Study On Spray And Combustion Characteristics Of Diesel/Furan Blend Fuel Based On Vsualization

With the energy crisis,intensifying environmental problems and increasingly stringent emission regulations posing further challenges to the development of internal combustion engine,exploring renewable green energy sources has become an effective solution.Furan-based fuels made from wood fibers have high conversion efficiency,their physical and chemical properties are similar to gasoline,and furan,as the fuel with the lowest number of carbon atoms,the most volatile and high oxygen content among them,is considered a very promising fuel for internal combustion engine blending,but there is a lack of research on furan as an internal combustion engine blending fuel.Therefore,a study on the spray and combustion characteristics of diesel/furan blended fuels is carried out to provide a theoretical basis and experimental basis for the application of furan in diesel engine.In this paper,three test fuels were blended with diesel fuel at 0%,10% and 20% by volume,respectively,and were recorded as D100,D90F10 and D80F20.Based on a constant volume combustion chamber,Spray images of the liquid and gas-liquid phases of three fuels at injection pressures of 80 MPa,100 MPa,120 MPa and 140 MPa were taken by the direct-photography and ripple-shadowing methods respectively,images of the combustion of each fuel at each injection pressure were taken by direct photography at a background pressure of 4MPa and a background temperature of 800 K.The spray characteristics parameters were obtained by the background difference method and the inter-frame difference method using Matlab software;the combustion characteristics parameters were obtained by the two-colour method and the binarisation method.Analysis of the experimental data led to the following main conclusions:(1)Blending furan in diesel fuel helps to reduce the amount of liquid phase spray and increase the spray vapor phase ratio,significantly improving the fuel evaporation atomisation effect,with D80F20 showing the best atomisation effect.Compared to D100,the liquid phase spray penetration distance of the blended fuel increased,and the liquid phase spray cone angle and spray area decreased,with the maximum reduction of 36.5% and 56.3% in the liquid phase spray area of D90F10 and D80F20.Compared to D100,the vapor-liquid phase spray penetration distance,spray cone angle and spray area of the blended fuel increased,with the maximum increase in vapor-liquid phase spray area of D90F10 and D80F20 being 12.6% and20.3% respectively.Of the three fuels,D80F20 consistently has the largest percentage of vapor phase spray area.The increase in injection pressure increased both the liquid and vapor-phase spray characteristics of the fuel,which contributed to the atomisation and mixing of the fuel,the effect of furan in reducing the area of liquid phase spray is strengthened,and the effect of furan in increasing the area of gas-liquid phase spray is weakened.,the effect of furan on increasing the vapor phase spray area ratio decreased with the increase in injection pressure.In addition,the blending of furan with diesel fuel reduces the liquid-phase boundary coalescence of the fuel mixture,but increases the vapor-liquid phase boundary coalescence,which helps to improve in-cylinder fuel-air mixing.Compared to D100,the maximum increase in vapor-liquid phase boundary coalescence was 15.9% and 31.2% for D90F10 and D80F20 respectively.The increase in injection pressure contributes to the increase in liquid phase and vapor-liquid phase boundary coalescence of each fuel,and the effect of furan on increasing vapor-liquid phase boundary coalescence increases with the increase in injection pressure.(2)The blending of furan in diesel fuel resulted in a longer stall period,shorter burn duration and a significant increase in combustion temperature.Relative to D100,the of the fuel blend increases,with D80F20 having the largest flame lift-off length.Compared to D100,the KL of the fuel mixture is significantly lower,that is the soot emissions are reduced,with the maximum reduction of 75.4% and 91.5% after the accumulation of D90F10 and D80F20.As D80F20 has the best atomisation,sufficient premixing time and longest flame lift-off length,all of which promote full flame combustion,D80F20 has the lowest soot emissions,even close to 0 at 140 MPa injection pressure.relative to D100,the mixed fuel flame luminous intensity is significantly reduced,with the maximum reduction in total luminous intensity for D90F10 and D80F20 being 49.3% and 76.9%.The increase in injection pressure shortens the stagnation period and combustion duration of the fuel,while the combustion temperature increases,and the difference in stagnation period,combustion duration and combustion temperature between different fuels increases;the flame lift-off length of the fuel increases,and the effect of furan in increasing the flame float length increases;the soot emissions and flame luminous intensity of the fuel decrease,and the effect of furan in reducing soot emission increases,but the effect of furan in reducing the total The effect of furan in reducing the total flame luminosity decreases and then increases with increasing injection pressure.