Numerical Simulation And Optimization Of Supersonic Spray Nozzle

With the rapid development of China railway transportation,the requirements for the production and manufacture of high-speed trains are getting higher and higher.Putty spraying is an indispensable process in the manufacturing process of rail vehicles,which can improve the surface roughness of the car body and improve the appearance.During the spraying process,controlling factors such as the size,distribution and velocity of the atomized particles of the putty can improve the quality of the putty coating.In this thesis,a novel nozzle structure for spraying putty is proposed to improve the atomization effect.Based on the CFD method,the numerical simulation of gas-liquid two-phase flow was carried out on the designed spray nozzle by using the fluid simulation software Fluent.First,the distribution of the atomization flow field inside and outside the nozzle and the distribution of atomized droplets are obtained;secondly,from the structural parameters of the nozzle,the influence of different structural parameters on the atomization performance is studied,and the structural parameters are analyzed based on the response surface method and genetic algorithm.Optimized;finally,the influence of working parameters on atomization performance was studied based on the optimized structure.The main contents of the research are as follows:Numerical simulation of nozzle atomization was carried out with putty as the liquid material.The study found that: after the atomized droplets are ejected from the nozzle outlet,the droplet distribution is roughly conical,and the droplet diameter gradually decreases with the increase of the axial distance.The diameter of the atomized droplet in the central part of the sampling section is larger than that of the surrounding The droplet diameter is large.The influence of three structural parameters on the atomization effect is studied by studying the diameter of the liquid inlet,the position of the liquid inlet and the angle between the liquid inlet and the axis.The results show that: the smaller the diameter of the liquid inlet,the better the atomization effect;the position of the liquid inlet close to the nozzle outlet,the better the atomization effect;the smaller the angle between the liquid inlet and the axis,the better the atomization effect.Based on the response surface method,the influence of the diameter of the liquid inlet,the position of the liquid inlet,and the angle between the liquid inlet and the axis on the atomization effect was studied.The study found that the diameter of the liquid inlet had the most significant influence on the atomization effect,followed by the angle between the liquid inlet and the axis,and the position of the liquid inlet had the least significance.And through the analysis of the obtained three-dimensional response surface,the interaction between the diameter of the liquid inlet and the angle between the liquid inlet and the axis is the strongest.A genetic algorithm is used to solve the optimal structural parameters.After calculation,the diameter of the liquid inlet is 0.05 mm,the position of the liquid inlet is 2.5mm,the angle between the liquid inlet and the axis is,and the corresponding average particle diameter is 3.7145μm.According to the obtained structural parameters,the model is reconstructed,meshed,and the error between the average particle diameter and the predicted result obtained by simulation calculation is less than 0.05%,indicating that the optimization has certain reliability.The influence of working parameters on the atomization effect was studied.The study found that: with the increase of liquid feed velocity,the atomized droplet Sotel particle diameter(SMD)increased,and the atomization cone angle did not change;with the increase of injection pressure,the atomized droplet Sotel particle diameter(SMD)It gradually decreases,and the atomization cone angle gradually increases.