In this study, several explosion tests of flammable gas mixture were conducted to observe the behaviors of explosion flame propagating in a space where obstructions were fixed. All the tests were conducted in an explosion vessel with 90cm of length, 20cm~*20cm of profile size, and 36 liters of volume. LPG, a flammable gas mainly for household use, was used as fuel in the tests because many accidents had occurred when handling this gas. Several plate type obstruction with different blockage ratio to the profile of vessel were fixed in the vessel. To make the propagation of explosion flame visualized, all the tests were videotaped by using high-speed camera. Explosion pressures were also measured by a strain-type transducer. It is shown in the tests that the higher the blockage ratio of obstruction ,the larger the size of eddy formed at the back of obstruction, the higher the flame velocity when flame passed the obstruction. In the case of a plate-type obstruction, it could be observed that flame velocity temporarily decreased due to the formation of eddy at the back of obstruction. Along with the breaking of this eddy, flame propagation was again rapidly accelerated. The higher the blockage ratio of obstruction, the larger the explosion pressures in front of the obstruction. The explosion pressures at the back of obstruction, however, were not so greatly influenced by the blockage ratio of obstruction.
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