Research On The Deformation And Brokencharacteristics Of Single Droplet In The Heated Airflow

On the background of the process of broken and atomization that fuel occur in the high temperature and high speed envirament of engine combustion, putting forward the subject which the mechanistic research on the deformation and broken characteristics of a droplet in the heated airflow. This research begin with three kinds of methods which contain the basic theory, numerical simulation and experimental analysis. Research on the mechanistic issue that deformation-broken characteristics and broken patterns of droplet in the heated airflow.The researchful results show that: the deformation and fragmentation process of droplet is caused by the interaction between aerodynamic force which causes droplet to deformate and break with surface tension and viscous force which hinder this process to happen. The surface tension of droplet is far greater than the viscous force when the droplet stadys at Cold air, mainly considering the aerodynamic force and surface tension effects on the deformation and breakage of droplet. With the increasement of droplet temperature, the surface tension coefficient of droplet begins to decrease,means that reduce the surface tension,when happen in the condition of evaporation, the surface tension of the droplet tends to zero.The main different mechanisms between cold airflow and heat airflow have the following two points:⑴With air temperature increased,the resistance in the process of droplet deformation and breakage happen to transform,based on WE parameter which seem as the variational law of characteristic parameters in the process of droplet deformation and breakage in the cold airflow,now will no longer fit the processe of droplet deformation and breakage in heat airflow.⑵Due to thermal evaporation, the liquid film which is generated in the cold airflow will reduce the time of presence in heat airflow,and the developmental process of the droplet deformation and breakage in gas will be changed.Through the experimental method,research the dimensionless time of deformation,the dimensionless time of broken,the rate of droplet deformation, the variational rule of droplet group after the droplet breaken,then improve the characteristic study of droplets in the heat airflow.And research the variational rule which the rate of droplet deformation along with the change of WE parameter,the influences which initial diameter of droplet and relative velocity of gas-liquid on the rate of droplet deformation,finally verify mechanism that the theory of droplet internal flowing in the process of droplet breakage.Based on the experiment,utilize the VOF method and k-epsilon turbulent model to combine with a user-defined function of heat transfer and evaporative model UDF, research on the deformation and fragmentation process of droplet in the heated airflow by using numerical simulation with the different experimental conditions,finally completed to compare with experimental method and optimize the experimental conclusion.