Influence of obstacle blockage on flame propagation, overpressure and local temperature of vapor deflagration in narrow ship channel-like space

A special study mainly concerning the influence of blockage ratio on flame propagation, overpressure and local temperature distribution characteristic of combustible vapor deflagration in narrow channel of ship was conducted. Rectangular obstacles with 30∼55 % blockage ratio were tested. The flame propagation, overpressure and local temperature were recorded and analyzed. Results indicated that obstacle edges have obvious shear action to flame front, which the front structure and surface area would be obviously stretched. The presence of obstacles could enhance the turbulence intensity of local fluid and induce more turbulent flame, leading to a significantly increased propagation speed. In current tests, flame propagation speed increased firstly and then decreased with the blockage ratio, and the maximum flame speed could reach 97.5 m/s. Overpressure also performs a non-monotonous variation, which could be attributed to the fact that obstacles can not only positively stimulate the deflagration by enhancing local turbulence intensity, but also have an obstructing effect on the propagation of flame and pressure wave. This means, there is a critical blockage ratio, at which the overpressure is maximized, and this critical value is found to be around 40 % in current experimental conditions. Meanwhile, the propagation of deflagration overpressure and flame involved the obvious coupling effect, and the overpressure and flame reached peaks almost simultaneously. This work is expected to provide some basic references for the emergency disposal of combustible liquid vapor deflagration accidents.