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 at a constant speed of 1500 rpm. The effects of methanol to diesel energy share (MDES) and injection scheduling on combustion stability, 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 brake thermal efficiency (BTE). Increase in the MDES resulted in a reduction in NOx and smoke emissions 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). Coefficient of variation of IMEP, peak pressure and BTE were deteriorated which limited the usable MDES to 43%. DPI of diesel i.e. early pilot for enhancing the reactivity of the charge along with main injection for combustion phasing, was then applied at a fixed diesel quantity corresponding to an MDES of about 50%. The injection timings of the pilot and main and their relative quantities were varied and optimized based on the BTE. An increase in the pilot quantity improved the combustion stability and the values of COV of IMEP were lesser than 2%. When compared to neat diesel operation, SPI at 50% MDES reduced NOx and smoke emissions by 49% and 91% respectively. Further reductions in NOx by 14.5% and enhancement in MDES to about 53% along with improved combustion stability were possible with DPI.