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A new type of dual fuel supply system has been developed. This system is able to economically convert conventional diesel engines into dual-fuel engines like LPG/Diesel engines and CNG/Diesel engines, which are capable of either using single diesel fuel or using dual-fuel including both diesel and CNG fuel or both diesel and LPG fuel. These diesel-LPG engines have been applied to the diesel buses in the public transportation of Guangzhou city, one of the biggest cities in China, owning to their low soot emissions, excellent operating performances and extremely low cost as well. Compared with the diesel baseline engine, it was found that there were a significant reduction in soot emission and an improvement of the fuel consumption with the diesel-LPG engine. Also the strategy on LPG content is discussed in order to meet the demands for soot emission, fuel economy, transient performance and output power at the same time.

This paper deals with the combustion chamber shape effects on in-cylinder air motion and performance of a DI diesel engine. Three different shapes of diesel engine combustion chamber are selected and simulated by means of multidimensional modeling technique. The turbulence, squish and turbulence energy in cylinder are systemically analyzed. To validate the numerical model, experimental study is made on a single cylinder DI diesel engine. The results show that, by optimizing the combustion chamber shape, the duration of high turbulence in cylinder is prolonged, and the diffuse combustion during the later period of combustion process is enhanced. Therefore a good trade-off of NOx, smoke and fuel consumption is achieved by retardation of fuel injection.