Study On Characteristics Of Ultrasonic Cavitation In Cylinder And Breakup And Evaporation Of Fuel Droplets With Bubble

The fineness of fuel crushing is an important factor to determine the combustion efficiency of internal combustion engines,it is also a decisive factor in promoting energy conservation and emission reduction.This paper proposes to feed ultrasonic energy into the combustion chamber,to excite the internal cavitation core of the fuel liquid,produce ultrasonic cavitation.The characteristics of breakup and evaporation of fuel droplets with cavitation were studied.This paper provides theoretical support for the research of new catalytic combustion technology of internal combustion engine.Based on Rayleigh-plesset equation,considering the influence of in-cylinder environment and ultrasonic attenuation,a dynamic model of a single cavitation bubble in a fuel liquid excited by ultrasound is derived.The dynamic characteristics of cavity under different ultrasonic and liquid parameters were obtained by comparing the change of cavity size with and without cylinder.Based on the VOF multiphase flow model,a two-dimensional simulation model of single bubble ultrasonic cavitation is built by Fluent software.Using UDF to simulate the change of ultrasonic pressure,the numerical simulation of the collapse process of a single bubble excited by ultrasound was carried out,and the cloud images of the bubble shape,pressure and velocity flow field were obtained respectively in the first and second stage of the collapse.The pressure limit and the velocity of the central jet caused by the cavitating collapse are analyzed,and the effects of different ultrasonic pressure amplitudes on bubble collapse were compared.A two-dimensional simulation model of single fuel droplet(including cavitation)was established.With single-phase droplets as the contrast object,the process of deformation and breakup of droplets with cavitation bubble in gas flow is simulated under different Weber numbers.The effects of the presence or absence of the bubble and the initial radius of the bubble on the equivalent diameter and the breakup time of droplets were analyzed and compared.The model of droplet heat transfer was analyzed by the change of flow field temperature in the process of droplet evaporation.The mass evaporation rate was used to measure the evaporation efficiency of droplets with or without bubble and with different initial radius...