Research On Spray,combustion And Soot Formation Of Ethanol/hydrogenated Catalytic Biodiesel Blends

Green renewable energy is an effective way for internal combustion engines to achieve "carbon neutral" and "carbon peaking".In recent years,ethanol has attracted more interested than gasoline due to its high-octane value,and the premixed gas formed is less prone to ignition than gasoline.Ethanol fuel is a renewable fuel that can be obtained directly through industrial production,and it has a promising future as an alternative fuel.However,ethanol has high latent heat of vaporization and low heat value,and achieving its stable ignition and combustion is a key challenge.Based on this,this project proposed the blending of ethanol with ultra-high activity hydrogenated catalytic biodiesel to address the current scientific frontier problem of unstable ignition and combustion of ethanol fuel by direct injection and compression ignition,and conducted a study on the spray combustion and soot generation characteristics of ethanol/hydrogenated catalytic biodiesel/n-octanol blends by using advanced optical diagnostic technology.The spray atomization,ignition combustion and soot generation patterns of this blends were obtained,providing a theoretical basis and experimental basis for promoting the application of this blends in engines.The main research works and innovations in the full paper are as follows.1.The study of ethanol and hydrogenated catalytic biodiesel blending was carried out,and it was found that n-octanol can be used as a co-solvent for ethanol/hydrogenated catalytic biodiesel blends.The blending process of ethanol/hydrogenated catalytic biodiesel/n-octanol blends was obtained,and the highpressure injection of ethanol blended fuel was realized.The distillation characteristics of blended fuel with different blending ratios were studied.2.The spray,ignition amd combustion characteristics of ethanol/hydrogenated catalytic biodiesel blends were investigated in a constant volume combustion chamber using multiple optics methods.The results show that the spray penetration is limited by the evaporation rate at low temperature.While at high temperature,the evaporation rate of each fuel is faster,and the fuels do not differ much in the spray penetration in the early stage.The liquid length of different fuels increases with the increase of vaporization latent heat under combustion conditions.Under the same operating conditions,the liquid length of the blending fuel in descending order is E30H60O10>E15H75O10>D100.The influence mechanism of vaporization latent heat and cetane number on ignition and combustion is different under different ambient temperature.At 750 K,the higher vaporization latent heat of E15H75O10 leads to a longer ignition delay period than D100.However,with the increase of ambient temperature,the order of ignition delay period from high to low is E30H60O10>D100>E15H75O10.The ignition rate of each fuel is accelerated,and the influence of vaporization latent heat is no longer significant.At this time,the ignition delay period is significantly affected by cetane number.E15H75O10 has comparable ignition and combustion characteristics to diesel fuel in terms of ignition delay and liftoff length.Furthermore,increasing the ambient temperature from 750 K to 900 K reduces the ignition delay by 81.5%.The ignition delay is reduced by 50.6% when the oxygen concentration rises from 15% to 21%.3.The high frequency diffused background-illumination extinction method and two-colore method were applied to investigate the soot formation of methanol/hydrogenated catalytic biodiesel under quasi-steady state and reansient environment,respectively.The experimental results show that with the increase of ethanol ratio in the mixed fuel,the initial generation time of soot is delayed,and the initial position of soot is also farther away from the axial position of the nozzle.Under the same operating conditions,the carbon smoke concentration of D100 is higher than that of E15H75O10 and E30H60O10 blended fuels,and as the ethanol blending ratio in the blended fuel increases,the carbon smoke concentration decreases.The influence of temperature on the carbon smoke generation of ethanol/hydrogenated catalytic biodiesel blended fuel is higher than that of diesel.In transient environments,both E30H60O10 and E15H75O10 blended fuels can achieve stable compression ignition.Under high and low soot conditions,both blended fuels have the maximum soot generation at-25 °ATDC injection timing;Under the same operating conditions,compared to E30H60O10 fuel,E15H75O10 fuel has more soot generation,and E30H60O10 has significantly less flame distribution on the combustion chamber wall.When the appropriate mixing ratio of ethanol and hydrogenated catalytic biodiesel is 15:75,it has similar ignition and combustion characteristics and lower soot emissions to diesel.4.The combustion reaction mechanism of ethanol/hydrogenated catalytic biodiesel/n-octanol blends was constructed,and a three-dimensional numerical model of the engine was established to verify the accuracy of the combustion model.Numerical simulations were conducted on the combustion and emissions of E15H75O10 blends at different pre-injection times under high carbon smoke conditions.It was found that at the pre-injection time of-25 ° ATDC.The combustion center of gravity is closer to the top dead center and has the lowest emissions of particulate matter,carbon monoxide,and unburned hydrocarbons;When the proportion of pre-injection fuel injection is 20%,the combustion produces the smallest emissions of particulate matter,carbon monoxide,and unburned hydrocarbons.