| Promoting industrial energy saving and emission reduction is the key to transforming the economic development mode.While developing and using alternative environmentally friendly biofuels,studying the evaporation and fragmentation of fuel droplets has important practical value for improving fuel atomization,improving engine power,and reducing pollutant emissions.The micro-explosion effect of mixed biofuel gas-containing droplets can fully atomize the fuel and significantly optimize the combustion and emission characteristics in the engine cylinder.In this paper,a single biodiesel / ethanol mixed fuel gas-containing droplet is taken as the research object,a gas-containing droplet simulation model is established,and the bubble growth and micro-explosion characteristics of the gas-containing droplet at normal temperature are studied.Considering mass transfer,the characteristics of evaporation and microexplosion of high-temperature gas-containing droplets and the micro-explosion of high-temperature moving gas-containing droplets are studied.The main research work and results are as follows:Firstly,based on the establishment of a simulation model of biodiesel / ethanol gas-containing droplets,the VOF method is used to study the bubble growth and micro-explosion process of the gas-containing droplets at room temperature.The pressure difference between the inside and outside of the bubbles is explored and analyzed.The influence of droplet initial radius ratio and droplet ratio on the bubble growth and micro-explosion characteristics of gas-containing droplets are studied.Studies have shown that the bubble growth process at room temperature is dominated by the pressure difference between the inside and outside of the bubble.At the same time,the initial radius ratio of the bubble and the different ratios will also affect the growth process of the bubble to a certain extent.When the fuel in the gas-containing droplets is mixed in equal volume,the micro-explosion of the gas-containing droplets is more favorable.Secondly,the research on bubble growth,droplet evaporation and micro-explosion in gas-containing droplets under high temperature environment is carried out,and the micro-explosion process of bio-diesel / ethanol gas-containing droplets at high temperature and the growth characteristics of bubbles during micro-explosion are explored.The evaporation characteristics and micro-explosion characteristics of droplets are studied.The effects of temperature on bubble growth,droplet evaporation and micro-explosion in gas-containing droplets at high temperature are analyzed.The results have shown that within a certain range,the higher the ambient temperature,the greater the pressure difference between the inside and outside of the bubble,the smaller the initial radius ratio of the bubble,and the equal volume of fuel in the gas-containing droplets,the more beneficial it is to promote the micro-explosion of the gas-containing droplets.Finally,the micro-explosion process of high-temperature moving gas-containing droplets is studied,and the morphological changes of biodiesel / ethanol gas-containing droplets during micro-explosion at different airflow rates and different environmental temperatures are investigated.The study has found that aerodynamic force is the key factor for the deformation and micro-explosion of gas-containing droplets that dominate the high-temperature movement.The airflow velocity and ambient temperature will affect the evaporation and micro-explosion characteristics of gas-containing droplets.There are 91 Figures,4 tables and 80 references in this thesis. |
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