Comparative Study On Spray Characteristics Of Liquid Fuels And Liquefied Fuel

With the proposal of our country’s“dual carbon”goal and the increasingly stringent emission regulations,higher requirements for efficient and clean combustion of internal combustion engines are constantly being put forward.In gasoline direct injection engines,spray characteristics have an important impact on combustion.However,under the current mainstream multi-hole injectors,spray collapse may occur,affecting fuel distribution,which in turn adversely affects combustion and emissions.Existing studies have shown that spray collapse is closely related to the characteristics of single jet.Therefore,in order to optimize the formation quality and combustion performance of the mixture,it is necessary to have a more comprehensive understanding of the jet characteristics.For this reason,gasoline is used to characterize the fuel n-hexane,isooctane and liquefied petroleum gas.Characterization of fuel propane,in-depth study and analysis of its jet characteristics.Under different fuels,the effects of fuel temperature(T_fuel)and ambient pressure(P_amb)on jet width and penetration distance were studied.With the change of T_fuel and P_amb,liquid fuel n-hexane and isooctane show similar laws in the evolution characteristics of jet width and penetration distance,while liquefied fuel propane shows different characteristics.With the increase of T_fuel,the width of the liquid fuel flashing jet near the nozzle increases,and the penetration distance decreases;with the decrease of P_amb,the width near the nozzle increases,and the penetration distance increases.The liquid fuel non-flash-boiling jet morphology is less affected by the T_fuel,while the far-field width increases slightly and the penetration distance decreases significantly with the increase of P_amb.However,with the increase of T_fuel,the width of liquefied fuel decreases,which is different from that of liquid fuel.With the change of back pressure,its width evolution characteristics are similar to that of liquid fuel,and the evolution of penetration distance shows a non-monotonic trend.Due to the competitive relationship between environmental resistance and liquid phase evaporation.The above results show that the jet morphology exhibits complex evolution characteristics with the change of thermodynamic conditions.In order to further understand the core influencing factors of jet morphology,the correlation between the jet width at different axial distance and different control parameters of liquid fuel and liquefied fuel are analyzed.The correlation between the parameters mainly includes the superheat degree R_p,the nucleation rate X,the evaporation amount x,the phase change chemical potential Δμ,and the environmental resistance,i.e.,P_amb.By comparison,it is found that the liquid fuel jet width has a good correlation with x·P_amb^-0.5 and Δμ·P_amb^-0.5,as the correlation coefficient is above 0.89,indicating that the phase transition has been basically completed near the nozzle.but the liquefied fuel propane at different fuel temperatures the control parameter does not show a good correlation,and the propane jet width gradually decreases with the increase of oil temperature under similar control parameters.This phenomenon indicates that with the increase of temperature,propane only relying on flash boiling evaporation is not enough to release superheated heat and its surface evaporation will be significantly enhanced.Therefore,after further fitting the temperature and the above control parameters,it is found that for liquefied fuel,the new control parameter x·P_amb^-0.5·λ·T^-1 and Δμ·P_amb^-0.5·λ·T^-1 shows better correlation with the propane jet width,as the correlation coefficient is above 0.95.