本研究在假設二維軸對稱與穩態條件下,以有限體積法聯立求解連續方程式、動量方程式、能量方程式、紊流方程式以及電流連續方程式,使用安培定律計算流場電流分佈,利用歐姆定律計算磁場大小,以分析電漿火炬內部電漿氣體流場基本特性。本研究使用虛擬網格技巧,利用計算區間分割進行平行化計算,以縮短計算時間。本研究利用上述數學模型及數值方法,模擬非傳輸型井式直流水蒸氣電漿火炬流場,先使用水蒸氣質量流率為5 g/s與電流為180 A的實驗結果,以決定在該工作條件下電漿火炬內部陰極最大電流密度約為3.73×10^7 A/m2,電弧長度約為234 mm。在利用此條件以得到當電流為125~200 A與質量流率為3.01~7.78 g/s時,陰極最大電流密度約為2.07~4.14×10^7 A/m2,電弧長度約在210~330 mm之間,電壓約在400~545 V之間,出口處平均溫度約在8200~11000 K之間,出口處平均速度約在900-2300 m/s 之間。
Based on steady and axis-symmetric assumption, this research employs a parallelized scheme based on MPI functions to simulate the flow field inside plasma torch with taking the induced electrical and magnetic effects into account, where magneto-hydrodynamic equations, including the continuity equation, the momentum equations, the energy equation, the current continuity equation and the turbulence transport equations are solved by a finite volume discretization in a segregated manner. By the comparison with experimental measurement mass flow rate 5 g/s and current 180 A, maximum current density about cathode is approximately 3.73107 A/m2, and the arc length is about 234 mm. The numerical predictions suggest that with current of 125-200 A and mass flow rate of 3.01-7.78 g/s, the maximum current density of cathode 2.07-4.14107 A/m2, the arc length 210-330 mm, the electrical potential 400-545 V, the average temperature of the nozzle exit 8200-11000 K and the average velocity of the nozzle exit 900-2300 m/s.