| The development of biomass fuels is currently an effective way to address energy shortages and environmental pollution problems.Among them,Jatropha biodiesel has been widely studied by scholars at home and abroad because of its wide source and clean emissions.However,the density and viscosity of jatropha biodiesel are relatively large,which affects the atomized combustion of fuel in the cylinder.Adding butanol to Jatropha curcas biodiesel can not only improve the gasification ability of biodiesel in the process of evaporation and combustion,but also effectively reduce the emission of pollutants from diesel engine.In this paper,taking butanol/jatropha biodiesel as the research object,the single-drop evaporation test device was used to carry out the experimental study on the single droplet evaporation characteristics,micro-explosion mechanism and parameter influence of butanol/jatropha biodiesel.This paper first introduces the preparation process and method of butanol/jatropha biodiesel.Pure jatropha biodiesel was prepared by alkaline transesterification method,and different volumes of butanol were directly mixed into pure jatropha biodiesel by direct mixing method to obtain test oil.The composition of the single-drop evaporation test apparatus and the test operation method are described in detail.With the help of the matlab tool to calculate and process the image data,the automatic extraction of the diameter data of the droplet evaporation process is realized.Secondly,the accuracy of the test device was verified by repeating the test several times.The single-droplet fuel droplets with BUT20(20% mixed with butanol biodiesel)were used as the research object.The evaporation characteristics of butanol/jatropha biodiesel were studied by single droplet evaporation test.And combined with the evaporation time of each stage of the droplets,the evaporation rate of the fuel droplets and the morphology of the single droplet evaporation process,the micro-explosion mechanism of the droplets at low temperature(773K)and high temperature(973K)was obtained.The influence of three major factors affecting droplet evaporation(the mass fraction of butanol blended in the droplet,the ambient temperature and the initial volume of single droplet)on the evaporation of the droplets was also studied.The fuel evaporation characteristics were comprehensively analyzed by combining the droplet normalized diameter squared characteristic curve,evaporation time of each stage,fuel droplet evaporation rate and single droplet evaporation process morphology.The results show that the BUT20 fuel evaporation is stable and slow at low temperature,and there is obvious expansion and micro-explosion phenomenon when BUT20 fuel single droplet evaporation at high temperature.When butanol is blended in the jatropha biodiesel,the larger the blending ratio,the more the decomposition and evaporation of the droplets are promoted.The initial volume of the droplet has an effect on the evaporation rate of the fuel droplet,but the effect is not significant.With the increase of ambient temperature,the characteristics of the single droplet evaporation of butanol/jatropha biodiesel showed obvious changes,so the liquid droplet temperature had the greatest influence on the evaporation process of fuel droplets.Finally,based on the evaporation model of infinite heat and mass transfer,a multi-component droplet evaporation model combined with thermal radiation is proposed.The evaporation rate of butanol/fatty acid methyl ester fuel droplets was calculated and the calculated values were compared with the experimental values.The results show that the simulation results can be consistent with the experimental results.By simulating the evaporation process of droplets,the variation law of fuel evaporation with temperature can be obtained,which provides a theoretical basis for revealing the micro-explosion mechanism and the influence law on atomization characteristics. |
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