Advancing the start of diesel injection timing is an effective way to enhance thermal efficiency and reduce greenhouse gas (GHG) emissions of natural gas/diesel dual-fuel (NDDF) engine. However, severe thermodynamic conditions under high engine load conditions may increase the propensity for engine knocking when advancing the start of diesel injection (SODI). In this study, the strategy of split diesel injection (two-pulse injection) is used and its feasibility as a method to reduce knocking intensity and improve thermal efficiency of NDDF engine is investigated. The results reveal that advancing single diesel injection timing significantly increases knocking intensity, whereas split diesel injection strategy decreases knocking intensity. The results also show that, when using split diesel injection, the flame kernels do not propagate as fast and deep as in the case of single diesel injection. This slows down the pressure and temperature rise rate in the unburned end-gas region and thus reduces knocking tendency. Moreover, the early partially burning of the premixed natural gas – air mixture in the squish region dilutes the unburned end-gas and consequently makes it resistant to auto-ignition. NDDF engine with split diesel injection can reach a maximum thermal efficiency that is comparable to that observed under knocking conditions of single diesel injection. Using either, single or split, diesel injection strategy reduces GHG emissions of NDDF engine (up to 12%) compared to its counterpart diesel engine. However, the lowest GHG emissions of NDDF engine with single diesel injection strategy is recorded under knocking conditions.

提前开始柴油喷射正时是提高热效率并减少天然气/柴油双燃料（NDDF）发动机温室气体（GHG）排放的有效方法。但是，在推进柴油喷射（SODI）时，高发动机负载条件下的严酷热力学条件可能会增加发动机爆震的可能性。在这项研究中，使用分流柴油喷射（两脉冲喷射）策略，并研究了其作为降低爆震强度和提高NDDF发动机热效率的方法的可行性。结果表明，提前单次柴油喷射正时会显着提高爆震强度，而分体柴油喷射策略会降低爆震强度。结果还表明，使用分流柴油喷射时，火焰核的传播不像单次柴油喷射那样快而深。这减慢了未燃烧的尾气区域中的压力和温度上升速度，从而降低了爆震趋势。此外，在压缩区域内，预混天然气和空气混合物的早期部分燃烧会稀释未燃烧的终端气体，因此使其具有抗自动点火的能力。采用分流柴油喷射的NDDF发动机可达到的最大热效率可与单柴油喷射爆震条件下观察到的相比。与同类柴油发动机相比，采用单发或分流柴油喷射策略可减少NDDF发动机的温室气体排放（最多12％）。但是，在爆震条件下，采用单柴油喷射策略的NDDF发动机的温室气体排放最低。