94 / 2021-09-28 16:08:32

Acceleration characteristics of compound flame in the initial stage of gas/coal dust explosion

gas/coal dust explosion；compound flame；flame acceleration；disaster strengthening

In order to clarify the strengthening mechanism of gas / coal dust coupling explosion disaster, 20L spherical, a high-speed schlieren and a PIV were used to study acceleration characteristics and pressure change of composite flame in the initial stage of gas / coal dust explosion, and the flow field characteristics of the explosion moment were analyzed. The results show that compared with the methane / air explosion, at the same methane concentration, the flame propagation speed in the initial stage of the gas / coal dust explosion is slightly reduced, the flame cell structure is reduced, and the flame floating phenomenon almost disappears. The Markstein length decreases with the increase of methane concentration and are all positive, indicating that the development of composite flame tends to be stable in the initial stage of explosion, which is conducive to the participation of coal dust particles in combustion reaction. When the concentration of methane is close to the best equivalent concentration, the smaller the particle size of coal dust or the increase of the mass concentration of coal dust is close to the best concentration, the composite flame can be accelerated, resulting in the increase of the composite explosion power. The low concentration gas / coal dust composite system is more sensitive to the increase of coal dust mass concentration, and with the increase of coal dust concentration, the influence of methane concentration on the gas / coal dust composite system gradually decreases. The initial explosion intensity has an important influence on the gas / coal dust composite system. Due to the high initial explosion intensity of 9% gas / coal dust explosion system, the negative pressure in the center of the composite flame makes most of the coal dust particles do centripetal movement, and a large number of coal dust particles gather around the front of the flame. At the same time, a large number of large vortices in opposite directions are formed around the front of the flame, which promotes the rapid contact between the coal dust surface and oxygen, and intensifies the combustion reaction. The research results will provide guidance for the prevention and control of gas / coal dust coupling explosion disaster.