Estimation of Stress and Strain using Fem Analysis for Mechanical Load on Steam Turbine Shaft

IJSRD - International Journal for Scientific Research & Development| Vol. 4, Issue 05, 2016 | ISSN (online): 2321-0613

Estimation of Stress and Strain using Fem Analysis for Mechanical Load on Steam Turbine Shaft Sujata Deshmukh1 Asst. Prof. A.P.Ninawe2 Dr.A.V.Vanalkar3 1 P.G. Student 2Assistant Professor 3Professor 1,2,3 Department of Mechanical Engineering 1,2,3 K.D.K College of Engineering Abstract— in this paper the study of a typical reaction turbine has been carried out. A reaction turbine is a mechanical device which converts the thermal energy in pressured steam in useful mechanical work i.e. rotation of turbine shaft. Due to the dynamic action of steam mechanical forces are acting on the turbine shaft. The mechanical forces acting on the shafts are calculated analytically. The mechanical forces are in the form of tangential, axial and centrifugal thrust. A typical turbine rotor is considered. The model of turbine rotor is prepared by using CAD software and analysis is done by using FEM software. The mechanical forces acting on turbine shaft are calculated analytically.

Then these forces are applied on the software model. The suitable boundary conditions are applied. Material properties are updated and FEM analysis is carried out in ANSYS software.

Key words: Steam Turbine Shaft, Mechanical, FEM I. INTRODUCTION Due to the action of pressurised moving steam the mechanical forces are acting on the steam turbine shaft, The mechanical forces are in the form of tangential ,axial and centrifugal thrust.

The tangential and axial forces are calculated by drawing velocity diagram. The centrifugal force is calculated by using standard formula .

Stress and strain induced in the shaft due to above calculated load are then analysed.

A static structural analysis is carried out.

There are many FEA packages available for carrying out these analysis. In this study for modelling CAD package creo parametric is used and for analysis ANSYS is used. One degree model of turbine shaft is considered for analysis. Suitable boundary conditions need to be applied on the shaft in order to realistically model the actual situation.

The appropriate element type is selected for meshing. The no of nodes and elements are selected and a static structural analysis is carried out.

Fig. 1: one degree model of turbine rotor The above figure shows the one degree model of the turbine shaft. Model from creo parametric is translated to IGES format using initial graphics exchange specification translator.

A. Meshing of the model The IGES format of model is read in ANSYS. For meshing the model solid 187 element in ANSYS is used. Solid 187 is a higher order 3D -10 node tetrahedral element . It has a quadratic displacement behaviour and it is well suited for modelling irregular meshing.

II. MODELING The rotor model with blades is made in CAD software.

Since the turbine rotor is an axis symmetric body only one degree model of turbine rotor is considered.

Fig. 2: Meshing using solid 187 element It has plasticity, hyper-elasticity, creep, large stress, large strain capabilities.

The type of element selected supports the static structural analysis. 10248 elements and 6509 nodes are selected in this model.

III. MATERIAL PROERTIES The material 30CrMoVSteel is considered for analysis. The following material properties are updated with the engineering data.

Young’s modulus : 214 E X 1000 MPa

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Estimation of Stress and Strain using Fem Analysis for Mechanical Load on Steam Turbine Shaft (IJSRD/Vol. 4/Issue 05/2016/058)

Density Poisson’s ratio

: 7800 Kg/m3 : 0.288

A. Boundary Conditions The boundary conditions are most critical to decide. It should stipulate the actual working conditions of the model.

The boundary conditions which simulate the environment in which the turbine rotor operates are updated on the meshed model.

Fig. 5: Equivalent strain distribution V. CONCLUSION Thus the analysis of stress and strain on the turbine shaft due to mechanical load is carried out, REFERENCES

1) 2) 3) 4) 5)

Fig. 3: Boundary conditions Generator End of LPT Ux=Uy=Uz=0 Lateral surface , no constraints Upper surface , no constraints HPT free end , no constraints 5.Central axis Ux=Uy= 0,Uz ,free

B. Application of Load The load is applied on the upper surface (grooves in which the blade is mounted) of shaft. All the grooves are selected and load is applied as follows.  Tangential load is applied in x direction  Centrifugal load in y direction  Axial load in z direction

[1] Engineering for Gas Turbines and Power. 1988; 110(1): 63-69 Power Generation Handbook Kiameh P. New York: McGraw-Hill; 2002 [2] Technology Characterization: Steam Turbines.

Arlington: Energy and Environmental Analysis, 2008.

[3] Large power steam turbines: Design and Operation, Volume I. Leyzerovich A. Penn Well Books.7th ed.;1997.

[4] Modeling of Off-Design Multistage Turbine Pressures Cooke D. by Stodola’s Ellipse 1983:205–34.

[5] Power Generation Handbook Kiameh P. New York: McGraw-Hill; 2002 [6] Large power steam turbines: Design and Operation, Volume I. Leyzerovich A. Penn Well Books.7th ed.;1997.

[7] “Finite element Design Analysis theory and Programming”, Krishnamnurthy Tata Mc. Graw Hill, New Delhi.

IV. RESULT Static structural analysis is carried on the turbine shaft and following results are obtained.

The maximum equivalent stress is 442 N/mm2 and the maximum equivalent strain is 0.0022116.

Fig. 4: Equivalent stress distribution

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