Study On Vapor And Liquid Spary Charicteristics Of Diesel-biodiesel-n-pentanol Blends

Internal combustion engine has been widely used in the world because of its high efficiency and stability.However,with the increasing shortage of petroleum resources and environmental pollution,finding efficient and clean alternative fuels has become an important way to solve the problem.As an oxygen-containing biomass fuel,n-pentanol has many advantages,such as high cetane number,high calorific value and good intersolubility with diesel.Biodiesel,which is basically free of sulfur and aromatic hydrocarbons,has good low-temperature start-up performance and similar physical and chemical properties to diesel,so scholars have done a lot of research on it.The quality of the mixture directly determines the combustion characteristics of the cylinder,and the spray atomization process of the fuel is an important part of the formation of the mixture.Therefore,it is necessary to study the vapor and liquid spray characteristics of the diesel-biodiesel-n-pentanol mixture.Based on the self built optical visualization spray test rig,with high speed camera and schlieren instrument,high speed direct shooting and schlieren technology were used to compare the fuel injection pressure(80,120,160 Mpa)and different ambient backpressure(3,4,5 MPa)of pure diesel(D100),D100 mixed biodiesel(DB20)with volume ratio of 20% and DB20 blending volume of 20% amyl alcohol(DBP20)of three fuel.The process of spray gas liquid two phase development was photographed under different ambient temperatures(573,623,673 K).Then,the original image was processed by using the MATLAB image processing program written by ourselves,and the characteristic parameters of the spray gas liquid two phase were finally obtained.The results showed that the liquid phase penetration distance,cone angle and projection area increased,the gas phase cone angle,projection area and boundary gas entrainment decreased,while the gas phase cone angle and boundary gas entrainment increased significantly when n-pentanol was added to DB20.With the increase of injection pressure,the gas penetration distance,cone angle,projection area and boundary gas volume of the three fuel sprays increased significantly.The liquid phase of D100 and DB20 increased with the increase of liquid phase,while the DBP20 liquid phase penetration distance changed little.In addition,the gas phase projection area and boundary gas entrainment of D100 and DBP20 increased significantly with the increase of injection pressure than that of DB20.With the increase of ambient back pressure,the gas phase penetration distance and projection area of the three fuels decrease.Under low ambient pressure(3,4 MPa),the gas phase projection area of DBP20 decreases more than that of D100 and DB20.With the increase of ambient temperature,the liquid penetration,cone angle,projection area and boundary gas entrainment of the three fuels decreased significantly,while the gaspenetration and boundary gas entrainment of D100 and DBP20 increased significantly.In addition,the decreases of liquid penetration distance and cone angle of DBP20 with increasing temperature are larger than those of D100 and DB20,and the gas entrainment of DBP20 increases faster than that of D100 and DB20 at low temperature(573K~623K).