HC and CO Formation Factors in a PCI Engine

Since the mixture become relative lean and homogeneous when ignition occurs in PCI engines, NOx and PM can be reduced simultaneously. However, HC and CO emissions in PCI engines are higher by one order than conventional direct injection diesel engines.

The influence factors of HC and CO emissions for conventional direct-injection diesel engines have been analyzed by a lot of studies. In spite of the mechanism of HC formation in PCI would different to conventional direct-injection diesel because of injection timing in PCI engine is considerably earlier than that of a conventional diesel engine, there are not many works on HC and CO emissions of PCI engine.

In this study, the characteristics of HC and CO emissions in a PCI engine were investigated by changing combustion chamber geometry (cavity diameter), topland volume, and injection timing. At the same time, the simulations of spray and air-fuel mixture formation were conducted by using GTT code. The relationship between HC and CO formations and mixture distribution was tried to clarify.