrease in r f
f) After optimum r f the speci1047297c thrust decreases as r p
increases but the speci1047297c fuel consumption stilldecreases as r p increases
g) The optimum value of compressor pressure ratio r f at
1700 K is 14
Appendix A General Algebraic ModelingSystem (GAMS)
Systems approach
Planning management and design are a critical element of sustainable economic development and expansion In the
process of planning and design there is a need to critically
analyze the true economic costs bene1047297ts and environmental
consequences of projects A lack of this analysis can often
lead to a level of design quality which falls far short of
optimal with respect to the utilization of scarce economic
and natural resources and will not improve the ecological
balance of systems in general
Systems analysis can aid in identifying those likely
situations where a minimum investment of funds and
energies will produce maximum gains in terms of resource
allocations economic development and environmental wel-
fare Generally speaking systems analysis is the art andscience of disassembling complex phenomena into smaller
isolated more readily understood subsystems and analyz-
ing the interactions between the subsystems and between
the subsystems and the larger environment [21] The central
method used in water resource systems analysis is to couple
the descriptions of physical and socioeconomic systems
through the use of mathematical models
A system is a collection of components and their
interrelationships forming an entity (eg a riverbasin)
which is acted upon by external forces in1047298uences or inputs
(precipitation) and produces a speci1047297c effect or output
(stream 1047298ow) That is a system is a set of objects whichtransforms an input into an output the exact output
produced depending on certain system properties or para-
meters (eg soil types vegetation topography) This
transformation depends upon the parameters of the system
and the design policies imposed on it
Systems analysis involves the construction and linkage of
mathematical models of the physical and subsystems
associated with resource allocation systems The purpose
of constructing these models is to aid engineers planners
and decision makers in identifying and evaluating alter-
native designs and to determine which ones meet project
objectives in an ef 1047297cient manner
Optimization of gas turbines for sustainable turbojet propulsion 119
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These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
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Theoretical and practical engineering developments were
necessary for the design building and testing of an engine
with an afterburner [12] Other research works studied the
effects compressor pressure ratio on thrust and other perfor-
mance parameters [13] In military applications there were
special studies on the factors which determine the proper choice
of engine cycle for a combat aircraft to suit the requirements of the designed mission [14] Some researchers used energy and
exergy analyses with a turbojet engine over 1047298ight altitudes
ranging from sea level to 15000 m to determine the relative
effects of operating variables [15]
The main objective of this work is carrying out energy
analysis for the different components of the turbo jet engine
[16] Consequently optimum performance including maximum
speci1047297c thrust and minimum speci1047297c fuel consumption are
obtained [17] This will be done through an analytical method
using Excel and a speci1047297ed software using the language of the
General Algebraic Modeling System (GAMS) for comparison
[1819]
2 Theoretical analysis
A schematic diagram of the turbojet engine and the
relevant T -s diagram are shown in Figures 1 and 2
21 Overall performance
The heating value of the fuel is H vfrac14 43100 kJkg The
thrust of turbojet engine is produced from summation of
momentum and pressure components
F frac14 m C 5 C aeth THORN thorn A5 P5 Paeth THORN eth1THORN
To get the speci1047297c thrust (F s) divide Eq (1) by mass 1047298ow
Figure 1 Turbojet engine Figure 2 T-s diagram
Nomenclature
A area (unit m 2)
a speed of sound (unit ms)
Alt altitude (unit m)
C a inlet air velocity (unit ms)
C 5 exit air velocity (unit ms)
C p constant pressure speci1047297c heat (unit kJ(kg∙K))
F thrust (unit N)
F s speci1047297c thrust (unit (N∙s)kg)
f ac actual fuel air ratio
f th theoretical fuel air ratio
H v heating value (unit kJkg)
h enthalpy (unit kJkg)
Ma Mach number
m mass 1047298ow rate (unit kgs)
ORL optimum running line
P pressure (unit bar)
P x pressure at some point x (unit bar)
R ideal gas constant (unit J(kg∙K))
r f optimum compressor pressure ratior p compressor pressure ratio
SFC speci1047297c fuel consumption (unit kg(N∙s))
T temperature (unit K)
T x temperature at some point x (unit K)
TIT turbine inlet temperature (unit K)
wc compressor work (unit kJkg)
wtc turbine work needed for driving the compressor
(unit kJkg)
Greek letters
γ ration of speci1047297c heats
η isentropic ef 1047297ciency
ρ 1047298uids density (unit kgm 3
)
Subscripts
a air
c compressor
cc combustion chamber
d diffuser
g gas
j nozzle
m mechanical
pr propulsive
t turbine
Optimization of gas turbines for sustainable turbojet propulsion 115
8172019 Jet Report
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rate
F s frac14 C 5 C aeth THORN thorn A5=m
P5 Paeth THORN eth2THORN
Hence the speci1047297c fuel consumption related to the propul-
sive ef 1047297ciency of the turbojet engine is shown as
SFC frac14 f ac=F s eth3THORN
η pr frac14 2= 1 thorn C 5=C a
eth4THORN
Diffuser (a-1)
T 1 frac14 T a thorn C 2a=2C pa eth5THORN
P1=Pa
frac14 T 1s=T a
ethγ a=ethγ a 1THORNTHORNeth6THORN
ηd frac14 T 1s T aeth THORN= T 1 T aeth THORN eth7THORN
Hence
P1 frac14 Pa 1 thorn ηd C 2a=2C pT a ethγ a=ethγ a 1THORNTHORN
eth8THORN
Compressor (1 ndash 2)
P2=P1
frac14 T 2s=T 1
ethγ a=ethγ a 1THORNTHORNeth9THORN
ηd frac14 T 2s T 1eth THORN= T 2 T 1eth THORN eth10THORN
Hence
T 2 frac14 T 1 thorn T 1=ηc
P2=P1
ethethγ a 1THORN=γ aTHORN 1
h i eth11THORN
Combustor (2 ndash 3)
From energy balance equation
eth1 thorn f THORNC pg T 3 298eth THORN thorn f H v thorn C pa 298ndashT 2eth THORN frac14 0 eth12THORN
f th frac14 C pg T 3 298eth THORN thorn C pa 298 T 2eth THORN
= H v thorn C pg 298 T 3eth THORN
eth13THORN
ηcc frac14 f th= f ac eth14THORN
P3 frac14 P2 1 ΔΡcc=P2 eth15THORN
Turbine (3 ndash
4)wtc frac14 wc=ηm eth16THORN
C pg T 3ndashT 4eth THORN frac14 C pa T 2ndashT 1eth THORN=ηm eth17THORN
T 4 frac14 T 3ndash C pa T 2ndashT 1eth THORN=ηmC pg
eth18THORN
From the isentropic relations
ηt frac14 T 3ndashT 4eth THORN= T 3 T 4seth THORN eth19THORN
Hence
T s4 frac14 T 3ndash T 3ndashT 4eth THORN=ηt eth20THORN
P4 frac14 P3 T s4=T 3 ethγ g=ethγ g 1THORNTHORN
eth21THORN
Nozzle (4 ndash
5)
T c frac14 T 4 2= γ g thorn 1
eth22THORN
Pc frac14 P4 1 1=η j
γ g 1
= γ g thorn 1 ethγ g=ethγ g 1THORNTHORN
eth23THORN
The nozzle is choking if (P4 Pa)4(P4 Pc)
Then
P5frac14Pc T 5frac14 T c
C 5 frac14 γ g RT 5 05
eth24THORN
ρ frac14 P5= RT 5eth THORN eth25THORN
Table 1 The range of operating conditions for the turbojet
engine
r p 9 11 13 DP 16
15
TIT K 1400 1500 1600 1700 1800
Ma 05 06 07 08 09
Alt m 6000 8000 1000 13000 15000
Yousef SH Najjar Ibrahim AI Balawneh116
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 48
A5=m
frac14 1= ρC 5eth THORN eth26THORN3 Discussion of results
The speci1047297c thrust (F s) and speci1047297c fuel consumption
(SFC ) are calculated at design point and other off-design
conditions and shown as in Table 1
Carrying out the variation of compressor pressure ratio
r p while keeping the other variables namely TIT Ma and
altitude the same at the design point results in Figure 3
The optimum r p for maximum speci1047297c thrust (F s) is 14 The
Figure 3 Relation of F s with SFC at design point but variable r p
Figure 4 Relation of F s with SFC at design point with variable TIT
Figure 6 Relation of F s with SFC at design point with variable
altitude
Figure 7 Performance carpet at Alt frac14 13000 m and Ma frac1408
Figure 8 Performance carpet at Alt frac14 8000 m and Ma frac1408Figure 5 Relation of F s with SFC at design point with variable Ma
Optimization of gas turbines for sustainable turbojet propulsion 117
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 58
in1047298ection at this point is expected to be due to the effect of
the relative increase of (compressorturbine) work ratio
Carrying out the variation of turbine inlet temperature
(TIT ) while keeping the other variables namely r p Ma and
altitude at the design point results in Figure 4 Increasing
TIT increases F s and SFC but this is limited of course by
the metallurgical limit of the turbine blades From sensitiv-
ity analysis reducing turbine inlet temperature TIT by 10from the design point the SFC decreases by 68 and F sby 67
Carrying out the variation of Ma while keeping the other
variables namely r p TIT and altitude the same as at the
design point results in Figure 5 Increasing of madecreases
the F s and increases SFC because the engine drag increases
with aircraft speed From sensitivity analysis reducing Ma
by 10 from the design point the SFC decreases by 146
and F s increases by 235
Carrying out the variation of altitude while keeping the
other variables namely r p TIT and Ma the same as at the
design point results in Figure 6 After 11500 m the F s and
SFC remain constant because ambient temperature
andspeed of sound remains constant
A carpet of performance is produced as shown inFigure 7 This depicts the relation between F s and SFC
over wide range of operating conditions including r p and
TIT while keeping Ma and altitude at design conditions
Figure 8 is drawn similarly but at Alt frac14 8000 m whereas
Figure 9 at Mafrac1406
Figure 9 Performance carpet at Alt frac14 13000 m and Ma frac1406
Table 2 Relative effect of 10 reduction in operating variables
from design point on performance
Variable F s (N∙skg) SFC (kg(h∙N))
r p 00217 thorn134
TIT K 67 68
Ma thorn235 146
Alt m No effect No effect
Figure 10 Optimum values of (r f ) and (TIT ) that give maximum (F s)
and minimum (SFC ) at Alt frac1413000 m and Ma frac1408
Figure 11 The optimum running line (ORL ) superimposed on the
performance carpet
Table 3 Relative effect of 10 reduction in TIT on performance
along the ORL
Variable Effect
r f 1143
F s 121
SFC 46
Figure 12 Comparing points on the ORL using the analytical model
of this work with that from GAMS
Yousef SH Najjar Ibrahim AI Balawneh118
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 68
Carrying out the sensitivity analysis it was possible to
calculate the relative effects of 10 drop of operating
variables from the design point on performance as depicted
in Table 2
4 Optimization
When considering the design of a turbojet the basic
thermodynamic variables at the disposal of the designer are
the TIT and r p which are used to get the optimum
performance of a turbojet Performance optimization is
intended to 1047297nd the maximum F s and minimum SFC of
the engine [20]
The method of optimization utilized here searches for the
optimum compressor pressure ratio r f at certain TIT for
which the turbojet engine has optimum performance that
gives maximum F s and minimum SFC
For each TIT there is r f that gives maximum F s hence
the optimum running line (ORL ) was formed over wide
range of operating conditions using the analytical model
with excel
A computer program called GAMS was used to solve the
optimization problem for comparison GAM was originally
developed to provide a high-level language for the compact
representation of large and complex models (Appendix A)
The optimum running points at different combinations of
operating conditions are plotted in Figure 10 The locus of
these points forms the optimum running line (ORL ) reco-
mmended for the engine to follow This line is super imp-
osed on the carpet of performance as shown in Figure 11
to show how the optimum performance is achieved over
wide range of operating conditionsCarrying out sensitivity analysis for the effect of TIT on
performance it was possible to obtain the corresponding
variation in r f F s and SFC as shown in Table 3
Its obvious from Figure 12 that there is difference in r f values between GAMS and the analytical model but in
some cases the values are very close The difference bet-
ween GAMS and the analytical method is due to the nesting
steps carried out by the GAMS leading to F s as function of
r p because the equation has one independent variable But
in the analytical method the problem is dealt with in
consecutive detailed steps using excel
5 Conclusions
a) Sensitivity analysis shows that reducing turbine inlet
temperature TIT of the turbojet engine by 10 results
in 68 increase in SFC and 67 in F s
b) On the other hand reducing the pressure ratio r p by
10 results in 134 increase in SFC and 0022
decrease in F s
c) After altitude of 11500 m there is no effect for
increasing altitude on F s and SFC This is due to the
ambient temperature and hence the speed of sound
which remaining constant after this altitude
d) Reducing Ma by 10 results in 146 decrease in SFC
and 235 increase in F s
e) The value of optimum pressure ratio r f for maximum
speci1047297c thrust increased as the turbine inlet tempera-
ture TIT increased A 10 decrease in TIT results in
1143 decrease in r f
f) After optimum r f the speci1047297c thrust decreases as r p
increases but the speci1047297c fuel consumption stilldecreases as r p increases
g) The optimum value of compressor pressure ratio r f at
1700 K is 14
Appendix A General Algebraic ModelingSystem (GAMS)
Systems approach
Planning management and design are a critical element of sustainable economic development and expansion In the
process of planning and design there is a need to critically
analyze the true economic costs bene1047297ts and environmental
consequences of projects A lack of this analysis can often
lead to a level of design quality which falls far short of
optimal with respect to the utilization of scarce economic
and natural resources and will not improve the ecological
balance of systems in general
Systems analysis can aid in identifying those likely
situations where a minimum investment of funds and
energies will produce maximum gains in terms of resource
allocations economic development and environmental wel-
fare Generally speaking systems analysis is the art andscience of disassembling complex phenomena into smaller
isolated more readily understood subsystems and analyz-
ing the interactions between the subsystems and between
the subsystems and the larger environment [21] The central
method used in water resource systems analysis is to couple
the descriptions of physical and socioeconomic systems
through the use of mathematical models
A system is a collection of components and their
interrelationships forming an entity (eg a riverbasin)
which is acted upon by external forces in1047298uences or inputs
(precipitation) and produces a speci1047297c effect or output
(stream 1047298ow) That is a system is a set of objects whichtransforms an input into an output the exact output
produced depending on certain system properties or para-
meters (eg soil types vegetation topography) This
transformation depends upon the parameters of the system
and the design policies imposed on it
Systems analysis involves the construction and linkage of
mathematical models of the physical and subsystems
associated with resource allocation systems The purpose
of constructing these models is to aid engineers planners
and decision makers in identifying and evaluating alter-
native designs and to determine which ones meet project
objectives in an ef 1047297cient manner
Optimization of gas turbines for sustainable turbojet propulsion 119
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 78
These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 38
rate
F s frac14 C 5 C aeth THORN thorn A5=m
P5 Paeth THORN eth2THORN
Hence the speci1047297c fuel consumption related to the propul-
sive ef 1047297ciency of the turbojet engine is shown as
SFC frac14 f ac=F s eth3THORN
η pr frac14 2= 1 thorn C 5=C a
eth4THORN
Diffuser (a-1)
T 1 frac14 T a thorn C 2a=2C pa eth5THORN
P1=Pa
frac14 T 1s=T a
ethγ a=ethγ a 1THORNTHORNeth6THORN
ηd frac14 T 1s T aeth THORN= T 1 T aeth THORN eth7THORN
Hence
P1 frac14 Pa 1 thorn ηd C 2a=2C pT a ethγ a=ethγ a 1THORNTHORN
eth8THORN
Compressor (1 ndash 2)
P2=P1
frac14 T 2s=T 1
ethγ a=ethγ a 1THORNTHORNeth9THORN
ηd frac14 T 2s T 1eth THORN= T 2 T 1eth THORN eth10THORN
Hence
T 2 frac14 T 1 thorn T 1=ηc
P2=P1
ethethγ a 1THORN=γ aTHORN 1
h i eth11THORN
Combustor (2 ndash 3)
From energy balance equation
eth1 thorn f THORNC pg T 3 298eth THORN thorn f H v thorn C pa 298ndashT 2eth THORN frac14 0 eth12THORN
f th frac14 C pg T 3 298eth THORN thorn C pa 298 T 2eth THORN
= H v thorn C pg 298 T 3eth THORN
eth13THORN
ηcc frac14 f th= f ac eth14THORN
P3 frac14 P2 1 ΔΡcc=P2 eth15THORN
Turbine (3 ndash
4)wtc frac14 wc=ηm eth16THORN
C pg T 3ndashT 4eth THORN frac14 C pa T 2ndashT 1eth THORN=ηm eth17THORN
T 4 frac14 T 3ndash C pa T 2ndashT 1eth THORN=ηmC pg
eth18THORN
From the isentropic relations
ηt frac14 T 3ndashT 4eth THORN= T 3 T 4seth THORN eth19THORN
Hence
T s4 frac14 T 3ndash T 3ndashT 4eth THORN=ηt eth20THORN
P4 frac14 P3 T s4=T 3 ethγ g=ethγ g 1THORNTHORN
eth21THORN
Nozzle (4 ndash
5)
T c frac14 T 4 2= γ g thorn 1
eth22THORN
Pc frac14 P4 1 1=η j
γ g 1
= γ g thorn 1 ethγ g=ethγ g 1THORNTHORN
eth23THORN
The nozzle is choking if (P4 Pa)4(P4 Pc)
Then
P5frac14Pc T 5frac14 T c
C 5 frac14 γ g RT 5 05
eth24THORN
ρ frac14 P5= RT 5eth THORN eth25THORN
Table 1 The range of operating conditions for the turbojet
engine
r p 9 11 13 DP 16
15
TIT K 1400 1500 1600 1700 1800
Ma 05 06 07 08 09
Alt m 6000 8000 1000 13000 15000
Yousef SH Najjar Ibrahim AI Balawneh116
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 48
A5=m
frac14 1= ρC 5eth THORN eth26THORN3 Discussion of results
The speci1047297c thrust (F s) and speci1047297c fuel consumption
(SFC ) are calculated at design point and other off-design
conditions and shown as in Table 1
Carrying out the variation of compressor pressure ratio
r p while keeping the other variables namely TIT Ma and
altitude the same at the design point results in Figure 3
The optimum r p for maximum speci1047297c thrust (F s) is 14 The
Figure 3 Relation of F s with SFC at design point but variable r p
Figure 4 Relation of F s with SFC at design point with variable TIT
Figure 6 Relation of F s with SFC at design point with variable
altitude
Figure 7 Performance carpet at Alt frac14 13000 m and Ma frac1408
Figure 8 Performance carpet at Alt frac14 8000 m and Ma frac1408Figure 5 Relation of F s with SFC at design point with variable Ma
Optimization of gas turbines for sustainable turbojet propulsion 117
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 58
in1047298ection at this point is expected to be due to the effect of
the relative increase of (compressorturbine) work ratio
Carrying out the variation of turbine inlet temperature
(TIT ) while keeping the other variables namely r p Ma and
altitude at the design point results in Figure 4 Increasing
TIT increases F s and SFC but this is limited of course by
the metallurgical limit of the turbine blades From sensitiv-
ity analysis reducing turbine inlet temperature TIT by 10from the design point the SFC decreases by 68 and F sby 67
Carrying out the variation of Ma while keeping the other
variables namely r p TIT and altitude the same as at the
design point results in Figure 5 Increasing of madecreases
the F s and increases SFC because the engine drag increases
with aircraft speed From sensitivity analysis reducing Ma
by 10 from the design point the SFC decreases by 146
and F s increases by 235
Carrying out the variation of altitude while keeping the
other variables namely r p TIT and Ma the same as at the
design point results in Figure 6 After 11500 m the F s and
SFC remain constant because ambient temperature
andspeed of sound remains constant
A carpet of performance is produced as shown inFigure 7 This depicts the relation between F s and SFC
over wide range of operating conditions including r p and
TIT while keeping Ma and altitude at design conditions
Figure 8 is drawn similarly but at Alt frac14 8000 m whereas
Figure 9 at Mafrac1406
Figure 9 Performance carpet at Alt frac14 13000 m and Ma frac1406
Table 2 Relative effect of 10 reduction in operating variables
from design point on performance
Variable F s (N∙skg) SFC (kg(h∙N))
r p 00217 thorn134
TIT K 67 68
Ma thorn235 146
Alt m No effect No effect
Figure 10 Optimum values of (r f ) and (TIT ) that give maximum (F s)
and minimum (SFC ) at Alt frac1413000 m and Ma frac1408
Figure 11 The optimum running line (ORL ) superimposed on the
performance carpet
Table 3 Relative effect of 10 reduction in TIT on performance
along the ORL
Variable Effect
r f 1143
F s 121
SFC 46
Figure 12 Comparing points on the ORL using the analytical model
of this work with that from GAMS
Yousef SH Najjar Ibrahim AI Balawneh118
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 68
Carrying out the sensitivity analysis it was possible to
calculate the relative effects of 10 drop of operating
variables from the design point on performance as depicted
in Table 2
4 Optimization
When considering the design of a turbojet the basic
thermodynamic variables at the disposal of the designer are
the TIT and r p which are used to get the optimum
performance of a turbojet Performance optimization is
intended to 1047297nd the maximum F s and minimum SFC of
the engine [20]
The method of optimization utilized here searches for the
optimum compressor pressure ratio r f at certain TIT for
which the turbojet engine has optimum performance that
gives maximum F s and minimum SFC
For each TIT there is r f that gives maximum F s hence
the optimum running line (ORL ) was formed over wide
range of operating conditions using the analytical model
with excel
A computer program called GAMS was used to solve the
optimization problem for comparison GAM was originally
developed to provide a high-level language for the compact
representation of large and complex models (Appendix A)
The optimum running points at different combinations of
operating conditions are plotted in Figure 10 The locus of
these points forms the optimum running line (ORL ) reco-
mmended for the engine to follow This line is super imp-
osed on the carpet of performance as shown in Figure 11
to show how the optimum performance is achieved over
wide range of operating conditionsCarrying out sensitivity analysis for the effect of TIT on
performance it was possible to obtain the corresponding
variation in r f F s and SFC as shown in Table 3
Its obvious from Figure 12 that there is difference in r f values between GAMS and the analytical model but in
some cases the values are very close The difference bet-
ween GAMS and the analytical method is due to the nesting
steps carried out by the GAMS leading to F s as function of
r p because the equation has one independent variable But
in the analytical method the problem is dealt with in
consecutive detailed steps using excel
5 Conclusions
a) Sensitivity analysis shows that reducing turbine inlet
temperature TIT of the turbojet engine by 10 results
in 68 increase in SFC and 67 in F s
b) On the other hand reducing the pressure ratio r p by
10 results in 134 increase in SFC and 0022
decrease in F s
c) After altitude of 11500 m there is no effect for
increasing altitude on F s and SFC This is due to the
ambient temperature and hence the speed of sound
which remaining constant after this altitude
d) Reducing Ma by 10 results in 146 decrease in SFC
and 235 increase in F s
e) The value of optimum pressure ratio r f for maximum
speci1047297c thrust increased as the turbine inlet tempera-
ture TIT increased A 10 decrease in TIT results in
1143 decrease in r f
f) After optimum r f the speci1047297c thrust decreases as r p
increases but the speci1047297c fuel consumption stilldecreases as r p increases
g) The optimum value of compressor pressure ratio r f at
1700 K is 14
Appendix A General Algebraic ModelingSystem (GAMS)
Systems approach
Planning management and design are a critical element of sustainable economic development and expansion In the
process of planning and design there is a need to critically
analyze the true economic costs bene1047297ts and environmental
consequences of projects A lack of this analysis can often
lead to a level of design quality which falls far short of
optimal with respect to the utilization of scarce economic
and natural resources and will not improve the ecological
balance of systems in general
Systems analysis can aid in identifying those likely
situations where a minimum investment of funds and
energies will produce maximum gains in terms of resource
allocations economic development and environmental wel-
fare Generally speaking systems analysis is the art andscience of disassembling complex phenomena into smaller
isolated more readily understood subsystems and analyz-
ing the interactions between the subsystems and between
the subsystems and the larger environment [21] The central
method used in water resource systems analysis is to couple
the descriptions of physical and socioeconomic systems
through the use of mathematical models
A system is a collection of components and their
interrelationships forming an entity (eg a riverbasin)
which is acted upon by external forces in1047298uences or inputs
(precipitation) and produces a speci1047297c effect or output
(stream 1047298ow) That is a system is a set of objects whichtransforms an input into an output the exact output
produced depending on certain system properties or para-
meters (eg soil types vegetation topography) This
transformation depends upon the parameters of the system
and the design policies imposed on it
Systems analysis involves the construction and linkage of
mathematical models of the physical and subsystems
associated with resource allocation systems The purpose
of constructing these models is to aid engineers planners
and decision makers in identifying and evaluating alter-
native designs and to determine which ones meet project
objectives in an ef 1047297cient manner
Optimization of gas turbines for sustainable turbojet propulsion 119
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 78
These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 48
A5=m
frac14 1= ρC 5eth THORN eth26THORN3 Discussion of results
The speci1047297c thrust (F s) and speci1047297c fuel consumption
(SFC ) are calculated at design point and other off-design
conditions and shown as in Table 1
Carrying out the variation of compressor pressure ratio
r p while keeping the other variables namely TIT Ma and
altitude the same at the design point results in Figure 3
The optimum r p for maximum speci1047297c thrust (F s) is 14 The
Figure 3 Relation of F s with SFC at design point but variable r p
Figure 4 Relation of F s with SFC at design point with variable TIT
Figure 6 Relation of F s with SFC at design point with variable
altitude
Figure 7 Performance carpet at Alt frac14 13000 m and Ma frac1408
Figure 8 Performance carpet at Alt frac14 8000 m and Ma frac1408Figure 5 Relation of F s with SFC at design point with variable Ma
Optimization of gas turbines for sustainable turbojet propulsion 117
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 58
in1047298ection at this point is expected to be due to the effect of
the relative increase of (compressorturbine) work ratio
Carrying out the variation of turbine inlet temperature
(TIT ) while keeping the other variables namely r p Ma and
altitude at the design point results in Figure 4 Increasing
TIT increases F s and SFC but this is limited of course by
the metallurgical limit of the turbine blades From sensitiv-
ity analysis reducing turbine inlet temperature TIT by 10from the design point the SFC decreases by 68 and F sby 67
Carrying out the variation of Ma while keeping the other
variables namely r p TIT and altitude the same as at the
design point results in Figure 5 Increasing of madecreases
the F s and increases SFC because the engine drag increases
with aircraft speed From sensitivity analysis reducing Ma
by 10 from the design point the SFC decreases by 146
and F s increases by 235
Carrying out the variation of altitude while keeping the
other variables namely r p TIT and Ma the same as at the
design point results in Figure 6 After 11500 m the F s and
SFC remain constant because ambient temperature
andspeed of sound remains constant
A carpet of performance is produced as shown inFigure 7 This depicts the relation between F s and SFC
over wide range of operating conditions including r p and
TIT while keeping Ma and altitude at design conditions
Figure 8 is drawn similarly but at Alt frac14 8000 m whereas
Figure 9 at Mafrac1406
Figure 9 Performance carpet at Alt frac14 13000 m and Ma frac1406
Table 2 Relative effect of 10 reduction in operating variables
from design point on performance
Variable F s (N∙skg) SFC (kg(h∙N))
r p 00217 thorn134
TIT K 67 68
Ma thorn235 146
Alt m No effect No effect
Figure 10 Optimum values of (r f ) and (TIT ) that give maximum (F s)
and minimum (SFC ) at Alt frac1413000 m and Ma frac1408
Figure 11 The optimum running line (ORL ) superimposed on the
performance carpet
Table 3 Relative effect of 10 reduction in TIT on performance
along the ORL
Variable Effect
r f 1143
F s 121
SFC 46
Figure 12 Comparing points on the ORL using the analytical model
of this work with that from GAMS
Yousef SH Najjar Ibrahim AI Balawneh118
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 68
Carrying out the sensitivity analysis it was possible to
calculate the relative effects of 10 drop of operating
variables from the design point on performance as depicted
in Table 2
4 Optimization
When considering the design of a turbojet the basic
thermodynamic variables at the disposal of the designer are
the TIT and r p which are used to get the optimum
performance of a turbojet Performance optimization is
intended to 1047297nd the maximum F s and minimum SFC of
the engine [20]
The method of optimization utilized here searches for the
optimum compressor pressure ratio r f at certain TIT for
which the turbojet engine has optimum performance that
gives maximum F s and minimum SFC
For each TIT there is r f that gives maximum F s hence
the optimum running line (ORL ) was formed over wide
range of operating conditions using the analytical model
with excel
A computer program called GAMS was used to solve the
optimization problem for comparison GAM was originally
developed to provide a high-level language for the compact
representation of large and complex models (Appendix A)
The optimum running points at different combinations of
operating conditions are plotted in Figure 10 The locus of
these points forms the optimum running line (ORL ) reco-
mmended for the engine to follow This line is super imp-
osed on the carpet of performance as shown in Figure 11
to show how the optimum performance is achieved over
wide range of operating conditionsCarrying out sensitivity analysis for the effect of TIT on
performance it was possible to obtain the corresponding
variation in r f F s and SFC as shown in Table 3
Its obvious from Figure 12 that there is difference in r f values between GAMS and the analytical model but in
some cases the values are very close The difference bet-
ween GAMS and the analytical method is due to the nesting
steps carried out by the GAMS leading to F s as function of
r p because the equation has one independent variable But
in the analytical method the problem is dealt with in
consecutive detailed steps using excel
5 Conclusions
a) Sensitivity analysis shows that reducing turbine inlet
temperature TIT of the turbojet engine by 10 results
in 68 increase in SFC and 67 in F s
b) On the other hand reducing the pressure ratio r p by
10 results in 134 increase in SFC and 0022
decrease in F s
c) After altitude of 11500 m there is no effect for
increasing altitude on F s and SFC This is due to the
ambient temperature and hence the speed of sound
which remaining constant after this altitude
d) Reducing Ma by 10 results in 146 decrease in SFC
and 235 increase in F s
e) The value of optimum pressure ratio r f for maximum
speci1047297c thrust increased as the turbine inlet tempera-
ture TIT increased A 10 decrease in TIT results in
1143 decrease in r f
f) After optimum r f the speci1047297c thrust decreases as r p
increases but the speci1047297c fuel consumption stilldecreases as r p increases
g) The optimum value of compressor pressure ratio r f at
1700 K is 14
Appendix A General Algebraic ModelingSystem (GAMS)
Systems approach
Planning management and design are a critical element of sustainable economic development and expansion In the
process of planning and design there is a need to critically
analyze the true economic costs bene1047297ts and environmental
consequences of projects A lack of this analysis can often
lead to a level of design quality which falls far short of
optimal with respect to the utilization of scarce economic
and natural resources and will not improve the ecological
balance of systems in general
Systems analysis can aid in identifying those likely
situations where a minimum investment of funds and
energies will produce maximum gains in terms of resource
allocations economic development and environmental wel-
fare Generally speaking systems analysis is the art andscience of disassembling complex phenomena into smaller
isolated more readily understood subsystems and analyz-
ing the interactions between the subsystems and between
the subsystems and the larger environment [21] The central
method used in water resource systems analysis is to couple
the descriptions of physical and socioeconomic systems
through the use of mathematical models
A system is a collection of components and their
interrelationships forming an entity (eg a riverbasin)
which is acted upon by external forces in1047298uences or inputs
(precipitation) and produces a speci1047297c effect or output
(stream 1047298ow) That is a system is a set of objects whichtransforms an input into an output the exact output
produced depending on certain system properties or para-
meters (eg soil types vegetation topography) This
transformation depends upon the parameters of the system
and the design policies imposed on it
Systems analysis involves the construction and linkage of
mathematical models of the physical and subsystems
associated with resource allocation systems The purpose
of constructing these models is to aid engineers planners
and decision makers in identifying and evaluating alter-
native designs and to determine which ones meet project
objectives in an ef 1047297cient manner
Optimization of gas turbines for sustainable turbojet propulsion 119
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 78
These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 58
in1047298ection at this point is expected to be due to the effect of
the relative increase of (compressorturbine) work ratio
Carrying out the variation of turbine inlet temperature
(TIT ) while keeping the other variables namely r p Ma and
altitude at the design point results in Figure 4 Increasing
TIT increases F s and SFC but this is limited of course by
the metallurgical limit of the turbine blades From sensitiv-
ity analysis reducing turbine inlet temperature TIT by 10from the design point the SFC decreases by 68 and F sby 67
Carrying out the variation of Ma while keeping the other
variables namely r p TIT and altitude the same as at the
design point results in Figure 5 Increasing of madecreases
the F s and increases SFC because the engine drag increases
with aircraft speed From sensitivity analysis reducing Ma
by 10 from the design point the SFC decreases by 146
and F s increases by 235
Carrying out the variation of altitude while keeping the
other variables namely r p TIT and Ma the same as at the
design point results in Figure 6 After 11500 m the F s and
SFC remain constant because ambient temperature
andspeed of sound remains constant
A carpet of performance is produced as shown inFigure 7 This depicts the relation between F s and SFC
over wide range of operating conditions including r p and
TIT while keeping Ma and altitude at design conditions
Figure 8 is drawn similarly but at Alt frac14 8000 m whereas
Figure 9 at Mafrac1406
Figure 9 Performance carpet at Alt frac14 13000 m and Ma frac1406
Table 2 Relative effect of 10 reduction in operating variables
from design point on performance
Variable F s (N∙skg) SFC (kg(h∙N))
r p 00217 thorn134
TIT K 67 68
Ma thorn235 146
Alt m No effect No effect
Figure 10 Optimum values of (r f ) and (TIT ) that give maximum (F s)
and minimum (SFC ) at Alt frac1413000 m and Ma frac1408
Figure 11 The optimum running line (ORL ) superimposed on the
performance carpet
Table 3 Relative effect of 10 reduction in TIT on performance
along the ORL
Variable Effect
r f 1143
F s 121
SFC 46
Figure 12 Comparing points on the ORL using the analytical model
of this work with that from GAMS
Yousef SH Najjar Ibrahim AI Balawneh118
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 68
Carrying out the sensitivity analysis it was possible to
calculate the relative effects of 10 drop of operating
variables from the design point on performance as depicted
in Table 2
4 Optimization
When considering the design of a turbojet the basic
thermodynamic variables at the disposal of the designer are
the TIT and r p which are used to get the optimum
performance of a turbojet Performance optimization is
intended to 1047297nd the maximum F s and minimum SFC of
the engine [20]
The method of optimization utilized here searches for the
optimum compressor pressure ratio r f at certain TIT for
which the turbojet engine has optimum performance that
gives maximum F s and minimum SFC
For each TIT there is r f that gives maximum F s hence
the optimum running line (ORL ) was formed over wide
range of operating conditions using the analytical model
with excel
A computer program called GAMS was used to solve the
optimization problem for comparison GAM was originally
developed to provide a high-level language for the compact
representation of large and complex models (Appendix A)
The optimum running points at different combinations of
operating conditions are plotted in Figure 10 The locus of
these points forms the optimum running line (ORL ) reco-
mmended for the engine to follow This line is super imp-
osed on the carpet of performance as shown in Figure 11
to show how the optimum performance is achieved over
wide range of operating conditionsCarrying out sensitivity analysis for the effect of TIT on
performance it was possible to obtain the corresponding
variation in r f F s and SFC as shown in Table 3
Its obvious from Figure 12 that there is difference in r f values between GAMS and the analytical model but in
some cases the values are very close The difference bet-
ween GAMS and the analytical method is due to the nesting
steps carried out by the GAMS leading to F s as function of
r p because the equation has one independent variable But
in the analytical method the problem is dealt with in
consecutive detailed steps using excel
5 Conclusions
a) Sensitivity analysis shows that reducing turbine inlet
temperature TIT of the turbojet engine by 10 results
in 68 increase in SFC and 67 in F s
b) On the other hand reducing the pressure ratio r p by
10 results in 134 increase in SFC and 0022
decrease in F s
c) After altitude of 11500 m there is no effect for
increasing altitude on F s and SFC This is due to the
ambient temperature and hence the speed of sound
which remaining constant after this altitude
d) Reducing Ma by 10 results in 146 decrease in SFC
and 235 increase in F s
e) The value of optimum pressure ratio r f for maximum
speci1047297c thrust increased as the turbine inlet tempera-
ture TIT increased A 10 decrease in TIT results in
1143 decrease in r f
f) After optimum r f the speci1047297c thrust decreases as r p
increases but the speci1047297c fuel consumption stilldecreases as r p increases
g) The optimum value of compressor pressure ratio r f at
1700 K is 14
Appendix A General Algebraic ModelingSystem (GAMS)
Systems approach
Planning management and design are a critical element of sustainable economic development and expansion In the
process of planning and design there is a need to critically
analyze the true economic costs bene1047297ts and environmental
consequences of projects A lack of this analysis can often
lead to a level of design quality which falls far short of
optimal with respect to the utilization of scarce economic
and natural resources and will not improve the ecological
balance of systems in general
Systems analysis can aid in identifying those likely
situations where a minimum investment of funds and
energies will produce maximum gains in terms of resource
allocations economic development and environmental wel-
fare Generally speaking systems analysis is the art andscience of disassembling complex phenomena into smaller
isolated more readily understood subsystems and analyz-
ing the interactions between the subsystems and between
the subsystems and the larger environment [21] The central
method used in water resource systems analysis is to couple
the descriptions of physical and socioeconomic systems
through the use of mathematical models
A system is a collection of components and their
interrelationships forming an entity (eg a riverbasin)
which is acted upon by external forces in1047298uences or inputs
(precipitation) and produces a speci1047297c effect or output
(stream 1047298ow) That is a system is a set of objects whichtransforms an input into an output the exact output
produced depending on certain system properties or para-
meters (eg soil types vegetation topography) This
transformation depends upon the parameters of the system
and the design policies imposed on it
Systems analysis involves the construction and linkage of
mathematical models of the physical and subsystems
associated with resource allocation systems The purpose
of constructing these models is to aid engineers planners
and decision makers in identifying and evaluating alter-
native designs and to determine which ones meet project
objectives in an ef 1047297cient manner
Optimization of gas turbines for sustainable turbojet propulsion 119
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 78
These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 68
Carrying out the sensitivity analysis it was possible to
calculate the relative effects of 10 drop of operating
variables from the design point on performance as depicted
in Table 2
4 Optimization
When considering the design of a turbojet the basic
thermodynamic variables at the disposal of the designer are
the TIT and r p which are used to get the optimum
performance of a turbojet Performance optimization is
intended to 1047297nd the maximum F s and minimum SFC of
the engine [20]
The method of optimization utilized here searches for the
optimum compressor pressure ratio r f at certain TIT for
which the turbojet engine has optimum performance that
gives maximum F s and minimum SFC
For each TIT there is r f that gives maximum F s hence
the optimum running line (ORL ) was formed over wide
range of operating conditions using the analytical model
with excel
A computer program called GAMS was used to solve the
optimization problem for comparison GAM was originally
developed to provide a high-level language for the compact
representation of large and complex models (Appendix A)
The optimum running points at different combinations of
operating conditions are plotted in Figure 10 The locus of
these points forms the optimum running line (ORL ) reco-
mmended for the engine to follow This line is super imp-
osed on the carpet of performance as shown in Figure 11
to show how the optimum performance is achieved over
wide range of operating conditionsCarrying out sensitivity analysis for the effect of TIT on
performance it was possible to obtain the corresponding
variation in r f F s and SFC as shown in Table 3
Its obvious from Figure 12 that there is difference in r f values between GAMS and the analytical model but in
some cases the values are very close The difference bet-
ween GAMS and the analytical method is due to the nesting
steps carried out by the GAMS leading to F s as function of
r p because the equation has one independent variable But
in the analytical method the problem is dealt with in
consecutive detailed steps using excel
5 Conclusions
a) Sensitivity analysis shows that reducing turbine inlet
temperature TIT of the turbojet engine by 10 results
in 68 increase in SFC and 67 in F s
b) On the other hand reducing the pressure ratio r p by
10 results in 134 increase in SFC and 0022
decrease in F s
c) After altitude of 11500 m there is no effect for
increasing altitude on F s and SFC This is due to the
ambient temperature and hence the speed of sound
which remaining constant after this altitude
d) Reducing Ma by 10 results in 146 decrease in SFC
and 235 increase in F s
e) The value of optimum pressure ratio r f for maximum
speci1047297c thrust increased as the turbine inlet tempera-
ture TIT increased A 10 decrease in TIT results in
1143 decrease in r f
f) After optimum r f the speci1047297c thrust decreases as r p
increases but the speci1047297c fuel consumption stilldecreases as r p increases
g) The optimum value of compressor pressure ratio r f at
1700 K is 14
Appendix A General Algebraic ModelingSystem (GAMS)
Systems approach
Planning management and design are a critical element of sustainable economic development and expansion In the
process of planning and design there is a need to critically
analyze the true economic costs bene1047297ts and environmental
consequences of projects A lack of this analysis can often
lead to a level of design quality which falls far short of
optimal with respect to the utilization of scarce economic
and natural resources and will not improve the ecological
balance of systems in general
Systems analysis can aid in identifying those likely
situations where a minimum investment of funds and
energies will produce maximum gains in terms of resource
allocations economic development and environmental wel-
fare Generally speaking systems analysis is the art andscience of disassembling complex phenomena into smaller
isolated more readily understood subsystems and analyz-
ing the interactions between the subsystems and between
the subsystems and the larger environment [21] The central
method used in water resource systems analysis is to couple
the descriptions of physical and socioeconomic systems
through the use of mathematical models
A system is a collection of components and their
interrelationships forming an entity (eg a riverbasin)
which is acted upon by external forces in1047298uences or inputs
(precipitation) and produces a speci1047297c effect or output
(stream 1047298ow) That is a system is a set of objects whichtransforms an input into an output the exact output
produced depending on certain system properties or para-
meters (eg soil types vegetation topography) This
transformation depends upon the parameters of the system
and the design policies imposed on it
Systems analysis involves the construction and linkage of
mathematical models of the physical and subsystems
associated with resource allocation systems The purpose
of constructing these models is to aid engineers planners
and decision makers in identifying and evaluating alter-
native designs and to determine which ones meet project
objectives in an ef 1047297cient manner
Optimization of gas turbines for sustainable turbojet propulsion 119
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 78
These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 78
These mathematical models are able to predict a systems
response to different design alternatives and conditions The
models are a set of mathematical expressions (partial or
ordinary differential or algebraic equations) describing the
physical biological chemical and economic processes
which take place in the system Most systems models are
based on statements of basic conservation laws (mass
energy and momentum) but they can also be empiricalor statistical Systems analysis models are generally broken
down into two categories simulation models and optimiza-
tion models
Simulation and optimization models
Optimization models provide a means of reducing the
number of alternatives which need to be simulated in detail
ie screening them These models search the space of
possible design variable values and identify an optimal
design andor operating policy for a given system design
objective and set of constraints The sensitivity of the
optimal solution to changes in the model parameter scan
be readily determined and tradeoffs between several con-
1047298icting objectives can also be calculated with most optimi-
zation models These models are usually extensions of
simulation models and include as unknowns the design or
operating variables (decision variables) of each alternative
Model building process
In this procedure the model outputs are compared with
actual historical or measured outputs of the system and the
parameters are adjusted until the model predicted and the
measured values agree Then a model veri1047297cation exercise
is carried out in which an independent set of input data is
used in the model and the predicted results are compared
with measured outputs and if they are found to agree the
model is considered to be veri1047297ed and ready for use in
simulation or optimization
Book organization
Examples of optimization models from several technical
areas of interest are covered in Part 1 general equationssolving water resources management agricultural manage-
ment canal design power system design and management
heat transfer and 1047298uid 1047298ow
These models are presented for the purpose of introdu-
cing the reader to the possibilities of modeling these
systems using optimization techniques There are certainly
many additional application areas and techniques that could
be covered but the examples selected cover a wide enough
range to introduce the reader to the topic Part 2 of the book
covers many of the basics of the modeling language used in
this book That language is the General Algebraic Modeling
System (GAMS)
High-level modeling system for mathematical program-
ming problems [19] This section of the book is intended to
provide the reader with suf 1047297cient information to construct
simple models without having to read through the full
language documentation
By using GAMS it was found that the modeling
languages are more useful than the other types of modeling
packages such as LINGO [22] since these products do not allow the easy construction of general modeling structures
such as those needed for solving differential equations
References
[1] M Akyurt NJ Lamfon YSH Najjar MH Habeebullah
TY Alp Modeling of waste heat recovery by looped water-
in-steel heat pipes The International Journal of Heat and
Fluid Flow 16 (4) (1995) 263-27
[2] YSH Najjar M Akyurt Combined cycles with gas turbine
engines Journal of Heat Recovery Systems amp CHP 14 (2)
(1994) 93ndash103[3] YSH Najjar N Jubeh Comparison of performance of
compressed - air energy - storage plant (CAES) with
compressed - air storage with humidi1047297cation (CASH)
Proceedings of the Institution of Mechanical Engineers
(IMechE) 220 Part A Journal of Power and Energy 220
(2006) 581ndash588
[4] YSH Najjar Some performance characteristics of the gas
turbine combustor using heavy fuels Journal of the Institute
of Energy LV 425 (1982) 187ndash194
[5] YA Cengel MA Boles Thermodynamics an Engineering
Approach 7th ed Mc-Graw Hill 2007
[6] F Noori M Gorji A Kazemi H Nemati Thermodynamic
optimization of ideal turbojet with afterburner engines using
non-dominated sorting genetic algorithm II Aerospace Engi-
neering 224 (2010) 1285ndash1296
[7] NU Rahman JF Whidborne A numerical investigation
into the effect of engine bleed on performance of a single-
spool turbojet engine Aerospace Engineering 222 (2008)
939ndash949
[8] A Cavcar M Cavcar Impact of aircraft performance
differences on fuel consumption of aircraft in air traf 1047297c
management environment Aircraft Engineering and Aero-
space Technology 76 (2004) 502ndash515
[9] DP Bakalis AG Stamatis Data analysis and performance
model calibration of a small turbojet engine Aerospace
Engineering 1 (2011) 78ndash85
[10] A Wood P Pilidis A variable cycle jet engine for ASTOVLaircraft Aircraft Engineering and Aerospace Technology 69
(1997) 534ndash539
[11] UK Saha M Miltra SJ Menon NT Jhon SS Gajapathi
Preliminary design analysis of a lightweight combat aircraft
Aerospace Engineering 222 (2008) 507ndash513
[12] J Cooper L Dingle Engineeringan afterburner for a
miniature gas turbine engine Aircraft Engineering and
Aerospace Technology 77 (2005) 104ndash108
[13] J Yin P Pilidis KW Ramsden SD Probert Assessment
of variable-cycle propulsion systems for ASTOVL Aircraft
Engineering and Aerospace Technology 72 (2000) 537ndash544
[14] RM Denning NA Mitchell Trendsin military aircraft
propulsion Aerospace Engineering 203 (1989) 11ndash23
Yousef SH Najjar Ibrahim AI Balawneh120
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121
8172019 Jet Report
httpslidepdfcomreaderfulljet-report 88
[15] SC Kaushika RV Siva SK Tyagib Energy and exergy
analyses of thermal power plants Review Renewable and
Sustainable Energy Reviews 15 (2011) 1857ndash1872
[16] YSH Najjar SF Al-Sharif Thermodynamic optimization
of turbofan cycle Aircraft Engineering and Aerospace
Technology 78 (2006) 467ndash480
[17] DS Pascovici S Sorato SO Ogaji P Pilidis Overview of
coupling noise prediction for turbofans engine and aircraft
performance Aerospace Engineering 222 (2008) 515ndash529
[18] A Zanj A Kalabkhani MA Abdous H Karimi Model-
ling simulation and optimization of a hot pressurization
system for a liquid propellant space engine and comparison
with experimental results Aerospace Engineering 224 (2010)
1141ndash1150
[19] A Brook D Kendrick A Meeraus R Raman GAMS a
User Guide GAMS Development Corporation Washington
DC 1998
[20] T Katra šnik F Trenc Innovative approach to air manage-
ment strategy for turbocharged diesel aircraft engines Aero-
space Engineering 1 (2011) 173ndash198
[21] CW Churchman The Systems Approach Dell Publishing
Co New York 1968
[22] L Schrage Optimization Modeling with LINGOrsquo Lindo
Systems 1999
Optimization of gas turbines for sustainable turbojet propulsion 121