Combustion and emission characteristics of an electronically-controlled common-rail dual-fuel engine

An experimental investigation was carried out to study the effect of injection timing, diesel injection pressure, substitution rate of natural gas as well as engine load on the combustion and emission characteristics of an electronically controlled common-rail diesel/natural gas dual fuel engine. The tests were conducted at a fixed engine speed of 1200 r/min, while other parameters were varied in reference to different study purposes. It can be concluded from the experimental results that maximum in-cylinder pressure and maximum heat release rate as well as the combustion noise are generally increased as injection timing advances and injection pressure increases, while decreases at higher substitution rate. Concerning the emission characteristics, THC and CO emissions could be improved by advancing injection timing and increasing diesel injection pressure with penalty on NOx emissions; in addition, THC emissions are significantly increased at higher load and higher substitution rate, while CO emissions reduce considerably with increasing load but tend to be less sensitive to substitution rate; NOx emissions can be mitigated by application of higher substitution rate and get worse as engine load increases.