Effects of pilot diesel injection strategies on combustion and emission characteristics of dual-fuel engines at part load conditions

The high level of UHC and CO emissions and poor performance are the Achilles heel of the dual-fuel engines at part load condition. In this research, the KIVA-3V code has been used to simulate, and analyze the combustion process of a dual-fuel diesel engine at part loads. To resolve these problems, the effects of three injection strategies including single and split injection timing, and the number of injector nozzle holes have been investigated on engine combustion and emission characteristics. Results indicate that by advancing the baseline injection timing of the diesel fuel from - 17 to - 70 CAD ATDC, the maximum pressure value increases from 46 bars to 84.2 bars, UHC and CO emissions decrease 98% and 99%, respectively, and NOx, emissions increase 339%. In the split injection, the optimum injection timings of pilot diesel fuel are -80 and -60 CAD ATDC for the first and second pulses. In addition, UHC and CO emissions decrease 98% and 99.9%, respectively. Finally, in the third strategy, with increasing injector nozzle holes, ignition and combustion start earlier, and the maximum pressure value, NOx, and CO emissions increase, but UHC emissions decrease.