Flame and pressure development of large-scale CH4-air-N2 explosions. Buoyancy effects and venting requirements.
Sapko-MJ; Furno-AL; Kuchta-JM
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8176, 1976 Oct; :1-32
The pressure and flame development of the methane-air-nitrogen system was investigated in the Bureau's 127-foot diameter sphere to define buoyancy effects and to develop relationships for predicting venting requirements. Pressure rise (deltap) is defined as a function of time (t) and nitrogen dilution and is shown to deviate noticeably from the cubic law (deltap=kt3), depending upon the period of combustion and the mixture composition. Corresponding flame speed (Sf) and burning velocity (Su) data are given which show that Sf is time dependent and that N2 dilution has a greater effect than air dilution in inhibiting the flame propagation. The Su data agree with "accepted" values and are unique in that they are based on much larger flames than those used in other investigations. Downward propagation limits are shown to depend mainly upon buoyant forces, which can affect the burning of even stoichiometric CH4-air systems. Theoretical expressions, based on the mixture burning velocity and expansion ratio, are given for predicting the venting requirements for ignitions of hydrocarbon-air-nitrogen mixtures in spherical or cubical enclosures.
Ventilation; Mining-industry; Underground-mining; Explosions; Explosives; Explosion-venting
IH; Report of Investigations
NTIS Accession No.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 8176