等离子体发生器的数值模拟方法

NUMERICAL SIMULATION METHOD OF PLASMA ARC GENERATOR

根据流体质量、动量及能量守恒方程和麦克斯韦方程组建立等离子体发生器的数学模型,包含一部分钨极以避免对阴极电流密度分布的假设,根据平均有效粘性系数与动力粘性系数之比判断等离子电弧所处的流动状态,用ANSYS有限元分析软件进行求解,得到不同类型的等离子体发生器所产生的等离子电弧的温度和速度分布,研究喷嘴尺寸、电极形状和等离子电弧类型等对等离子电弧特性的影响。结果表明,大孔道比的喷嘴产生的电弧温度更高,速度更大,孔道比甚至会改变等离子电弧的流动状态;与锥形电极的电弧在电极端部取得温度最大值不同,球形电极的电弧在约束喷嘴端口处得到温度最大值;转移型电弧比非转移型电弧具有更高的温度和速度。研究结果对等离子体发生器的数值模拟法研制具有重要的参考意义。

A mathematical model for plasma arc generator is established based on the mass, momentum and energy conservation equations and the Maxwell equations. The model includes a part of tungsten electrode to avoid the assumption of current density distribution near the cathode. The flow state of the plasma arc is also considered. The model is solved with the ANSYS finite element analysis software. The temperature and velocity distributions of the plasma arcs produced by different plasma arc generators are analyzed. The effects of nozzle size, electrode tip shape and arc type on the plasma arc characters are studied, The results show that nozzle with a bigger aperture ratio may produce a higher temperature and higher velocity plasma arc. The aperture ratio even may change the flow state of the plasma arc, The plasma arc with a rounded-tip cathode got the highest temperature near the exit of the nozzle, while the one with a subulate-tip cathode got the highest temperature at the front of the cathode. The transferred plasma arc has a higher temperature and velocity than non-transferred plasma arc. The work has testified that mathematical simulation is meaningful for the development of plasma arc generator.