基于局域热力学平衡假设, 建立等离子喷涂射流的三维非稳态湍流模型, 运用计算流体力学软件ANSYS CFX模拟了氩/氢等离子喷涂过程中等离子特性分布以及喷枪内部场变化对射流形态的影响, 并与高速摄像机的拍摄结果进行了对比。结果表明: 模拟得到的射流波动明显, 其形态与试验得到的结果吻合较好; 喷枪内与射流域等离子体特性分布表现出明显的三维特征, 其中速度分布的三维特征较之温度的更加明显; 射流射入大气中后, 温度和速度均沿轴向衰减, 随着射流发展, 与冷空气的卷吸作用愈明显, 等离子体与冷空气之间能量和动量交换愈剧烈, 大约距离喷枪出口27.4 mm处其温度和速度的衰减加剧; 射流域速度分布较之温度分布受空气影响更大。

A three-dimensional transient turbulent model of plasma jet on the basis of local thermodynamic equilibrium (LTE) hypothesis was established. The characteristics of plasma distribution and the impact of fields in plasma torch on jet patterns during Ar/H2 plasma spraying using computational fluid dynamics software ANSYS CFX. The simulated results were compared with experiment results observed by a high-speed camera. The results show that simulated jets were obviously fluctuating, which agreed well with experimental results. The plasma distributions in plasma torch and jet region showed clear three-dimensional characteristic. Compared with the temperature distribution, the plasma velocity distribution had stronger three-dimensional characteristics. Both temperature and velocity decreased along axial direction when the plasma jet went into atmosphere. As jet developed, the temperature and velocity started greatly decreasing at the palace about 27.4 mm away from the torch exit, because of the enhancing of cold-air entrainment into plasma and then the increasing exchange of energy and momentum between plasma and cold air. Compared with temperature, the velocity distribution was more easily influenced by air.