Effect of Diesel Multiple Injection on Marine DMCC Engines

To investigate the effect of pilot injection on the performance, combustion, and gas emissions of marine diesel/methanol compound combustion(DMCC)engines, a marine diesel engine was modified into the one featuring DMCC combustion mode. Further, bench tests for the marine DMCC engine were conducted in pure diesel mode and diesel/methanol dual fuel mode under three normally used operating cases, i. e., 25%, 50%, and 75% of the full load with propeller characteristics. The testing results display that, in dual fuel mode, a pilot injection strategy can significantly increase methanol replacement rates and reduce brake specific fuel consumption(BSFC). Moreover, the higher the load, the larger the reduction in BSFC. When the pilot injection strategy was applied, ignition was initiated earlier;this change was more obvious in dual fuel mode than in pure diesel mode. When the pilot injection strategy was applied in the dual fuel mode, the peaks of the heat release and pressure rise rates remarkably declined; at the same time, the constant volume combustion ratio and the thermal efficiency increased. And NOx emissions remarkably decreased in dual fuel mode by 24.97%, 37.98%, and 40.02% for 25%, 50%, and 75% operating cases, respectively. Further, PM emissions increased slightly but remained lower than that in pure diesel mode without pilot injection. © 2020, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.