The Simulation Of The Characteristics Of Gas-liquid Diesel Droplet Evaporation And Droplet Impingement

Energy-saving and emission reduction is the eternal theme of the development of the automotive industry.Fragmentation,atomization and evaporation of fuel droplets and their mixing with air are of great importance for improving engine economy and improving emissions.The key to developing efficient and low-pollution engine technology is to improve the mixing process of atomization and evaporation of the fuel jet in the engine cylinder through various technical means.The gas-liquid droplet spray can significantly improve the combustion and emission characteristics of the engine.Therefore,the basic research on the droplet evaporation characteristics of gas-liquid diesel was studied in this paper.Then the characteristic of droplet impingement when impacting on heated wall was also researched based on the influence of droplet evaporation.The research work can enrich the research contents of droplet evaporation characteristics,and provide the theoretical basis for more fully evaporating fuel droplets and air mixing.In this paper,the bubble growth process was simulated based on the bubble dynamics and the one-dimensional bubble growth model.The growth process of gas bubbles in the gas-liquid diesel droplets was researched.The two-dimensional model of liquid droplet evaporation was established.FLUENT software was used to study the growth,fragmentation and evaporation process of gas-liquid diesel droplets in high temperature environment.The effects of ambient temperature,initial bubble radius and gas-liquid properties on the growth,fragmentation and evaporation of gas-liquid droplets were analyzed.Secondly,the process of gas-liquid droplet fragmentation and evaporation in convective environment was studied.First of all,the single phase diesel droplet was analyzed in the convective environment,such as oscillating deformation,bag breaking,multiple mode fragmentation and shear breakup.The droplet morphology and evaporation characteristics of gas-liquid diesel droplets in high temperature convective environment were studied emphatically.The effects of ambient temperature,ambient pressure and initial diameter of bubble on the droplet breaking and evaporation characteristics of gas-liquid diesel droplet were researched.Next,the evaporation characteristics of droplet under high temperature and pressure environment and under supercritical conditions were studied.The influence of ambient temperature,initial temperature of liquid droplet and initial diameter of droplet on the evaporation process was analyzed.The evaporation model was modified under supercritical conditions.The effects of ambient pressure,ambient temperature,droplet initial temperature and droplet initial diameter on the evaporation characteristics in supercritical environment were researched.Finally,the combined Level Set-VOF method is used to study the effect of droplet evaporation and heat transfer on the rebound and fracture of the droplet impacted on heated surface.The Leidenfrost phenomenon was observed when the droplet hit the heated wall.The influence of wall temperature,droplet initial diameter and impact velocity on the heated wall motion of the droplet was studied.The critical conditions of the movement of the droplet on the heated wall were also put forward.