oatiudye deea

and unit exergy cost rate of the LM6000 are determined to be 3798.80 US$/h and 24.37 US$/GW,

over thn. Thein theptuall

plants [1]. In large industrial power plants, a considerable amount

most protable because of making an increase in energy efciencyand having lower running costs alongwith reducing carbon dioxideand noxious exhaust [4,7,16e18].

Nowadays, exergo-economic method is a powerful tool tostudy and optimize for energy systems. Thermo-economic analysis

main goal of exergy analysis is determination of location andanalysis usually

energy system andy quantifying theprovides a tech-the costs of indi-nd nal products.capital investmente expenses, cost of

exergy destruction, and cost of exergy loss from overall system.Furthermore, for a system, destruction rates of each componentmay not have the same value. So exergy analysis is required but itis not an enough solution. With thermo-economic analysis, it isassigned an average cost for every exergy ow rates. These averagecosts enable the calculation of cost rates at the inlet and outlet ofthe units. Finally using thermo-economic parameters, energy,exergy and economic evaluations of a system have beencompleted [19,21,23e29].

* Corresponding author. Tel.: 90 222 3350580; fax: 90 222 3221619.E-mail addresses: onderturan@anadolu.edu.tr, science.onder.turan@gmail.com

Contents lists availab

Ener

els

Energy 74 (2014) 638e650(O. Turan), tei.hakan@gmail.com (H. Aydin).of primary energy may be saved via a more extensive usage ofcogenerations. In one hand, maintaining energy savings may beensured only by performing thermodynamic analyses [2,3]. On theother hand, increasing concern about environment is causing toaction to reduce CO2 emissions from power plants. One way toreduce to emissions on the environment is to use cogenerationsystems. The advantages of cogeneration systems are evaluated bymany researchers [4e17]. These power plants are also generally

amount of irreversibility of a system. Exergypredicts the thermodynamic performance of anefciency of system components by accuratelentropy generation. Thermo-economic methodnique to evaluate the cost of inefciencies orvidual process streams, including intermediate aThis method covers all pertinent costs, such asfor each component, operating and maintenancplants: the steam turbine, gas turbine, and diesel engine based second law of thermodynamics are used as an exergy analysis. TheLM6000EnergyExergyExergo-economyCogenerationAero derivative gas turbine

1. Introduction

Gas turbines are widely used allration systems for power generatioproduction of both thermal energy,water, and electricity. There are concehttp://dx.doi.org/10.1016/j.energy.2014.07.0290360-5442/ 2014 Elsevier Ltd. All rights reserved.and destructions and to regulate operation conditions and maintenance of aero-derivative gas turbineeet. Furthermore, it will be benecial of similar power generation systems in any environment.

2014 Elsevier Ltd. All rights reserved.

e world in the cogene-se systems involve theform of steam or hot

y different cogeneration

combines the exergy analysis with economic constraints. In ther-modynamic analysis, study is generally focused on relationshipbetween mass ows and energy exchanges [19,20]. Many engi-neers and scientists suggest that the thermodynamic performanceis best evaluated using exergy analysis [21,22]. The conservation ofmass and conservation of energy principles together with theKeywords:

respectively. It is expected that results of this study are useful to identify the cost ows of fuel, products,Available online 30 July 2014 order to match exergetic and economic values. As a result of exergy analysis, exergetic efciency of theLM6000 is obtained to be 39%. On the other hand, exergo-economic results show that exergy cost rateExergetic and exergo-economic analysesturbine engine

Onder Turan a, *, Hakan Aydin b

a Faculty of Aeronautics and Astronautics, TR-26470, Eskisehir, Turkeyb TUSAS Engine Industries, Eskisehir, Turkey

a r t i c l e i n f o

Article history:Received 3 June 2014Received in revised form6 July 2014Accepted 8 July 2014

a b s t r a c t

The number of aero-derivfollowing decades. This stLM6000 gas turbine enginexergy and exergy costs for

journal homepage: www.f an aero-derivative gas

ve gas turbines used in cogeneration systems will continue to rise inis focused on detailed exergetic and exergo-economic analyses of anrived from CF6e80C2 aircraft turbofan engine. In this regard, balances ofch components and LM6000 gas turbine engine are carefully considered in

le at ScienceDirect

gy

evier .com/locate/energy

2. System description

The LM6000 is rated to provide more than 43 MW at interna-tional standard atmosphere condition. More than 1000 LM6000 gasturbine engines have been produced that they had over 21 millionhours of operation and used in marine application and powerplants to produce electricity and heat. The value of shaft outputpower with ambient temperature and main components of theLM6000 are shown in Figs. 1 and 2, respectively [45,48].

The LM6000 is a simple-cycle, two-shaft, high-performance gasturbine that is derived fromGeneral Electric CF6e80C2 high bypassturbofan aircraft engine used in several types of wide bodycommercial aircraft, including Boeing 747e400. The LM6000 has a5-stage LPC (low-pressure compressor), a 14-stage variable-geometry HPC (high-pressure compressor), an annularcombustor, a 2-stage HPT (high-pressure turbine), a 5-stage LPT(low-pressure turbine), an AGB (accessory gearbox) assembly, andaccessories [45,48e50]. The air is compressed in LPC and HPC bythe ratios of approximately 2.4 and 12, resulting in a totalcompression ratio of 30 relative to ambient. From the HPC, the air isdirected into the signal annular combustor section, where it mixeswith the fuel from fuel nozzles. The hot gas that results fromcombustion is directed into HPT that drives HPC. This gas furtherexpands through LPT, which drives LPC and output load. Natural gasand distillate oil are the fuels most frequently utilized by aero de-

nergy 74 (2014) 638e650 639For more than a half-century, gas turbine engines have beenused for commercial airliners. For nearly as long, manufacturershave built industrial gas turbines adapting directly from existingaircraft engines to drive electricity generators and pump oil andgas. The industrial gas turbine market including aero derivative gasturbines was estimated to be $15.6 billion worldwide in 2010. Aeroderivative gas turbines have historically been limited to midsizeunits of roughly 18e65 MWeach. Worldwide, aero derivative unitsaccount for approximately 10e20 percent of gas turbine capacity inrecent years' orders, totalling roughly 6000 to 8000 MW per year.However, for mid-size units with capacities of 18e65 MW, aeroderivative units account for approximately two thirds of gas turbinecapacity sold in recent years. For electricity generation and oil/gasoperations, Rolls Royce projects with aero derivative units will beworth $70 billion in sales plus another $50 billion for associatedservices over the next 20 years [30e32]. GE (general electric), theleading provider of aero derivative gas turbines, estimates havingover 2300 aero derivative units in service for electricity generationworldwide, totalling 80,000 MW of capacity [33].

In the literature, exergy, exergo-sustainability and exergo-economic analyses of aircraft engines such as turboprop, turbojetand turbofan have been investigated by many researchers[25,34e44]. In addition to these, there exist many additionalstudies on exergy and thermo economy analyses of cogenerationpower plants as well [1,45e47]. Only one study [45] has addressedexergo-sustainability for LM6000. In this paper [45], exergeticsustainability indicators of the LM6000 gas turbine engine basedpower plant system are investigated for two congurations (withand without steam turbine cycle). Exergy efciency, waste exergyratio, recoverable exergy rate, exergy destruction factor, environ-mental effect factor and exergetic sustainability index are selectedas sustainability parameters and then exergetic sustainability in-dicators for two congurations are executed to identify level ofsustainability impact of the LM6000 gas turbine [45].

Cogeneration companies have investment and technologyinsertion plans to grow the LM6000 well beyond its current ratingwithout increasing the engine's shipboard size and weight foot-print. The LM6000 is the high power member of LM aero deriv-ative gas turbine offerings used extensively for marine propulsionand cogeneration applications. Benets aero derivatives have ahigh power to weight ratio that is extremely important for shipapplications where equipment weight and size are issues that cansignicantly impact costs. Besides, this engine offers fuel ef-ciency, long life, and low maintenance. The LM6000 gas turbine isderived from GE's CF6e80C2 high bypass turbofan engine used inA300, A310, B747e400 and B767 aircrafts. Through a literaturereview, it is noticed that any studies on exergetic and exergo-economic analyses of the LM6000 gas turbine engine have notappeared to the best of the authors' knowledge. These reasonsmake this study original and become the main motivation. Basedon information about importance of the LM6000 gas turbine en-gine, the objectives of this study are to analyze exergetic andexergo-economic values of the LM6000 gas turbine. In this regard,main steps of this contribution are to determine of exergy pa-rameters, form the exergy cost balance equations for eachcomponent and perform exergo-economic analysis of the LM6000gas turbine and engine components using the exergy cost balanceequations. It is expected that this methodology usually helpsdetermine the appropriate allocation of economics resources so asto optimize the design and operation of the LM6000 gas turbine.Another output of this study contributes to an understanding ofthe exergo-economic pattern of an aero-derivative gas turbineengine for cogeneration systems. This study can also be extendedand implemented to other aero derivative LM series gas turbine

O. Turan, H. Aydin / Eengines.ciencies [51e53].rivatives [46,49,50].

3. Methodology

3.1. Energy and exergy analyses: theoretical background

Energy-based approach is based on the principle of conservationof energy applied to any system. For a general steady state, steady-ow process, four balance equations (mass, energy, entropy andexergy) are applied to nd the work and heat interactions, rate ofexergy decrease, rate of irreversibility, energy and exergy ef-Fig.1. Shaft output power of the LM6000 engine [48].

ergO. Turan, H. Aydin / En640The mass balance equation can be expressed in the rate form as.

X_min

X_mout (1a)

Where _m is the mass ow rate, and the subscript in stands for inletand out for outlet. The general energy balance can be expressedbelow as the total energy inputs equal to total energy outputs.

X_Ein

X_Eout (1b)

Energy conservation suggests that for a steady-state process, theFirst Law may be represented:

Xh ke peinmin

Xh kepeoutmout

XQ W 0

(1c)

where min and mout denote the mass ow across the system inletand outlet, respectively, Q represents the heat transfer across the

Fig. 2. a) The LM6000 generator set [48] b) Schematicy 74 (2014) 638e650system boundary, W is the work (including shaft work, electricity,and so on) transferred out of the system, and h, ke, and pe denotethe specic values of enthalpy, kinetic energy, and potential energy,respectively. This energy balance can be simplied, assumingnegligibly small changes in kinetic and potential energy and noheat or work transfers:

XHi;in

XHj;out (1d)

Where Hi,in represents the various energy (or enthalpy) streamsowing into the system, and Hj,out the different energy outputs.

First Law or energy analysis takes no account of the energysource in terms of its thermodynamic quality. It enables energy orheat losses to be estimated, but yields only limited informationabout the optimal conversion of energy. In contrast, the Second Lawindicates that, whereas work input into a system can be fully con-verted to heat and internal energy, not all the heat input can beconverted into useful work. Exergy provides a quantitative basis to

illustration of the LM6000 gas turbine engine [45].

hex _Exout_Exin

1_Exdest_Exin

(9a)

Where out stands for net output or product or desiredvalue or benet, and in stands for given or fuel.

The improvement potential in the rate form, denoted _IP, is givenby.

_IP 1 hex

_Exin _Exout

(9b)

In addition to exergy efciency and improvement potential rate,the exergy destruction rate ( _Exdest) is useful for the evaluation of asystem [28,63]. Exergy destruction rate measures the rate of exergydestruction or consumption due to irreversibilities within the de-vice. It is the difference between exergy inputs and outputs forsteady-state processes. The exergy destruction rate _Exdest isexpressible as [42]:

nergymeasure the degradation of energy in a process and contains bothFirst and Second Laws [54]. The exergy loss in a system orcomponent is determined by multiplying the absolute temperatureof the surroundings by the entropy increase [55e57]. As a conclu-sion, exergy method also helps in understanding and improvingefciency, environmental impact and economic performance aswell as sustainability [58].

Note that, whereas energy is a conserved quantity, exergy is notand is always destroyed when entropy is produced. In the absenceof electricity, magnetism, surface tension and nuclear reaction, thetotal exergy of a system ( _Ex) can be divided into four components,namely (i) physical exergy ( _ExPH) (ii) kinetic exergy ( _ExKN ) (iii)potential exergy ( _ExPT) and (iv) chemical exergy ( _ExCH) [55].

_Ex _ExPH _ExKN _ExCH _ExPT (2a)Although exergy is extensive property, it is often convenient to

work with it on a unit of mass or molar basis. The total specicexergy on a mass basis may be written as follows [55]:

ex exPH exKN exCH exPT (2b)The general exergy balance can be written as follows [55]:

X_Exin

X_Exout

X_Exdest (3a)

_Exheat _Exwork _Exmass;in _Exmass;out _Exdest (3b)

_Exheat X

1 T0Tk

_Qk (3c)

_Exwork _W (3d)

_Exmass;in X

_minjin (3e)

_Exmass;out X

_moutjout (3f)

Where _Qk is the heat transfer rate through the boundary at tem-perature Tk at location k and _W is the work rate.

The ow (specic) exergy is calculated as follows:

ex h h0 T0s s0 (4)

Where h is enthalpy, s is entropy, and the subscript zero indicatesproperties at the restricted dead state of P0 and T0.

The rate form of the entropy balance can be expressed as [55]

_Sin _Sout _Sgen 0 (5)

Where the rates of entropy transfer by heat transferred at a rate of_Qk andmass owing at a rate of _m are _Sheat _Qk=Tk and _Smass _ms,respectively [55].

Taking the positive direction of heat transfer to be to the system,the rate form of the general entropy relation given in Eq. (5) can berearranged to give [55]:

_Sgen X

_moutsout X

_minsin X _Qk

Tk(6)

It is also usually more convenient to nd _Sgen rst and then toevaluate the exergy destroyed or the irreversibility rate _I directlyfrom the following equation, which is called GouyeStodola relation

O. Turan, H. Aydin / E[59]:_I _Exdest T0 _Sgen (7)Assuming air to be a perfect gas, the specic physical exergy of

air is calculated by the following relation [60]:

exa;per Cp;aT T0 T0 ln

TT0

RaT0 ln

PP0

(8a)

The specic chemical exergies of natural gas on a unit mass basiscan be determined from Eq. (8b) [40,61].

exch;fhPR

gfy1:033 0:0169HC 0:0698 1

C(8b)

Where gf denotes the fuel exergy grade function which is calcu-lated to be 1.0308 for natural gas.

Numerous ways of formulating exergy efciency for variousenergy systems are given in detail elsewhere [62]. It is very usefulto dene efciencies based on exergy. There is no standard set ofdenitions in the literature. Here, exergy efciency is dened as theratio of total exergy output to total exergy input, i.e.

Table 1The LM6000 gas turbine engine thermodynamic data.

Station no Location _m (Kg/s) T (K) P (kPa) Exergydestruction(MW)

Exergyefciency

2 LPC inlet(Air inlet)

119.5 288 100.7 (LPC) 1.29 (LPC) 0.889

2.5 LPC outlet(HPC inlet)

119.5 383 247

3 HPC outlet(Combustorinlet)

119.5 815 3034 (HPC) 7.79 (HPC) 0.871

3f Fuel supply 2.39 293 2200 (CC) 25.91 (CC) 0.8513w Water supply 2.3 293 17004.1 Combustor

outlet(HPT inlet)

124 1550 2882

4.5 HPT outlet(LPT inlet)

124 1144 724 (HPT) 1.62 (HPT) 0.974

5 LPT outlet(Exhaust)

124 770 111 (LPT) 2.72 (LPT) 0.953

Source: [45,49]

74 (2014) 638e650 641_Exdest _Exin _Exout (9c)

hex;HPT _WHPT

_Ex41 _Ex45(13c)

LPT (low pressure turbine):

X_Exin;LPT

X_Exout;LPT

X_Exdest;LPT (14a)

X

PR US$/kg 0.7

ergy 74 (2014) 638e650hex;HPC _Ex3 _Ex25

_WHPC(11d)

CC (combustor):

X_Exin;CC

X_Exout;CC

X_Exdest;CC (12a)

_Ex3 _Exfuel _Exwater _Ex4 X

_Exdest;CC (12b)

hex;CC _Ex4

_Ex3 _Exfuel(12c)

HPT (high pressure turbine):

X_Exin;HPT

X_Exout;HPT

X_Exdest;HPT (13a)hex;LPC _Ex25 _Ex2

_WLPC(10d)

High pressure compressor:

X_Exin;HPC

X_Exout;HPC

X_Exdest;HPC (11a)

_WHPC _Ex25 _Ex3 X

_Exdest;HPC (11b)

_WHPC _ma;HPCh3 h25

(11c)3.2. Exergy analysis of the LM6000 gas turbine engine

In this study, exergy analysis of the LM6000 gas turbine is to beperformed based on operating parameters given in Table 1. In thisregard, assumptions made are (i) air and combustion gas ows inthe engine are assumed to behave ideally (ii) combustion reactionis complete (iii) compressors and turbines are assumed to beadiabatic (iv) ambient temperature and pressure values are 288 Kand 100.7 kPa, respectively (v) LHV (lower heating value) of naturalgas is used (vi) engine accessories, pumps (fuel, oil and hydraulic)are not included in the calculations (vii) kinetic and potentialexergies are neglected (viii) chemical exergy is neglected otherthan the combustor.

With these assumptions, preliminary exergetic evaluation of gasturbine components can therefore be expressed using the followingauxiliary equations:

Low pressure compressor:

X_Exin;LPC

X_Exout;LPC

X_Exdest;LPC (10a)

_WLPC _Ex2 _Ex25 X

_Exdest;LPC (10b)

_WLPC _ma;LPCh25 h2

(10c)O. Turan, H. Aydin / En642_Ex41 _WHPT _Ex45 X

_Exdest;HPT (13b)_Ex45 _WLPT _Ex5 _Exdest;LPT (14b)

hex;LPT _WLPT

_Ex45 _Ex5(14c)

3.3. Sensitivity and uncertainty analysis

Within many test equipment the temperature sensors, pressureprobes, fuel ow meter, speed sensors and torque sensors arehighly important for energy and exergy analysis, so theyll briey bediscussed in this section. To ensure the correct measurements, allmeasurement equipment should be calibrated periodically and themeasurement errors should be within acceptable tolerances ofsensors. Various temperature sensors are utilized to measure theambient air temperature and cold and hot gases temperatures atdifferent engine stations. The main measuring devices, calibratedrange, accuracy or relative error of various instruments for pa-rameters are listed in Table 4. An error analysis based on the ac-curacies of direct measurements is conducted to determine themaximum possible errors of exergetic parameters. The adoptedanalysis method is the differential method of propagating errorsbased on Taylor's theorem. It gives the maximum error of a functionas follows:

Dy X vf

vxiDxi

2sy f

0@x1; x2; :::xn

1A (14d)

As a result, the maximum relative root mean square errors forexergetic outputs during the experiment are tabulated in Table 5. Itcan be seen that the average possible error for all components andengine itself was below 1%. It should be clearly noted that theestimated errors in the measurements of the derived quantities donot signicantly inuence the nal results.

4. Exergo-economic analysis

The exergo-economic methodology is used in the design ofenergy conversion systems to calculate the costs of nal products aswell as the costs of the exergy destroyed within each component. Itcan be considered as an exergy-aided cost reduction approach. Thisis essential to detect cost-ineffective processes and identify

Table 2The LM6000 gas turbine engine thermo-economic parameters.

Item Unit Value

CIC US$ 8,500,000OM US$/yr 112,000I % 10J % 10

N yr 20

t h/yr 8,000LHV kJ/kg 44,600

Where CICLM6000SLM6000, PWF and j are capital cost, salvage value,

_ZTLM6000

ACICLM6000t

(20)

Hourly levelized capital investment cost of kth component( _Z

CICk );

_ZCICk _Z

CICLM6000

PECkP (21)

Table 3The purchased equipment cost and levelized cost rate associated with capital in-vestment, operating and maintenance costs of the LM6000 gas turbine engine andcomponents.

Component PEC(US$) _ZCICk (US$/h) _Z

OMk (US$/h) _Z

Tk (US$/h)

LPC 1,700,000 24.6 12 36.6HPC 1,700,000 24.6 14 38.6Combustor 1,275,000 18.4 42 60.4HPT 2,125,000 30.7 47 77.7LPT 1,700,000 24.6 22 46.6LM6000 8,500,000 123 137 260

O. Turan, H. Aydin / Energy 74 (2014) 638e650 643present value factor and salvage rate (%), respectively.PWF (present value factor) [40,64];

PWF 11 in (17)

ACIC (annual capital cost) [40,64];

ACICLM6000 PWFLM6000CRFi;n (18)CRF (capital recovery factor);

CRF i1 in

1 in 1 (19)technical options which could improve the cost effectiveness ofoverall energy system. Exergo-economic method is a unique com-bination of exergy analysis and cost analysis conducted at thecomponent level. It provides a designer or operator of an energyconversion systemwith information crucial to the design of a cost-effective system. This information cannot be supplied through en-ergy, exergy, and cost analyses conducted separately. Exergo-economy is an exergy-aided cost reduction approach that usesthe exergy costing principle. In this method, we seek the appro-priate trade-offs mainly between capital-investment-related costsand fuel costs [2,12,17,19,20,53]. In this paper, exergo-economicanalysis of LM6000 gas turbine engine was executed as well.

4.1. Levelized cost method

Exergo-economic parameters are explained below from Eq. (15)through Eq. (25). The PW (present worth) and S (salvage value) (S)of a gas turbine engine can be calculated by using Eqs. (15) and (16),respectively [40,64].

PWLM6000 CICLM6000 SLM6000PWFi;n (15)

SLM6000 j$CICLM6000 (16)Annualized equipment cost of the engine:

Table 4Specications of measuring devices.

Instrument Calibrated range Accuracy

Low range thermocouple 0e150 F 1 Fk-type thermocouple 0e675 F 2.7 Fk-type thermocouple 675e2000 F 4 FPressure probe 0e20 psi 0.003 psiPressure probe 0e300 psi 0.02 psiTorque sensor 0e800 lbf-ft 2 lbf-ftFuel ow 0e1000 pph 0.005 pph

1 C 0.55(F-32), 1 psi 6.894 kPa, 1 lbf-ft 1.355 N m, 1 pph 0.000126 kg s1LPC and HPC

HPT (high pressure turbine):

erg_C4 _ZTHPT _CW ;HPT _C45 (37)where _CW;LPC is LPC work cost and _C1 0

_WLPCcW;LPC _ZTLPC _Ex25c25 (30)

42:5cW;LPC 36:6 37:2c25 0 (31)

HPC (high pressure compressor):

_CW;HPC _C25 _ZTHPC _C3 where _CW;HPC is HPC work cost

_WHPCcW;HPC _Ex25c25 _ZTHPC _Ex3c3 (32)

221:04cW;HPC 37:2c25 38:6 226:9c3 0 (33)

CC (combustor):

_C3 _Cfuel _ZTCC _C4 (34)

_Ex3c3 _Exfuelcfuel _ZTCC _Ex4c4 (35)

226:9c3 533:8c4 5902:4 0 (36)implicitly. For the explicit formulation of the auxiliary equation, F(exergetic fuel) and P (exergetic product) rules may be used: the Frule refers to the removal of exergy from an exergy stream withinthe component being considered. It states that the average speciccost associated with this removal of exergy (which is part of exergyof fuel). It must be equal to the average specic cost at whichremoved exergy has been supplied to the same stream in upstreamcomponents. The P-rule is related to the supply of exergy to anexergy streamwithin the component. It states that each exergy unitis supplied to any stream associated with the exergetic product of acomponent at the same average cost. Using cost balances andauxiliary equations, cost rates and costs per unit of exergy arecalculated for each exergy stream in the overall system[27,40,65e67]. Generally, cost balance and auxiliary equations ofLM6000 components are followed below:

LPC (low pressure compressor):

_C1 _CW ;LPC _ZTLPC _C25 (29)inside the control volume. Some exergo-economic parameters arelisted in Table 2.

4.2. Exergo-economic balance equations

To solve exergo-economic balance equations, in general, if thereare Nout exergy streams exiting the component, Nout1 auxiliaryequations should be formulated. Based on the thermo-economicmethod used, auxiliary equations are formulated explicitly oroperating and maintenance and total levelized cost of equipment

O. Turan, H. Aydin / En644_Ex4c4 _ZTHPT _WHPTcW;HPT _Ex45c45 (38)rf

_Cf F _Cet

LHVch

5;842:84 US$=h (50)

Fuel cost per hour ( _Cf ) has been calculated as 5842 US$ per hour.

The levelized cost values and exergetic _C (US$/h), _c (US$) cost values ofmain components at investigated stations can be calculated by usingEqs. 15e48.533:8c4 221cW;HPT 308 c45 77:7 0 (39)

LPT (low pressure turbine):

_C45 _ZTLPT _CW;LPT _C5 (40)

_Ex45c45 _ZTLPT _WLPTcW;LPT _Ex5c5 (41)

308c45 46:6 198:3cLPT 100c5 0 (42)

For the LM6000 gas turbine engine:

_C1 _C3f _ZLM6000 _Cgen _C5 (43)

(assumption C1:

0)

c3f _ZLM6000 _WgencW;LPT _C5 (44)

6102 155:8cLPT 100c5 0 (45)

Assumptions:

_C41_Ex41

_C45_Ex45

cf F rule (46)

_C45_Ex45

_C5_Ex5

cf F rule (47)

cW;LPT cW;LPC; cW ;HPT cW;HPC; c41 c45 c5; (48)The PEC (purchased equipment cost) of main engine components

has been obtained by adding average costs of all other engine equip-ment costs such as accessories, frames and gearbox. The componentcosts are approximately estimated ones and not indicate the exact

prices. Hourly levelized capital investment cost ( _ZCICk [US$/h]), hourly

operating and maintenance costs ( _ZOMk [US$/h]) and total costs of the

engine and its components are presented in Table 3. They have beencalculated in accordance with using the exergo-economic equationsbased on parameters listed in Table 2.

The FCe (levelized fuel cost), and _Cf (fuel cost) ( _Cf )calculations canbe given as follows;

F _Ce Pr _mf 3600t 48;182;400 US$ (49)

y 74 (2014) 638e650Exergoeconomic factor:

destruction and loss associated with that component.With this parameter, it could be possible to decide whether the

Fig. 3. Exergy ow diagrams of the LM6000 components.

O. Turan, H. Aydin / Energy 74 (2014) 638e650 645further improvements are benecial. This factor (fk) is obtained by.

fk Zk

Zk ck

_Exdest;k _ExL;k (51)

Where the subscripts of dest and L denote the destruction and loss,respectively.

5. Results and discussion

Exergy analysis is used to determine exergetic efciency andThe exergoeconomic factor, fk, is a parameter which shows therelative importance of a component cost to the cost of exergyexergy destruction related to process irreversibilities. Moreover

Fig. 4. Exergy destruction of tenergy, exergy and economic analyses allow one to calculate thecosts of thermodynamic inefciencies which can then be includedinto the thermo-economic analysis.

Through exergetic analysis, it is also possible to determine theirreversibility generation for the LM6000 gas turbine components.It estimates the contribution of each to the total irreversibilitygeneration. Expressions for exergetic values of each station areformulated in Eqs. (1)e(9). Fig. 3, obtained from energy and exergyanalyses, shows the input and output exergy values for gas turbineengine components using Table 1. The exergetic structure of theLM6000, which is called component exergy ow diagram in Fig. 3,is a graphical representation of component inleteoutlet exergydistribution. It should be mentioned that destruction of eachcomponent is the difference between inlet and outlet exergies. Aswe know, exergy efciency, exergy destruction and improvementpotential rates given in Figs. 3e6, evaluate the exergetic perfor-

mance of the LM6000 gas turbine engine and its components.

he LM6000 components.

Fig. 5. Exergy efciency of the LM6000 components.

O. Turan, H. Aydin / Energy 74 (2014) 638e650646As shown in Fig. 3, the value of inlet exergy ow passing fromthe LPC, HPC and CC increases from 11.62 to 174.18 MW, while thevalue of outlet exergy ow increases from 10.33 to 148.27 MW atthe same stations. Besides, outlet exergy ow decreases betweenthe CC eLPT stations, ranging from 148.27 MW to 82.84 MW.Meanwhile, the values of inlet exergy for the HPT and LPT are foundto be 148.27 MW and 85.56 MW, respectively. As shown clearly inFig. 3, inlet exergy decreases signicantly passing from CC to LPT.However, considering outlet exergy ows between the CC and HPT,small decreases are observed, lying in the range between 148.27and 146.65 MW. As expected, this reduction is particularly signi-cant between the HPT and LPT.

In order to better understand the location and magnitude ofexergy destruction rates for the LM6000 gas turbine engine, we canrefer to Fig. 4, showing the value of exergy destruction rate for theLPC, HPC, CC, HPT and LPT. The unit with the great exergydestruction is found to be 25.91 MW in the CC. Highest exergydestruction rate is hopefully caused by internal irreversibilities inthe CC. The performance of various gas turbine components isdescribed as in terms of gures of merit, which allow energy andexergy analyses including losses to be made efciently. IsentropicFig. 6. IP rates of the LMefciencies of the LPC, HPC, HPT and LPT can be considered as g-ures of merit. The gures of merits have changed as technology hasimproved over the years. With respect to the technology level, thesignicant increase in isentropic efciency allows a markeddecrease of exergy destruction rates for rotating components of aturbomachinery. Analyses show that exergy destruction rate is1.62 MW for the HPT and 2.72 MW for the LPT. Correspondingvalues for the LPC and HPC are found to be 1.29 MW and 7.79 MW,respectively.

Fig. 5 shows the exergy efciency of the LM6000 gas turbinecomponents. As expected, the CC shows the poorest exergy ef-ciency (85.1%) due to internal irreversibilities. On the other hand,exergy efciency attains around 88.9 and 87.1% for the LPC and HPC,respectively. Furthermore, it increases signicantly in turbinecongurations, ranging from 97.4% for the HPT to 95.3% for the LPT.The values of exergy efciency of the HPT and LPT change astechnology level and work interaction between corresponding theLPC and HPC.

Another aspect considered in this study is the IP (improvementpotential) rates regarding the LM6000 components derived fromEq. (9) (b). According to Fig. 6, the CC has the highest IP rate6000 components.

Fig. 7. Exergetic performance values of the LM6000 gas turbine engine.

O. Turan, H. Aydin / Energy 74 (2014) 638e650 647(3.856MW). On the other hand, the HPTand LPT have lower IP rateswith values of 0.042 and 0.128 MW, respectively. As evident fromFig. 6, IP rate lies in between 0.143 and 1.003 MW for the LPC andHPC.

The overall LM6000 gas turbine engine comprises with exergyefciency about 39% as shown in Fig. 7. In same gure, it is worthnoting that exergy destruction value of the LM6000 is calculated as39.3 MW. Moreover, exergy destruction is found to be 67.8 MW inFig. 7.

Fig. 8 shows the exergy ow rate of the overall LM6000 gasturbine and component inleteoutlet. Focusing our attention on theLM6000 net work, exergy ow rate is obtained to be 155.88 GW/h.

In order to calculate exergy cost rate and unit exergy cost, the

values of equipment cost, operating and maintenance costs, lev-elized cost rate and other exergo-economic parameters were taken

Fig. 8. Exergy ow rate (GW/h) of thefrom Tables 2,3 According to the economic evaluation method,thermo-economic features of the LM6000 and its components areshown in Figs. 9 and 10. In these gures, the values of exergy costrate and unit exergy cost of the gas turbine station ows can also becompared. Examining exergy costing ow paths in Figs. 9 and 10,regarding the economic analysis, highest exergy cost rate is ob-tained at the HPT inlet with the value of 12,282.09 GW/h, whilelowest exergy cost rate is found in LPC work (1035.24 GW/h)(Fig. 9). For the LM6000 gas turbine, exergy cost rate is found to be3798.80 US$/h.

Fig. 10 shows the results obtained for unit exergy cost for eachcomponent inleteoutlet and also for the LM6000 gas turbine en-gine. The unit exergy cost values of each component are also given

and can be compared. Among the different gas turbine stations,unit exergy cost is minimum in CC (14.61 US$/GW). However,

LM6000 engine and components.

ergO. Turan, H. Aydin / En648higher unit exergy costs are obtained in HPC and CC inlet. After CC,unit exergy cost is obtained for HPT and LPT stations in the range of23.01e24.37 US$/GW. Meanwhile, unit exergy cost rate attainsaround 24.37 US$/GW for the LM6000 gas turbine engine (Fig. 10).

Finally, Fig. 11 shows the exergoeconomic factor (fk) parameter.A high value of fk indicates that the reasons for the high costs arethe sum of the capital investment and the Operating and Mainte-nance costs whereas the low value of fk illustrates that the exergyconsumption including losses and destructions caused by inef-cient use of energy resources as fuel is a dominant factor. It is clearfrom the Fig. 11 that HPT is the highest ratio with 35.97%, while theLPC and LPT have second and third ones with the values of 21.90%and 17.14%, respectively. Exergoeconomic factors of CC and HPC areobtained at relatively low values.

Fig. 9. Exergy cost rate (US$/h) of the

Fig. 10. Unit cost rate (US$/GW) of they 74 (2014) 638e6506. Conclusions

The exergy analysis provides more meaningful and useful in-formation than the energy analysis. In addition to this, exergo-economic analysis can provide extra information to exergy anal-ysis. The results from exergo-economic analysis suggest cost-basedinformation for identifying potential locations for processimprovement. Some concluding remarks drawn from the LM6000gas turbine engine study may be listed as follows:

i. The exergetic efciency of the LM6000 has been calculated as39%.

ii. The highest exergy destruction occurs in the combustionchamber as 25.91 MW values.

LM6000 engine and components.

LM6000 engine and components.

nergyiii. Exergy efciencies are calculated to be 88.9% for the LPC,87.1% for the HPC, 85.1% for the CC, 97.4% for the HPT and95.3% for the LPT.

iv. Highest exergy cost rate is obtained at the HPT inlet with thevalue of 12,282.09 GW/h, while lowest exergy cost rate isfound in LPC work (1035.24 GW/h).

v. Unit exergy cost is minimum in CC with the value of 14.61US$/GW. Unit exergy cost is obtained for HPT and LPT sta-tions in the range of 23.01e24.37 US$/GW.

vi. HPT is the highest exergoeconomic factor with 35.97%, whilethe LPC and LPT have second and third ones with the valuesof 21.90% and 17.14%, respectively.

vii. Exergoeconomic factors for CC and HPC are obtained atrelatively low values in the range of 2.25%e4.67%.

viii. The LM6000 produces 43.3 MW shaft horse power to drivethe generator. As of this, power turbine exergy cost and unitexergy cost are calculated to be 3798.80 US$/h and 24.37US$/GW, respectively.

Aero-derivative gas turbines have been powering cities, in-dustries and maritime eets for 40 years. Today, these engines arealso helping meet environmental and economic challenges. TheLM6000 gas turbine engines have been in commercial service for 15years. The results of this study will help to understand the exergyefciencies of an LM6000 gas turbine engine and its components.The results can focus an engineer's attention on components wherethe greatest potential is destroyed. As a conclusion, the authors

Fig. 11. Exergoeconomic factor of system units.

O. Turan, H. Aydin / Eexpect that the analysis given here will be benecial to everyone. Italso gives benecial information how to identify the cost of it andits main components. The costs may vary from operator to operatorand also many parameters such as time between overhaul, over-haul costs, operational conditions, fuel costs, periodical mainte-nance costs.

For further works, other conventional exergoeconomic methodand advanced exergoeconomic analysis may be applied to theLM6000 engine. Besides, exergo-environmental and advanceexergy analyses can help improve the environmental impact ofaero-derivative engines, and of course, this can be considered innext studies.

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Glossary

ACIC: annual capital cost ow (US$ yr1)ER: exchange rate (TL US$1)F _C: annual fuel cost ow (US$ yr1)f: Function for error and sensitivity analysisfk: exergoeconomic factorh: specic enthalpy (kJ kg1)HPC: high pressure compressorHPT: high pressure turbinehPR: fuel heating value (kJ kg

1)I _P: exergetic improvement potential rate (MW)i: interest rate (%)j: salvage rate (%)KE: kinetic energy (kJ)LPC: low pressure compressorLPT: low pressure turbine_m: mass ow rate (kg sn1)N,n: engine life time (year)P: pressure (kPa)PE: potential energy (kJ)PEC: purchased equipment cost (US$)Pr: fuel sell price (TL kg1)PW: present worth (US$)PWF: present worth factorQ: heat (kJ)R: specic gas constant (kJ kg1 K1)x: parameter for error and sensitivity analysisS: entropy (J K1)S: salvage value (US$)T: temperature (C or K)V: velocity (m sn1)W: work (kJ)_W: power (MW)_Z: capital cost ow (US$ h1)

Greek Letters

j: specic exergy (kJ kg1)g: specic heat ratior: density (kg m3)h: efciency4: operating and maintenance factort: the total annual number hours of system (h)

Subscripts and superscripts

a: airch: chemicalcomb: combustordest: destructionf: fuelgen: generatedi: component for error and sensitivity analysisin: inletk: kth componentkn: kineticL: lossout: outletOM: operating and maintenanceper: perfectph: physicalpt: potentialT, Tot: totalz: height (m)0,1, 2: station numbering of engine component

Exergetic and exergo-economic analyses of an aero-derivative gas turbine engine1 Introduction2 System description3 Methodology3.1 Energy and exergy analyses: theoretical background3.2 Exergy analysis of the LM6000 gas turbine engine3.3 Sensitivity and uncertainty analysis

4 Exergo-economic analysis4.1 Levelized cost method4.2 Exergo-economic balance equations

5 Results and discussion6 ConclusionsReferences