高速电弧喷涂熔滴速度的数值模拟及试验

熔滴速度是电弧喷涂涂层性能的主要影响因素之一。本基于空气动力学和二相流流体力学理论建立了高速电弧喷涂雾化气流化和熔滴速度的数学模型，并进行了数值模拟；同时用试验方法测试了气流速度及Al,3Cr13熵滴在不同喷涂距离处的平均速度；数值计算结果与试验数据基本吻合。结果表明，雾化气流的速度和距喷嘴一定距离内将保持初始速度（约650m/s)，然后随喷涂距离的增大而衰减，这与超音速气流通过Laval喷管后所产生的膨胀波和压缩波相互作用有关；熔滴在雾化飞行过程中经历了先加速后减速的过程，小熔滴能在较短的距离内被加速到最大速度；达到最大速度之后，小熔滴由于惯性力较小而迅速减速，而大熔滴则因较大的惯性力而减速不明显；熔滴速度的变化是由熔滴的Reynolds数决定的。Al和3Cr13熵滴的最大速度在0．3m喷涂距离之内均超过音速。

Numerical Simulation and Measurement of Droplet Velocity During High Velocity Arc Spraying

Droplet velocity is one of main factors influencing the coating properties.Based on the theories of gas dynamics and multiphase fluid mechanics,the velocity problems of the atomization gas and droplet during high velocity arc spraying (HVAS) were modeled and solved by a numerical method,and experiments were carried out to measure the average velocity changes using Al and 3Cr13 wires.A good agreement between the numerical and experimental results was observed.The results showed that the exit velocity of atomization gas maintained the original velocity (approximately 690m/s) for a certain distance,then decreased with increasing distance from the nozzle,and this corresponded to the interaction between expansion wave and compression wave after the supersonic velocity gas passing the Laval tube.The in flight droplets experienced an acceleration deceleration velocity profile.The smaller droplets could reach higher maximum velocity at shorter flight distance.Beyond the flight distance where the maximum velocity was reached,the smaller droplets were decelerated rapidly due to their lower inertia force.On the other hand,the larger droplets did not exhibit a marked deceleration because of their high inertia force.And the droplet velocity was determined by Reynolds number.Simulation and measurement proved that the maximum velocities of Al and 3Cr13 droplets were greater than the velocity of sound during high velocity arc spraying.