Experimental Investigation Of Effects Of Pilot Injection And Fuel Properties On Low Temperature Combustion In Diesel Engine

In face of these strict environmental regulations all over the world,high emissions of NOx and soot have been the bottlenecks,which restrict a faster development of the diesel engines.In this paper,the Exhaust Gas Recirculation(EGR)was introduced to realize the low temperature combustion(LTC)mode to decrease the emissions of soot and NOx in a four-cylinder light diesel engine.In the experiment,different pilot injection strategies and blended fuels were used to conduct the comparative study of effects of pilot injection and fuel properties on LTC in diesel engine.Four different fuels including pure diesel(D100)and three blended fuels(D70G30?D70B30 and D70B15G15)were investigated.The results showed that,the addition of gasoline or n-butanol could enlarge the spray cone angle and improve the spray characteristics.Compared to D100,blended gasoline or n-butanol into diesel could reduce soot emissions and lead to an increase in the NOx emission,peak of in-cylinder pressure and heat release rate,in-cylinder temperature,MPRR and BSFC.However,the addition of gasoline or n-butanol to diesel could offset the reduction of combustion efficiency,induced by the adoption of pilot injection strategies.When the EGR rate was higher than 27%,the soot,CO and THC emissions of the four fuels deteriorated rapidly,and the particle number concentration and mass concentration increased.Nevertheless,blended gasoline or n-butanol to diesel could greatly offset the increase of particle emissions,induced by the adoption of high EGR rate.The soot,CO and THC emissions of blended fuels were less sensitive to the variations in the EGR rate.For four fuels,the adoption of pilot injection led to great deterioration in soot emissions.However,the addition of gasoline or n-butanol to diesel could greatly offset the above phenomenon.The smaller pilot-main interval couid resulted in a remarkable reduction of BSFC.The introduction of pilot injection could release the deterioration in the NOx emissions,induced by the addition of gasoline or n-butanol to diesel.Compared to D100,the total particle mass concentration and peak diameter of particle number concentration of blended fuels decreased,and both of them were continued to decrease with the increase of n-butanol blended ratio.Regardless of how of the injection parameters were adjusted,the accumulation number concentration of D100 was always higher than that of blended fuels.The pilot injection strategies could reduce the total particle number concentration,especially for the particle number concentration below 23 nm particle size.The adoption of pilot injection strategies could lead to an increase in Geometric Mean Diameter(GMD)of four fuels.Howecer,the GMD of three blended fuels were always less than that of D100.Additionally,compared to D100,the GMD of blended fuels was more sensitive to the variations in the pilot injection strategies.