Experimental investigation of the oxidation behaviour and thermal kinetics of diesel particulate matter with non-thermal plasma

Abstract

A thermogravimetric analyser was used to research the oxidation behaviour of diesel particulate matter (PM) generated in a diesel engine. The effects of engine operating conditions, plasma intensity and thermogravimetric analysis (TGA) ramp rate on PM oxidation behaviour were investigated. Non-isothermal analysis was used to calculate the activation energy E by both the Friedman–Reich–Levi (FRL) and Flynn–Wall–Ozawa (FWO) methods. The TGA profiles shifted to higher temperature evidently with decreasing engine load while they moved towards higher temperature with increasing speed. Engine work conditions had little influence on high volatility soluble organic fraction (HVSOF) content; however, it differed greatly for low volatility soluble organic fraction (LVSOF). The starting and final oxidation temperature dropped greatly when enhancing plasma intensity. Ash percentage decreased greatly with increasing plasma intensity that it was 37%, 5% for 2.5, 5.0 kV voltage applied. Large amounts of ash were oxidisable with the presence of plasma though they were non-oxidisable at common atmosphere (even high temperature). The activation energy of PM was in the range of 53.8–85.1 kJ/mol and 62.7–72.7 kJ/mol as calculated by FRL and FWO, respectively. The calculated activation energies were much lower than reported in other studies.