Numerical Investigations Of The Effect Of Particle Diameter And Carry Gas On Gas-particle Two-phase Impinging Velocity In Cold Spraying

This paper is supported by National Natural Science Fund with the detailed theme of the cold aerodynamics spray coating functional mechanism research.Supersonic cold gas dynamic spray is a new technology to form a high quality coating.Owning to many advantages,it has attracted significant attentions from scholars home and abroad.But as a newly-developed technology,it is short of perfect theory and the coating quality and the spray efficiency should be improved.Moreover,the supersonic gas flow is difficult to be experimentally observed during the cold spray process,therefore,numerical method was also employed to reproduce the complex flow field and then find some effective methods to optimize the experimental program.It has been widely recognized that the numerical method takes an important role in the investigation on cold spraying.The compressible axisymmetric N-S equations are discredited by using the finite volume method.The flow field of the impinging jet outside the nozzle is simulated in this paper.The non-structural grid was used to mesh the flow field.The S-A turbulence model is utilized for modeling the.turbulent flow in this simulation.The coupling between the pressure and velocity was solved by simple algorithm.Furthermore,owning to the axisymmetrical feature of the flow field,a two-dimensional model was established to reduce the computational time. The acceleration of particles was computed using discrete phase modeling(DPM).The interaction of particle with gas was not considered in this study.Based on the existing research,numerical method was used to investigate the flow field of the impinging jet.The distribution of the thermal parameters such as pressure,temperature and velocity were observed by using a commercial software Fluent.On the other hand,the effects of the shockwave,the standoff distance between the nozzle and the substrate,the size of particle and the type of the carrier-gas on the flow field and particle impact velocity were also examined.Finally,the influence of the porous nozzle exit section on the flow field and coating formation was preliminarily investigated in this study.