Cataract Detection

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Volume-5, Issue-3, June-2015

International Journal of Engineering and Management Research

Page Number: 24-28

Structural & Thermal Analysis of Gas Turbine Blade at Varying

Operating Conditions

R.D.V.Prasad1, Behera V Ravi Teja2, M.S.S. Srinivasa Rao3 1,2

Assistnat.Professor, Department of Mechanical Engineering, Anil Neerukonda Institute of Technology & Sciences, Visakhapatnam, Andhra Pradesh, INDIA

3

Sr. Assistant Professor, Department of Mechanical Engineering, Anil Neerukonda Institute of Technology & Sciences, Visakhapatnam, Andhra Pradesh, INDIA

ABSTRACT

The model is done in Solid Works as per the standards. Solid model is then imported to ANSYS workbench environment so as to perform thermal and static structural analysis. In thermal analysis, the model is given heat flux, convective heat transfer and ambient gas temperature and then is solved for temperature distribution over the blade.

The obtained temperature distribution is taken as the thermal load into the static structural analysis. In static structural analysis, the model is given BCs and structural loads viz; centrifugal force, tangential force and pressure. The model is then solved for stresses and deflections. The von-Misses stress and Total deformation plots are taken for various operating conditions i.e., temperatures and speeds. The results are then compared for variable gas temperatures and turbine speeds.

Keywords — Thermal analysis, static structural, von- Misses stress, deformation, speeds.

I. INTRODUCTION

The gas turbine in its most common form is a rotary heat engine operating by means of series of processes consisting of compression of air taken from the atmosphere, increase of gas temperature by constant-pressure combustion of the fuel in the air, expansion of hot gases and finally discharge of the gasses to the atmosphere, the whole process being continuous. It is similar to petrol and diesel engines in working medium and internal combustion but is akin to the stream turbines in its aspect of the steady flow of the working medium. Today the gas turbine is prominent as an aircraft power

plant with outputs ranging from the few hundreds of Newton of thrust to over 1000KN as a shaft power unit, the smallest in regular service is 5HP & the largest being 35000HP.

Reliability, minimum cost, minimum supervision and minimum starting time. 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. It is essential to incorporate the Computer Aided Engineering in the turbocharger development and design process. We have made analysis of the stress caused by external force and pressure on a single blade of a gas turbine.

II. LITERATURE REVIEW

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maximum efficiency. That means, the Gas turbine having

maximum reliability, minimum cost, minimum supervision and minimum starting time. The gas turbine obtains its power by utilizing the energy of burnt gases and the air. This is at high temperature and pressure by expanding through the several rings of fixed and moving blades. A high pressure of order 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 drives the compressor so it is coupled to the turbine shaft. John.v et.al.[3] studied on the design and analysis of Gas turbine blade, CATIA is used for design of solid model and ANSYS software for analysis for F.E.model generated, by applying boundary condition, this paper also includes specific post-processing and life assessment of blade .HOW the program makes effective use of the ANSYS pre-processor to mesh complex turbine blade geometries and apply boundary conditions. Here under we presented how Designing of a turbine blade is done in CATIA with the help of co-ordinate generated on CMM. And to demonstrate the preprocessing capabilities, static and dynamic stress analysis results, generation of Campbell and Interference diagrams and life assessment. The principal aim of this paper is to get the natural frequencies and mode shafe of the turbine blade. V.Raga Deepu et.al.[4] Studied on a Gas turbine is a device designed to convert the heat energy of fuel in to useful work such as mechanical shaft power. Turbine Blades are most important components in a gas turbine power plant. A blade can be defined as the medium of transfer of energy from the gases to the turbine rotor. The turbine blades are mainly affected due to static loads. Also the temperature has significant effect on the blades. Therefore the coupled (static and thermal) analysis of turbine blades is carried out using finite element analysis software ANSYS. A.K.Matta et.al.[5] studied the stress analysis for N – 155 & Inconel 718 material. On solid blades it is reported that Inconel 718 is better suited for high temperature operation.

III. DEFINITION OF PROBLEM

The definition of the problem is to know the response of the stresses on the blade to the variations in

gas temperatures & turbine speeds. In this project we

performed structural and thermal analysis by applying various gas temperatures & turbine speeds. By doing above analysis we found stresses developing on blade & the temperature distribution over the blade.

Modelling of the turbine blade is done using SOLIDSWORKS 2013, which facilitates collaborative engineering across various disciplines. The thermal and static structural analysis of turbine blade is done using ANSYS 15, which is a dedicated finite element package used for determining the temperature distribution and heat

flux, variation of stress and deformation across the turbine blade.

IV. RESULTS AND DISCUSSIONS

AT 1000°C & 3000 r.p.m

Fig:1 Temperature

Distribution

From the above result, it is clear that the temperatures are very high at tip of the blade & it goes on decreasing when it reaches the hub

Fig:2 Heat Flux Distribution

From the above heat flux distribution ,it is clear that the amount of heat flux is more near the intersection of the blade & the hub

Fig:3 Equivalent Stresses(Von-Mises)

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Fig:4 Deformation

From the above result, it is evident that the deformation is distributed in an ascending manner from the bottom of the hub to the tip of the blade.

At 800°C, 3000 R.P.M

Fig:5 Temperature Distribution

Fig:6 Equivalent Stresses (Von-Mises)

Fig:7 Deformation

At 800°C, 3500r.p.m

Fig:8 Temperature Distribution

Fig:10 Deformation

At 800°C, 4000 R.P.M

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Fig:13 Deformation

Likewise, the plots were taken even for other operating conditions i.e., speed ranging from 3000 – 4000 rpm and gas temperatures ranging from 8000 – 11000

SPEED (r.p.m)/ TEMP (°C)

C.

Table: 1

RANGE OF TEMPERATURES RECORDED ON BLADES AT CORRESPONDING GAS TEMPERATURES

3000 MAX-MIN °C 3500 MAX-MIN °C 4000 MAX-MIN °C

800 782.9-530.4 782.7-528.8 782.1-528.6

900 882.8-630.1 882.6-628.1 882.6-628.1

1000 974.18-717.5 974.1-715.9 974.0-715.0

1100 1074.1-816.8 1073.9-815.2 1073.5-815.1

From the above table, it is clear that the temperatures are maximum at the tip of the blade & it goes on decreasing & the temperature is minimum at the base of the hub.

TABLE: 2

RANGE OF VON MISES STRESSES RECORDED ON BLADES AT CORRESPONDING GAS TEMPERATURES SPEED (r.p.m)/ TEMP (°C) 3000 MAX-MIN MPa 3500 MAX-MIN MPa 4000 MAX-MIN MPa

800 264.8-0.67 266.08-0.91 268.56-1.19

900 312.23-0.67 313.6-0.91 316.09-1.19

1000 354.1-0.67 355.38-0.91 357.85-1.2

1100 401.47-0.66 402.74-0.91 405.21-1.2

From the above table, it is clear that the von mises stresses goes on increasing with the increase in

temperature. Also stresses are affected by the increase of the speed. Stresses increase with the increase in speed of the rotor.It’s clear from the above tabular column, that the main factor in the stress rise is Gas temperatures, and in turn the Speeds has got very less impact on the Stresses obtained.

TABLE: 3

RANGE OF DEFORMATIONS RECORDED ON BLADES AT CORRESPONDING GAS TEMPERATURES SPEED (r.p.m)/ TEMP (°C) 3000 MAX-MIN mm 3500 MAX-MIN mm 4000 MAX-MIN mm

800 0.069 - 0 0.075 - 0 0.083 - 0

900 0.077 - 0 0.083 - 0 0.090 - 0

1000 0.084 - 0 0.090 - 0 0.097 - 0

1100 0.092 - 0 0.098 - 0 0.105 - 0

From the above table, it is clear that the deformations are maximum at the tip of the blade & it goes on decreasing & the deformation is zero at the base of the hub. The analysis was carried out for steady state heat transfer conditions. 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. From the above experiment, it is evident that the amount of von-Mises stresses are greatly affected by the thermal load but not by the structural loads.

V. CONCLUSION

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.

REFERENCES

[1] S.Gowreesh, N.Sreenivasalu Reddy and N.V.Yogananda Murthy. “CONVECTIVE HEAT TRANSFER ANALYSIS OF AERO GAS TURBINE BLADE USING ANSYS”, International journal of Mechanics of solids, vol4, No.1, March 2009 (ppt55-62).

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journal of Engineering Education and technology, Vol.2,

No.3, Nov 2010.

[3] John.V, T.Ramakrishna. “THE DESIGN AND ANALYSIS OF GAS TURBINE BLADE”, International Journal of Advanced Research and Studies, Vol 2, No.1, Dec 2012.

[4] V.Raga Deepu, R.P.Kumar Ropichrla. “DESIGN AND COUPLED FIELD ANALYSIS OF FIRST STAGE GAS TURBINE ROTOR BLADES”, International journal of Mathematics and Engineering, Vol 13, No.2, Pages: 1603-1612.

[5] A K Matta, D Venkata rao, P Ramesh babu, R Umamaheswara rao, “Analysis of Turbine Blades with Materials N 155 & Inconel 718”, International

journal of advances in Science and Technology, vol

4,No.1,2012.