【作者】 程江伟；

【导师】 刘传绍；

【作者基本信息】 河南理工大学 ， 机械工程， 2011， 硕士

【摘要】 在冷喷涂工艺中,喷管内外的气体轴向速度和颗粒速度对喷涂效果影响很大,研究喷涂参数对气固两相速度的影响具有重要意义。虽然很多学者对冷喷涂气固两相流进行数值模拟研究,但大多没有考虑基板的影响,针对冷喷涂工艺参数优化的研究较少。本文采用数值模拟方法对冷喷涂过程中气固两相流流场进行研究。首先建立整个冷喷涂射流区域的物理模型,并且对计算区域进行网格划分以及边界条件的定义;然后采用二维数学模型,进行湍流的数值模拟计算,研究不同载气、喷涂压强、喷涂温度和喷涂距离对流场加速的影响规律;最后建立离散相模型,对气固两相流流场进行数值模拟,分别采用Ti、Cu、Au粉末作为喷涂材料,每种材料选用不同颗粒直径,研究不同喷涂材料以及同种材料不同颗粒直径的加速规律。研究结果表明:氦气的加速特性优于氮气和空气;随着喷涂温度和喷涂压强的提高,气体轴向速度和颗粒速度也随之提高;不同喷涂距离对喷管内流场没有影响;提高喷涂温度可以明显改善喷涂效果;密度小的小直径颗粒和密度较大的大直径颗粒不容易被加速到较高的速度,应根据材料的密度和颗粒直径选择合适的喷涂参数。模拟结果和前人的实验成果一致,本研究可为冷喷涂工艺参数优化和喷涂实验提供指导。更多还原

【Abstract】 The gas axis velocity and particle velocity in and out of the nozzle have great influence on the coating effect in the process of cold spray, It is very important to study the effect of different spray Parameters on gas axial velocity and particle velocity. Although many scholars research gas-particle two phase by numerical simulation,but mostly without considering the influence of the substrate, research of parameter optimization for cold spraying is also less.We obtained the influence of different spray parameters on gas and particle velocity by studied the gas-solid two phase flow in cold spray using numerical simulation. First establish physical model of jet region and dividing the grid and define boundary conditions,Then a two-dimensional mathematical model is presentedand used to study the flow. Research the effect of different carrier gas ,pressure, temperature and spraying distance on gas velocity .Finally discrete phase model is establish to numerical simulation the two phase flow, seperately accelerate Ti, Cu and Au power,Every material select different diameters,get the accelerate characteristics of different materials and the same material with different particle diameter.Simulation results show that the acceleration of helium is better than nitrogen and air.With the spray temperature and pressure increased, the gas axial velocity and particle velocity also increase.Differernt spray distance have no effect on the flow in the nozzle. Improve spraying temperature can significantly improve spraying effect.Smaller particles with low density can not obtain a high-speed because their inertia are small, so the particle speed and direction easily changed with the vortex flow before the substrate. larger particles with high density also not easy to be accelerated to a higher speed, because their inertia too big, these are bad for spraying. material particles should be in an appropriate range,and we should select appropriate coating parameters according to material density and particle diameter. It will offers reference for cold spray experiment and optimize the spray parameters.更多还原