ABSTRACT

In order to reduce the damage caused by a gas explosion in a ventilation duct, a Large Eddy Simulation (LES) model was used to simulate the hydrogen/air explosion process in the ventilation duct under different side vent. The results show that in the process of flame propagation, the large size side vent near the ignition end produces a larger discharge effect, which causes more serious distortion and longer time for the flame front passing through the side vents. The influence mechanism of the side vent on the flame propagation is different at different stages of flame propagation. When the flame front is behind the side vent, the positive flow field traction on the flame front increases the contact area between the flame front and unburned gas, and thus accelerates the flame propagation. When the side vent is 1 m away from the ignition end, with the side vent diameter increasing from 40 mm to 80 mm, the peak flame propagation speed increases by 19.02% before the flame reaches the vent. When the flame front passes through the side vent, the exhaust of the side vent and the disturbance of the vertical flow field can restrain the flame propagation. However, when the flame front is in front of the vent, the synergistic effect between turbulent vortex and reverse flow field causes the flame propagation speed to fluctuate greatly. The influence of the side vent size on the explosion relief effect is restricted by the side vent position. When the side vent is located in the pressure rising section, the pressure relief effect of the side vents with different sizes is very great and is almost unaffected by the size of the side vent. When the side vent is 1 m away from the ignition end, the peak overpressure in the tube decreased by 50.75%, 52.88% and 55.43%, respectively, when the diameter of the side vent was 40 mm, 60 mm and 80 mm. On the contrary, when the side vent is outside the pressure rising section, the pressure relief effect of the side vent will be weakened, and vents with different sizes have a great alteration to pressure relief effect. For the side vent being 5 m from the ignition end, the peak overpressure in the tube decreased by 4.49%, 13.41%, and 35.51%, respectively, when the diameter of the side vent was 40 mm, 60 mm, and 80 mm.

摘要

为了减少通风管道内气体爆炸造成的破坏，采用大涡模拟（LES）模型对不同侧通风口下通风管道内的氢气/空气爆炸过程进行模拟。结果表明，在火焰传播过程中，靠近点火端的大尺寸侧排风口产生较大的放电效应，导致火焰锋面通过侧排风口的变形更严重，时间更长。在火焰传播的不同阶段，侧通风口对火焰传播的影响机制是不同的。当火焰锋在侧通风口后方时，火焰锋上的正流场牵引增加了火焰锋与未燃烧气体的接触面积，从而加速了火焰的传播。当侧通风口距点火端1m时，随着侧通风口直径从40 mm增加到80 mm，火焰到达通风口前的峰值火焰传播速度增加了19.02%。当火焰锋通过侧通风口时，侧通风口的排气和垂直流场的扰动可以抑制火焰的传播。但是，当火焰锋在通风口前方时，湍流涡流与反向流场的协同作用使火焰传播速度波动较大。侧排气口尺寸对泄爆效果的影响受侧排气口位置的限制。当侧排气口位于升压段时，不同尺寸的侧排气口的泄压效果非常大，几乎不受侧排气口尺寸的影响。当侧通风口距点火端1m时，当侧排气口直径为40 mm、60 mm和80 mm时，管内峰值超压分别下降50.75%、52.88%和55.43%。相反，当侧排气口在升压段外时，侧排气口的泄压效果会减弱，不同尺寸的泄压口对泄压效果有很大的影响。对于距点火端5 m处的侧排气孔，当侧排气孔直径为40 mm、60 mm和80 mm时，管内峰值超压分别降低了4.49%、13.41%和35.51%。不同尺寸的排气孔对泄压效果有很大的改变。对于距点火端5 m处的侧排气孔，当侧排气孔直径为40 mm、60 mm和80 mm时，管内峰值超压分别降低了4.49%、13.41%和35.51%。不同尺寸的排气孔对泄压效果有很大的改变。对于距点火端5 m处的侧排气孔，当侧排气孔直径为40 mm、60 mm和80 mm时，管内峰值超压分别降低了4.49%、13.41%和35.51%。