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
[email protected] 2 Department of Mechanical Engineering, Budge Budge Institute of Technology, Kolkata, India
[email protected] 3 Department of Mechanical Engineering, Nehru College of Engineering and Research Centre, Kerala, India
[email protected] 4 Department of Mechanical Engineering, Malabar College of Engineering and Technology, Kerala, India
[email protected] 5 Department of Management & Fashion Technology, DC School of Management & Technology, India
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
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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 105
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Modulus of Elasticity 2x105 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 K
14.5 x 10 -6
W/m K 12.2 x 10 -6
W/m 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 50oC. 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
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A medium range engine with rating 500 kW produces around 60-80 bar of pressure and the
temperature inside combustion chamber varies from (800 – 1200) oC. 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 - 8000 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
6.1.1 Axisymmetric Model:
Fig.3 Axisymmetric model of Exhaust Valve
6.2 Model with Mesh:
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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
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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)
Conductivity in element in x, y, and z
directions. For steady state, the Laplace equation applies,
…….. (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:
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Fig.6 Thermal Analysis Result – Temperature distribution
Fig.7 Nodal Displacement
Nimonic 80A
Fig.8 Thermal Analysis Result – Temperature distribution
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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
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21-4 N 0.90383 Nimonic 80 A 0.705281 Nimonic 105 0.601797
8.1 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, 2013.
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[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. 169-173.
[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 2012.
[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.122-126.
[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, 2014.
[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 408-423.
[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, 2014.
[8] Ashouri H, “Thermo-mechanical analysis of diesel engines cylinder heads using a two-
layer viscoelasticity model with considering viscosity effects”, international journal of
automotive engineering, volume 5 , number 2; page(s) 1026 to 1038, June 2015
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