Transient Thermal and Mechanical Analysis of the Exhaust Valve Using Finite Element Method

Internal combustion engines produce exhaust gases at extremely high temperatures and pressures. As these hot gases pass through the exhaust valve, temperatures of the valve, valve seat, and stem increase. To void any damage to the exhaust valve, heat is transferred from the exhaust valve through different parts, especially the valve seat contact. Because of exposure to hot exhaust gases, the valve burning of an internal combustion engine is a critical issue. In this study, for thermal analysis the exhaust valve of the XU7 engine at the maximum power is considered. Modeling and analysis is performed using axisymmetric, at two steps in FLUENT and ANSYS software and the exhaust valve, seat, guide and spring are modeled. At first step taking into consideration exhaust gas flow from exhaust valve, transient thermal analysis using FLUENT software is performed from an initial conditions and followed until the steady state condition. The maximum temperature of the valve is obtained in steady state condition and it’s value is 700 ºC. At two steps using ANSYS software and temperature distribution as a result of previous step, thermal stress analysis is performed and the result shows that the maximum stress happened at the edge of the head, and with the value of more than 100 MPa. Also, the structural analysis is done where the structural stresses is smaller than the thermal stresses.