Production of long, laminar plasma jets at atmospheric pressure with multiple cathodes

Abstract

Plasma jets from conventional non-transferred arc plasma devices are usually operated in turbulent flows at atmospheric pressure. In this paper, a novel non-transferred arc plasma device with multiple cathodes is introduced to produce long, laminar plasma jets at atmospheric pressure. A pure helium atmosphere is used to produce a laminar plasma jet with a maximum length of >60 cm. The influence of gas components, arc currents, anode nozzle diameter, and gas flow rate on the jet characteristics is experimentally studied. The results reveal that the length of the plasma jet increases with increasing helium content and arc current but decreases with increasing nozzle diameter. As the gas flow rate increases, the length of the plasma jet initially increases and then decreases. Accordingly, the plasma jet is transformed from a laminar state to a transitional state and finally to a turbulent state. Furthermore, the anode arc root behaviours corresponding to different plasma jet flows are studied. In conclusion, the multiple stationary arc roots that exist on the anode just inside the nozzle entrance are favourable for the generation of a laminar plasma jet in this device. KEYWORDSanode arc root, arc plasma, jet length, laminar plasma jet, multiple cathodes 1.

Plume transition from solid to hollow with increasing the bias value of a sinusoidal voltage applied to an argon plasma jet

“…Atmospheric pressure plasma jet, able to generate a remote plasma plume, has attracted much attention in the past decade. As one of the most important parameters, plume length has been investigated extensively . Up to now, several centimeters long plume can be generated in inert gases .…”

Fluctuation of arc plasma in arc plasma torch with multiple cathodes*

“…A detailed description of the plasma generator can be found in our recent reports. [18,23,24] Six individual modulated DC power supplies (IGBT source,140 V/250 A; Jin Yi Power Co., Ltd, Anhui, China) are connected to the cathodes and anode. The conversion efficiency of the power supply is higher than 90%, and the current fluctuation is less than 10%.…”

“…The optical emission spectrum diagnosing has been done in a previous work and the electron density is of the order of 10 15 cm 3 , which is lower than that in a constricted helium arc of the order of 10 16 cm 3 . [23,24] The special discharge phenomenon is closely related to the plasma forming gas type, self-induced magnetic field of adjacent arcs, arc currents, etc. The radiation from the diffuse arc is so weak that the plasma column and anode arc roots are visible.…”

“…Recently, we developed a novel arc plasma torch with multiple cathodes. [23,24] Its special structure can provide a new way to observe the arc column and anode arc root. In this paper, we report on investigations of the fluctuation phenomenon of arc plasma in an arc plasma torch with multiple cathodes.…”

Three-dimensional chemical non-equilibrium simulation of an argon transferred arc with cross-flow

“…Since their emergence in industry, such torches have been subject to several problems, such as the lifetime of the electrodes, the stability of the arc, and the overall efficiency of the plasma torch [1][2][3][4][5][6]. Intensive experimental efforts [7][8][9][10][11] and numerical simulations [12][13][14][15][16][17] have been conducted in an attempt to achieve a good understanding of the interactions between the arc, flow and electrodes. However, our knowledge of non-transferred plasma torches is mainly based on indirect observations due to the lack of access of diagnostics to the inside of the torch.…”