Magnetohydrodynamic Numerical Study in a Supersonic Plasma Torch
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摘要: 针对设计的喉径2 mm、工作电流为100 A的拉瓦尔喷嘴，在二维轴对称模型的基础上，对超音速等离子体炬中的流动及其外部射流进行了数值模拟。通过在阳极喷嘴内部采用基于磁矢量势的磁流体动力学模型，避免了对磁感应强度的复杂积分计算，得到了喷嘴内部多场耦合的结果及外部射流的流动状态, 分析了喷嘴内部电磁场对等离子体的加速作用及射流发展过程。结果显示，等离子体经历了亚音速→跨音速→超音速的发展过程，最终获得2.3Ma的超音速射流。研究结果为超音速等离子体炬的工业应用提供了理论基础。
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关键词:
- 超音速等离子炬 /
- 基于磁矢量势磁流体动力学 /
- 多场耦合 /
- 等离子射流
Abstract: A laval nozzle with a throat diameter of 2 mm and working current 100 mA was introduced, and on the basis of 2D rotational symmetry model, numerical simulation was taken for the plasma flow in and outside the plasma torch.By adoptting the magnetic vector potential magnetohydrodynamic (MHD) model for the internal nozzle, we avoided the complex integral calculation of self-induction magnetic field intensity, obtained the nozzle internal field coupling and external jet flow state.The impact of nozzle internal electromagnetic field on plasma acceleration and the jet development process were analyzed.The results show that the plasma experiences a 3-stage processes from subsonic to transonic, and to supersonic (2.3Ma).It provides a theoretical basis for the industrial application of supersonic plasma torch. -
图 5 超音速等离子炬轴线压强与速度对比
Figure 5. Contrast between the axis pressure and velocity of supersonic plasma torch
图 6 超音速等离子体炬喷嘴外部压力等值线图
Figure 6. Pressure contours outside the supersonic plasma torch nozzle
图 9 超音速等离子炬轴线电流密度与电压值的对比
Figure 9. Contrast between the axis current density and the axis voltage of the supersonic plasma torch
表 1 MHD模型边界条件
Table 1. Boundary conditions of MHD model
Boundary p v T φ A DM - ∂v/∂r=0, vr=vθ=0 ∂T/∂r=0 ∂φ/∂r=0 ∂Az/∂r=0, ∂Ar/∂r=0 GH - 0 T=1 000 K φ=0 ∂Az/∂r=0, ∂Ar/∂r=0 KLM p=0.1 MPa - T=300 K ∂φ/∂r=0 Az=0, Ar=0 CE p=0.3 MPa vz=0.85 mm/s T=300 K ∂φ/∂r=0 ∂Az/∂r=0, ∂Ar/∂r=0 AB - 0 T=3 000 K J is given ∂Az/∂r=0, ∂Ar/∂r=0 
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