Numerical Simulation Research Of The Internal Flow Field Cold Of The Spray Gun Nozzle And Structural Optimization

With the rapidly development of modern industrial production, the surface of machine parts and components of mechanical products have become increasingly demanding performance. At the same time, the consumption of energy materials which caused by the corrosion and wear is immeasurable. Using the effective surface engineering technologies to strengthen and repair the surface of the part is a good way .the advantage is that it can save costs, inprove part service life and reduce environmental pollution etc.Cold spray technology is very economic and practical. It is used for surface coating materials, which can improve and enhance the surface properties of materials. And the ultimate aim is improving the quality of the product surface. The cold spray technology achieved the deposition of metal coatings under the low temperature. The process has no heat-affected to the powder particles, the coatings has low residual stress and no oxidation, and does not change the materials nature.In this thesis, a commercial fluent software is used to simulate the internal flow field of spray gun which is the most critical parts in cold spray technology.Compared with the results based on the analysis, studied the internal structure parameters of the spray on the characteristics of gas-solid flow.The results show that:the parameters which influence the internal flow field are inlet gas pressure, inlet gas temperature, particle size and morphology of the internal structure of the nozzle. The higher the inlet gas pressure and temperature are, the higher the outlet pressure and temperature are; the big the particle size is, the worse the particle acceleration is; When the nozzle convergence half-angle is 42°, the speed incremental which obtained by the two-phase flow is maximum; The smaller expansion half-angle is, the bigger the nozzle exit particle velocity is; the export shape of the spray gun effective the size of the spray area; Increasing the length of straight pipe after the expansion segment can export a higher particle velocity. The internal structure of the nozzle is optimized to a certain degree. By comparing the simulation in the nozzle before and after optimization, get the results:the exit velocity of nozzle after optimization is the highest among all the simulation results.