湍流的诱导及其对瓦斯爆炸过程中火焰和爆炸波的作用

Induction of Turbulent Flow and Its Effects on Flame and Explosion Wave in Gas Explosion

在实验的基础上,研究了管内瓦斯爆炸过程中湍流的诱导及其对瓦斯爆炸过程中火焰和爆炸波的影响作用。研究结果表明,管道面积突变对瓦斯爆炸过程中湍流的产生具有重要影响。管道面积突变(变大、变小)时,产生附加湍流,并使下游火焰气流的湍流度增加,瓦斯爆炸过程中火焰的传播速度迅速提高,并可诱导激波的产生。在80×80mm等截面直管中(瓦斯浓度为理论上最猛烈的爆炸浓度9.5%),瓦斯爆炸最大火焰传播速度为40.8m/s,管内各点均为压力波信号,当管道加装一Φ300mm圆管形成面积突扩11倍和突缩11倍两断面后,面积突扩处(L/D=22)火焰速度增大5.05倍,达到64.4m/s,面积突缩处(L/D=28)火焰速度为156.0m/s,增大4.55倍,并在L/D=48倍处形成激波(超压1.6976atm、波速416.7m/s),在L/D=98倍处,激波强度最大。在面积突变管内加装加速环可使瓦斯爆炸过程中湍流度加剧,火焰的传播速度更高,激波生成的位置(L/D=28)、最强点位置(L/D=70)均前移,激波强度增大。研究结果对指导现场如何防治瓦斯爆炸,减轻瓦斯爆炸的威力具有一定的指导意义。

This paper examines experimentally the induction of turbulent flow and its effects on the flame and explosion wave. The results show that the sharp change of cross sections has great influences on production of turbulent flow in gas explosion. As the cross section abruptly changes (increase or decrease), additional turbulent flow is produced resulting in the increase of turbulence in downstream flame gas flow, and the dramatic increase of propagation speed of the flame and hence shock wave is induced in gas explosion. In the straight tube with constant cross section measuring 80×80mm and filled with methane with concentration of (9.5%) resulting in the most severe explosion in theory, the maximum propagation speed of the flame in explosion is (40.8)m/s, and the pressure wave signals are detected at all locations of the tube; as the tube was installed with a section of round tube of Ф300 to form two cross sections with area sharply increased or decreased by 11times, the flame speed is increased by 5.05 times to 64.4m/s at the sharply increasing section (L/D=22) and by 4.55 times to 156.0m/s at the sharply decreasing section (L/D=28), and a shock wave forms with the pressure of 1.6976ata and the speed of 416.7m/s at the location L/D=48 as well as the maximum intensity at the location L/D=98. The addition of acceleration coil in tube with sharply changing section will further increase the turbulence of flow, the flame speed and move forward the location (L/D=28) where shock wave forms and the location (L/D=70) where shock wave reaches the maximum intensity, and increase the intensity of shock wave. These results may be useful in the field prevention and control of gas explosion and the relief of the gas power explosion.