Influence of obstacles on flame propagation and gas movement ahead of flame in an open space—Effects of nets laid on floor

An investigation of the influence of obstacles on flame propagation has been performed in an open space confined only by a floor. One wire net or several nets piled on top of each other were laid on the floor as continuous obstacles. In the presence of nets, the flame shape became more slender than without ones. The highest flame speed under the nets-laid condition was about four times as fast as that under the nets-free one, although no transition to detonation was found. The velocity of gas flow ahead of the flame, which seems to be intimately related to the flame propagation, has also been calculated by using a simple model. The calculation proved that “an imaginary center of thermal expansion of gas due to combustion” moved downward to the floor under the nets-laid condition, and it could also explain some data observed for flame propagation.