Improved combustion performances and lowered emissions of CNG-diesel dual fuel engine under low load by optimizing CNG injection parameters

The reduced amount of pure air entering a cylinder caused by the existence of CNG fuel in the cylinder, causing a decrease in volumetric efficiency on dual fuel engine, which has a negative effect on combustion performances and emissions especially carbon monoxide and hydrocarbon. The injection parameters of CNG fuel include the timing and duration of injection have an important role as the initial control of the injected CNG fuel and the volume of CNG fuel put into the cylinder through the air inlet. Thus, the amount of pure air that enters can be conditioned through these two parameters, in order to obtain the volumetric efficiency and ideal fuel-air mixture so that it can improve combustion performances and emissions on dual fuel engines under low load. This research was conducted on CNG-diesel dual fuel engine by optimizing the timing of CNG injection from 70° to 150° ATDC and the duration of CNG injection from 70° to 150°CA with 20° intervals at low load. The results explained that by retarded the timing of CNG injection (130° ATDC) yielding a value of cylinder pressure and heat release rate (HRR) was the highest with emissions of hydrocarbon (HC), carbon monoxide (CO) and particulate matter (PM) were lower and also the amount of CNG volume inserted into the cylinder was more large with optimal CNG injection duration of 110°CA on CNG-diesel dual fuel engine under low load.