THERMO MECHANICAL ANALYSIS OF ENGINE VALVE AND VALVE SEAT INSERT BY FINITE ELEMENT METHOD

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1 Volume 119 No , ISSN: (on-line version) url: THERMO MECHANICAL ANALYSIS OF ENGINE VALVE AND VALVE SEAT INSERT BY FINITE ELEMENT METHOD G.Ragul 1, Samrat Majumdar 2, S. Sankar 3, Prasidh E Prakash 4, Dehesinghraja J 5 1 Department of Mechanical Engineering, Budge Budge Institute of Technology, Kolkata, India ragulme90@gmail.com 2 Department of Mechanical Engineering, Budge Budge Institute of Technology, Kolkata, India samratmajumdar26@gmail.com 3 Department of Mechanical Engineering, Nehru College of Engineering and Research Centre, Kerala, India shanmugasundaramsankar@yahoo.com 4 Department of Mechanical Engineering, Malabar College of Engineering and Technology, Kerala, India prasidhearath@gmail.com 5 Department of Management & Fashion Technology, DC School of Management & Technology, India dhesinghpsg2006@gmail.com Abstract In this investigation deals with the stress induced in a valve due to high thermal gradient and high pressure inside the combustion chamber. To analyze the valve ANSYS has been used as the tool. A thermal and structural analysis is performed on the valve. In the first stage of analysis the temperature distribution across the valve is determined. In the second stage this temperature distribution is transferred on to another element and pressure load was applied on the valve to determine the displacement distribution in the valve. The above said process will be repeated for the different valve materials and finally the best material will be suggested for the valve based on its strength and thermal properties capability. 1. Introduction Fontanesi, S, Cicalese, G, Tiberi, A, [1] introduced the concept of thermal behaviour of IC engines of high performance on direct injected of SI engine for sport car, Goli Udaya Kumar, Venkata Ramesh Mamilla [2] studied the failure of inlet and exhaust valve in different working condition failure like fatigue, high pressure inside cylinder and due to load impact. [3] Naresh Kr. Raghuwanshi, Ajay Pandey. et.al, [3] studied the failure of the intake and outlet valves by various types of failures due to thermal and mechanical effect through various research paper as review 821

2 paper. Ajay Pandey, R. K. Mandloi [4] studied the failure of valve by SEM and also analysed by the compression and result is by temperature changes the grain size also because more wear of valve material. Shamsudeen, A; Abdullah, S, et.al, [5] designed and simulation of CNGDI based on FEA method as the result they improved the stress and displacement analysis, S. Fontanesia M. Giacopinia [6] in this work studies about the failure in engine around the water jacket, valves, spark plug and also analysis done in CFD. Baek, H., Lee. Et.al, [7] studied the increase of engine fuel consumption, knock behaviour and also valve train durability. Ashouri H [8] introduced the concept of reduce the thermo-mechanical failure by cyclic test under low compressive stress and also reduce the fatigue crack in the lining region and the life time also calculated by FEM. Keywords: Thermal and Structural analysis, Exhaust valve, Temperature distribution, FEA, ANSYS 2. Dimensions of Exhaust Valve Fig.1 Valve seat Fig.2 - Dimensions of Exhaust Valve 3. Material Properties Table: Mechanical Properties of Valve Properties 21-4N Nimonic 80A Nimonic

3 Modulus of Elasticity 2x10 5 N/mm 2 2.2x 10 5 N/mm 2 2.2x 10 5 N/mm 2 Thermal Expansion 18.8 x 10-6 W/m 14.5 x 10-6 W/m K 12.2 x 10-6 W/m K K Thermal Conductivity 14.5 W/m K 13 W/m K 10 W/m K 4. MODELING AND ANALYSIS The assumptions which are made while modeling the process are given below:- 1. The valve material is considered as homogeneous and isotropic. 2. The domain is considered as axis-symmetric. 3. Inertia and body force effects are negligible during the analysis. 4. The analysis is based on pure thermal loading and structural and thus only stress level due to the above said is done. The analysis does not determine the life of the exhaust valve. 5. The exhaust valve model used is of solid type. 6. The thermal conductivity of the material used for the analysis is uniform throughout. 7. The specific heat of the material used is constant throughout and does not change with temperature. 8. Under normal operation, when the valve is properly seating at the cam ramp, stresses arising from seating are quite moderate. They can become very high when the valve train is improperly engineered so that the valve bounce occurs, or when the engine is over speeded or the valve lash is improperly set. In this analysis the stresses due to valve seating has been not taken into account assuming a normal operation. 9. The distortion stresses in a valve arise due to misalignment of valve with the seat. The valve head must deflect to accommodate to the seat, and this causes bending stresses in the stem. Under most conditions, gas pressures and spring loads will be sufficient to bring the valve head into conformity with a mildly distorted seat. 10. The engine considered for the analysis is a medium range engine (500 kw). It is assumed that it is water cooled. 11. The heat generated inside the chamber is taken away by water chamber around cylinder liner and in the cylinder head. 12. The temperature of water in the chamber is maintained at 50 o C. Heat from valve is lost through this water only. 13. The valve keeps popping up and down. The analysis has been done for a stationary valve assuming that the fatigue life of the valve is very high and the stress arising due to that has been neglected. 5. DEFINITION OF PROBLEM DOMAIN The sources of stress in an exhaust valve are as follow- 1) Thermal stresses (Temperature gradient) 2) Mechanical stresses (Stress arising from seating, Distortion Stress) 6. Gas pressure and mechanical load 823

4 A medium range engine with rating 500 kw produces around bar of pressure and the temperature inside combustion chamber varies from ( ) o C. The combustion process for spark ignition and compression ignition are different. Even the condition inside the chamber is different for SI and CI engines. The condition here taken is for CI engines. But the same analysis can be done for SI engines by varying the boundary conditions. The heat generated inside the chamber is so high that it becomes very important to remove it continuously. The heat transfer from an engine takes place in following ways - 1. Water cooled - medium and large engines are usually water cooled the range of such engines varies from 100 hp hp. 2. Sodium cooled - this takes place in very large engines. 3. Air cooled - Most of the small engines and some medium engines are air cooled. The above mentioned stresses induced in the exhaust valve results in valve failure during repeated gas pressure loading and thermal loading. This could be overcome by changing the valve materials as stresses induced are influenced by the material of the exhaust valve. 6.1 Creating a Finite Element Model and Mesh Axisymmetric Model: 6.2 Model with Mesh: Fig.3 Axisymmetric model of Exhaust Valve 824

5 Fig.4 Dimensional model of Exhaust Valve with mesh Fig.5 Boundary Conditions. (1) ρ = density c = specific heat T = temperature t = time Velocity vector for mass transport Heat flux vector 825

6 The above equation is the first law of thermodynamics applied to a differential control volume. In case of thermal analysis of the valve there is no transport of mass across the boundary. The velocity vector term in the equation is zero for this case. 7. Fourier's Law Fourier's Law is used to relate the heat flux vector to the thermal gradient: (2) (3) directions. For steady state, the Laplace equation applies, Conductivity in element in x, y, and z.. (4) Where and are thermal conductivity in x and y directions respectively. The solution to this equation may be obtained by analytical, numerical, or graphical techniques. The objective of any heat transfer analysis is usually to predict heat flow or the temperature which results from a certain heat flow. The solution of above equation will give the temperature in a two-dimensional body as a function of the two independent space coordinates x and y. 8. RESULTS AND DISCUSSION Thermal analysis of the exhaust valve for different materials such as 21-4N, Nimonic 80A and Nimonic 105 are carried out. The properties of different exhaust valve materials such as thermal conductivity, thermal expansion, density, specific heat, young s modulus are given as input for the steady state analysis. The boundary conditions at the outer and the inner surfaces are given as input which has been considered for the specified operating conditions is given as the thermal load in to the FEA model. The results for the two different exhaust valve materials are given below. As the analysis carried out was steady state thermal, the results for both the materials are almost same. 21-4N: 826

7 Fig.6 Thermal Analysis Result Temperature distribution Fig.7 Nodal Displacement Nimonic 80A Fig.8 Thermal Analysis Result Temperature distribution 827

8 Fig.9 Nodal Displacement Nimonic 105: Fig.10 Thermal Analysis Result Temperature distribution Fig.11 Nodal Displacement Table.2: Result and Comparison Material Displacement (mm) of node 2,3 828

9 21-4 N Nimonic 80 A Nimonic Structural Analysis Static structural analysis of the exhaust valve for different materials such as 21 4N, Nimonic 80A and Nimonic105A is carried out. The properties of different exhaust valve materials such as thermal expansion, young s modulus are given as input for the structural analysis. The outer surface is constrained which has been given as the mechanical load in to the FEA model. The results for the three different valve materials are given below. It has been concluded from the results that among the three materials chosen for the structural analysis, the Nimonic105A are best as far as stiffness are concerned compared to the other two material as the maximum displacement in the Nimonic105A is greater than the other two material which is evident in the figure above. 9. CONCLUSIONS In this study, the steady state thermal analysis of the exhaust valve for the different materials such as 21 4N, Nimonic 80A and Nimonic105A have been performed. ANSYS software is applied to the steady state thermal analysis problem with outer and inner surface temperature as thermal boundary conditions. To obtain the simulation of thermal behavior appearing in different valve material, the basic governing equation for the heat conduction is solved with the initial boundary conditions with thermal conductivity as the property is solved for the two materials. Structural analysis for the three materials produces excellent result by treating the problem as coupled field analysis. From the structural analysis results for all the three valve materials, it s been concluded that the displacements values for the Nimonic105A is very less than the values of other material steel for the same thermal load and Structural loads. It s evident from the analysis, the best material for the valve is Nimonic105A as far as thermal and structural behavior is concerned. References: [1] Fontanesi, S, Cicalese, G, Tiberi, A, Combined In-cylinder / CHT Analyses for the Accurate Estimation of the Thermal Flow Field of a High Performance Engine for Sport Car Applications., "Combined In-cylinder / CHT Analyses for the Accurate Estimation of the Thermal Flow Field of a High Performance Engine for Sport Car Applications," SAE Technical Paper,

10 [2] Goli Udaya Kumar, Venkata Ramesh, Mamilla, Failure analysis of internal combustion engine valves by using ansys,, American International Journal of Research in Science, Technology, Engineering & Mathematics, 5(2), December 2013-February 2014, pp [3] Naresh Kr. Raghuwanshi, Ajay Pandey, R. K. Mandloi, Failure Analysis of Internal Combustion Engine Valves: A Review, International Journal of Innovative Research in Science, Engineering and Technology Vol. 1, Issue 2, December [4] Ajay Pandey, R. K. Mandloi, Effects of High Temperature on the Microstructure of Automotive Engine Valves, Int. Journal of Engineering Research and Applications, Vol. 4, Issue 3 (Version 1), March 2014, pp [5] Shamsudeen, A; Abdullah, S; Ariffin, A K Ali, design and simulation of a cylinder head structure for a compressed natural gas direct injection engine, International Journal of Automotive and Mechanical Engineering; Kuantan Vol. 9, [6] S.Fontanesia, M. Giacopinia, Numerical investigation of the cavitation damage in the wet cylinder liner of a high performance motorbike engine, Engineering Failure Analysis, Volume 44, September 2014, Pages [7] Baek, H., Lee, S., Han, D., Kim, J, Development of Valve train System to Improve Knock Characteristics for Gasoline Engine Fuel Economy, Development of Valve train System to Improve Knock Characteristics for Gasoline Engine Fuel Economy, SAE Technical Paper 2, [8] Ashouri H, Thermo-mechanical analysis of diesel engines cylinder heads using a twolayer viscoelasticity model with considering viscosity effects, international journal of automotive engineering, volume 5, number 2; page(s) 1026 to 1038, June

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