Analysis of Combustion Chamber Temperature and Heat Flux in a DOHC Engine

Cylinder head and piston temperatures and heat fluxes were measured in a DOHC engine. Measurements for the combustion chamber were made at different engine speeds and engine loads. Twenty-one instantaneous temperature probes were totally embedded in a cylinder head and a piston. Major conclusions of this research include; 1) the instantaneous temperature on the cylinder head was affected by flame traveling distance, gas flow characteristics, and cooling passage; 2) all temperatures at the exhaust valve heads with different engine loads are much higher than those at the intake valve heads; 3) the instantaneous surface temperature at around exhaust valve pocket is higher than that at piston crown center; 4) the instantaneous temperatures of the top-ring groove and the second land are also varied; and 5) heat flux in the piston crown is largely occurred during the expansion stroke and the heat flux has dissimilar trend to the temperature distribution.