FRVT - Artículos en Revistas Internacionales

Permanent URI for this collectionhttp://48.217.138.120/handle/20.500.12272/396

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Author: search.filters.author.Cejas, EzequielSubject: search.filters.subject.Gas temperature.

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    Quantitative Schlieren Diagnostics Applied to a Millisecond Pulsed‑DC Hybrid Discharge in Atmospheric Pressure Air.
    (2022) Cejas, Ezequiel; Chamorro, Juan Camilo; Prevosto, Leandro
    The gas temperature of a hybrid discharge in atmospheric pressure air is investigated by using quantitative schlieren imaging. The discharge is stabilized in a pin-to-plate electrode geometry and operated in a millisecond pulsed-DC regime with current amplitudes up to 75 mA and a duration of 10 ms, applied at a frequency of 100 Hz. An equilibrium com position model is considered to account for the production of N, O, and NO, which infu ence the Gladstone–Dale coefcient of air at high-gas temperatures. Also, a procedure is described which allows the determination of the errors introduced in the time-average gas refraction index due to gas temperature fuctuations. The results show that the axial values of the gas temperature profles span a large range from~1000 to 5000 K, nearly following the evolution of the discharge current. The temperature values found agree well with those reported in the literature for atmospheric pressure air plasmas, ranging from micro-glow to hybrid discharges.
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    Ambient Species Density and Gas Temperature Radial Profiles Derived from a Schlieren Technique in a Low Frequency Non-thermal Oxygen Plasma Jet.
    (2017) Chamorro, Juan Camilo; Prevosto, Leandro; Cejas, Ezequiel; Kelly, Héctor; Mancinelli, Beatriz; Fischfeld, Gerardo
    A quantitative interpretation of the schlieren technique applied to a non-thermal atmospheric-pressure oxygen plasma jet driven at low-frequency (50 Hz) is reported. The jet was operated in the turbulent regime with a hole-diameter based Reynolds number of 13,800. The technique coupled to a simplified kinetic model of the jet effluent region allowed deriving the temporally-averaged values of the gas temperature of the jet by processing the gray-level contrast values of digital schlieren images. The penetration of the ambient air into the jet due to turbulent diffusion was taken into account. The calibration of the optical system was obtained by fitting the sensitivity parameter so that the oxygen fraction at the nozzle exit was unity. The radial profiles of the contrast in the discharge off case were quite symmetric on the whole outflow, but with the discharge on, relatively strong departures from the symmetry were evident in the near field. The time-averaged gas temperature of the jet was relatively high, with a maximum departure of about 55 K from the room temperature; as can be expected owing to the operating molecular gas. The uncertainty in the temperature measurements was within 6 K, primarily derived from errors associated to the Abel inversion procedure. The results showed an increase in the gas temperature of about 8 K close to the nozzle exit; thus suggesting that some fast-gas heating (with a heating rate *0.3 K/ls) still occurs in the near field of the outflow.