The effects of obstructions on overpressure resulting from premixed flame deflagration

This paper introduces a new experimental set-up for investigating the effec ts of obstruction geometry, blockage ratio and venting pressure on overpres sures resulting from premixed flame deflagration. Obstructions shaped as cy linders, triangles, squares, diamonds and plates or walls are studied here covering blockage ratios ranging from about 10% to more than 75%. It is fou nd that the deflagration overpressure increases with increasing venting pre ssure. Also, the maximum overpressure increases, generally with increasing blockage ratio but the rate of increase depends on the obstruction geometry . The wall/plate type obstruction leads to the highest overpressures and th e cylindrical obstruction yields the lowest overpressure. The time taken to reach the maximum overpressure decreases with increasing blockage ratio an d changes with obstruction geometry implying that the flame accelerates fas ter due to changed local turbulence levels and length scales. (C) 2001 Else vier Science Ltd. All rights reserved.