Detonation Propagation in Hydrogen/Methane-Air Mixtures in a Round Tube Filled with Orifice Plates
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摘要: 在内径48 mm、长度5 800 mm的含环形障碍物圆管内,进行了氢气-空气及氢气-甲烷-空气的爆轰波传播试验研究,确定了爆燃转爆轰(Deflagration-to-Detonation Transition,DDT)极限。环形障碍物阻塞比为0.56,间距分为两种,即S=D和S=2D,其中S为障碍物间距,D为管道内径。火焰的速度由安装在管道壁面上的光电二极管采集得到。试验测量得到的火焰为准爆轰或阻塞火焰。在S=2D情况下得到的火焰速度均比S=D情况下的火焰速度高,并且靠近DDT极限时速度波动更明显,表明在间距较大的情况下爆轰的重起爆循环周期更长,类似于"弛振爆轰"。对于氢气-空气,障碍物间距为D时在DDT极限处有d/λ>1(富氧条件下d/λ=1.6,贫氧条件下d/λ=1.4),间距为2D时更容易形成爆轰的重起爆,在DDT极限处与准则d/λ≈1一致;对于氢气-甲烷-空气,甲烷的添加使爆轰更不稳定,对于两种间距的障碍物得到的DDT极限均有d/λ≈1(d和λ分别为障碍物内径和爆轰胞格尺寸)。说明障碍物间距对爆轰波传播有显著的影响,即间距的增大更有利于爆轰波的传播。为形成准爆轰,障碍物内径必须至少可以容纳一个爆轰胞格,同时障碍物间距足够大从而引起爆轰的重起爆。Abstract: In this study experiments were carried out in a round tube, 5 800 mm in length and 48 mm in inner-diameter, filled with orifice plates, to investigate the detonation of hydrogen-air mixtures and stoichiometric hydrogen-methane-air mixtures, and the DDT (Deflagration-to-Detonation Transition) limits were determined.The blockage ratio of the orifice plates was 0.56, and the spacing was divided into two, i.e., S=D and S=2D, in which S and D are the obstacle spacing and the tube diameter.The flame velocity was obtained using photodiodes mounted on the tube wall.The results show that the flame regime observed is the quasi-detonation or the choked flame.The flame velocity measured for S=2D is larger than that for S=D, and the velocity fluctuation is more significant.This indicates that the cycle of the detonation failure and re-initiation is longer for S=2D, which is similar to the "galloping detonation".For hydrogen-air mixtures, detonation re-initiation occurs more aptly at S=2D, and the limits correlate well with d/λ≈1.In the case of hydrogen-methane-air mixtures, the DDT limits for S=D and S=2D are both consistent with d/λ≈1, where d and λ are the inner diameter of the orifice plate and the detonation cell size.The results indicate that the obstacle spacing has a significant effect on the propagation of detonation, i.e., detonation propagates more aptly for increased spacing.To generate the quasi-detonation, the opening of the orifice plate has to be large enough to contain at least one cell size while the spacing has to be large enough to form detonation re-initiation.
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Key words:
- gas explosion /
- orifice plates /
- DDT limits /
- hydrogen-methane
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表 1 氢气-空气的DDT极限
Table 1. DDT limits for hydrogen-air mixtures
Obstacle spacing Lean limit/% φ d/λ L/λ Rich limit/% φ d/λ L/λ D 22 0.67 1.6 7.0 48 2.20 1.4 6.4 2D 21 0.63 1.1 7.2 49 2.29 1.0 6.6 表 2 化学计量比下氢气-甲烷-空气的DDT极限
Table 2. DDT limits for stoichiometric hydrogen-methane-air mixtures
Obstacle spacing Limit (X) d/λ L/λ D 0.75 0.9 4.0 2D 0.75 0.9 6.1 -
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