内送粉超声速等离子喷涂流场特性分析

Numerical Analysis of Plasma Flow with Supersonic Plasma Gun

关键词:  数值模拟  超声速喷枪  流场特性

Key words:  Numerical simulation  Supersonic plasma gun  Flow field characteristic

摘要:

应用流体控制方程、传热传质方程、粒子输运方程、Maxwell电磁场方程建立多场耦合数学模型，通过数值计算方法研究超声速等离子喷枪内外等离子体流动特性。所采用的内送粉三维模型包含阴、阳电极固体以及阳极边界层区域，考虑了等离子气体的电离与复合反应，以及局域热平衡效应，得到了超声速等离子喷涂在纯氩和氩氢混合气氛中的气流温度场、速度场分布以及电弧电压分布。结果表明:在加入氢之后，喷枪内等离子体温度提高了30%，速度提高了67%；喷枪外气流速度和温度在距喷嘴出口0~50mm间梯度变化大于喷涂距离50~100mm，且径向速度和温度梯度变化随着喷涂距离增大越来越小。计算得到的电弧电压与测量值相差4.4%，说明了考虑阳极边界层后计算模型的合理性。

Abstract:

A multi-physic fields coupling mathematical model was established using fluid controlling equations，heat and mass transfer equations，species transport equations and Maxwell's electromagnetic equations，to predict flow field characteristics inside and outside supersonic plasma gun. The three-dimensional model contained cathode，anode and anode boundary layers，and took ionization and recombination reactions，as well as non-local thermal equilibrium into consideration. The contours of temperature and velocity of plasma jet were displayed under argon and argon-hydrogen working conditions，and arc voltage was also described. The results show that gas temperature inside plasma gun increases by 30%，and velocity increases by 67% after hydrogen was added to working gas. Besides，gas temperature and velocity decrease more sharply at distance of 0~50mm from nozzle exit than that of 50~100mm，while the decrease rate of the velocity and temperature are reduced with increasing axial distance. The relative error of calculated arc voltage is 4.4%，compared with measured value，illustrating the reasonableness of model after considering anode boundary layer.