Investigation On Propagation Of Premixed Methane-air Explosion Flame In Tube

Aiming at the situation of explosive disaster of methane and other industrial flammable gases, some research on premixed methane-air flame propagating in tube was investigated experimentally and theoretically. The phenomena of flame propagation were described systematically.Based on square transparent experimental tube with 1.5m long, photoelectrical transducer, pressure transducer and high-speed video camera was used to set up optical and pressure signal testing system. The results show below:(1) In small-scale tube, the ignition end is airtight and the other end is closed by paper. Pressure distribution regularity of premixed methane-air gases in the process of flame propagation with or without obstacle plate is basically identical. At first, the pressure increases gradually along the tube until peak pressure emergence in the middle of tube and then begins to fall. Pressure falls rapidly at the open end.(2)Obstacle plates stimulate flame propagation, which can increase flame speed remarkably. The speed of flame propagation with obstacle plates of D shape is more than one scalar grade and the maximum speed is 250m.s^-1. The peak explosion pressure also increases remarkably, which can arrive at 0.5MPa. The influence of blockage ratio of obstacle plate on the speed of flame propagation is dominating, while that of the space of repeated obstacle plates on the flame speed is subordinately.(3)When methane concentration is at about optimal concentration (about 10%(V)), flame velocity and explosion pressure reach maximum.(4)Under testing condition, the arrival time of each optical signal in each measurement spots corresponds to trigger of pressure signal. The moment of strong light shows that pressure is large, or we can say that flame propagation generates large pressure. The duration of pressure is longer than flame signal.(5) In the experiment, the tube is 1.5m long, the ratio of the tube length to the size of the tube side is 15. In so small-scale tube, methane-air premixed gas cannot lead to the phenomena of detonation in the case of obstacle plates or not.The paper gets the formula that deal with flame speed and pressure in tube through simple theoretical analysis. The resulting formula is according with the testing results, which provides a approximate method for calculating parameter of explosionflame in tube. At the same time, flame propagation process under simple condition is simulated numerically. Numerical calculation result basically reflects change of parameter field.The research has some effect on preventing and controlling explosion disaster of methane in mine and other flammable gases. It deepens our understanding to combustion and explosion problem in explosion theory, and it also deepens our understanding to flame propagation in combustion theory.