Experimental Investigation of Multiple injection strategies on combustion stability, performance and emissions in a Methanol-Diesel Dual fuel Non-Road engine 2020-01-0308
In this work methanol was port injected while diesel was injected using a common rail system in a single cylinder non road CI engine. Experiments were conducted with single (SPI) and double (DPI - pilot and main) injection of the directly injected diesel at 75% load and a constant speed of 1500 rpm. The effects of methanol to diesel energy share (MDES) and injection scheduling on combustion stability, engine efficiency and emissions were evaluated. Initially in the SPI mode the methanol to diesel Energy Share (MDES) was varied while the injection timing of diesel was always fixed for best efficiency. Increase in MDES resulted in reduction in NOx and smoke because of the high latent heat of vaporization of methanol and the oxygen available. Enhanced premixed combustion led to a raise in brake thermal efficiency (BTE). Combustion stability i.e. coefficient of variation of IMEP and peak pressure was deteriorated which limited the MDES to 50%. DPI of diesel i.e. early pilot for enhancing the reactivity of the charge and main for combustion phasing, was then applied at a fixed diesel quantity corresponding to about 50% MDES. The injection timings of the pilot and main and their relative quantities were varied and optimized based on BTE. An increase in pilot quantity improved the combustion stability. There was a small decrease in the BTE with SPI which was restored when pilot injection was employed. When compared to neat diesel operation, SPI at 50% MDES reduced NOx and smoke emission by 49% and 91% respectively. Further reductions in NOx and smoke and enhancement in MDES along with improved combustion stability were possible with DPI. The paper will present and discuss detailed results on heat release, combustion stability, performance and emissions at different MDES values and injection strategies.