In order to accurately grasp the characteristics and influencing factors of gas explosion in heading face, the mathematical model of gas explosion was determined. According to the actual size of a heading face of a coal mine, a 3D geometric model with a length of 100 m was established, and the effects of ignition energy and gas explosion equivalent on the gas explosion characteristics of the heading face were analyzed. The results show the following. (1) The mathematical models for numerical simulation of gas explosion can accurately simulate the gas explosion and its propagation process. The time-space step size has a great influence on the simulation results. The grid spacing for numerical simulation of mine gas explosion is determined to be 0.1 m and the time step length is determined to be 0.001 s. (2) The ignition energy has a limited effect on gas explosion characteristics. It only has a certain influence on the gas explosion process, but has little influence on the overpressure of shock wave. The larger the ignition energy is, the faster the explosion reaction speed is, and the maximum overpressure increases slightly. When the ignition energy increases to a certain value, the time of peak shock wave and the maximum overpressure both tend to be stable. The ignition energy has little effect on gas explosion characteristics when an explosion accident occurs underground with a large amount of gas accumulation. (3) The gas explosion equivalent has a great influence on the overpressure of gas explosion shock wave. The higher the explosion equivalent is, the greater the pressure is, and the peak value of the shock wave overpressure increases with the explosion equivalent as a power function. The research results have important guiding significance for the research and development of new technology for prevention and control of gas explosion.
Keywords:Amorphous alloys only have short-range ordered structure [1] . Recently, metal-metalloid amorphous alloy catalysts obtained by chemical reduction with hypophosphite or borohydride have drawn much attention owing to their superior catalytic activity and selectivity as well as corrosion resistance [2][3][4][5][6][7][8][9] . Since the amorphous structure is metastable, the crystallization process of the amorphous catalysts can occur spontaneously during the reaction, especially at high temperature. There are two problems to be solved when amorphous alloys are used as catalysts, one is how to increase their surface area to improve the catalytic activity, and the other is how to elevate their crystallization temperature to keep the catalytic activity. Supported amorphous alloy can solve the problems above. Studies revealed that the inhibition of the diffusion of alloy component elements by depositing an amorphous alloy on a suitable carrier with high surface area is one of the promising routes [10][11][12] to improve its thermal stability and catalytic activity. However, studies on the preparation and application of catalyst CoP/TiO 2 have not been reported so far. In this paper, both the supported and unsupported CoP amorphous alloy catalysts were prepared by electroless plating. The crystallization process was investigated by treating the samples at the elevated temperature from 500 K to 700 K. The structural properties and catalytic activity of supported and unsupported CoP amorphous alloy catalysts were discussed. The decomposition rate of
To study the decompression effects of shaft explosion-proof door at different lifting heights, this paper designed the gas explosion testing system. Based on the test results, this paper made a numeric analysis of the change regularities of the shock wave overpressure when the shaft explosion-proof door was lifted at different heights. Finally, this paper determined the proper lifting height of the shaft explosion-proof door and put forward the active decompression concept. The research showed that (1) the shock wave overpressure at the explosion-proof door decreased in a power exponential relationship as the lifting height increased. When the lifting height increased from 0 cm to 5 cm, the peak overpressure at the explosion-proof door decreased from 36.06 kPa to 22.47 kPa, dropping by 37.7%. When it was lifted at a height of 40 cm, the overpressure dropped to 11.20 kPa and the decompression reached 68.9%. (2) The overpressure at the ventilator decreased in a power exponential relationship as the lifting height increased. When the lifting height of the explosion-proof door increased from 0 cm to 5 cm, the decompression ratio reached the maximum 18.4%. After that, the decompression effect became worse and worse. (3) The explosion-proof door could depressurize and protect the ventilator at gas explosion but with limited effects. To protect the ventilator and the explosion-proof door to the maximum, it was suggested that the pressure sensor was set up somewhere in the mine where the gas explosion is likely to occur. In this way, the explosion was sensed in time and the explosion-proof door could be actively lifted for decompression. This paper was of great guiding significance in optimizing the design of the explosion-proof door equipment, reducing the loss of gas explosion accidents as well as carrying out the emergency rescue.
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