(54s) Maximum Explosion Overpressure of Methane/Air Mixture in Enclosures with Different Opening Degrees

TNO Multi-Energy method has a wide application in gas/vapor explosion. Many researchers use this method to calculate the overpressure vs. distance in many scenarios of gas/vapor mixture explosion. TNO Multi-Energy method gives a series of formulas to calculate gas explosion overpressure in different Confined Strengths. However, the Confined Strengths are only qualitative description without quantitative definition. Therefore, the non-quantitative relationship between Confined Strengths and opening degrees makes confuse when using the method in many cases. For many gas storage house or vapor generating workshop, it is hard to select confined strength according to the opening ratio of the enclosure. 56 kinds of methane-air mixture explosions in 4 different sizes of cubic enclosures with 14 kinds of opening degrees each were simulated by using CFD commercial software, FLACS. A correlation of the maximum overpressures in different opening degrees was proposed based on NFPA venting standard and FLACS simulations. To validate the correlation, series of tests were conducted in 100 cm ×100 cm ×160 cm enclosure with different opening degrees. 107 g methane gas which is about the 1.05 times of the flammable gas requirement of equivalent concentration was filled in the sealed box. The opening part of the enclosure was sealed with polyethylene film with thickness of 0.01 mm. The overpressure of four kinds of opening degrees was getting by NI data acquisition and computer system. The Confined Strengths parameters in TNO Multi-Energy method were quantified by using the proposed correlation. 10 Confined Strengths in TNO Multi-Energy method was quantified by the character of opening degree, F in this paper based on the correlation. The correlation and the quantified parameters can be used to calculate the maximum explosion overpressure of methane-air mixture in low blocking scenarios, such as storerooms, warehouses, or rooms with/ without opening areas, etc. It can be helpful as reference to the safety managers or relative researchers.