Experimental Analysis on Soot Formation Process In DI Diesel Combustion Chamber by Use of Optical Diagnostics

Soot formation process inside the combustion chamber of an DI diesel engine is focused as a phenomenological basic scheme by using several optical diagnostics technique for the improvement of diesel exhaust emission. We have conducted the series of optical measurement research for the clarification of combustion field in an DI diesel engine. Then, this paper is a kind of review by adding the fuel vapor properties and particle image velocimetry (PIV) analysis with focusing the soot formation process. The experiments were carried out in a small sized high-speed DI diesel engine installed with an optical access view. The spray characteristics and its flow field in 2-D field were measured by laser sheet scattering (LIS) method and PIV scheme. Fuel vapor concentration field was also detected quasi-quantitatively as 2-D distribution by laser-induced exciplex fluorescence (LIEF) method, which is based on application of the TMPD/naphthalene exciplex system, relating to soot formation (initiation) process. Here, the heterogeneity of the vapor concentration should be discussed for the soot initiation, and the 2-D distribution of soot particles in several planes in the chamber was obtained with applying a laser-induced incandescence (LII) method. Further, measurement of the flow field inside the flame after an ignition was tried to clarify the effect of turbulence properties on soot formation and oxidation processes. Then, the effects of the spray properties, the vapor concentration, flow field characteristics on the soot formation process were discussed based on the experimental date obtained by optical diagnostics.