Measurement of Soot Particles in Combustion Chamber of Diesel Engine

Abstract

Soot emission is one of the most serious disadvantages of diesel engines. Although it is an urgent need to find an appropriate method to reduce it, no practical means have yet been developed nor has the mechanism of soot formation been made clear enough. The authors have concentrated on an optical measurement named the “transmissive light extinction method” to investigate the soot behavior in a diesel combustion chamber.In the 1st report, the theoretical principle and its reductions to practical methodology were presented, as well as discussions on applicability of the method to diesel combustion flame.This paper reports on an attempt made to apply the transmissive light extinction method to an actual measurement of soot particles in a diesel combustion chamber.First, an experimental engine was developed, which was installed with a disk shaped combustion chamber with quartz windows on its both sides to allow optical access. It was also equipped with a 2nd stage piston, over the original 1st stage one, which was designed for non-lubricated operation to prevent oil mist from intruding into the combustion chamber.With the experimental engine, measurements of soot particles in actual diesel combustion flame were performed. The progress of the soot density with time was successfully obtained, showing a quick generation of soot particles soon after the initiation of combustion, and a considerable amount of soot formation in later part of diffusion combustion period.