Effects Of Obstacles On Methane Explosion In Different Concentrations

As one of the important clean energy sources,natural gas has important applications in industry and civil use.Methane is not only one of the main components of natural gas,but also the most dangerous gas in coal mining.Methane-air premixed gas,whether in coal mining or industrial applications,is a huge hazard in the event of an explosion.In the mining process of coal mines,although some measures to prevent explosions were installed underground,gas explosions were still frequent.The main reason was that the research on gas explosion mechanism was not deep enough.Due to the release of coal seam gas,the premixed gas with different concentration distribution was formed in the finite space,and the gas explosion occurred after the ignition source.Therefore,based on the experimental equipment of gas explosion,this paper studies the influence of different gas concentration distribution and obstacles on the methane explosion characteristics,and discusses the mechanism of the explosion characteristics of obstacles on different methane concentration distributions.Based on the actual situation,this paper builds the experimental platform.Using two 100 mm×100 mm×500 mm pipe,the pipe containing the ignition source is called the ignition pipe,and the other is called the vent pipe,using sealing membrane to partition between two pieces of pipe sealing,respectively for the two pipes required for different concentrations of methane gas filling the experiment.The research contents are as follows:(1)The concentration of methane in the ignition terminal pipeline were 8%,9.5% and 12%,respectively.The concentration of methane in the pipe at the outlet of the vent were 4%,8%,9.5%,12% and 16%,respectively,which constituted the experimental condition gas with different concentration distribution.(2)An obstacle was set up on the pipeline at the outlet of the pressure relief port.The concentration of 9.5% methane was used in the ignition terminal pipeline and the methane concentration were 4%,8%,9.5%,12% and 16% at the outlet of the pressure relief port.(3)The influence of the change of the section position of the pipe on the explosion characteristics of the 9.5% methane concentration gas was studied by the obstacles with different shapes and different blocking rates.The following conclusions were drawn from the experimental study:In the methane explosion characteristics of different concentration distribution in the pipe research,ignition port pipes of methane concentration was 12%,pressure end pipeline of methane concentration was 8%,could explode maximum peak pressure in the pipeline explosion.In the blast pipe at the same time,the high concentration to low concentration of methane explosion pressure produced by the combustion of methane gas transmission,than low concentration to high concentrations of methane gas explosion pressure produced by the combustion of methane gas transmission.In contrast to obstacles,the peak pressure generated by an obstacle's explosion appears to increase first,then decrease,and then increase as the concentration of the vent increases.When there were obstacles,the pressure peak increased with the concentration.The velocity of flame propagation was increasing,decreasing and increasing,and the velocity of flame propagation in earlier stage was less related to the distribution of methane concentration in pressure relief port.The pressure relief port pipeline methane concentration were less than 9.5%(including 9.5%),the average flame propagation speed increased with the distance of obstacle ignition becomes smaller.Methane concentration in discharge pipeline pressure port were greater than 9.5%,the flame propagation time increased with the distance of obstacle point source increase.In the study of the influence of different spacing ratios on the methane explosion characteristics,the influence of obstacles on the premixed gas explosion characteristics increased with the increase of spacing ratio.When the barrier was distributed uniformly in the center of the pipeline,the effect of the gas deflagration was the most.When the blocking rate was lower than 50%,the average flame speed increased with the increase of the spacing ratio.When the blocking rate exceeds 50%,the average propagation velocity of flame was basically unchanged.The increase rate of explosion pressure shows the trend of first increasing and then decreasing with the increase of obstruction blocking rate.The ratio of the distance between the obstacle and the wall surface of the pipe changes,and the impact on the rate of increase of the explosion pressure of the rectangular plate obstruction with a blocking rate of 50% was the greatest.Compared to pitch ratio was 0,the deflagration overpressure between the pitch ratios 0.25 and 0.5 increased by 55.6% and 101.8%,respectively.