Experimental Investigation On The Gasoline /PODE Dual-fuel HPCC Combustion

Highly Premixed Charge Combustion,HPCC,which is based on concentration and reactivity stratification of mixed charge,can achieve ultra-low NO_x and soot emissions with high efficiency over a wide operating regime by introducing low reactivity through early port injection and high reactivity fuel through direct injection.However,there still exist some problems on HPCC,such as low indicated thermal efficiency,high maximum pressure rise rate and soot emissions under heavy load conditions.Gasoline/PODE dual-fuel HPCC can achieve stoichiometric combustion with low NO_x and soot emissions at high load,but the thermal efficiency still needs to be further improved.In this study,the intake parameter and the fuel injection strategy are investigated to control the in-cylinder thermodynamic state and the distribution characteristics of the mixture on a modified single-cylinder engine,to explore the mechanism and control strategy to further improve the combustion and emission of gasoline/PODE HPCC at high load.Firstly,the effects of intake parameters on the HPCC combustion and emission characteristics are investigated.The results show that the total heat capacity of the intake air in the cylinder is the main reason for the maximum temperature of gasoline/PODE HPCC combustion.By reducing the excess air ratio and increasing the total heat capacity of the intake air,both the ignition delay and combustion duration can be prolonged and the maximum pressure rise rate is thus reduced.The combining of air dilution and EGR dilution can significantly improve the indicated thermal efficiency at high load,in addition,both NO_x and soot emissions can meet the emission regulations without post-treatment.Based on the above study,the effects of injection strategies on gasoline/PODE HPCC combustion and emissions are further investigated.Results show that the use of split injection strategy can shorten the ignition delay and advance the auto-ignition timing.With the increasing pilot injection ratio,the effects of injection interval and main injection timing on the maximum pressure rise rate and indicated thermal efficiency are enhanced.Split injection strategy can significantly improve indicated thermal efficiency,THC and soot emissions,however,penalty in maximum pressure rise rate was also observed with such strategy.The use of PODE has the potential to reduce carbon emissions.However,considering the emission and pressure rise rates,single injection strategy appears to be more suitable for gasoline/PODE HPCC.