Study On Spray And Combustion Characteristics Of Emulsified Diesel Blending With Water

Facing the increasingly serious energy situation and environmental protection pressure, how to solve the problem of internal combustion engine emissions and fuel shortages became an important issue in the field of internal combustion engine research. Emulsified diesel blending with water is a kind of idea alternative energy sources because of its good characteristics of energy conservation and emissions. This paper explored a visualization research on spray and combustion characteristics of emulsified diesel blending with water by using a constant volume chamber system combined with schlieren method and high-speed camera, study the influence of different environmental factors on the emulsified diesel spray and combustion characteristics, meanwhile we study the contrast of pure diesel and similarity and difference of emulsified diesel spray and combustion characteristic, deeply discuss the mechanism of emulsified diesel energy conservation and emissions reduction, promote the application of emulsified diesel in the actual engineering.First, this paper studied spray and combustion characteristics of emulsified diesel under different environmental factors, analyzed it around the effect of environmental conditions on the ability of spray entraining air, fuel crushing ability, temperature rise and distribution of equivalence ratio. The result shows that, with the increase of injection pressure, the ability of spray entraining air becomes stronger, the ignition delay and combustion duration becomes shorter and the INFL and the combustion area also becomes smaller. Increasing the oxygen content can significantly increase the environmental temperature and reaction speed, so that the INFL and combustion area become much bigger. Higher ambient temperature leads to shorter ignition delay and LOL, and the INFL become much brightness, makes more SOOT generation. However, increasing the ambient temperature can accelerate the oxidation and decomposition of SOOT, leads to a rapid decay of INFL and combustion area in the late period of combustion. With the increase of ambient density, emulsified diesel spray can entrains more air, so that the temperature rise of mixing air is faster, the higher local temperature leads to ignition sooner. But high ambient density makes the peak of INFL obviously increased, which means the rate and density of SOOT generation increased largely. Increasing the water content of emulsified diesel can make ignition delay longer, but it can shorten the combustion duration, and the INFL and high brightness area of emulsified diesel is much smaller and uniform than diesel.Then, this paper carried on a comparative study of diesel and emulsified diesel blending with 20% water(W20), we study the spray and combustion flame structure of these two fuels, and the result shows that, within the range of this paper's experimental condition, the W20's ignition delay, INFL and combustion area under the same condition are all smaller than the diesel, which indicates that the emulsified diesel blending with water can effectively reduce the generation of SOOT, at the same time,due to the high temperature can promote the phenomenon of “micro explosion” and water gas reaction, so under the condition of high temperature, emulsified diesel can inhibit the generation of SOOT more significantly. This paper also found W20 has a threshold point between 7.5kg/m3 and 10kg/m3 which affect the ability of spray entraining air, this threshold point determines the speed of temperature rise of mixing air and whether the temperature of mixing air can quickly achieve the fuel pyrolysis temperature, it also determines whether the emulsified diesel's combustion reaction jump from low temperature combustion phase to heat flame reaction phase, however, diesel doesn't have such a threshold point among this paper's experimental conditions.