Investigations on the heat transfer within intake and exhaust valves at various engine speeds

摘要

The heat transfers within the intake valve differs than the exhaust valves, due to the difference in the boundary condition surrounding each valve. This paper concerns a comparison of the heat transfer coefficient (HTC) at various engine speed and the temperature distribution through exhaust valves and intake valves. The boundary condition are assessed using basic concept of heat transfer and correlation related to internal cbustin engine. To assess perfectly the real effect of the valves surrounding, an adequate subdivision of the valve is used where the heat transfer coefficient and the adiabatic wall temperature (AWT) for each subdivision are evaluated during one engine cycle. An average value of these two parameters is calculated and introduced as a boundary condition in a FEM model. This procedure is repeated for diverse engine speeds, and therefore, the trend of the real boundary condition in term of HTC and AWT are given versus engine speed. The comparison in term of HTCs shows different behaviour of valves surrounding mainly in the seat and stem zones. The obtained model is used to highlight the temperature map of an exhaust valve and intake valves for the different operating condition in addition to zones of fort thermal gradient and thus, areas of maximum thermal load can be specified, which help automobile manufactures to avoid valves failures.