Measurements of Soot Particles in Single Spray Combustion by a Rapid Compression Machine

Abstract

The size distribution of single soot particles (the fuel was gas oil) in single fuel spray combustion by a rapid compression machine was measured with electron micrographs and calculated by the small angle scattering method of X-rays. It was studied in relation to the compression ratio of a combustion chamber and the volume of fuel injection. The size of crystallites in a single soot particle was measured with an X-ray diffractometer.
The results of this experiment are summarized as follows:
(1) The size distribution of single soot particles is not affected by the compression ratio and the volume of fuel injection. It is the same as the distribution of single soot particles in a wick flame.
(2) A single soot particle is a sphere of 300Å in diameter in the maximum distribution.
(3) The size of crystallites in a single soot particle is 13.96Å. It is 1/15-1/25 the size of a single soot particle in the maximum distribution examined by the electron micrographs (×12300) .
(4) The size distribution of single soot particles in this experiment shows much the same tendency as the one calculated by Guinier plot method.
The results of this experiment indicate that a soot is composed of many spherical single soot particles and that it is formed by a great many microscopic cristllites. As described above, the essential structure of soot particles is one of the important factors in the investigation of soot formation in combustion processes.