Experimental Study On Dual-fuel Compression Ignition Engine Fueled With Coal-based Methanol/PODE

Nowadays more and more researches focus on reducing engine emissions,increasing thermal efficiency and finding ideal alternative energy.Engine using dual-fuel compression ignition combustion mode can get high thermal efficiency and ultra-low PM and NOx emissions,which is helpful to achieve energy conservation and emission reduction of internal combustion engine.Because of excellent performance of combustion and emissions,coal-based methanol and PODE can catch the alternative energy researchers' attention gradually.In this thesis,using high latent heat of vaporization,high octane number fuel(coal-based methanol)and low viscosity,high cetane number fuel(PODE)to form the whole coal based dual fuel composition.With the affects of methanol energy proportion,compression ratio and PODE supply advance angle on combustion,economy and emission characteristics of methanol/PODE dual-fuel compression ignition combustion mode is studied by a series of bench test,and compared with previous research results,to analyze the ability of this combustion mode to alleviate the problem of high THC and CO emission at light load and combustion roughly at heavy load.The results show that:(1)Engine using the methanol/PODE dual-fuel compression ignition combustion mode,the heat releases rate curve has obviously “double-peak” shape.The pressure rises rate,the heat releases rate and effective thermal efficiency are higher than original engine.The maximum pressure and the maximum temperature are same as original engine.NOx emissions can be reduced significantly,but THC,CO,HCHO and methanol emissions increased.(2)The pressure rises rate and the heat releases rate increased with increment of fuel supply advance angle,and the maximum of pressure and temperature raised in high speed,however in low speed operating condition,the change of the fuel supply advance angle lead to the decline of pressure and temperature.With the decrease of fuel supply advance angle,the thermal efficiency is increased slightly,and emissions of NOx and HCHO are reduced.The change of fuel supply time has a limited impact on THC,CO and methanol emissions.(3)The maximum of pressure and temperature,the pressure rises rate and the heat releases rate are increased with the reducing of compression ratio in high speed operating condition,but it's harmful to thermal efficiency and the emission of NOx,CO and methanol.THC emissions are increased in low speed,decreased with the speed increases gradually,and finally the THC emission is close to the original engine.The change of compression ratio not affects HCHO emission.(4)Engine using methanol/PODE dual-fuel compression ignition combustion mode,cannot improve the problem that rough combustion in heavy load,but the emission of THC is decreased significantly in light load,and CO emissions are reduced slightly.A new way to achieve dual coal-based fuel compression ignition combustion mode is developed,which is not only solve the common problem of dual-fuel compression ignition that high emission of THC,but also has great significance for the clean utilization of coal resources.