减压直流非转移电弧及等离子体射流波动特性研究

Fluctuations of Arc Voltage and Jet Flow in Non-Transferred DC Plasma at Reduced Pressure

实时测量了减压直流纯氩等离子体的弧电压和射流高温区的瞬时离子饱和电流。结合射流高温区的瞬时形貌,探讨了在真空室压力500～10000Pa条件下电弧及等离子体射流的波动特性。结果表明:当气流量较小和真空室压力较低时,射流流场呈现较好的稳定性。随着气流量和真空室压力增加,弧电压出现高频脉动,射流能量分布的空间和时间稳定性逐渐变差,离子饱和电流信号变得紊乱;即使由于电源特性引起电弧功率300Hz的波动幅度高达35%,依然能够产生流场较稳定的等离子体射流;静电探针检测等离子体射流的瞬时离子饱和电流可作为了解射流波动特性的一种快速响应方法。

The fluctuations of plasma jet,generated at a reduced pressure ranging from 500 Pa to 10000 Pa,were characterized by imaging the shape of the plasma jet with a high speed video camera and by profiling the real-time ion saturation current spectra with a double electrostatic probe.The variations in the arc voltage were experimentally evaluated by varying the plasma generation conditions,such as the gas flow rate and pressure.The results show that the plasma jet remains stable at a fairly small gas flow rate and a low pressure.As the gas flow rate and pressure increase,the high frequency voltage fluctuation intensifies,accompanied with deterioration of time and special stabilities of plasma jet energy,and with higher frequency perturbation in the ion current.A steady plasma jet can be easily maintained,in spite of a possible input power perturbation up to 35% at 300 Hz.We suggest that the double electrostatic probe is capable of effectively characterizing the plasma jet.