Experimental study of premixed flame propagation over various solid obstructions

Accounting for the probability of an explosion is essential in the design o f plants and onshore or offshore gas or oil exploration platforms. This, of course, will have major implications on the safety of personnel both in te rms of potential loss of life and the possibilities of escalation processes , which could lead to catastrophic consequences. The mechanisms which enhan ce explosion overpressures, therefore, need to be established with some cer tainty in order to ensure that all aspects of the safe design of structures and processes and the safe protection of personnel are taken into account. This paper presents an experimental investigation of the interaction of pr opagating premixed flames with various solid obstructing bodies to quantify the role of generated turbulence in flame acceleration and structure. Thre e different obstructions with circular, triangular and square cross-section s are studied here covering blockage ratios ranging from about 10% to 78%. High-speed video images were used to track the propagating flame front and the volume of trapped mixture behind the obstacle downstream from the ignit ion point. Images taken at different times after ignition are presented and discussed in terms of flame structure and acceleration. It is found that o bstructions with square cross-sections result in the fastest flame accelera tion followed by triangular and circular cross-sections. Also, flame speed is found to increase with increasing area blockage ratio. The volume of tra pped unburned mixture is found to be high when square and triangular obstac les are used. (C) 2000 Elsevier Science Inc. All rights reserved.