Direct injection of a diesel-butane blend in a heavy duty engine

LPG (Liquefied Petroleum Gas) has for long been used in passenger cars. Presently, LPG sup-ply systems have also attracted considerable at-tention for heavy duty use. LPG can be applied in these engines combining port fuel injected LPG with a direct injection of diesel. These engines equipped with a port fuel injection (PFI) system suffer from the problems of poor brake thermal efficiency and high HC emissions. In this investigation a butane-diesel pre-mixed blend is injected directly (DI) into the cylinder. For direct injected butane, hydrocarbon emis-sions were found to be an order of magnitude lower than for port fuel injected butane. Furthermore, the experiments have shown that nitric oxides are not negatively affected compared to the diesel baseline. At a butane mass fraction of one-third and a 6 bar IMEP load point, smoke emissions decreased by 50%. Because a high combustion efficiency is retained, fuel cost savings can be significant, at more than 6 percent.