Investigation of combustion and emissions of natural gas-diesel dual-fuel PPCI engine

Premixed combustion concepts like HCCI and PPCI have attracted much attention, since these concepts offer possibilities to reduce engine out emissions to a low level, while still achieving good efficiency. Recently researchers have shown that premixed combustion concepts with two fuels with a large difference in auto-ignition properties can generate a spatial gradient of fuel-air mixtures and reactivity offers improved fuel efficiency and lower NOx and smoke exhaust emissions when compared to conventional diesel diffusion combustion due to longer ignition delay. The increased availability of natural gas in the world has renewed interest in order to realize fuel cost savings and reduce pollutant emissions due low carbon content. Thus, premixed combustion using natural gas as a less reactive fuel and diesel fuel with a higher reactivity fuel warrants consideration. This study presents results from an experimental study of Natural Gas-Diesel premixed operation on a single cylinder diesel engine. After that, a computational study using the CFD software has been conducted to investigate the in-cylinder phenomena in different situations. The results reveal both low NOx and smoke emissions can be achieved in dual fuel PPCI concept in compared to conventional diesel but at the expense of increasing of unburned hydrocarbon emissions.