Experimental Study On Low Temperature Combustion Fuelled With N-Butanol-Diesel-PODE_3-4 Blended Fuels

Low Temperature Combustion(LTC)for n-butanol/diesel blendings is considered as a new combustion process for diesel alternative fuel and widely investigates in the word.NOx and Soot emissions can be simultaneously reduced due to the lowered combustion temperature by adopting large amount of exhaust gas recirculation(EGR).However,the reduction of Soot emission is very limited due to its low oxygen content.At the same time,the CO and HC emissions increase due to the low cetane number value and low ignitability of n-butanol.The addition of PODE3-4 can solve the problem of low combustion efficiency because of the high cetane number value,high ignitability and high oxygen content of PODE3-4,and further reduce the Soot emission of n-butanol/diesel blended fuel.Based on this,in this paper the low temperature combustion was realized by using fuel injection strategy coupling EGR.Experimental studied the effects on combustion and emissions characteristics of diesel engine under low temperature combustion fueled with pure diesel(denoted D100),diesel blended with 20%n-butanol by volume(denoted BD20),diesel blended with 20%PODE3-4 by volume(denoted PD20),and the BD20 blended with 10%and 20%PODE3-4 by volume(denoted BDP10 and BDP10,respectively).The results shown that,at the BMEP0.4-0.8MPa,the time of heat release for pilot injection phase and the time of heat release for main-injection phase of BDP20 delayed most,followed by BDP10,BD20 and D100,the peak in-cylinder pressure and heat release rate for main-injection phase of the four fuels in ascending order were D100,BD20,BDP10 and BDP20.At the BMEP1.2MPa,the time of heat release for pilot injection phase of BDP20 delayed most,followed by BDP10,BD20 and D100,the time of heat release for main-injection phase of BDP20 was advanced most,followed by BDP10,BD20 and D100,and the peak in-cylinder pressure and heat release rate for main-injection phase of the four fuels in ascending order were D100,BD20,BDP 10 and BDP20.At the BMEP1.6MPa,the time of heat release delayed in the order D100<BD20<BDP10<BDP20,and the peak in-cylinder pressure and heat release rate in descending order were D100,BD20,BDP 10 and BDP20.With the increase of loads,Soot,CO and HC decreased,NOx increased for the D100,BD20,BDP 10 and BDP20,the accumulation particle number concentration and the total particle number concentration of D100,BD20,BDP 10 and BDP20 all decreased.The nucleation particle number concentration of D100 and BD20 first decreased and then increased,the nucleation particle number concentration of BDP 10 and BDP20 decreased at first,then increased and finally decreased;With the increase of EGR ratio,the in-cylinder pressure,the peak of heat release rate,in-cylinder temperature,maximum pressure rise rate,brake thermal efficiency and combustion efficiency decreased,while the brake specific fuel consumption increased for the D100,BD20,BDP10 and BDP20.At the middle and low EGR(<30%),with the increase of EGR,NOx emission decreased obviously,and there was no obvious change in Soot,CO and HC emissions.At large EGR(>30%),increasing EGR,Soot,CO and HC emissions increased sharply.And with the increasing of EGR,the total particle number concentration first decreased and then increased,total particle mass concentration first had no change and then increased sharply,nucleation particle number concentration decreased,accumulation particle number concentration increased and the particle geometric mean diameter first slowly changed and then increased rapidly;Adopting the pilot-injection strategy,the maximum pressure rise rate,Soot,CO and HC emissions increased,while the NOx decreased,the peak of nucleation particle number concentration decreased,the peak of accumulation particle number concentration,particle geometric mean diameter,total particle number concentration and total particle mass concentration for D100,BD20,PD20 and BDP20 all increased;With the increase of injection pressure,the spray penetration of D100,BD20,PD20 and BDP20 increased,spray quality improved,the time of heat release advanced,the peak of in-cylinder and heat release rate increased,maximum pressure rise rate increased,Soot and HC emission decreased,NOx emission increased,CO emission had no obviously change,the peak of accumulation number concentration,total particle number and mass concentration decreased.In addition,diesel blending with n-butanol prolonged the ignition delay period,and the combustion duration decreased,brake thermal efficiency increased,combustion efficiency decreased,brake specific fuel consumption increased,Soot emission decreased,NOx,CO and HC emissions increased;After the addition of PODE3-4 in n-butanol/diesel blended fuel,the time of heat release advance,combustion rate increased,the peak of heat release rate and in-cylinder pressure increased,the brake thermal efficiency and combustion efficiency further increased,Soot emission further increased,and the CO,HC,accumulation particle number concentration and total particle mass concentration decreased compared with BD20.