低温环境下甲烷爆炸流场特性模拟

Simulation study of flow field characteristics of gas explosion in low temperature environment

在低浓度煤层气含氧液化工艺过程中,甲烷浓度会处于爆炸极限范围内,存在爆炸危险。采用流场模拟平台,对密闭容器内低温环境条件下的甲烷爆炸过程进行了数值模拟。通过研究得出:在反应体系体积及初始环境压力不变的情况下,环境温度越低,最大爆炸压力越大,到达最大爆炸压力所需时间越长;爆炸流场以化学反应区为阵面分别建立正负流动区,并不断向壁面推进,火焰传播过程受化学反应区正反馈机制的影响,在密闭容器内出现点火、加速传播、衰减传播和猝灭4个阶段;随着环境温度的降低,火焰传播速度明显降低,火焰持续时间延长。该结论可为认清低温条件下的甲烷爆炸机理及预防低浓度煤层气含氧液化工艺爆炸事故提供依据。

The methane has a high risk of gas explosion because its concentration has come into the explosion limit range in the liquefaction process of low-concentration oxygen-bed methane. This gas explosion process was simulated on a flow field platform at low temperature in an air tight container. According to the simulation results, when the reaction system volume and environmental pressure are invariable, the lower the ambient temperature, the greater the maximum explosion pressure, and the longer the time it takes the methane gas to reach the maximum explosion pressure; the explosion flow field set up the positive and negative flow areas with chemical reaction zone as the front, and continually approaching the wall; the flame propagation process as affected by the chemical reaction is a positive feedback mechanism, and four phases--flame ignition, accelerated propagation, attenuated propagation and quenching--are found occurring in the airtight container; with the falling down of the am- bient temperature, flame propagation speed decreased markedly, and the flame duration extended. The resulting conclusions provide an important basis for understanding methane explosion mechanism and preventing explosion accidents in the liquefaction process of low-concentration oxygen-bed methane under low-temperature conditions.