含弱约束结构受限空间甲烷爆炸及传播特征实验研究

Experimental study on the characteristics of methane explosion and propagation in closed space with weak constraint structure

为研究含弱约束受限空间内甲烷爆炸压力升高及沿扩散管的传播特征,对不同体积分数甲烷的爆炸特征参数进行了系列实验。获得了含弱约束结构受限空间在不同浓度甲烷爆炸时的压力升高规律,研究表明,含弱约束受限空间内的甲烷爆炸压力升高趋势类似封闭空间,但压力峰值远小于封闭空间,封闭空间最大压力是含弱约束结构空间的3. 2倍。由于弱约束结构的存在,甲烷体积分数较低时破膜压力较大,腔体内高压持续时间较短,而接近爆炸当量浓度时腔体内高压持续时间增长。扩散管中的爆炸压力和火焰传播规律随甲烷体积分数变化呈现明显不同。在实验条件下,当甲烷体积分数低于7. 0%时,破膜激波与火焰锋面时间差最大为5. 255 ms,扩散管中的火焰主要为膨胀火焰。而甲烷体积分数高于7. 4%时,破膜激波与火焰锋面时间差为28～40 ms,说明在管外发生了二次爆炸,以湍流火焰为主。爆炸压力的沿管道传播则分为3种情况,甲烷体积分数低于7. 0%时,爆炸压力随传播距离增大而减小;甲烷体积分数为7. 4%和11. 0%时,爆炸压力随传播距离增大呈线性增大;甲烷浓度为当量浓度时,其压力传播特征类似于全管道甲烷爆炸的特征,随传播距离呈现锯齿形增大。实验结论对天然气长输管道、LNG和CNG储罐检修过程中的爆炸事故预防和含弱约束结构的其他气体泄爆具有参考意义。

In order to study the characteristics of methane explosion pressure rise in confined space with weak constraint and its propagation along the diffusion tube. A series of experiments were carried out on the characteristic parameters of methane explosion at different volume fraction. The regularity of pressure increase in the confined space with weak constraint structure with different volume fraction of methane explosion was obtained. The research shows that the rise characteristic of methane explosion pressure in the space with the weak constraint is similar to the closed space,but the peak pressure is much smaller than the closed space.The maximum pressure of the fully enclosed space is 3.2 times higher than the structure space with weak constraint.Due to the existence of constraint structure,when the volume fraction of methane is low,the blasting pressure is high,and the duration of high pressure in the cavity is short,while the duration of high pressure in the cavity increases when the concentration is close to the explosion equivalent.The propagation law of explosion pressure and flame in diffusion tube after film breaking was also obviously different as the change of methane volume fraction.Under the experimental conditions,when the methane concentration is low than7.0%,the maximum time difference between the burst shock wave and the flame front is 5.255 ms. The flame in the diffusion tube is mainly the expansive flame.Nevertheless when the methane concentration is high than 7.4%,the time difference is 28-40 ms.It suggests a second explosion of methane in the pipe,and the flame is mainly the turbulent flame.The propagation of explosion pressure can be divided into three situations. When the methane concentration is lower than 7.0%,the explosion pressure decreases with the increase of propagation distance. When the methane concentration is 7.4% and 11.0%,the explosion pressure increases linearly with the propagation distance.When the methane concentration is equivalent,its pressure propagation characteristics are identical to those of the gas explosion in the whole pipeline.The explosion pressure increases zigzag with propagation distance.The experimental results have reference significance for the prevention of explosion accidents and other gas burst with weak restrained structure during the overhaul of long gas pipeline,LNG and CNG storage tanks.