Abstract
To investigate the effect of the fuel injection pressure on the cooling loss in a diesel engine, the present study evaluated the turbulent characteristics of diesel spray combustion in an optically-accessible compression and expansion machine. Images of the diesel spray flame were taken by a direct photography using a CMOS camera, and the flame velocity field was estimated from the pairs of the images with an image correlation method. The velocity was separated into the high and low frequency components by a frequency separation method, and the turbulent intensity was examined. The flame temperature was determined with a two-color method in the compression and expansion machine, and the heat balance was obtained in a diesel engine with a cylinder bore and a stroke identical with the compression and expansion machine. The correlation between the turbulent properties, the flame temperature and the cooling loss was investigated while changing the fuel injection pressure.
