Recent developments in the control of particulate emissions from diesel vehicles

摘要

High-speed turbocharged direct injection diesel engines in cars were introduced some fifteen years ago, and with continuous engine refinement they have become increasingly popular, so today 50% of new cars in Western Europe are diesels. Hydrocarbons, CO, NO{sub}x and particulate matter (PM-"soot") emissions from diesels were markedly reduced during this period. In keeping with the general lowering of exhaust emissions impending legislation will require fitment of efficient diesel particulate filters (DPFs) on all new diesel vehicles. Trapped PM in DPFs must be removed, and with availability of ultra low sulphur diesel (ULSD) many heavy-duty vehicles were retrofitted with low temperature passive catalytic DPFs that oxidise already present NO to NO{sub}2 for PM combustion. This method is not suitable for cars, and high temperature oxygen regeneration is employed. The first DPFs on cars had an inorganic fuel additive to lower PM combustion temperatures, while second generation DPFs were catalysed and needed no fuel additive. The most recent DPFs have multiple catalytic functions and they are small enough to be mounted directly on the turbocharger. The nature of nano-sized PM, and how they are formed is being elucidated, and it appears the entire range of PM sizes can be prevented from entering the environment. DPF development requires much costly engine dynamometer or rolling road facilities to load DPFs with PM, and to alleviate this and facilitate fundamental research, a flexible laboratory diesel PM generator was developed.