Experimental And Numerical Simulation Study On The Disintegration Process Of An Internal Mixing Air Assisted Atomizer

Air atomization process refers to that the liquid is broken more thoroughly through the strong interaction between the high velocity air stream and the jet liquid,and its atomization effect is better than that of the only liquid phase spray atomization.In recent years,it has been widely used in many fields such as power machinery.Due to the advantages of low air consumption,good atomization performance and not easy to plug,an internal mixing air assisted atomizer is widely used in industry.In this paper,the experimental and numerical simulation methods were used to study two stages of the primary and the second atomization in the air atomization process.On the basis of water and air,the experimental and numerical simulation studies on the flow field of the internal mixing air assisted atomizer were carried out under various water supply pressures(0.3-0.4MPa)and air pressures(0.2-0.7MPa),and results are showed as follows:Firstly,an internal mixing air assisted atomizer’ spray cone angle,flow characteristics,droplet sizes and distribution are studied by the experimental method in this paper.Innovatively,experimental results are used as the input parameters in the numerical simulation study on two stages of the primary and the second atomization.Secondly,the study on the primary atomization stage of the internal mixing air atomization process is mainly focused on the judgment of liquid beam fragmentation and the formation of the initial droplet.According to the analysis of the flow characteristics of the nozzle,it can be seen that the gas-liquid interaction forms the annular liquid film at the exit of the nozzle,and then two kinds of calculation models of primary atomization based on the breakup of annular liquid film are established.The results show that the injection conditions have an important influence on the primary breakup of the internal mixing air atomization.With the increase of the air pressure and ALR,the annular liquid film thickness and the initial droplet size at the exit of the nozzle are gradually reduced.While the annular liquid film thickness and the initial droplet size at the exit of the nozzle are gradually increased with the increase of hydraulic pressure.By contrast,the numerical results of primary atomization are consistent with the experimental results at the exit of the nozzle.Thirdly,the study on the secondary atomization stage of the internal mixing air atomization process is mainly focused on the types of droplet fragmentation and the changes of droplet shape and size during the droplet movement to the spray field,and then the process of droplet fragmentation,collision and aggregation is analyzed.Therefore,the atomization characteristics of the spray field are accurately obtained.In this paper,based on the experimental results,a reasonable control equation and a computational sub-model is selected by FLUENT simulation software,and the spray cone angle,the gas-liquid phase flow and the injection pressure from the experiment are used as input parameters to calculate the droplet size,droplet size distribution and droplet size changes along the axial direction.In addition,the simulation results of simulation software are consistent with the experimental results.