issn 2304-7445 (print) journal of mechanical and ... 6 no 2 - 1.pdfvolume 6 number 2 december 2017...

VOLUME 6 NUMBER 2 December 2017

Journal of Mechanical and Industrial

Engineering Research

ISSN 2304-7445 (Print)

ISSN 2304-7461 (Online)

Journal of Mechanical and Industrial Engineering Research, Vol. 6, No.2, 2017

ISSN 2304-7445

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Journal of Mechanical and Industrial Engineering Research

ABOUT JOURNAL

The Journal of Mechanical and Industrial Engineering Research ( J. mech. ind. eng. res. / JMIER ) was

first published in 2012, and is published semi-annually (May and November). JMIER is indexed and

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The Journal of Mechanical and Industrial Engineering Research is an open access peer-reviewed

international journal to be of interest and use to all those concerned with research in various fields of, or

closely related to, mechanical and industrial engineering disciplines. Papers reporting original research or

extended versions of already published conference/journal papers are all welcome. Papers for publication

are selected through peer review to ensure originality, relevance, and readability.


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Publisher: Elite Hall Publishing House

Editor in Chief:

Dr. Mohammad Mohsin (India)

E-mail: [email protected]

Editorial Board:

Mr. Nachimani Charde

Department of Mechanical, Material and Manufacturing

Engineering, The University of Nottingham Malaysia Campus


Dr. Jake M. Laguador

Professor, Engineering Department

Lyceum of the Philippines University, Batangas City,

Philippines


Dr. Sudhansu Sekhar Panda

Assistant Professor, Department of Mechanical Engineering

IIT Patna, India

Email: [email protected]

Dr. G Dilli Babu

Assistant Professor, Department of Mechanical Engineering,

V R Siddhartha Engineering College, Andhra Pradesh, India


Mr. Jimit R Patel

Research Scholar, Department of Mathematics,

Sardar Patel University, India


Dr. Jumah E, Alalwani

Assistant Professor, Department of Industrial Engineering,

College of Engineering at Yanbu, Yanbu, Saudi Arabia


Dr. Swarup Kumar Nayak

Assistant Professor, School of Mechanical Engineering, KIIT

University

Bhubaneswar, India


Web: http://jmier.elitehall.com

ISSN 2304-7445 (Print)

ISSN 2304-7461 (Online)


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ANALYSIS OF CONVENTIONAL METHODOLOGY OF GAS

TURBINE ENGINE TESTING

Md. Tanvir Hasan1, Shariar Imroze Khan2, Motiur Rahman3 & Mubashera

Belal Tiasha4

1School of Electronic & Information Engineering, Beihang University,

Beijing, China.

2,3 & 4Department of Aeronautical Engineering, Military Institute of Science and Technology, Dhaka,

Bangladesh

Abstract-Numerous studies have been published over the years on gas turbine engines and testing method

of these engines that reduces fuel consumption, reduces manufacturing cost, increases safety and increases

service life of the engine. A short review of some of these publications is carried out here. This

paper contains the guidelines and procedures for conducting and reporting different tests briefly,

in order to determine and verify electrical power output, mechanical power, thermal

efficiency, turbine exhaust gas energy and other performance characteristics of gas turbine engines. It is

important that these performance tests are conducted with a high level of accuracy using best engineering

knowledge and industry practice in measurement technique and method. The reviews on this paper

applies to open-cycle gas-turbine engines, using combustion systems supplied with gaseous and liquid

fuels. Performance Testing requires thorough preparations. As the method of tests may vary from

component to component, it is important to note down test objectives. A clear determination of the testing

equipment must be completed before conducting the tests.

Keywords: Blade, Efficiency, Fatigue, Non-destructive, Turbine.

I. Introduction

The purpose of engine testing is to determine the performance characteristics of the engine and evaluate if

the manufactured engine meets the required performance characteristics needed to propel a

specific aircraft. The testing is done by inspecting each components of the engine, assembling the engine

and then running the engine in different harsh condition to see if the engine can withstand those conditions

and function properly. Factors that are monitored by testing are thrust, altitude effect, ram effect, effect of

engine speed, effects of humidity, temperature effect, water injection effect, effect of after burner,

propulsive efficiency, cycle efficiency, combustion efficiency and thermal efficiency.

II. Literature Review

Currently various research is carried out on turbine engines all over the globe. One of the

important research field is rugged boundary layer ingesting (BLI) inlet-fan combination. This research if

successful will greatly reduce fuel consumption, drag and weight of the aircraft. Generally on today’s jet


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aircraft engines are typically located away from the aircraft’s body so that turbulent layer is not ingested

by the engines. Currently

aerospace engineers believe that by placing engines near the turbulent surfaces they can reduce fuel burn.

III. Construction of gas turbine engines

Inlet: The inlet of a turbojet engine is usually located at the front of the engine i.e. compressor. The

purpose of inlet is admitting air to the forward end of the compressor. The inlet area is sometimes

controlled by inlet guide vanes. [1]

Compressor: The compressor has different functions. The primary function of the compressor is to

increase the pressure of the mass of air entering the inlet and then discharging it to the

combustion chamber. The quantity of air needed and pressure requirements of the combustion chamber

must be met by the compressor. The secondary function of the compressor is to provide bleed air to the

other accessories of the engine. [2]

Combustion Chamber: The purpose of the combustion chamber is to burn the air/fuel mixture and

release energy (kinetic) which is passed out as high-velocity jet through the rear of the engine. The major

portion of this energy drives the turbine which in turn rotates the compressors. The remaining energy

creates a reaction and finally passes out the rear as high-velocity jet as mentioned above. [2]

Turbine: Either single-stage or multistage the turbine transforms a portion of the kinetic energy of the

high- velocity gasses into mechanical energy to drive the compressor and other accessories.

Approximately the required energy to run the compressor is three-fourth of the burned fuel. The turbine

must supply this energy and still sustain high temperature and high-velocity jet. [2]

Exhaust: The exhaust of the gas turbine engine can be made up of many components as it has a lot of

functions. Although these components have many diverse functions they all have a

common function: They must direct the flow of high-velocity hot gases in such a way that the aircraft can

be propelled forward by the reaction force. [2]

Fig.1: Typical Gas turbine engine

IV. Testing of gas turbine engines


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The testing of a new or overhauled gas turbine engine is to ensure correct performance is accomplished on

and instrumented test stand. [2]. Testing can be primarily classified as either testing of the components and

then assembling the engine and testing performance. Performance testing can be either ground testing or

field testing.

Fig.2: Testing Procedure [2]

Testing could be either destructive or non-destructive. As the gas turbine is an expensive and

complicated power plant non-destructive tests are given priority. Key non-destructive tests are:

a. Magnetic Particle

b. X-Ray

c. Liquid Penetrant d. Eddy Current e. Ultrasonic

f. Acoustic Microscopy

g. Microwave

h. Laser Interferometry

Key destructive Tests are:

a. Bird Strike Test

b. Compressor Blade Detonation Test c. Hailstorm Testing d. Water Ingestion Test

e. Foreign Object Damage Test


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Fig.3: Hailstorm Testing

Fig. 4: Compressor Blade Detonation Test

The following parameters are measured during engine testing [2]:

a. Ambient air temperature (Tamb)

b. Ambient air pressure (Pamb) c. Exhaust total pressure (Pt7) d. Low-pressure compressor rpm (N1) e. High-pressure compressor rpm (N2) f. Exhaust-gas temperature (EGT) g. Fuel flow in pounds per hour (Pph) h. Thrust (Fn) i. Low-pressure compressor outlet pressure (Ps3) j. High-pressure compressor outlet pressure (Ps4)

V. Testing methods

Key procedures during engine testing:

a. Disassembly

b. Cleaning

c. Repair

d. Balancing

e. Assembling

There are different tests for different components of the engine.

Inlet Testing: By inlet testing flow characteristics is observed. As the purpose of the inlet is to direct air

to the compressor it is essential that the inlet must meet the design requirements. Convergence and

divergence both type of inlet can be used


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.

Fig. 5: Bell Mouth Air intake Fig. 6: Typical Compressor Surge Line on Compressor

Compressor Blade Testing: The efficiency and performance of the compressor blade is

crucial for steady flight. There are two stages of testing methods for compressor blades: (a)

Structural Inspection, (b) Performance. Compressor blade Test based on structural inspection:

a. Visual Inspection

b. Microstructural Evaluation c. Crack Evaluation

Compressor Test Measurements based on performance:

a. Suction Temperature b. Suction Pressure c. Discharge Temperature d. Discharge Pressure e. Flow Through Compressor (*Pressure, temperature also required at the flow measurement

point) f. Suction or Discharge Gas Composition g. Barometric Pressure h. Speed of Rotation i. Impeller Diameter j. Upstream and Downstream Piping arrangement k. Pipe Diameter (upstream and downstream) [4]

The isentropic efficiency is calculated from the isentropic and actual head:

(1)

The polytrophic efficiency is calculated based upon the polytrophic head and the polytrophic exponent,

np,

An example of a typical compressor surge line at various compressor speeds is shown in Figure:

Performance Map


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Combustion Chamber Testing: Combustion chamber is fed high pressure air by the compression

system. The combustor then heats this air at constant pressure. After heating, air passes from the

combustor through the nozzle guide vanes to the turbine. The combustion chamber must withstand

high temperature, as the as the flame temperature is above 1930 o C (3500 F).

Common combustion chamber failures:

a. Fracture b. Melting c. Liner Failure d. Weld Failure

Tests are done primarily on:

a. Micro structure

b. Material Strength c. Fuel/Air mixture d. Combustion Efficiency

Turbine Blade Testing: Turbine blades are attached together to make the turbine. The blades are

responsible for extracting energy from the high temperature, high pressure gas produced by the

combustor. [5]

Blade failures can be caused by a number of mechanisms under the turbine

operating conditions of high rotational speed at elevated temperatures. In general, blade

failures can be grouped into two categories [5]:

a. Fatigue, including both high (HCF) and low cycle fatigue (LCF)

b. Creep rupture

Like compressors are two stages of testing methods for turbine blades: (a) Structural Inspection, (b) Performance. Turbine blade Test based on structural inspection: a. Visual Inspection

b. Microstructural Evaluation

c. Crack Evaluation

As the turbine blades have to survive in this difficult environment; exotic materials like super

alloys and many different methods of cooling, such as internal air channels, boundary layer cooling, and

thermal barrier coatings are used. These key aspects of the turbine blades are evaluated in highly equipped

test facilities.

The material and blade twist has to be accurate to extract work form the turbine. Cooling the

blades is also a crucial aspect of maintaining the turbine. Tests are taken to ensure the cooling method is

sufficient to cool the blades. Cooling methods generally can be classified in two way:

a. Internal Cooling

i. Convection Cooling

ii. Impingement Cooling b. External Cooling

i. Film Cooling

ii. Cooling Effusion

iii. Pin Fin Cooling


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iv. Transpiration Cooling

Both of the cooling methods has to be evaluated and re- evaluated before assembling the blades.

Exhaust Testing: The exhaust of a gas turbine engine directs the high velocity gas through the rear of the

engine. The exhaust material must sustain the high velocity and high temperature gasses. The testing

of exhaust is limited to:

a. Alignment

b. Fatigue Resistance c. Material Testing d. Efficiency

VI. Results

The studies conducted in this paper were primarily on various existing methods. Studies show that non-

destructive tests are the most favorable test all over the world. Although in some cases destructive tests are

mandatory.

VII. Conclusion

New and improved testing methods are constantly surfacing. There are still some costly testing methods.

During field testing an engine is completely destroyed to check the intake of blades come off or not. This

methods costs an entire engine. Some important aspects of testing are given below:

a. Testing with cameras and sophisticated fatigue detection algorithm. b. Polymer composites and corresponding structural design and manufacturing techniques can

reduce the build time and testing time. c. Low pressure turbine weight savings through ultra-

high lift airfoil design, ultra high stage loading,

lightweight materials and design can increase engine efficiency and also increase test accuracy.

d. Technologies for light weight and low drag installation of high bypass ratio engines can cool the engine and reduce overhaul time which is essential for a better turn-around time.

NOMENCLATURE

η*: Efficiency

H*: Isentropic Head

H: Actual Head

Ψ*: Isentropic head coefficient Ψ: Actual head coefficient

REFERENCES

[1] FAA, Airframe & Powerplant Mechanics, Powerplant Handbook, pp 38-40, (2008).

[2] Michael J. Kroes, Thomas W. Wild, Aircraft Powerplants, pp 525-535, (2010).

[3] K. Brun, Marybeth G., Nored, Guideline for Field Testing of Gas Turbine and Centrifugal Compressor Performance, pp 15-25, (2006)

[4] Mehdi Tofighi Naeem, Seyed Ali Jazayeri, Nesa Rezamahdi, “Failure Analysis of Gas Turbine Blades”, pp 1-16, (2008)

[5] Boyce, M. P. (2006). Gas Turbine Performance Test. Gas Turbine Engineering Handbook,


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721-760.

[6] Henry Cohen, G.F.C. Rogers, H.I.H.Saravanamuttoo. "Gas Turbine

Theory." Goodreads.

[7] Treager, Irwin E. "Aircraft Gas Turbine Engine Technology." Alibris. N.p., n.d. Web. 01 Feb.

2017.

[8] Horlock, J.H. "Advanced Gas Turbine Cycles." Advanced Gas Turbine Cycles : J.H.

Horlock : 9780080442730. ELSEVIER SCIENCE & TECHNOLOGY, 01 Aug.

2003. Web. 01 Feb.2017.

[9] Oates, Gordon C. "Aerothermodynamics of Gas Turbine and Rocket Propulsion." Alibris. N.p.,

n.d. Web. 01 Feb. 2017.

[10] N. F., & N. P. (2012). Gas Turbine Aero Engine Ground Testing.


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