INFLUENCE OF THERMAL RADIATION FROM THE BURNED ZONE ON HEAT TRANSFER IN THE EXHAUST VALVE OF DIESEL ENGINE

Thermal radiation has a substantial influence on heat transfer in diesel engines. It is especially important during the combustion period of the engine cycle. In the paper a distribution of a radiative heat flux on walls of the combustion chamber is analyzed for different values of a crank angle. A charge in the chamber is divided into the burned and the unburned zones. It is assumed that the burned zone, rich in the soot particles, is the main source of radiation. Variation of the burned zone volume and shape during the combustion period is iaken into account. Calculation of radiative heat flux distribution on the chamber walls is carried out by a numerical solution of the appropriate integral equation using the point collocation method along with the local piece-wise interpolation technique. This procedure allows to find the radiative heat flux value on the head of the exhaust valve. Variation of the radiative heat flux supplemented with variation of the convective flux with the crank angle over the whole cycle of the engine operation are taken as the boundary condition for numerical investigation of a problem of temperature distribution in the exhaust valve. The finite element method, based on the Galerkin weighted residual approach is used to solve the problem. Influence of the crank angle and emissivity of the combustion walls on the maximum temperature in the exhaust valve are investigated.