Ionic wind produced by high voltage discharge has been proved as a promising technique in heat dissipation, food drying, electrostatic precipitation and air propulsion. On the other hand, the low wind velocity and the low energy efficiency of the ionic wind generators limit their performance in practical industrial applications. To improve this, a single needle-net electrode structure ionic wind generator driven by positive DC voltage is constructed and the effects of the applied voltage and the needle-net distance on the discharge characteristics have been investigated. The results show that with the increase of the applied voltage from 4 kV to 11 kV, the discharge shows four stages, burst pulse, streamer corona, glow corona and spark discharge, and the wind velocity increases monotonously and reach 1.90 m/s at 11 kV. At the same applied voltage, the shorter needle-net distance leads to the larger wind velocity. At 15 mm needle-net distance, the needle-net electrode structure ionic wind generator shows a maximum energy efficiency value of 2.19%. A metal circular plate is attached on the needle electrode to enhance the electric field in discharge spacing. It is found that the wind velocity and energy efficiency can be improved from 1.90 m/s to 2.35 m/s, and 1.87% to 3.14%, at same applied voltage and needle-net distance. The cooling experiment shows that the ionic wind generator with metal circular plate needle-net electrode has better heat dissipation effect.
Nanosecond (ns) pulsed dielectric barrier discharge (DBD) is considered as a promising method to produce controllable large-volume and high activity low-temperature plasma at atmospheric pressure, which makes it suitable for wide applications. In this paper, the ns pulse power supply is used to excite Ar DBD and the influences of the pulse parameters (voltage amplitude, pulse width, pulse rise and fall times) on the DBD uniformity are investigated. The gas gap voltage (Ug) and conduct current (Ig) are separated from the measured voltage and current waveforms to analyze the influence of electrical parameters. The spectral line intensity ratio of two Ar excited species is used as an indicator of the electron temperature (Te). The time resolved discharge processes are recorded by ICCD camera and a one-dimensional fluid model is employed to simulate the spatial and temporal distributions of electrons, ions, metastable argon atoms and Te. Combined the experimental and numerical results, the mechanism of the pulse parameters influencing on the discharge uniformity is discussed. It shows the space electric field intensity and the space particles’ densities are mainly responsible for the variation of discharge uniformity. With the increasing of voltage and pulse width, the electric field intensity and the density of space particles increased, which result in the discharge mode transition from non-uniform to uniform, and then non-uniform. Furthermore, the extension of pulse rise and fall times leads to the discharge transition from uniform to non-uniform. The results are helpful to reveal the mechanism of ns pulsed DBD mode transition and realize controllable and uniform plasma sources at atmospheric pressure.
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