International Journal of Recent Innovation in Engineering and Research Scientific Journal Impact Factor - 3.605 by SJIF

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ANALYSIS OF CERAMIC (SiC) COATED GAS TURBINE BLADE

USING ANSYS

Griffin.T1 and Rajesh Kumar.B

2

1M.E Engineering Design, Department of Mechanical Engineering, KCG College of Technology,

Karapakkam, Chennai, India 2Assistant Professor, Department of Mechanical Engineering, KCG College of Technology, Karapakkam,

Chennai, India

Abstract- The ability of gas turbine blades to withstand elongations is a major consideration

in their design because they are subjected to high tangential, axial, centrifugal forces during

their working conditions. Several methods have been suggested for the better enhancement of

the mechanical properties of blades to withstand these extreme conditions. This project

summarizes the design and analysis of Gas turbine blade, on which SOLIDWORKS is used

for design of solid model of the turbine blade with the help of the spline and extrude

options ANSYS software is used analysis of F.E. model generated by meshing of the blade

using the solid brick element present in the ANSYS software itself and thereby applying the

boundary condition. This project specifies how the program makes effective use of the

ANSYS pre-processor to analyse the complex turbine blade geometries and apply boundary

conditions to examine steady state thermal & structural performance of the blade which is

coated with SiC/SiC (Ceramic Matrix composites), and uncoated Titanium Alloy Ti 6Al 4V,

Inconel 718 Alloy, Multimet N155, Incoloy A286, Haynes 188. Finally stating the best suited

material among them from the report generated after analysis & to perform flow analysis using

CFD. From this the results are stated and reported.

Keywords- Thermal & Structural Analysis, Von-Misses stress, deformation, Flow Analysis.

I. INTRODUCTION

The gas turbine obtains its power by utilizing the energy of burnt gases and the air which is at

high temperature and pressure by expanding through the several rings of fixed and moving blades, to

get a high pressure of order of 4 to 10 bar of working fluid which is essential for expansion a

compressor is required. The quantity of working fluid and speed required are more, so generally a

centrifugal or axial compressor is required. The turbine drive 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 no losses in either component, the power developed by the turbine can be increased by

increasing the volume of working fluid at constant pressure or alternatively increasing the pressure at

constant volume. Either of there may be done by adding heat so that the temperature of the working

fluid is increased after compression.

To get a higher temperature of the working fluid a combustion chamber is required where

combustion of air and fuel takes place giving temperature rise to the working fluid. The turbine

escapes energy from the exhaust gas. Like the compressor, turbine can be centrifugal or axial. In each

type the fast moving exhaust gas is sued to spin the turbine, since the turbine is attached to the same

shaft as the compressor at the front of the engine, and the compressor will turn together, the turbine

may extract just enough energy to turn the compressor.

The rest of the exhaust gas is left to exit the rear of the engine to provide thrust as in a pure jet

engine. Or extra turbine stages may be used to turn other shafts to power other machinery such as the

rotor of a helicopter, the propellers of a ship or electrical generators in power stations.

II. LITERATURE REVIEW

Literature Review works as a study which gives a guideline to perform 3D Modelling &

analysis for the component. The facts and data which is required to solve the problem can be learned

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from it. Literature Review provides these information and suggestions in the form of journals and

other sources.

Various bodies of research have been performed in the past to address the problem of

unsteady heat transfer on turbine blades. These attempts include experimental, as well as

computational examinations of unsteady heat transfer (through shock waves) on the surface of a

turbine blade. While the problem of predicting shock-induced heat transfer continues to be difficult

on all levels, the benefit of doing so remains worthwhile. Useful analytical and numerical

simulations can potentially aid the turbine designer towards accurate predictions of blade heat

transfer.

III. METHODOLOGY

Problem definition.

Calculate the dimensions of blade profile

Generate the 3-dimentional computer models

Prepare finite element model of the 3D computer model

Pre-process the 3D model for the defined geometry

Mesh the geometry model and refine the mesh considering sensitive zones for results accuracy

Post process the model for the required evaluation to be carried out

Determine the temperature distribution along the blade profile.

Determine maximum stress induced in blades.

Perform Flow Analysis using CFD

Conclude the results.

IV. DEFINITION OF PROBLEM

The Aim of the project is to prefer the best suitable blade material for the gas turbine since

the existing alloys generates more heat during operation which leads to oxidation, hot corrosion,

Interdiffusion, Thermal Fatigue, in order to overcome these causes ceramic matrix composites

(Silicon Carbide) can be used as coating medium to rectify the problems. Comparison has been made

by using coating materials in design software to get a better replacement in future. In achieving this

aim, project objectives are set as below:

To understand the working principles, components, standards and theories through a literature

study.

To understand the working principle of FEA Software (ANSYS)

To understand the fundamental of heat transfer through thermal analysis of turbine blade.

To clearly justify the result and conclusion.

The knowledge gained from this project is to be able to understand the steps needed in

thermal analysis & structural analysis of turbine blade by using FEA method. The methods used in

this project can later be used in future as reference for similar research and development. There is the

wide range of study on the turbine blade. The turbine blade could be studied on the various areas

such as material improvement on the turbine blade, vibration on the turbine blade, air flow analysis

of the turbine blade and thermal stress analysis on the turbine blade.

V. TURBINE BLADE

A turbine blade is the individual component which makes up the turbine section of a gas

turbine. The blades are responsible for extracting energy from the high temperature, high pressure gas

produced by the combustor. To survive in this difficult environment, turbine blades often use exotic

materials like super alloys and many different methods of cooling, such as internal air

channels, boundary layer cooling, and thermal barrier coatings. Blade fatigue is a major source of

failure in steam turbines and gas turbines.

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Fatigue is caused by the stress induced by vibration, temperature, resonance within the

operating range of machinery.

VI. CREAMIC COATING

Silicon carbide is an excellent abrasive and has been produced and made into grinding wheels and

other abrasive products for over one hundred years.

The material has been developed into a high quality technical grade ceramic with very good

mechanical properties.

It is used in abrasives, refractories, ceramics, and numerous high-performance applications.

Structural and wear applications are constantly developing.

VII. MODELLING APPROACHES

Solidworks is used as the modelling tool in this project. The real time design of Gas Turbine

Blade is taken as the model. Modelling is made with the exact dimensions.It integrates easy-to-use

analysis tools with design to verify operation and performance during product development.

SolidWorks design analysis increases product innovation by reducing risk in design,

significantly reduces the number of physical prototypes needed, and helps lower material and other

costs.

TABLE I. MATERIAL PROPERTIES

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A) SPECIFICATION OF UNCOATED BLADE

B) SPECIFICATION OF COATED BLADE

Height of the blade = 120mm

Length of the blade (L) = 49.20 mm

Width of the blade (B) = 27.58 mm

Chord Width (c) = 9.5mm

Blade inlet angle (β1) = 136.4

0

Blade outlet angle (β2) = 68.2

0

Absolute flow angle (α) = 24.150

Speed of Turbine (N) = 3426 rpm

Diameter of blade mid span (D) = 1308.5 m

Diameter of convection holes, d1

= 2.5mm

d2= 2mm

d3=1.25mm

Height of the blade = 120mm

Length of the blade (L) = 49.90 mm

Width of the blade (B) = 28.28 mm

Chord Width (c) = 10.23mm

Blade inlet angle (β1) = 136.4

0

Blade outlet angle (β2) = 68.2

0

Absolute flow angle (α) = 24.150

Speed of Turbine (N) = 3426 rpm

Thickness of Ceramic Coating (t) = 0.35mm

Diameter of blade mid span (D) = 1308.5 mm

Diameter of convection holes, d1

= 1.8mm

d2=1.3mm

d3=0.55mm

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VIII. RESULT & DISCUSSIONS

A) THERMAL ANALYSIS

Boundary conditions provided for Temperature Distribution are Heat Flux & Convection. For

this analysis, Thermal Conductivity was the required mechanical properties for these alloys. The

temperature distribution of the blade depends on the heat transfer coefficient for gases and the

thermal conductivity of the material. The heat transfer coefficients are calculated by iterative process

and the same were adopted. The analysis was carried out for steady state heat transfer conditions.

The difference between uncoated & coated alloy in temperature distribution is observed from results

below.

TITANIUM ALLOY (Ti 6Al 4V)

Fig:-8.1 Temperature Distribution (Uncoated)

Fig:- 8.2 Temperature Distribution (Coated)

INCONEL 718

Fig:-8.3 Temperature Distribution (Uncoated)

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Fig:-8.4 Temperature Distribution (Coated)

MULTIMET N155

Fig:-8.5 Temperature Distribution (Uncoated)

MULTIMET N155

Fig:-8.6 Temperature Distribution (Coated)

INCOLOY A286

Fig:-8.7 Temperature Distribution (Uncoated)

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Fig:-8.8 Temperature Distribution (Coated)

HAYNES 188

Fig:-8.9 Temperature Distribution (Uncoated)

Fig:-8.10 Temperature Distribution (Coated)

It is observed that the maximum temperatures are prevailing at the leading edge of the blade

due to the stagnation effects. The body temperature of the blade doesn’t vary much in the radial

direction. However, there is a temperature fall from the leading edge to the trailing edge of the blade

as expected. From the above result, the alloy with coated exhibits

Better dissipation of heat compared to uncoated alloys. The coated Haynes 188 alloy

generates less heat compared to other alloys so it’s recommended for Higher Thermal operating

conditions.

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B) STRUCTURAL ANALYSIS

Structural Analysis is performed to determine the Total Deformation & Equivalent Stress

(Von-Mises) among the various alloys with & without the ceramic coating. Boundary conditions

required for the analysis are Centrifugal force, Tangential force, axial force & the temperature

obtained from thermal analysis is also imported.

TITANIUM ALLOY (Ti 6Al 4V)

Fig: - 8.11 Total Deformation (Uncoated)

Fig: - 8.12 Total Deformation (Coated)

Fig:- 8.13 Von-Mises Stress (Uncoated)

Fig:- 8.13 Von-Mises Stress (Coated)

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INCONEL 718

Fig: - 8.14 Total Deformation (Uncoated)

Fig: - 8.15 Total Deformation (Coated)

INCONEL 718

Fig:- 8.16 Von-Mises Stress (Uncoated)

Fig:- 8.17 Von-Mises Stress (Coated)

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MULTIMET N155

Fig: - 8.18 Total Deformation (Uncoated)

Fig: - 8.19 Total Deformation (Coated)

Fig: - 8.20 Von-Mises Stress (Uncoated)

Fig:- 8.21 Von-Mises Stress (Coated)

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INCOLOY A286

Fig: - 8.22 Total Deformation (Uncoated)

Fig: - 8.23 Total Deformation (Coated)

Fig: - 8.24 Von-Mises Stress (Uncoated)

Fig:- 8.25 Von-Mises Stress (Coated)

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HAYNES 188

Fig: - 8.26 Total Deformation (Uncoated)

Fig: - 8.27 Total Deformation (Coated)

Fig: - 8.28 Von-Mises Stress (Uncoated)

Fig:- 8.29 Von-Mises Stress (Coated)

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As the blades are not shrouded so the stress on the tip of the blade are lesser and higher

values of stress is coming on the root of the blades. It is evident that the deformation is distributed in

an ascending manner from the bottom of the hub to the tip of the blade. From the results from

structural analysis, it is clear that the Deformation & Von- Mises Stress is less in coated Haynes 188

Alloy compared to other alloys.so Coated Haynes 188 can be used in all sorts of Thermal &

Structural Conditions.

C) FLOW ANALYSIS

Fig:- 8.30 Contour Plot of Flow Velocity

Fig:- 8.31 Contour Plot of Flow Pressure

Fig:- 8.32 Flow of Streamline Velocity

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Fig:- 8.33 Flow of Streamline Pressure Gradient

Fig:- 8.34 Flow of Streamline Velocity

The Flow Analysis is performed using Fluid Flow (FLUENT), which was used to

demonstrate & understand the flow over turbine blade through velocity & pressure. The Boundary

condition applied are inlet velocity, Exit pressure, outlet pressure, Temperature, Inlet turbulence

intensity.

TABLE II: Temperature Distribution

Variables Unit Titanium

Alloy

Inconel

718

Multimet

N155

Incoloy

A286

Haynes

188

Uncoated

0C

1068

1002.6

956.5

946.11

945.42

Coated

1036.5

981.71

943.45

934.92

934.35

TABLE III: Total Deformation

Variables Unit Titanium

Alloy

Inconel

718

Multimet

N155

Incoloy

A286

Haynes

188

Uncoated

mm

0.46388

0.27912

0.39011

0.27749

0.23981

Coated

0.19977

0.17498

0.19204

0.17465

0.16645

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TABLE IV: Von-Mises Stress

Variables Unit Titanium

Alloy

Inconel

718

Multimet

N155

Incoloy

A286

Haynes

188

Uncoated

MPa

484.17

489.31

487.98

487.64

483.27

Coated

461.36

474.64

471.3

470.45

458.93

TABLE V: Flow Analysis

Variable 0 degree of AOA

Drag Force 313.619 N

Lift Force 74.48 N

Drag Coefficient 0.0093021

Lift Coefficient 0.0022088

IX. CONCLUSION

It is seen from above results all the materials are giving the considerable results; finally the

conclusion can be done on the basis of the best suitable material.

The temperature has a significant effect on the von Mises stress in the turbine blade.

Maximum elongation and temperatures are observed at the blade tip section and minimum

elongation and temperature variations at the root of the blade.

The thermal stresses are predominant in the analysis when compared to the Pressure and

Centrifugal forces.

Deformations gradually increase along the blade length from root to the tip portion of the

blade.

For the selection of the best material, Coated Haynes 188 Alloy performance better than other

alloys in all aspects such as Temperature Distribution, Total Deformation & Von-Mises

Stress.

The Flow Analysis is made possible to study the flow through velocity & pressure on the

Turbine Blade.

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