等离子炬
机械
火炬
喷嘴
阴极
喷射(流体)
弧(几何)
等离子体
等离子弧焊接
质量流量
体积流量
化学
波形
电压
原子物理学
材料科学
热力学
物理
机械工程
焊接
工程类
物理化学
冶金
量子力学
作者
Vincent Rat,Jean-François Coudert
标识
DOI:10.1088/0022-3727/49/6/065203
摘要
A low-power dc arc torch using nitrogen as plasma-forming gas is studied to highlight the modulation of plasma jet specific enthalpy and speed at the nozzle exit. A special design is used for the torch and by tuning the arc current and the mass flow rate a resonant oscillating mode is obtained in the kHz range, for which the arc voltage presents a periodic triangular waveform, which is the result of the combination of the input parameters. At stabilized current and following the voltage, the electric power is modulated for the specific enthalpy, the mass density and the speed of the plasma at the nozzle exit. A change in the plasma speed is accompanied by a change in the momentum of the jet, which must influence the pressure inside the torch and particularly in the cathode cavity, the volume of which stores the cold gas before it enters the arc region. Even though the torch is fed with a constant flow rate, the arc is subjected to a more or less fluctuating flow rate depending on the cathode cavity volume. The link between the fluctuating components of the different parameters is searched by using a conservation equation and solutions are obtained by means of Fourier analysis. The results obtained are consistent with speed measurements and time-resolved temperature measurements.
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