Investigations of flame front propagation between interconnected process vessels. development of a new flame front propagation time prediction model

摘要

For the case where a dust or gas explosion can occur in a connected process vessel, it would be useful, for the purpose of designing protection measures and also for assessing the existing protection measures such as the correct placement, to have a tool to estimate the time for flame front propagation along the connecting pipe. Measurements of data from large-scale explosion tests in industrially relevant process vessels are reported. To determine the flame front propagation time, either a 1m{sup}3 or a 4.25 m{sup}3 primary process vessel was connected via a pipe to a mechanically or pneumatically fed 9.4 m{sup}3 secondary silo. The explosion propagation started after ignition of a maize starch/air mixture in the primary vessel. Noadditional dust was present along the connecting pipe. Systematic investigations of the explosion data have shown a relationship between the flame front propagating time and the reduced explosion over-pressure of the primary explosion vessel for bothvessel volumes. Furthermore, it was possible to validate this theory by using explosion data from previous investigations. Using the data, a flame front propagation time prediction model was developed which is applicable for:-- gas and dust explosions up to a K value of 100 and 200 bar m s{sup}-1, respectively, and a maximum reduced explosion over-pressure of up to 7 bar;-- explosion vessel volumes of 0.5, 1, 4.25 and 9.4 m{sup}3, independent of whether they are closed or vented;-- connecting pipes of pneumatic systems with diameters of 100-200 mm and an air velocity up to 30 m s{sup}-1;-- open ended pipes and pipes of interconnected vessels with a diameter equal to or greater than 100 mm;-- lengths of connecting pipe of at least 2.5-7 m.