Flame Temperature and Ambient Gas Composition Effects on Soot Formation and Oxidation in Flame : Observation of Diesel Spray Combustion Using a Rapid Compression Machine

Abstract

A single-action rapid compression machine was developed to observe soot formation and oxidation processes in a diesel spray flame. The two-color method was applied to analyze the flame temperature and KL factor from the flame image taken by a high-speed camera. Variation in the surrounding gas-oxygen concentration was achieved by adding differing quantities of pure oxygen, nitrogen, carbon dioxide and argon gases when charging air, ranging from 17 to 25 vo1% 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 formation speed. Higher oxygen concentration resulted in higher flame temperature and faster soot oxidation speed in the flame. Carbon dioxide has a soot-reduction effect in spite of its lower flame temperature.