International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 060-065 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

Structural & Thermal Analysis of Gas Turbine Blade by Using F.E.M

P.V.Krishnakanth1, G.Narasa Raju2, R D V. Prasad3, R. Saisrinu4

PG Student1, Assoc. prof2, Asst. Prof3, M.tech Student4

1,2Dept. of Mechanical Engineering, BVC Engineering College, Odalarevu,3Dept. of Mechanical Engineering, BITS, Vizag, Andhra Pradesh, India,

4AU PG Student Vizag. Andhra Pradesh, India,

AbstractWithstanding of gas turbine blades for the elongations is

a major consideration in their design because they aresubjected to high tangential, axial, centrifugal forcesduring their working conditions. Several methods havebeen suggested for the better enhancement of themechanical properties of blades to withstand theseextreme conditions. This project summarizes the designand analysis of Gas turbine blade, on which CATIA V5is used for deign of solid model of the turbine blade withthe help of the spline and extrude options ANSYS 11.0software is used analysis of F.E. model generated bymeshing of the blade using the solid brick elementpresent in the ANSYS software itself and therebyapplying the boundary condition.

This project specifies how the program makes effectiveuse of the ANSYS pre-processor to analyse the complexturbine blade geometries and apply boundary conditionsto examine steady state thermal & structuralperformance of the blade for N 155, Hastealloy x &Inconel 625 materials. Finally stating the best suitedmaterial among the three from the report generated afteranalysis. From this the results are stated and reported.

1. INTRODUCTION

The gas turbine obtains its power by utilizing the energyof burnt gases and the air which is at high temperatureand pressure by expanding through the several rings offixed and moving blades, to get a high pressure of orderof 4 to 10 bar of working fluid which is essential forexpansion a compressor is required. The quantity ofworking fluid and speed required are more, so generallya centrifugal or axial compressor is required. The turbinedrive the compressor so it is coupled to the turbine shaft,If after compression the working fluid were to be

expanded in a turbine, then assuming that there were nolosses in either component, the power developed by theturbine can be increased by increasing the volume ofworking fluid at constant pressure or alternativelyincreasing the pressure at constant volume. Either ofthere may be done by adding heat so that the temperatureof the working fluid is increased after compression. Toget a higher temperature of the working fluid acombustion chamber is required where combustion of airand fuel takes place giving temperature rise to theworking fluid.

The turbine escapes energy from the exhaust gas. Likethe compressor, turbine can be centrifugal or axial. Ineach type the fast moving exhaust gas is sued to spin theturbine, since the turbine is attached to the same shaft asthe compressor at the front of the engine, and thecompressor will turn together, The turbine may extractjust enough energy to turn the compressor. The rest ofthe exhaust gas is left to exit the rear of the engine toprovide thrust as in a pure jet engine. Or extra turbinestages may be used to turn other shafts to power othermachinery such as the rotor of a helicopter, thepropellers of a ship or electrical generators in powerstations.

The present paper deals with the first type is centrifugalstresses that act on the blade due to high angular speedsand second is thermal stresses that arise due totemperature gradient within the blade material. Theanalysis of turbine blade mainly consists of thefollowing two parts: Structural and thermal analysis. Theanalysis is carried out under steady state conditionsusingAnsys software. The study has been conducted withthree different materials N155, Hastealloy X & Inconel625.

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 060-065 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

2. LITERATURE SURVEY

S.Gowreesh et.al(1) studied on The first stage rotorblade of a two stage gas turbine has been analysed forstructural, thermal, modal analysis using ANSYS11.0.which is a powerful Finite Element Methodsoftware. The temperature distribution in the rotor bladehas been evaluated using this software. The designfeatures of the turbine segment of the gas turbine havebeen taken from the preliminary design of a powerturbine for maximization of an existing turbo jet engine.it has been felt that a detail study can be carried out onthe temperature effects to have a clear understanding ofthe combined mechanical and thermal stresses.

.Kauthalkar et.al(2) the purpose of turbine technology isto extract, maximum quantity of energy from theworking fluid to convert it into useful work withmaximum efficiency. That means, the Gas turbinehaving maximum reliability, minimum cost, minimumsupervision and minimum starting time. The gas turbineobtains its power by utilizing the energy of burnt gasesand the air. This is at high temperature and pressure byexpanding through the several rings of fixed and movingblades. A high pressure of order 4 to 10 bar of workingfluid which is essential for expansion, a compressor isrequired. The quantity of working fluid and speedrequired are more so generally a centrifugal or axialcompressor is required. The turbine drives thecompressor so it is coupled to the turbine shaft.

John.v et.al(3) studied on the design and analysis of Gasturbine blade, CATIA is used for design of solid modeland ANSYS software for analysis for F.E.modelgenerated, by applying boundary condition, this paperalso includes specific post-processing and lifeassessment of blade .HOW the program makes effectiveuse of the ANSYS pre-processor to mesh complexturbine blade geometries and apply boundary conditions.Here under we presented how Designing of a turbineblade is done in CATIA with the help of co-ordinategenerated on CMM.And to demonstrate the pre-processing capabilities, static and dynamic stressanalysis results, generation of Campbell and Interferencediagrams and life assessment. The principal aim of thispaper is to get the natural frequencies and mode shafe ofthe turbine blade.

V.Raga Deepu et.al(4) Studied on a Gas turbine is adevice designed to convert the heat energy of fuel in touseful work such as mechanical shaft power. TurbineBlades are most important components in a gas turbinepower plant. A blade can be defined as the medium oftransfer of energy from the gases to the turbine rotor.The turbine blades are mainly affected due to staticloads. Also the temperature has significant effect on theblades. Therefore the coupled (static and thermal)analysis of turbine blades is carried out using finiteelement analysis software ANSYS.

In this paper the first stage rotor blade of the gas turbineis created in CATIA V5 R15 Software. This model hasbeen analysed using ANSYS11.0. The gas forces namelytangential, axial were determined by constructingvelocity triangles at inlet and exist of rotor blades. Aftercontaining the heat transfer coefficients and gas forces,the rotor blade was then analysed using ANSYS 11.0 forthe couple field (static and thermal) stresses.

3. COMPUTER AIDED ANALYSIS OFGAS TURBINE ROTOR BLADE

The model is created and analyzed using CATIA andANSYS. For automatic mesh generation and nodeselection is used. The structural, thermal modal modulesof ANSYS 11.0 are used for the analysis of the rotorblade. The rotor blade was analyzed for mechanicalstresses, temperature distribution, combined mechanicaland thermal stresses and radial elongations, naturalfrequencies and mode shapes.

The blade is then analyzed sequentially with thermalanalysis preceding structural analysis. The model isdiscretised using 8 noded plane element (plane 82) &solid 95 3D 20-nodes structural solid element.

4. NOMENCLATURE

Fa Axial forceFc Centrifugal forceFt Tangential forceE Young’s Modulus Deflectionµ Poisson’s ratio Stress

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 060-065 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

L LengthD Diameter of shaftN Speed of Turbine in RPMα Coefficient of thermal expansionRe Reynolds NumberNu Nusselt numberPr Prandtl number

4.1 Details of Turbine blade

D=1308.5 mm, N=3426 Rpm, L=117mm, d=2mm

Table 1 Mechanical properties of N155, Inconel 625 &Hastealloy X

properties

Units N155

Inconel 625

Hastealloy X

E Pa 143E09

150E09

144E09

ρ Kg/cum

8249

8400 8300

K W/m-K 20.0 10 25

μ --- 0.344

0.331 0.348

α E-06/oC 17.7 15 16

CP J/KgK 435 410 450

Meltingpoint

OC 1354

1350 1380

Yieldstress

MPa 550 1030 360

5. RESULTS & DISCUSSIONS

Thermal analysis:

From the post processing, the temperature variationobtained as shown in fig. From figure, it is observed thatthe temperature variations from leading edge to thetrailing edge on the blade profile is varying from913.8860C to 944.4890C throughout the blade and the

variation is linear along the path from both inside andoutside of the blade.

RESULTS OBTAINED:

MaterialType

Stress(N/mm2)

Deformation(mm)

Temperature( 0c )

N155 412.759 0.881842 913.886

HASTEALLOY X 937.208 1.808 942.411

INCONEL625ALLOY 910.375 1.742 944.489

For N155:

Thermal Analysis Results:

Temperature distribution in the blade,0C

For HASTEALLOY X:

Thermal Analysis Results

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 060-065 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

Temperature distribution in the blade, oC

For INCONEL 625 ALLOY:

Thermal Analysis Results

Temperature induced in the blade, oC

Structural analysis:The von misses stresses are obtained as shown in thefigure; it is observed that the maximum von missesstress is 412.759 N/mm2 for N155,

937.208 N/mm2 for Haste alloy X and 910.375N/mm2 for Inconel 625 alloy.

The deformations are obtained as shown in thefigure; it is observed that the maximum deformation is

0.881842 mm, 1.808 mm and 1.742 mm for N155, Hastealloy X and Inconel 625 alloy respectively.

From the above results it is observed that thestress and deformation are low for N155

RESULTS OBTAINED:

For N155:Structural Analysis Results

Stress induced in the blade, N/mm2

Deformation in Z-direction (Uz) in the blade, mm

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 060-065 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

For HASTEALLOY X:

Static Analysis Results

Stress induced in the blade, N/mm2

Deformation induced in Z direction, mm

For INCONEL 625 ALLOY:

Static Analysis Results

Stress induced in the blade, N/mm2

Deformation induced in Z direction, mm

6. CONCLUSION

The finite element analysis for structural and thermalanaysis of gas turbine rotor blade is carried out using

International Journal of Scientific Research Engineering & Technology (IJSRET)Volume 2 Issue2 pp 060-065 May 2013 www.ijsret.org ISSN 2278 – 0882

IJSRET @ 2013

solid95 element. The temperature has a significant effecton the overall turbine blades. Maximum elongations andtemperatures are observed at the blade tip section andminimum elongation and temperature variations at theroot of the blade. Maximum stresses and strains areobserved at the root of the turbine blade and uppersurface along the blade roots three different materials ofconstruction i.e., N-155,Inconel 625 & HASTEALLOYX materials. It is found that the temperature has asignificant effect on the overall stresses induced in theturbine blades. The blade temperatures attained andthermal stresses induced are lesser for Inconel 625 as ithas better thermal properties.

REFERENCES

1) S.Gowreesh, N.Sreenivasalu Reddy andN.V.Yogananda Murthy. “CONVECTIVEHEAT TRANSFER ANALYSIS OF a AEROGAS TURBINE BLADE USING ANSYS”,International journal of Mechanics of solids,vol4, No.1, March 2009(ppt55-62).

2) P.Kauthalkar, Mr.Devendra S.Shikarwar, andDr.Pushapendra Kumar Sharma. “ANLYSIS OF THERMAL STRESES DISTRIBUTIONPATTERN ON GAS TURBINE BLADEUSING ANSYS”, International journal ofEngineering Education and technology, Vol.2,No.3, Nov 2010.

3) John.V, T.Ramakrishna. “THE DESIGN ANDANALYSIS OF GAS TURBINE BLADE”,International Journal of Advanced Research andStudies, Vol 2, No.1, Dec 2012.

4) V.Raga Deepu, R.P.Kumar Ropichrla.“DESIGN AND COUPLED FIELDANALYSIS OF FIRST STAGE GASTURBINE ROTOR BLADES”, Internationaljournal of Mathematics and Engineering, Vol13, No.2, Pages: 1603-1612.

5) S.S.Rao,”The Finite Element method inEngineering”, BH Publications New Delhi, 3rdEdition, 1999.