Particulate Matter from Direct Injection Diesel Engines

Abstract

Particulate matter is a significant source of pollution from diesel engines and occurs when fuel burns in air deficit atmosphere, which is typical of diesel combustion with heterogeneous combustion. Particulate matter forms as a result of thermal cracking of fuel molecules under air deficiency. This leads to division of oxygen under acetylene and through polymerization to carbon rich macromolecules, which then agglomerate into the final particulates (Pischinger and Baker 2003). Diesel particulate matter is therefore a complex mixture of organic and inorganic compounds in solid and liquid phases (Johnson et al. 1994). The mathematical modelling of particulate matter is always concentrated around soot because of its complex nature. Experimental investigations on PM emissions from used engines indicate that PM emissions are higher during transient phases of test cycle as compared to cold start or cruise phase (Shah et al. 204). Few experimental investigations indicate a reduction in PM emissions up to 27% from engines using biodiesel in place of diesel on account on higher reactivity of soot formed from biodiesel (Storey et al. 2003). Norton et al. (1998) have studied Fischer Tropsch catalytic conversion process for diesel fuel and its impact on engine out emissions. The study indicates about 24% reduction in PM emissions from engine using diesel that has undergone Fischer Tropsch transformation. Different studies have been carried out to establish contributions of soot, unburnt HC from fuel and lubricating oil (Cartillieri and Trittari 1984, Cartillieri and Wachter 1987, Cartillieri and Herzog 1988).