Explosion suppression range and the minimum amount for complete suppression on methane-air explosion by heptafluoropropane

A visual explosion test system consisting of a 20 L explosion vessel and a horizontal pipeline of 6.5 m in length was adopted. The effects of heptafluoropropane (CF3CHFCF3) on methane-air explosion pressure, explosion flame structure and propagation velocity under different spraying ranges and amounts were systematically studied, and the suppression mechanism of CF3CHFCF3 on the methane-air explosion was analyzed. The experimental results show that the spraying range and amount of CF3CHFCF3 have a significant impact on the methane-air explosion. The presence of CF3CHFCF3 can promote the propagation of methane flame and increase the flame brightness under certain conditions. The reasonable setting of the spraying range and amount of CF3CHFCF3 can significantly weaken the explosion pressure of various parts in the pipeline. In the case of the same spraying amount of CF3CHFCF3, a larger CF3CHFCF3 spraying range not necessarily achieves the better the explosion suppression effect. Experimental analysis shows that in this experimental system, the explosion sup-pression effect of different spraying ranges from strongest to weakest at 1.72, 2.32 and 1.12 m, the minimum spraying amounts that can prevent 9.5 % methane-air premixed gas in the explosion suppression zone explosion flame propagation are 300, 300 and 360 mL, respectively.