Effect of diesel injection strategy on performance and emissions of CH₄/diesel dual-fuel engine

Methane/diesel dual-fuel combustion technology has the potential to reduce emissions of nitrogen oxides (NOx) and particulate matter (PM). However, this combustion mode still suffers from low thermal efficiency, high levels of unburned hydrocarbons (HC) and carbon monoxide (CO) emissions under low-load conditions. In the current study, experimental research was conducted to investigate the effect of diesel injection strategy, including single and split injections, on the performance and emissions of a methane/diesel dual-fuel engine. The experimental tests were carried out on a single-cylinder diesel engine at 1500 rpm under different engine load conditions. The results revealed that split injection strategy has a significant impact on the combustion of the dual-fuel engine. Moreover, the brake thermal efficiency increased by an average of 25.6 % compared to the single injection strategy at low load. Brake specific fuel consumption decreased by 20.4% with a pre-injection timing of 11 degrees bTDC at 20% engine load. Further, the pre-injection strategy contributed to the simultaneous reduction of NOx and combustion noise with a slight reduction of HC emissions. Finally, the inclusion of early post-injection resulted in improved brake thermal efficiency. NOx emissions decreased slightly, by delaying the post-injection timing for low to medium loads.