毕业设计-金属冷喷涂.docVIP

摘要 用FLUENT软件对拉瓦尔喷枪内的气固两相流动过程进行数值模拟，并对喷枪内气和固颗粒的速度、温度和压强进行分析，。冷喷涂技术的关键是拉瓦尔喷枪加速气流提高粉末速度在表面。气体进口参数出口气流速度影响。进口速度的变化对出口速度的影响较小，尤其是进口速度低于50m/s时，其变化基本上不会使出口速度有大的改变让进口气流压强有大的提高不实提高出口速度的方式是以提高进口气体温度为主，适当提高进口压强。为了对喷枪内气体流动过程有更深入的，应用重整化群(RNG)k–ε模型对流动过程进行数值模拟，对喷枪流道形状的变化，采用不均匀网格划分计算区域，并用二阶差分格式离散通用微分方程的对流相；SIMPLE算法来求解气体的运动。压强、温度、速度的分布做分析入口直径D1=15.2mm出口直径D2=14mm喉部半径Rcr=3.5mm渐缩角α=30°，长度L1=20.9mm；渐扩角 β=10°，渐扩段长度L2=55mm；总长L=mm。然后，对优化设计的喷枪进行数值模拟，得出最后的结果。 关键词：镁合金；拉瓦尔喷枪；(RNG)k–ε模型；SIMPLE算法 Abstract In order to study the cold spray technology on Mg alloy surface, the designed supersonic nozzle is optimized according to the theory of hydrodynamics and aerodynamics. The FLUENT software is used to simulate the gas-solid flow. The velocity, temperature and pressure of gas and solid particles are analyzed in the Laval Nozzle. According to the simulation results, the nozzle structure is improved to make the velocity of gas and particle best. The key of Cold Spray technology is accelerating the velocity of materials to supersonic in the Laval nozzle, then the powder of materials is deposited on the surface effectively. The speed of outlet was impacted by inlet parameters. At the same Laval nozzle structure, the speed of inlet less impact on outlet speed, particularly inlet velocity blow 50m / s. And increasing air pressure of inlet deeply is difficult realization. The main method of raising the speed of outlet is getting up the gas temperature of inlet with suitable pressure. Through analysis the data of simulation, appropriately extending the length of expanding nozzle’s zone can obtain both lower temperature and higher speed at outlet. A k-ε (RNG) model was used in the simulation in order to understand the character of the flows in Laval-Nozzle. According to the shape variation of the Laval-Nozzle, a structured non-uniform grid system has been used to divide the computation domain. The second-order difference style was selected for the discrimination of the convection in the differential equat