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.
Successful application of plasma-activated water (PAW) as an alternate source of nitrogen for agricultural application requires low specific energy consumption. This work reports on a dielectric barrier discharge (DBD) plasma reactor for the generation of PAW having low specific energy (SE) consumption. The SE to produce N in PAW was 3.26 GJ/kg of N, which is 68% lower than the lowest value reported to date for DBD-PAW systems. The PAW generated was characterized for its physico-chemical parameters, most of which showed a linear increase with activation time (ta). The concentration of hydrogen ion and that of the nitrate, which is the desired product for agricultural application, remained stable for four weeks in the PAW. The results indicate that minimal reactive oxygen species was formed in the plasma zone and only reactive nitrogen species (RNS) was formed confirming selectivity toward RNS.
This work investigates the reliability of the function called ‘regionprops’ which is used for measuring the 2D length of the plasma discharge. Work was conducted in a Rotating Gliding Arc (RGA) reactor, using air as plasma forming gas. Arc rotational images at three different gas flow rates i.e. 5, 25 and 50 litres per minute LPM were captured using high speed camera with an exposure of 100 μs. A total of 6799 images from all the three flow rates were considered for analysis. The 2D length of the discharge was measured by two methods namely, (a) ‘regionprops’ function (Python) and (b) manual tracing (ImageJ). The 2D arclength measured using ‘regionprops’ function matched very closely to that measured by manual hand tracing technique using ImageJ tool. A linear relation between both the methods was observed for all the three flow rates, with the coefficient of determination i.e. R 2 > 0.9 . The validation of ‘regionprops’ function shown in this work marks an important step as the function is simple to use and adapt compared to any other techniques such as shortest–path algorithm.
This work reports a study on using a gliding arc plasma reactor to produce ammonia from nitrogen plasma and water medium without using a catalyst. During the gliding arc plasma discharge, a plasma plume is formed and the vibrational and rotational excitation was observed at the tip of the plasma plume which touched the water below. This arrangement helped the formation of ammonia. The ammonia concentration was 2.12-5.69 ppm, and its production rate varied in the range of 0.63-0.68 mg/hr, having the energy efficiency in the range of 0.0249-0.0268 g-NH3/kWhr, depending on the plasma exposure time. The vibrational temperature increased from 2632 K (near the gas entry zone) to 3778 K (at the tip of the plasma plume interacting with the water), corroborated by the enhanced distribution of electron energy for vibration excitation (≈24%), compared to that for the electronic excitation (≈0.03%). The electron temperature dropped from 1.38 eV to 0.76 eV at the plasma zone interacting with the water. The work demonstrates the application of gliding arc plasma to generate eco-friendly ammonia (green ammonia), and the reactor proves to be promising for further optimization in the future.
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