Comparison of Heat Transfer Performance among Solid, Hollow and Sodium Encapsulated Engine Valves

摘要

The performance of an engine valve encapsulating sodium in the hollow was analyzed theoretically. Hollow valves are occasionally used due to the light weight to enhance efficiency and maximum rotation speed. Further, hollow valves encapsulating sodium in the hollow have been practically applied so that the heat transfer of the hollow valve is improved. However, there are little report on the performance of the sodium encapsulated engine valve quantitatively. In the present study, the heat transfer characteristics of a hollow valve and a sodium encapsulated valve were analyzed in comparison to a solid valve, by finite element method (FEM). As a result, the maximum temperature of the sodium encapsulated valve was lower by 413°C or 115°C than that of the hollow valve or the solid valve. Therefore, it has been concluded that the enhancement of efficiency and maximum rotation speed is possible without decreasing in the thermal performance by replacing the conventional solid or hollow valve to the sodium encapsulating valves.