Experimental study on the effect of bifurcations on the flame speed of premixed methane/air explosions in ducts

Bifurcations in process industries can significantly affect gas explosions in pipelines, ducts or underground roadways. Previous studies have addressed gas explosion propagation in bifurcations with two right angles. Three different types of bifurcations with different angles and incorporated positions were adopted in our experiments. The flame speeds were found to decrease dramatically in the bifurcation sections. Meanwhile, the bifurcation led to a strong flow reversal and turbulence, which enhanced premixed methane-air explosions in the ducts and reached a higher maximum flame speed as a result. The flame speeds and maximum values in two branches are close in ducts with two symmetrical branches. However, the maximum flame speed in the acute branch of the bifurcated duct was the highest. Upon shortening the bifurcation position, the minimum flame speeds in different types of bifurcated ducts were close, and the flame speeds seemed higher in ducts with a closer bifurcation position at the same distance.