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

•The effect of diesel injection strategy in a CH4 dual-fuel engine is investigated.•Diesel injection strategy plays a key role in the development of combustion process.•The split injection strategy has an important benefit in terms of fuel consumption.•Diesel pre-injection is effective in reducing NOx emissions and combustion noise.•Early post-injections resulted in improved BTE at low engine load. 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°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.