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Investigations of flame front propagation between interconnected process vessels: Development of a new flame front propagation time prediction model.
journal contributionposted on 23.11.2009, 10:16 by Markus Roser, Albrecht Vogl, Siegfried Radandt, W. Malalasekera, Robert M. Parkin
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 1 m3 or a 4.25 m3 primary process vessel was connected via a pipe to a mechanically or pneumatically fed 9.4 m3 secondary silo. The explosion propagation started after ignition of a maize starch/air mixture in the primary vessel. No additional 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 both vessel 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-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 m3, 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-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.
- Mechanical, Electrical and Manufacturing Engineering