Design and Analysis of Gas Turbine Blade by Potential Flow Approach

Transcription

1 V. Vijaya kumar et al Int. Jurnal f Engineering Research and Applicatins RESEARCH ARTICLE OPEN ACCESS Design and Analysis f Gas Turbine Blade by Ptential Flw Apprach V. Vijaya Kumar 1, R. Lalitha Narayana 2, Ch. Srinivas 3 M.Tech Student Department f Mechanical Engineering A.S.R. Cllege f Engineering Tanuku Head f the Department Department f Mechanical Engineering A.S.R. Cllege f Engineering Tanuku Assciate prfessr Department f Mechanical Engineering A.S.R. Cllege f Engineering Tanuku ABSTRACT The design features f the turbine segment f the gas turbine have been taken frm the preliminary design f a pwer turbine fr maximizatin f an existing turbjet engine. It was bserved that in the abve design, after the rtr blades being designed they were analyzed nly fr the mechanical stresses. As the temperature has a significant effect n the verall stress in the rtr blades, a detailed study is carried ut n the temperature effects t have a clear understanding f the cmbined mechanical and the thermal stresses. The first stage rtr blade f the gas turbine is analyzed fr the mechanical axial and centrifugal frces. Knwing the fluid cnditins at exit f the gas turbines, a value f static pressure was assumed at the turbine utlet. Frm this the crrespnding enthalpy drp required in the pwer turbine is calculated. The peripheral speed f rtr and flws velcities is kept in the reasnable range s t minimize lsses. In which the base prfiles available and is analyzed later fr flw cnditins thrugh any f the theretical flw analysis methds such as Ptential flw Apprach. Key wrds: Gas turbine blade, Mechanical and the thermal stresses, mechanical axial and centrifugal frces, Ptential flw Apprach, Static pressure, enthalpy drp I. INTRODUCTION The gas turbine in its mst cmmn frm is a rtary heat perating by means f series f prcesses cnsisting f air taken frm the atmsphere, increase f gas temperature by cnstant pressure cmbustin f the fuel in the whle prcess being cntinuus. It is similar t petrl and diesel engines in wrking medium and internal cmbustin but is akin t the steam turbines in its aspect f the steady flw f the wrking medium. Tday the steam turbine is preeminent as an aircraft pwer plant with utputs ranging frm a few hundreds f Newtn if thrust t ver 1000 KN. As a shaft unit the smallest in regular service is 5H.P. The utstanding characteristics f gas turbines, which make them eminent f all turbines, are as fllws: 1. It has a very simple mechanism. 2. It runs at higher speed. 3. It is very cmpact engine cmpared t ther requiring less weight and space. 4. It requires less maintenance cst. 5. Cheaper liquid fuel can be used, as phenmenn f detnatin des nt exist. 6. It is highly situated fr peak lad and standby pwer generatin and aircraft prpulsin. 7. It wrks at high perating pressures. 8. It has greater pwer t weight ratin than ther engines. 9. It requires less manpwer. II. BLADE MATERIALS: Vatallium [Cbalt ally based at a temperature rating abve 760] als called Haynes s stellite21 available in precessin cast frm with Carbn and Mlybdenum as hardening agents. Titanium allys. Haynes s series f ally [Nickel and Cbalt based allys with temperature ranging between ] with Carbn, Mlybdenum as hardening agents available in precessin cast frm. Ally steels. III. BLADES MANUFACTURING TECHNIQUES 1. Frging. 2. Casting. 3. Fabricatins. 4. Pwder metallurgy. IV. CHALLENGES The turbine plates are subjected t high temperature which leads t a higher thermal efficiency, higher pwer t weight rati and lw 187 P a g e

2 V. Vijaya kumar et al Int. Jurnal f Engineering Research and Applicatins specific fuel cnsumptin. If a blade is heated rapidly t a high temperature it causes uneven temperature distributin and several thermal stresses are develped with in the material. Beynd certain level f temperature (65-800C) the blade material des nt remain elastic and cntinuus t stretch under applied frces. This is called creep and if this exits fr a lng time fracture will ccur. V. OPTIONS PROPOSED TO OVERCOME THIS PROBLEM:- 1. A new material may be sught which is capable f peratin at high temperatures. 2. By blade cling which maintains the temperature f the blades at a value lw enugh t preserve the desired material prperties? BLADE COOLING:- is the mst effective way f maintaining high perating temperatures making use f the available material. Blade cling may be classified based n the cling medium as 1. Liquid cling. 2. Air-cling. STRUCTURAL ANALYSIS: The structural analysis is the mst cmmn analysis f finite element methd, which accmplishes varius structures such as bridges, naval, aernautical, mechanism husing and mechanism cmpnents such as pssible in ANSYS sftware. They are, Static analysis, Mdal analysis, Harmnic analysis, Transient dynamic analysis, Spectrum analysis, Buckling analysis, Explicit dynamic analysis, Fractured mechanics, Cmpsites, Fatigue, and P-methd. Out f these 11 analysis ptins generally we cnsider the static and mdal analysis ptins nly. In the analysis ptins we have H-methd and P-methd types f slutins. VI. STATIC ANALYSIS: A static analysis calculates the effects f static lads n the structure while ignring the inertia and damping effects such as thse caused by time varying lads but it can accmplish steady inertia lads static equivalent lads. Steady lading and respnse cnditins are assumed. The lads and the structures respnse are very slw in this analysis. The types f lads that can be applied in a static analysis include, Externally applied pressures and frces, Steady state internal frces (such as gravitatinal velcity), Impsed (nn-zer) displacements, Fluencies (fr nuclear swelling). A static analysis can als include linear and nn-linear analysis. Nn-linearity such as creep, large defrmatin, plasticity, stress stiffening, cntact elements, hyper elastic elements etc can be handled very easily. The prcedure fr static analysis cnsists f three steps includes, Build the mdel, Apply the lads and btain the slutins, Review the results. VII. THERMAL ANALYSIS: A thermal analysis calculating the thermal variatins and related thermal quantities in a system r cmpnent such as, The temperature distributin, The amunt f heat lst r gained, Thermal gradients, Thermal fluxes. Thermal analysis plays an imprtant rle in the designing f many cmpnents such as heat exchangers, turbines, internal cmbustin engines and piping systems. The thermal analysis is carried ut with static analysis t calculate thermal stresses. The basis f thermal analysis is the heat balance equatin btained frm the cnservatin f energy. The thermal analysis can slve all the mdes f heat transfer. Cnductin, cnvectin and radiatin ANSYS supprts 2 type f thermal analysis such as: Steady-state thermal analysis and transient thermal analysis. A steady state thermal analysis-lading situatin is the ne in where heat-string effects ver a perid f varying time can be ignred. In sme analysis thermal analysis cmbined with ther phenmenn are used as thermal-structural analysis and magnetic thermal analysis. This is called as steps includes, Build the mdel, Apply the lads and btain the slutins, Review the results. VIII. MAIN PARTICULARS OF BLADE: The material taken fr the blade is Ni-Cr (10% Chrmium and 90% Nicke10). Then material prperties f the element are as fllws: 1. Density : 8900 Kg/m2 2. Mdules f elasticity : Gpa 3. Pissn s ratin : Thermal expansin cefficient : 1.340e-5/k 5. Heat capacity : 444 J/Kg-K 6. Thermal cnductivity : 90.7 W/m-k The abve are the input material prperties fr the slutin ptin. The abve series f peratins are perfrmed in the PREPROCESSOR mdule. After the mdel is structured the lads are structured the lads are applied in the slutin mdule after defining the analysis ptin. IX. SOLUTION PROCESSOR: The lads are applied in the slutin prcessr after defining the analysis type. 188 P a g e

3 V. Vijaya kumar et al Int. Jurnal f Engineering Research and Applicatins Static Analysis. Cupled-field Analysis. X. CONSTRUCTION OF TURBINE ROTOR BLADE: T accmplish the analysis f a structure in ANSYA package steps are t be fllwed: 1. Build the mdel. 2. Apply the lads and btain the results. 3. Review the results. Here, we are cnsidering the blade fr analysis. S we need t define the list f peratins with respect t the structuring f the blades. PREPROCESSOR MODULE: In this mdule the fllwing sets f peratins are perfrmed. In this mdule structures t the built. BUILD THE MODEL: in mdeling the blade a series f peratins are t be fllwed. The list f peratins that are t fllws. 1. Create the key pints. 2. Create the lines. 3. Create the areas. 4. Meshing. 5. Extrusin. Building the mdel is the basic step invlved in mdeling the structure. The list f all the key pints thrugh which the basic utline f the structure is btained is as fllws: LIST OF ALL SELECTED KEYPOINTS: LOCATIONS (Z=0) N X Y All the areas are MAPPED meshes under PLANE42 with an element size 8 with quadrilaterals element. The areas 2,8,11,12,9,3,4 are extruded in the +Z directin t height f 5mm with element size 2. The areas 10,7,1 are extruded in the +Z directin f height 117mm. Nw the areas 11,7,3 are extruded in the Z directin t a height f 5mm. Nw the side areas f this vlume are extruded in the +_X directin f 3.8mm. All the extrusin peratins are carried under SOLID45element. We btain a ttal f 25 vlumes, 114 areas, 6042ndes, 98key pints and 118areas. THE POST PROCESSOR MODULE: 189 P a g e

4 V. Vijaya kumar et al Int. Jurnal f Engineering Research and Applicatins TEMPERATURE STRESS IN X STRESS IN Y 190 P a g e

5 V. Vijaya kumar et al Int. Jurnal f Engineering Research and Applicatins STRESS IN Z ANALYSIS RESULTS:- SOLUTION MECHANICAL THERMAL DEFORM IN X t DEFORM IN Y t DEFORM IN Z t STRESS IN X t STRESS IN Y t STRESS IN Z t VONIMISSES STRESS t VONIMISSES STRAINS.023e-9 t TEMPERATURE t TOTAL GRADIENT e-3 t STRESS TOTAL FLUX STRESS e-3 t XI. THE RESULTS ARE REVIEWED AFTER AND IT IS FOUND THAT: 1. The temperature varies between and The thermal energy f the structure varies between 0684E-5 t 0.966e The heat transfer ccurring in the structure varies between KJ t KJ. 4. The temperature fluxes and temperature gradients f the structural is fund. 5. The stresses and strains in the X, Y and Z directins are fund. 6. The strain energy value f the structure is bserved. 7. The stress intensity value f the structure is fund t be varying between (0.333 t 1852) It is bserved that the temperature is linearly varying inside and irregularly variatin n 191 P a g e

6 V. Vijaya kumar et al Int. Jurnal f Engineering Research and Applicatins bth ends f the flange i.e. suctin and exhausts side. XII. CONCLUSIONS The finite element analysis f turbine blade and rtr is carried ut n brick and isperimetric elements. The static, mdal and thermal analysis is carried ut. The temperature has a significant effect n the verall stresses in the turbine blade. Maximum elngatin and temperatures are bserved at the blade tip sectin and minimum elngatins and temperature variatins at the rt f the blade. Temperature distributin is almst unifrm at the maximum curvature regin alng the blade prfile. Temperature is linearly decreasing frm the tip f the rt f the blade sectin. Maximum thermal stresses are stresses are setup when the temperature difference is maximum frm utside t inside. The thermal stresses are predminant in the analysis. The rder fllws thermal, pressure and centrifugal frces. Maximum stresses and strain are bserved nly at blade regin in the rtr alng the blade length and elngatins in Y-directin are gradually varying frm the different sectins alng the rtr axis. REFERENCES [1]. Steam & Gas turbines and Pwer Plant Engineering, VII ed., 2004, Central Publishing Huse Allahabad. [2]. Fundamental f Internal cmbustin Engine by Gill, Smith, Ziurys [3]. I.C. Engine by Rgwsky [4]. I.C. Engine Analysis and Practice by E.F. Obert [5]. Gas Turbine Thery by Chen and Rgers [6]. I. C. Engine by V. Ganeshan [7]. Steam, Gas Turbines in Pwer plant Engineering, VII Ed. 2004, Central Publishing Huse Allahabad. [8]. wer_plants/gas_turbines.html [9]. px/tabid-1289/?gclid=ckumvnsy1pkcfc IvpAdLGl_Vw [10]. H-Saravanamutt/Gas-Turbine- Thery/ X.html 192 P a g e