Effects of diesel and methanol injection timing on combustion, performance, and emissions of a diesel engine fueled with directly injected methanol and pilot diesel

A three-dimensional simulation model coupled with detailed chemical kinetics mechanism is applied to investigate a diesel engine fueled with directly injected methanol and pilot diesel. The diesel is injected before top dead center (TDC) to act as a pilot, and then methanol is also directly injected afterwards diesel injection as the main fuel. The effects of diesel and methanol injection timing on the combustion, performance, and emissions are investigated. The results show that: advanced diesel and methanol injections have higher in-cylinder pressure peak; and the in-cylinder pressure peak decreases with the increase of dwell. The ignition delay reduces first and then remains unchanged with the increase of dwell. 50% burn point (CA50) increases in a nearly linear way with the increase of dwell. There are four different combustion phenomena with varied dwell. Too small dwell leads to misfire or roar combustion, and too large dwell is detrimental to fuel economy. Advanced diesel and methanol injections contribute to lower equivalent indicated specific fuel consumption (EISFC) and soot emission, but lead to higher ringing intensity (RI) and nitrogen oxides (NOx) emission.