Improvement of fuel economy of an indirect injection (IDI) diesel engine with two-stage injection

This paper focuses on the effects of early stage injection and two-stage injection on the combustion characteristics and engine performances of an indirect injection (IDI) diesel engine. In a direct injection (DI) diesel engine, HC emission increases with early stage injection because some of the fuel spray adheres to the cylinder wall and burns in the gap between the piston and the cylinder. On the other hand, since the fuel spray of early stage injection in an IDI diesel engine is injected into an auxiliary combustion chamber such as a swirl chamber, the IDI diesel engine could reduced the HC emission produced from the gap compared with a DI diesel engine. In a two-stage injection IDI diesel engine, NO and smoke emissions are improved when the amount of fuel in the first stage injection is small and the first stage injection timing is advanced over −80° TDC. And 20% improvement in fuel consumption is achieved when the first stage injection timing is advanced over −80° TDC. Conversely, HC and CO emissions of two-stage injection increases compared with that of conventional injection of an IDI diesel engine. However, CO emission can be improved a little when the first stage injection timing is advanced over −100° TDC and the second stage injection timing is retarded over TDC.