Characteristics of non-thermal AC arcs in multi-arc generator

To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration.A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.

Characteristics of DC arcs in a multi-arc generator and their application in the spheroidization of SiO2

We investigate characteristics of multi-arc torches with three pairs of electrodes(three cathodes and three anodes)and their performance on the spheroidization of SiO2 powder.The effect of electrode arrangement,including adjacent pattern(AD pattern,adjacent electrodes powered by one power supply)and opposite pattern(OP pattern,opposite electrodes powered by one power supply),on the dynamics of arc plasma is investigated based on synchronous acquisition of electrical and optical signals.The results show that both the voltage and spatial distribution of each arc of multiple arcs are more stable compared with those of a single arc.The fluctuation of an arc in multiple arcs mainly comes from the small-scale arc-to-arc restrikes among multiple arcs.Moreover,these arc-to-arc restrikes occur more frequently among multiple arc columns in OP pattern than in AD pattern.Moreover,the high-temperature area of the central region of arc chamber in OP pattern is larger than that in AP pattern.For the spheroidization of SiO2 in this multi-arc generator,the spheronization degrees of plasma treated silica in OP pattern are at least 20%higher than those in AD pattern.

Dynamic characteristics of multi-arc thermal plasma in four types of electrode configurations

The enhanced volume of thermal plasma is produced by a multi-arc thermal plasma generator with three pairs of discharge electrodes driven by three directed current power suppliers.Combined with a high-speed camera and an oscilloscope,which acquire optical and electric signals synchronously,the dynamic behavior of different kinds of multi-arc discharge adjusted by the electrode arrangement is investigated.Also,the spatial distributions and instability of the arc discharge are analyzed in four electrode configurations using the gray value statistical method.It is found that the cathodic arcs mainly show a contracting state,while the anodic arcs have a trend of transition from shrinkage to a diffusion-like state with the increase of the discharge current.As a result of the adjustment of the electrode configuration,a high temperature region formed in the center of the discharge region in configurations of adjacent electrodes with opposite flow distribution and opposite electrodes with swirl flow distribution due to severe fluctuation of arcs.The discharge voltage rises with increased discharge current in this novel multi-arc plasma generator.It is also found that anode ablation mainly occurs on the conical surface at the copper electrode tip,while cathode erosion mainly occurs on the surface of the inserted tungsten and the nearby copper.