Influence of gas dynamics on arc dynamics and the discharge power of a rotating gliding arc

Abstract

This work reports the design and characterization of a rotating gliding arc (RGA) reactor developed with novel electrode configuration. This RGA uses gas swirl discs having 'tangential gas entry ports/holes' (NH) to achieve arc rotation and does not employ any external magnets. This work investigates the effect of gas dynamics on (1) arc dynamics such as the arc's rotation and shape; (2) voltage fluctuation pattern; and (3) plasma discharge power for the designed RGA. Experiments were conducted using argon as the plasma forming gas with (a) two gas swirl discs (NH=3 and 12) and (b) three different gas flow rates (Q=5, 25 and 50 LPM) as control parameters. Cold flow simulation (CFS) studies using a multidimensional solver were used to understand gas dynamics. The arc rotational frequency (f arc ) measured from (1) a high-speed camera (HSC) and (2) fast Fourier transform (FFT) analysis of voltage, shows linear dependency on the Reynolds number (Re) calculated from CFS, with an R 2 =0.98. The agreement improves (R 2 =0.99) by applying linear fit only for the cases having turbulent Re. A close match between gas rotational frequency (f gas ) calculated from CFS and experimentally measured f arc is seen. The turbulent regime of the gas flow causes: (1) twisting and bending of the arc; (2) sawtooth-like voltage fluctuations with irregular and non-sinusoidal waveform; and (3) arc blow off. The highfrequency voltage fluctuations were reduced/absent when the flow Re reduced from ≈6.0×10 4 to ≈1.0×10 4 . These findings establish that the gas dynamics, in particular, the bulk flow phenomenon of the gas, has an explicit influence on arc dynamics of the RGA reactor. This novel RGA design has the potential to replace magnetically driven rotating gliding arc systems.

Effect of gas flow rate on breakdown voltage in a rotating gliding arc reactor

“…The hypothesis was verified for argon and nitrogen gas, operated at varying flow rates 5 and 50 SLPM controlled by mass flow controller (M/s Alicat Scientific). In previous work, authors have already verified that the flow nature of 5 SLPM and 50 SLPM in this RGA is transitional and turbulent, respectively, for both argon and nitrogen [4]. For this reason, these two flow rates are sufficient to change the collisional dynamics inside the reactor.…”

“…The rotation can be additionally supported by external magnets. In a gas vortex driven RGA, the pressure field inside the reactor increases radially from rotational axis towards the wall [4]. Further, the pressure field distribution pattern changes along the flow direction (axial) and is a major function of flow nature.…”

“…As mentioned earlier, once the arc is initiated due to breakdown, it is rotated by the gas vortex and elongated by the geometrical orientation of the electrodes during its rotation (see 3D view in figure 1). Further details on reactor and working of electrode configuration can be seen in earlier work of authors [1,4,5]. The discussion in this work is limited to the breakdown voltage without discussing the rotation of the arc in this RGA.…”

Development of a Swirl‐Induced Rotating Glow Discharge Reactor for CO2 Conversion: Fluid Dynamics and Discharge Dynamics Studies

“…This model has been used for other rotating arc discharges in the literature. [47][48][49] To reduce greatly the computational cost, k-ε interface is solved for stationary flow. This is suitable for an average flow field study to understand the swirl injector in a confined domain.…”

“…The fluid rotational frequency was calculated using the following expression. [49] Fluid rotational frequency, f ¼ V t 2πr (10) where V t is the maximum tangential velocity, and r is the radius of the electrode. The difference between the rotational frequency of the fluid and the glow discharge increases significantly in the turbulent www.advancedsciencenews.com www.entechnol.de regime.…”