Experimental Study On Scale Effect Of Gas Explosion Suppressed By Composite Powder Under Optimal Blockage Ratio

The frequent coal mine accidents pose a great threat to the coal mine safety production.Once an explosion accident occurs,it will cause serious casualties and huge economic losses.The explosion suppression system provides a guarantee for the safe production of coal mines.The suppression characteristics of active or passive measures on gas explosion have become a hot research topic for many scholars.The pressure relief port is a passive measure to release energy and has a good anti-explosion effect.At the same time,inhibitors play an important role in coal mine safety.The size of the opening blockage ratio has a significant effect on the inhibitor powder's anti-explosion efficiency.There are also large differences in the parameters of powder explosion suppression characteristics under different duct scales.In order to study the influence of pressure relief on powder suppression characteristics at different scales,this paper mainly completed two research objectives.The first goal is to systematically study the effect of different opening blocking ratios on the explosion inhibition characteristics of methane/air premixed gases.Based on the study of the influence of passive measures on active measures and the research on the anti-explosion characteristics of composite powders,another important goal is to carry out experimental research on the anti-explosion characteristics of composite powders in ducts with length to diameter ratios of 5-10,and the scale effect law of the powder explosion suppression is expected to be summarized.The research shows that the overpressure peak and the overpressure peak drop rate of the upper and lower ends of the pipeline changed with the opening blockage ratios are the same.As the opening blocking ratio increased,the overpressure peak increased slightly until?=0.7,and then rose sharply with the?value.For the overpressure peak drop rate,as the?value increased,the drop rate increased first and then decreased.At a medium blocking ratio?between 0.4 and 0.6,the drop rate reached maximum value.In the study of the scale effect under the powder suppression,compared with the inhibition efficiency of other powder concentrations,when the powder concentration was 160g/m~3 and 200 g/m~3,the overpressure peak drop rate in the pipeline of different lengths was almost the largest.Therefore,the length of the pipe has little effect on the optimal inhibitory concentration of the powder.However,under the inhibition of the powder concentration of 160g/m~3 and 200g/m~3,the two flame front position curves were close to each other as the length of the pipe increased from 40cm to 80cm;and when the pipe length was greater than 80cm,the two curves in the pipe were basically similar.This is due to the large difference in powder decomposition patterns in pipes of different lengths.The longer the length of the pipeline is,the more obvious the gradual transformation from the outer sheath decomposition of the particle cloud to the single particle decomposition,so that the same high-concentration powder inhibition effect is more significant.Moreover,for the spherical flame stage,the overpressure rise trend under the condition of large cross section area was relatively flat,the flame brightness was darker,so the intensity of the combustion was weaker,and the flame was strongly inhibited by the powder;the overpressure in the tube droped drastically in the later stage of flame propagation.At this time,the flame front was far away from the pressure relief port,indicating that the flame in the pipe with a larger cross-sectional area will be relieved earlier by the open end.The cross-sectional area of the pipe can also significantly affect the inhibitory effect of the powder,and the larger the cross-sectional area,the better the suppression effect.