Fire Safety Science Digital Archive

Experimental investigations of a flame propagation in H2-air mixtures in a tube with the moving on tube walls water film are executed. Sufficient differences in flame propagation with and without the moving water film are revealed. By means of the numerical modelling of a flame propagation in a smooth tube with the account of heat loses into tube walls and the comparison of numerical and experimental pressure-time histories it was found that the values of an effective flame turbulization factor are in the range 10 to 30 for the mixtures with the hydrogen concentrations from 15 to 30% (vol.), and the higher is the laminar burning velocity of the mixture, the lower is the effective turbulization factor. The significant intensification of the hydrogen-air mixtures combustion in the tube with the moving water film is shown. For the mixtures with relatively high burning velocities (hydrogen concentrations from 20 to 30% (vol.)) the maximum explosion pressure in the case of an availability of the moving water film is higher, and for the mixtures with the relatively low burning velocities (H2 concentration 15% (vol.)) - is lower than for the case with an absence of the moving water film. This effect is due to the competion between the heat loses increase by means of the water evaporation in the combustion products region and the heat loses decrease by means of the combustion intensification. The multi-peak structure of the pressure-time curve during the gaseous mixture explosion in the tube with the moving water film is revealed. A probable reason of this effect is a water film superheating at its contact with the hot combustion products till the temperature, which exceeds the limiting homogenic nucleation temperature and, the following explosive water film evaporation. The possibility of a hydroshock occurrence in a liquid which is adjacent to a cavity with the combustible hydrogen-air mixture during its combustion is found. The maximum value of the pressure in a pressure wave in the liquid is 2-3 times higher than the maximum explosion pressure.