瓦斯体积分数梯度分布及柔性置障耦合作用下爆炸灾变范围研究

Gas explosion catastrophic range under the coupling effect of the volume fraction gradient distribution and the corresponding flexible obstacles

为探究柔性置障与瓦斯体积分数分布状态对瓦斯爆炸传播特性的影响,以瓦斯爆炸事故灾变范围变化为主要研究内容,从冲击波、高温火焰等主要因素展开分析。在试验的基础上采取数值模拟方法,研究了不同体积分数分布和置障耦合作用下瓦斯爆炸传播过程中压力、火焰、温度的变化特征。物理模型是截面为0.20 m×0.20 m的水平矩形管道并加入薄膜隔段,设计9.5%-0 CH4、9.5%-3.5% CH4、9.5%-6.5% CH4、9.5%-9.5% CH44 种工况。结果表明隔膜障碍物使甲烷气体从高浓度到低浓度的条件下爆炸压力骤升,最大爆炸超压在隔膜后达到1.074 MPa,部分区域温度高达3 000 K。体积分数梯度差诱导瓦斯充分燃烧,反应速率升高,强化了柔性障碍物形成的激励作用,且有助于爆炸压力与火焰速度的提高使瓦斯爆炸的受灾范围进一步扩大。甲烷体积分数在6.5%以下工况时在距爆源65 m附近的压力可达0.175 MPa,9.5%的工况时在距爆源100 m处的压力仍保持在0.3 MPa,超高压力和温度需要长距离才能下降至常压常温,促使灾变范围增大。研究揭示了在体积分数梯度分布条件下,瓦斯爆炸事故中柔性障碍物的激励效应导致灾变范围扩大的物理机制,对事故调查中确定爆炸冲击波的波及范围和事故应急救援重点区域、提高救灾方案可靠性具有理论和实际意义。

The present paper is to explore the influence of the flexible obstacles and the gas volume fraction distribution status on the propagation features of the gas explosion for the mediumscale pipelines.For the above said purpose,we have analyzed the gas explosion accident catastrophe range from the point of view of the dominant factors,such as the shock wave and the high temperature flame,etc.Based on the experience gained from our experiments,we have done numerical simulations to examine such characteristic features,as those of pressure,flame,and temperature changes in the process of the gas explosion propagation under the coupling effect of the volume fraction gradient distribution and the obstacles concerned.The physical mode that can be imagined is a rectangular horizontal tube with its crosssection being 0.20 m × 0.20 m added with a thin diaphragm segment and its 4 working conditions designed as 9.5 %-0 CH4,9.5%-3.5% CH4,9.5%-6.5% CH4,9.5%-9.5% CH4.Through a numerical simulation of the 4 designing conditions,say,the pressure peak,the flame temperature and the catastrophic range,the result of the designing results can be presented as follows:The flexible obstacles tend to cause the explosion pressure of the methane gas to increase abruptly under the highto-low tendency concentrated conditions.The maximum explosion overpressure can then be made so high as to reach 1.074 MPa behind the diaphragm and push the local area temperature up to3 000 K.And,then,the volume fraction gradient distribution can lead the local gas to get fully combusted and in turn to push up the reaction rate to strengthen the incentive effect and result in flexible obstacles.All this may help to increase the explosion pressure and the flame speed,which can further expand and extend to the disaster area of the gas explosion in a sphere of 65 m wide nearby from the explosion source to 0.175 MPa under the working condition below 6.5% CH4.The pressure strength of 9.5% of the condition at 100 m from the explosion source can be kept at 0.3 MPa,whereas it is necessary for the ultra-high pressure and high temperature to get dropped to the normal pressure and normal temperature for a long distance and prompt an increase in the scope of catastrophe.Thus,it can be seen that the given research helps to disclose the physical mechanism of the catastrophic expansion range to be caused by the excitation effect of flexible obstacles in a gas explosion accident under the condition of the concentrated gradient distribution,which can be regarded as a great theoretical and practical significance to determine the scope of the explosion shock waves and the main areas of emergency rescue,which can be expected to promote the reliability of the disaster relief plan in the accident investigation.