FLAME PROPAGATION IN MIXTURES OF H-2 AND AIR IN A TUBE WITH A MOVING WATER FILM ON THE TUBES WALLS

Flame propagation has been investigated experimentally in mixtures of H-2 and air in a tube with a moving water film on the tube's walls. Si gnificant differences in flame propagation with and without the moving water film are revealed. For mixtures with relatively high burning ve locities (hydrogen concentrations from 20 to 30 vol. %), the maximum e xplosion pressure with a moving water him is higher than for those wit hout one. Also, for mixtures with relatively low burning velocities (H -2 concentration 15 vol. %), the maximum explosion pressure is lower w ith a moving water him than for those without one. This effect is due to a competition between increased heat losses by water evaporation in to the combustion products and lower heat losses because of combustion intensification. A multipeak structure of the pressure-time curve dur ing explosion of the gaseous mixture in the tube with a moving water f ilm is revealed. A likely reason for this is the water film experienci ng superheating where it contacts the hot combustion products until th e temperature exceeds the limiting homogeneous nucleation temperature, and explosive evaporation of the water film follows. There is also th e possibility of a shock wave in the liquid adjacent to a cavity in th e combustion mixture of hydrogen and air during its combustion. The ma ximum pressure in such a pressure wave in the liquid is 2-3 times high er than the maximum explosion pressure.