1. DESIGN AND ANALYSIS OF GAS TURBINE BLADES USING F.E.ABY
A.K.MATTA

2. ABSTRACT
The first stage rotor blade of a two stage gas turbine has been analyzed for structural, thermal,and modal analysis
The first stage rotor blade of the gas turbine is analyzed for the mechanical and radial elongations resulting from the tangential, axial and centrifugal forces
The material of the blade was specified as N155. This material is an iron based super alloy
For Modeling and analyses of the gas turbine blade ,CAD Software packages namely CATIA,ANSYS 9.0,Hypermesh and V5R15 have been used.
The results obtained are discussed and reported.

3. INTRODUCTION
Turbine stages may be used to turn shafts to power other machinery such as the rotor of a helicopter, the propellers of a ship or electrical generators in power stations.
The major cause of break down in turbo machine is the failure of rotor blade.The failure of the rotor blade may lead to catastrophic consequences both physically and economically.
Proper design of the turbo machine blade plays a vital role in the proper functioning of the turbo machine.

4. OBJECTIVES OF THE PROJECT
Determination of geometric characteristics from gas dynamic analysis.
Determination of steady loads acting on the blade and stressing due to them.
Determination of natural frequencies and mode shapes.
Determination of unsteady forces due to stage flow interaction.
Determination of dynamic forces and life estimation based on the cumulative damage fatigue theories.

5. Literature Review Author Description M.Venkatarama Reddy
Influence of taper, twist, thickness in rotor blade using Finite element analysis.
Dr. K. Ramachandra
Paper, aero engine gas turbine blades are aerofoil in cross section and are twisted mounted on annular plate, which in turn is fixed to rotating disc.
Stuart Moffatt
Paper on blade forced response prediction for industrial gas turbines. In this paper forced response prediction is given. The mode shapes and natural frequencies are determined by finite element analysis.
S.S.Rao
The Finite Element method in Engineering
O.C.Zeinkiewicz
The Finite Element method in Engineering Science

6. FE MODELING
Aerofoil profile of the rotor blade is generated on the XY plane with the help of key points .Then a number of splines were fitted through the keypoints.
By using these points, blade model is created in CATIA, V5R15 with the help of commands like spline,extrude,add.And the modal is exported into HYPERMESH7.0 and meshed it by using commands like automesh, tetmesh and exported into ANSYS 9.0.
The shaded area are extruded upwards through the blade height along the positive Z direction, Areas 4,5,6 were extruded downwards along the negative direction also the shaded areas are extruded along the X-direction using 3 –D 20 node Brick elements. And a 3-D Model of rotor blade is created.

7. MODEL OF ROTOR BLADE

8. Young’s Modulus of Elasticity (E) = 2 ×105 N/mm2
The model was assigned with following material properties:
Young’s Modulus of Elasticity (E) = 2 ×105 N/mm2
Density (ρ) = ×103 Kg/m3
Coefficient of thermal expansion (α ) =6.12×10-6 /0C

9. Thermal analysis
From the post processing, the temperature variation obtained as shown in fig. From figure, it is observed that the temperature variations from leading edge to the trailing edge on the blade profile is varying from C to C at the tip of the blade and the variation is linear along the path from both inside and outside of the blade. Considerable changes are not observed from the first 6 mm length from the leading edge and from there to next 36 mm length of blade the temperature is gradually decreasing and reaching to a temperature of C and for another 4 mm length it is almost constant. Wherever maximum curvature is occurring the temperature variation is less. The temperature decreases gradually along X-direction.
The thermal stresses are obtained as shown in the fig from figure, it is observed that the maximum thermal stress is 1217N/mm2and the minimum thermal stress is. the maximum thermal stress is less than the yield strength value i.e,1450N/mm2so,based on these values.
For the thermal analysis the design of turbine blade is safe.

10. Temperature distribution in the blade,0C

11. Thermal stress in the blade,N/mm2

12. Structural analysis
The von mises stresses are obtained as shown in the fig from figure , it is observed that the maximum von mises stress is N/mm2 this value is less than the yield strength value.the maximum deformation in Z direction is mm.based on these values For the structural analysis the design of turbine blade is safe based on the strength criteria and rigidity criteria.

13. Von mises stress induced in the blade,N/mm2

14. Substep is 0.4093mm and the frequency is 20.122.
Modal analysis
Maximum deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ for first
Substep is mm and the frequency is
Maximum deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ for second Substep is mm and the frequency is
Maximum deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ for third Substep is mm and the frequency is

15. Resultant deformation(Usum) of gas turbine rotor blade at 20HZ.

16. Deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ for first substep.

17. Deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ
Deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ.for second substep.

18. Deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ
Deformation in Z (Uz) direction of gas turbine rotor blade at 20HZ.for third substep.

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

20. CONCLUSION
The finite element analysis of gas turbine rotor blade is carried out using 20 noded brick element. The structural, thermal and modal analysis is carried out.
The temperature has a significant effect on the overall stresses in the turbine blades.
Maximum elongations and temperatures are observed at the blade tip section and minimum elongation and temperature variations at the root of the blade.
Temperature distribution is uniform at the maximum curvature region along blade profile.
Temperature is linearly decreasing from the tip of the blade to the root of the blade section.
Maximum stress induced is within safe limit.
Maximum thermal stresses are setup when the temperature difference is maximum from outside to inside.
Maximum stresses and strains are observed at the root of the turbine blade and upper surface along the blade roots.
Elongations in X-direction are observed only at the blade region in the along the blade length and elongation in Y-direction are gradually varying from different sections along the rotor axis.

21. FUTURE SCOPE
Studies can be carried out using advanced materials to obtain improved performance.

22. REFERENCES
S.S.Rao,”The Finite Element method in Engineering”, BH Publications New Delhi, 3rd Edition, 1999.
O.C.Zeinkiewicz,”The Finite Element method in Engineering Science”, Tata McGraw Hill, 2nd Edition, 1992.
M.Venkatarama Reddy. Influence of taper, twist, thickness in rotor blade using Finite element analysis.
Dr. K. Ramachandra. Paper, aero engine gas turbine blades are aerofoil in cross section and are twisted mounted on annular plate, which in turn is fixed to rotating disc.
Stuart Moffatt. Paper on blade forced response prediction for industrial gas turbines. In this paper forced response prediction is given. The mode shapes and natural frequencies are determined by finite element analysis.

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