Study On The Effects Of Water Content And Dispersed Water Particle Size On Spray Characteristics Of Water Emulsified Diesel Fuels

As one of the most promising alternative fuels for compression ignition engines,water emulsified diesel has attracted much attention because of its potential to reduce soot and NOx emissions and improve combustion heat efficiency.The unique micro-explosion phenomenon in water emulsified fuel is considered to be one of the important reasons for energy saving and emission reduction of water emulsified diesel.Therefore,it is of great practical significance to get insight into the energy-saving and emission-reducing mechanism of water emulsified diesel fuels and the micro-explosion characteristics in the spray and combustion process under the condition of internal combustion engine.In this paper,an electric heating constant volume combustion chamber,a high-power pulsed LED light source and backlight optical diagnostic technology are used to study the effects of water content on the evaporating spray charictristics of pure diesel(W0)and water emulsified diesel fuels with different water content of 10%,20% and 30%(W10,W20 and W30).The results show that the addition of water in diesel fuel can obviously enhance the atomization and evaporation processes of fuel spray.With the increase of water content,the evaporating spray cone angle and volume of the test fuels are increased,and the influence of water evaporation and micro-explosion on the overall expansion ability of the spray is enhanced.With the increase of injection pressure,the evaporating spray penetation of water emulsified diesel is increased,while the quasi-steady spray cone angle remains unchanged as the water evaporation and micro-explosion is enhanced with the rise of injection pressure.And the effects of injection pressure on evaprorating spray process of W30 is strengthed,compared to W10 emulsified diesel.As the ambient density increases,the axial penetration distance of the water emulsified diesel decreases,and the spray cone angle increases as the mass of entrainment air and the promotion effect of the water on the expansion of the spray is increased.The evaporating spray volume of the tese fuels under higher ambient density condition exceeds that of lower ambient density’s with the fully develop of the spray structure,and the influence of ambient density on the spray process is more obvious with the increase of water content.Subsequently,the effects of dispersed water particle size on the evaporating spray charactristics are investigated.Pure diesel(W0)and water emulsified diesel fuels with different dispersed water particle size(W20 and W20-2)are used as test fuels and the dispersed water particle size of W20 and W20-2 is 5.08μm and 6.91μm respectively.The results show that the evaporating spray penetration and spray volume of the water emulsified diesel fuel is increased with the increase of the dispersed water particle size in the emulsion fuel.As the injection pressure increases,the effect of dispersed water particle size of the emulsion fuel on the evaporating spray is gradually reduced.With the increase of ambient density,the evaporating spray penetration and volume of the W20-2 are obviously larger than that of the W20,and the evaporating spray cone angle of the W20-2 is smaller than that of the W20.