Measurement of Soot Particles in Combustion Chamber of Diesel Engine

Abstract

The authors have been studied on an optical measurement named the “transmissive light extinction method” to investigate the soot density and its behavior in a diesel combustion chamber. In the previous reports, the theoretical principle of the method was discussed and its applicability was examined in a few calibration tests. The method was applied to the actual measurement of soot density in an experimental engine which was modified to provide a facility to visualize the inside of the combustion chamber. The experiment was successful in obtaining the progress of the particle density of soot and proved that the method was rather easy to apply and reliable.However, since the method is principally a local measurement, ie. a measurement on line in sight, it has a limitation in explaining the behavior of soot throughout the entire combustion process.Then this time, the authors set about highspeed photographing of transmitted light all through the combustion chamber. In this, soot was recognized as shadow. An optical arrangement was made to remove the disturbance of the flame light on the shadowgraph. It also enabled simultaneous photographing of the direct image of the combustion flame on the same film. Besides, an image processing system was developed and used for analysis of the photographed results.As a result, soot behavior was successfully observed as a total picture comparing it with that of fuel spray and combustion flame. In this way, the result of the local measurement by the transmissive light extinction method was explained fairly well.