| As the most efficient mobile power device,diesel has been widely used in our life and military equipment.But,it is difficult to start in a low temperature environment.And our contrary has a vast area and the cold area is widely distributed in winter.Therefore,this problem must be solved.Considering the difficulty of diesel cold start may be due to the large viscosity of diesel oil,poor volatility,and the poor mixing effect of oil and gas in the cylinder,diesel is blended with some relatively light kerosene or gasoline to improve the atomization characteristics of the fuel.Therefore,this paper intends to study the spray combustion characteristics of diesel blended with kerosene or gasoline in a constant volume combustion bomb.A high-speed camera was used to obtain liquid/gas-phase spray,and combustion images under different low-temperature conditions using the method of Mie-scattering,Schileren,and direct photograph respectively.Then Matlab image processing technology was used to extract relevant data of oil and gas organization and ignition characteristics:For the spray characteristics: With the increase of the kerosene or gasoline blend ratio,the liquid fuel spray penetration distance of the mixed fuel is shortened,the cone angle and the volume is reduced;however,there is no significant change in the gas phase spray.With the increase of ambient temperature,the liquid-phase penetration distance and volume of the two types of mixed fuels decreased,but the cone angle did not change significantly;the gasphase penetration,cone angle and volume did not change significantly.With the increase of the environmental density,the liquid and gas phase spray penetration distances and volumes of the two types of mixed fuels decrease,but the cone angle of them increases.For the ignition characteristics: Mixed fuel fires are caused by the blue cool flame,which then quickly turns into a high-temperature yellow flame.With the increase of background temperature and density,the ignition delay time is obviously shortened.With the increase of kerosene blending ratio,the ignition delay period is shortened and then increased.But for gasoline,the ignition delay period increased.With the change of blending ratio,ambient temperature and density,the variation trend of the flame float length and the percentage of blue flame in the total flame intensity of the two types of mixed fuels is consistent with the delayed combustion period.But the flame strength are opposite to the ignition delay time.As the background temperature decreases and the blend ratio of gasoline increases,the misfire rate of the fuel increases,accompanied by the occurrence of unstable combustion.The unstable combustion can be roughly divided into three types: only the blue cool flame appears,the unsteady conversion of cool flames to high temperature hot flames,the stable conversion of cool flame to high temperature hot flame. |
