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Ignition of Hydrocarbon–Oxygen Mixtures by Means of a Nanosecond Surface Dielectric Barrier Discharge
摘要： Ignition of hydrocarbon–oxygen mixtures by means of a nanosecond surface dielectric barrier discharge (NSDBD) was studied experimentally. The propagation velocity of the flame wave and the ignition delay time in mixtures of oxygen with methane, ethane, ethylene, and dimethyl ether were measured using a high-speed camera. The experiments were carried out at room temperature and gas mixture pressures in the range of 0.75–1.25 atm. It is shown that, for all hydrocarbons under study, the flame velocity decreases with reducing pressure and stoichiometric ratio, as well as when the mixture is diluted with molecular nitrogen. Theoretical analysis of the processes in the NSDBD plasma and measurements of the flame velocity in hydrocarbon-containing mixtures without plasma agree qualitatively with the measurement results, except for the increasing dependence of the flame velocity on the pressure, which is decreasing in experiments without a discharge plasma.
关键词： ignition,nanosecond surface dielectric barrier discharge,flame velocity,ignition delay time,hydrocarbon–oxygen mixtures
更新于2025-09-10 09:29:36
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Experimental investigation on the optical emission spectroscopy of dielectric barrier discharge plasma actuators at different atmospheric pressures
摘要： The experiment of dielectric barrier discharge (DBD) plasma actuator using an asymmetrical electrodes configuration is conducted to investigate optical emission spectroscopy of the plasma discharge at pressures from 0.02 to 0.1 Mpa in air mixed with various concentrations of Ar (0%, 20%, 50%, and 80%). The measurements were performed with a sinusoidal driven DBD having an amplitude of 12 kV and a frequency of 1 kHz. The diffuse DBD discharge images and the optical emission spectra are recorded successfully, and the effects of pressure and concentration of Ar are investigated, respectively. It is found that the emission intensities of air discharge increase with decreasing the pressure but increasing the concentration of Ar to some extent. Especially, when the pressure is lower than 0.04 Mpa or the concentration of Ar is over 50%, the emission intensities increase obviously rapidly. The experimental results indicate that the low pressure environment and the high concentration of Ar are beneficial to improve the performance of the DBD plasma discharge actuators.
关键词： atmospheric pressure,plasma actuator,optical emission spectroscopy,dielectric barrier discharge,Ar concentration
更新于2025-09-09 09:28:46
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Temporal variation of the spatial density distribution above a nanosecond pulsed dielectric barrier discharge plasma actuator in quiescent air
摘要： The thermal perturbation caused by a nanosecond pulsed dielectric barrier discharge (ns-DBD) plasma actuator may lead to boundary layer transition. Hence, understanding of the thermal flow induced by the ns-DBD plasma actuator will contribute to the development of an efficient flow control device for various engineering applications. In this study, the spatial density distribution related to the thermal flow was experimentally investigated using both qualitative and quantitative schlieren techniques. The focus of this study is to understand the initial temporal variation of the spatial density distribution above the ns-DBD plasma actuator in quiescent air. The quantitative visualisation showed that a hot plume is generated from the edge of the exposed electrode and moves slightly towards the ground electrode. A possible explanation is that an ionic wind and/or an induced jet leads to the movement of the hot plume. However, the plasma-induced flow (the ionic wind and the induced jet) is generated after the primary plasma discharges; namely, the hot plume does not move immediately after the first plasma discharge. At almost the same time as the movement of the hot plume, consecutive plasma discharges enhance the density of the hot plume; thereafter, the density reaches almost a steady state.
关键词： nanosecond pulsed dielectric barrier discharge,plasma actuator,schlieren techniques,boundary layer transition,thermal perturbation
更新于2025-09-09 09:28:46
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Square superlattice pattern with discharge holes due to direction-selective surface discharges in dielectric barrier discharge
摘要： We report a square superlattice pattern with discharge holes due to direction-selective surface discharges (SDs) in a dielectric barrier discharge system for the ?rst time. The instantaneous images with an exposure time of 10 ls (half cycle of voltage) taken using a high-speed video camera show that the directions of surface discharges (SDs) of the small spots are selective, which are different from the directions of SDs of the large spots diffused in all directions. In each positive half cycle of voltage, the graphs captured using an intensi?ed charge-coupled device show that the large spot discharges after the small spots and locates at the center of the square formed by the SDs induced by small spots but not their cross point. In each negative half cycle of voltage, the large spots discharge before the small spot and press the SD of the small spot to stretch along the midperpendicular of two adjacent large spots. In a word, the direction-selective surface discharges play a crucial role for the formation of the pattern with the discharge holes in the dielectric barrier discharge system.
关键词： direction-selective surface discharges,square superlattice pattern,dielectric barrier discharge,discharge holes
更新于2025-09-04 15:30:14
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Numerical Investigation on the Transient Evolution Mechanisms of Nonlinear Phenomena in a Helium Dielectric Barrier Discharge at Atmospheric Pressure
摘要： In this paper, the evolution and transition mechanisms of typical nonlinear phenomena in an atmospheric pressure helium dielectric barrier discharge (DBD) are investigated from the perspective of transient evolution properties through fluid modeling. By gradually up-regulating the interelectrode gap width, the discharge (steady state) evolves from symmetric single-period (SP1), through asymmetric single-period (AP1), into Period-2 (P2) state. Similar evolution trace can also be obtained when increasing the driving frequency. Right after the initial breakdown, the discharge goes through several transient periods featuring unstable asymmetric current pulses before the establishment of steady-state discharge. As the bifurcation parameter increases in excess of the critical value, the discrepancy between the seed electron level of positive and negative discharges accumulates over the transient periods, switching the discharge into AP1 state. After then, a further elevation in the gas gap width (or driving frequency) leads to the generation of a “moderate intensity” positive pulse. With the “moderate intensity” positive pulse and a stronger positive pulse emerging alternatively in the temporal waveform sequence, the discharge evolves into P2 state. Finally, based on the transient evolution mechanisms, a preliminary state-controlling method regarding the use of a first-peak-leveled applied voltage is proposed, which may shed light on the modification of nonlinear states in some practical DBD application scenarios.
关键词： Dielectric barrier discharge (DBD),nonlinear states,mode transition,transient evolution,state-controlling method
更新于2025-09-04 15:30:14
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Fast gas heating of nanosecond pulsed surface dielectric barrier discharge: Spatial distribution and fractional contribution from kinetics
摘要： The effect of heat release in reaction with charged and electronically excited species, or so-called fast gas heating (FGH) in nanosecond surface dielectric barrier discharge (nSDBD) in atmospheric pressure air is studied. 2D numerical simulations based on PASSKEy code (PArallel Streamer Solver with KinEtics code) are conducted. The code is based on the direct coupling of a self-consistent fluid model with detailed kinetics, an efficient photo-ionization model and Euler equations. The choice of local field approximation for nSDBD modeling with simplified kinetics is discussed. The reduced electric field and the electron density are examined at both polarities for the identical high-voltage pulses 24 kV in amplitude on the high voltage electrode and 20 ns FWHM. The distribution of the fast gas heating energy and the resulting gas temperature field are studied and compared with existing references. The input of different reactions to appearing hydrodynamic perturbations is analyzed.
关键词： nanosecond surface dielectric barrier discharge,plasma modeling,fast gas heating,nSDBD
更新于2025-09-04 15:30:14