Performance scaling of inductive pulsed plasma thrusters with coil angle and pulse rate
Performance scaling of inductive pulsed plasma thrusters with coil angle and pulse rate
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DOI：
10.1088/0022-3727/49/2/025201
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发表时间：
2016-01
期刊：
影响因子：
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通讯作者：
A. K. Martin
中科院分区：
文献类型：
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作者：
A. K. Martin
为了研究锥形线圈电感脉冲等离子体推力器的性能，建立了其电路模型；该模型可以容纳锥角从0°（一个直的theta-pinch线圈）到90°（一个平面线圈）。等离子体被视为可变形的段塞，响应线圈施加的力，其沿径向和轴向移动。径向运动方程包括由等离子体压力引起的恢复力，这是在假设电子居群是等温的情况下推导出来的，而离子是等温的，绝热的，或者是冲击波加热的，这取决于径向速度的大小和符号。利用QuickField测量了线圈和等离子体段塞的电感及其互感。当角度小于90°时，效率和比冲均有局部最大值；然而，这两个量的绝对最大值出现在90°。高脉冲率操作被发现产生动态效率（不包括电离成本）高达60-70%，在3000 - 5000s范围内的ISP，即使是一个中等喷射功率（5kw）的设备。这种操作模式还允许消除脉冲气体阀，这将是一个重要的系统级简化。另一种可选的电感重捕获模式，即电流在第二次过零时中断，被发现只会导致1-2%的效率牺牲，同时为这种推进器提供了其他显著的系统级优势。
A circuit model for an inductive pulsed plasma thruster was developed in order to investigate the performance of thrusters with conical coils; the model can accommodate cone-angles from 0° (a straight theta-pinch coil) to 90° (a planar coil). The plasma is treated as a deformable slug that moves both radially and axially in response to the force applied by the coil. The radial equation of motion includes a restoring force due to the plasma pressure, which is derived under the assumption that the electron population is isothermal, while the ions are isothermal, adiabatic, or shock-heated depending on the magnitude and sign of the radial velocity. The inductance of the coil and the plasma slug, and their mutual inductance, was determined using QuickField. A local maximum in efficiency and specific impulse was found for angles less than 90°; however the absolute maximum for both these quantities occurs at 90°. High pulse-rate operation was found to yield dynamic efficiencies (excluding ionization cost) as high as 60–70% for ISP in the range of 3000–5000 s, even for a device with modest jet-power (5 kW). This mode of operation also permits elimination of the pulsed gas valve, which would be a significant system-level simplification. An alternate mode of inductive recapture, in which the current is interrupted at the second zero-crossing, was found to result in a sacrifice of only 1–2% in efficiency, while offering other significant system-level benefits for this kind of thruster.