The impact of methanol injecting position on cylinder-to-cylinder variation in a diesel methanol dual fuel engine

Methanol fumigation strategy in multi-cylinder diesel engine has received great attentions in recent years. Experimental work was conducted in a turbocharged inline 4-cylinder diesel engine fueled with diesel methanol dual fuel (DMDF). Three different methanol injection positions were chosen to investigate into their effect on cylinder-to-cylinder variation. The results indicate that the unevenness degree of each cylinder reduces as injection timing of diesel (ITd) retarded. The unevenness degree of engine is better when methanol injectors are fixed at intake manifold (Case 1) and at distal end of inlet duct (Case 2) than fixed at near end of inlet duct (Case 3). The cylinder-to-cylinder variation has a tendency to increase with an increase in methanol substitution percent (MSP). With the increasing engine load, the COVIMEP of 4 cylinders reduces. In addition, the COVIMEP rises with an increasing MSP under 50% and 75% engine loads, while it has no significant change under 100% engine load. The COVpmax first increases and then decreases with the increase in engine load, and it has the maximum value under 75% engine load. Although there is a linear increase in the THC and CO emissions with the increase in MSP, the difference of THC and CO emissions between the three cases is very small under various engine loads. Under 50% and 75% engine loads, the soot emission in all three cases decreases slowly with the increase in MSP, and the difference of soot emission in three cases is small. Under 100% engine load, the soot emission in three cases first increases and then decreases with the increase in MSP, and the emission gaps fall apart further with the increase in MSP.