FLAME TEMPERATURE AND AMBIENT GAS-COMPOSITION EFFECTS ON SOOT FORMATION AND OXIDATION IN FLAME - (OBSERVATION OF DIESEL SPRAY COMBUSTION USING A RAPID COMPRESSION MACHINE)

A single-action rapid compression machine was developed to observe soo t formation and oxidation processes in a diesel spray flame. The two-c olor method was applied to analyze the flame temperature and KL factor from the flame image taken by a high-speed camera. Variation in the s urrounding gas-oxygen concentration was achieved by adding differing q uantities of pure oxygen, nitrogen, carbon dioxide and argon gases whe n charging air, ranging from 17 to 25 vol% of oxygen concentration, to examine the effect of flame temperature. The initial gas temperature has a great effect not only on ignition delay but also on soot formati on speed. Higher oxygen concentration resulted in higher flame tempera ture and faster soot oxidation speed in the flame. Carbon dioxide has a soot-reduction effect in spite of its lower flame temperature.