Effect of Chamber Geometry on Flame Behavior in a DI Diesel Engine

Abstract

The effects of the combustion chamber geometry on flame behavior were investigated in an optically accessible DI diesel engine. The flame behaviors in three different chamber geometries including the production version were observed through both windows installed in the piston crown and the head using a high-speed camera and a pseudo-endoscope system, respectively. Comparing the velocity distribution in the flame inside each chamber measured by applying image processing, it is found that (1) the chamber geometry has a significant effect on the flame velocity, that is, the velocity in the reentrant type chamber is larger than in the dish type chamber during the expansion period. Also, in the observation of the spreading of the flames over the squish area taken by the endoscope, the image shows that (2) the flame distribution inside and outside the chamber is considerably affected by the chamber geometry, and the reentrant type chamber prevented the flame from spreading over its squish area. Correlating the flame behaviors with exhaust smoke, it is found that (3) for further smoke reduction it is important to achieve an active combustion during the period of diffusion combustion and desirable distribution of fuel and that of flame in the chamber simultaneously.