Experimental Research On The Effect Of Ventilation Openings On Flashover

The flashover is an unique phenomenon in the developing process of the building fire, which is a phenomenon of fire transition from partial combustion to the entire one in an enclosure. And it marks the indoor fire transit from early stages to full development. Flashover is the result of heat accumulation. Domestic and foreign research institutions study a lot on the influencing factors of fire flashover. The research methods include two categories:experiments and numerical calculations. There are many factors affecting the occurrence of flashover, which include the fire source parameter, the heat conductive performance of lining materials, the ventilated parameter, the piling density of the combustible substance as well as the room dimension and the configuration etc. Prediction methods are also many.This article mainly analyses influences of ventilated openings to flashover. The experimental results show that in the one-side opening situation, namely fuel burning with no forced wind pressure and convection, the opening position lower, the maximum temperature higher, it's much easier to cause the flashover; As other conditions are certain, the occurrence of the flashover relates to the ventilation factor. In experiments by changing the height of the opening, flashover will occurs only when ventilation factor is proper, if the value is too small, the combustion rate can only maintain at a relatively low level, which cannot cause the flashover, while when the ventilation factor is bigger than some definite value, it is disadvantageous to transform from the fuel control to the ventilated control, also cannot cause the flashover, which tallies with the theoretical results; when there is another opening in the opponent wall, air flow speeding up, the flashover can be caused easily; With the forced ventilation the speed and the direction of wind can both influence the flashover. When the degree between the wind direction and the wall is 45°, it's easy to cause the flashover; The flashover can occur only when the wind speed is in some extent.