This paper reports the experimental investigation of the dielectric barrier discharge in which the gap area is filled with a two-phase mixture (TPM), air and solid particles. We found that there are two kinds of discharges in the TPM. One is the surface discharge generated on the surface of the solid particles and the other is the filament discharge generated in the air void. For the case of low volume fraction of solid particles, the surface discharge starts to occur when the applied voltage is higher than the onset voltage. At a further voltage increase, the filament discharge takes place at the same time. For the case of high volume fraction, such as the packed-bed reactor, only the surface discharge exists. Under the condition of the same volume fraction, the larger the diameter of the solid particles, the lower the surface discharge onset voltage. As a conclusion, we think that the plasma reactor using the form of low volume fraction of solid particles may be a better choice for waste-gas treatment enhanced by catalysts.

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In this paper, the uniformities of dielectric barrier discharges (DBDs) produced by different mesh electrodes are studied. If the aperture of the mesh electrode is long enough, the discharge spots are periodic. If the aperture is smaller than 0.5 mm, the discharge spots will be distributed randomly and even more densely than when produced by a planar electrode. Because the evaluation of the uniformity of the DBD, which consists of a large number of microdischarges, is different from that of a glow DBD or a Townsend DBD, the coefficient of variation (CV) of the gray level distribution of the discharge light emission is used to describe the uniformity of the DBD. The smaller the value of CV, the more uniform is the discharge. The experimental results show that the uniformity of the DBD produced by some mesh electrodes is even better than that by a planar electrode if the aperture of the mesh electrode is small enough. On the other hand, a new dimensionless scale invariant (h), which includes the combined effect of the aperture and the normalized change rate of the field strength of the avalanche head, is presented to analyze the physical mechanisms leading to a relatively uniform DBD according to the condition of the slow development of many avalanches at a low electric field. The calculated results show that the variation trend of h for different mesh electrodes is almost the same as that of the CV. This means that the dimensionless scale invariant h can be used to study the discharge uniformity.

The uniform dielectric barrier discharges (DBD) consisting of numerous microdischarges in a long time‐scale may also meet the needs of industrial applications. In contrast to the glow DBDs, their uniformity is significantly influenced by the spatial distribution of microdischarges. In this paper, the streamers distribution in DBDs with rotating electrodes and the effects of the rotational speed on the discharge uniformity are investigated using a flow simulation and the SD of image gray levels, respectively. The simulation results show that the neutral gas flow caused by the electrode rotation has a great effect on the shape and length of the streamers. This has mainly contributed to the discharge remnant in the volume traveled by the neutral gas, which affects the discharge distribution. The SD of gray levels sharply decreases with an increase of the rotational speed, which indicates that the discharge uniformity can be effectively improved by the electrode rotation. When the rotational speed is over 3 000 rpm, the SD keeps almost constant, even with an increase of the applied voltage and frequency. It has similar characteristic as a uniform discharge.

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