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.
Studies on coal pyrolysis via a thermogravimetric analyzer (TGA) are typically performed under a variety of temperature increases beginning at ambient temperature. A main limitation in these procedures is that the reaction temperatures (generally lower than 1000 °C) are typically lower than those met in pulverized coal boilers and ash flow temperatures (AFTs; generally higher than 1100 °C). In this paper, five Chinese coals are clarified to low-or mid-AFT coals as their AFTs increase. They were then prepared in TGA at several temperatures below or above their AFTs under N 2 atmosphere for approximately 30 min after a heating procedure at a rate of 80 °C/min. The coal and residual char samples were collected and analyzed via X-ray diffraction and compared to the chemical thermodynamic calculation. The secondary weight loss appeared between 1200 and 1450 °C in the TG curves of four mid-AFT coals but not the low-AFT coal. The results showed that this secondary weight loss was caused by the carbothermal reduction and carbothermal reduction nitridation reaction between minerals and carbon, which led to the appearance of silicon carbide, aluminum nitride, and silicon nitride. The low concentrations of SiO 2 and Al 2 O 3 and high concentrations of Fe 2 O 3 and CaO inhibited the secondary weight loss process in high-temperature coal pyrolysis. The reason why the secondary weight loss was not present in low-AFT coal was possibly due to low-melting eutectic noncrystal matters consisting of calcium oxide and ferrum oxide. These fused low-melting eutectic noncrystal matters stopped the carbothermal reaction at high pyrolysis temperatures and inhibited the production of SiC, AlN, and Si 3 N 4 .
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