Flame propagation in mixtures of H 2 and air in a tube with a moving water film on the tube's walls

Abstract

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. Significant differences in flame propagation with and without the moving water film are revealed. For mixtures with relatively high burning velocities (hydrogen concentrations from 20 to 30 vol. %), the maximum explosion pressure with a moving water film is higher than for those without one. Also, for mixtures with relatively low burning velocities (H 2 concentration 15 vol. %), the maximum explosion pressure is lower with a moving water film than for those without one. This effect is due to a competition between increased heat losses by water evaporation into the combustion products and lower heat losses because of combustion intensification. A multipeak structure of the pressure-time curve during explosion of the gaseous mixture in the tube with a moving water film is revealed. A likely reason for this is the water film experiencing superheating where it contacts the hot combustion products until the temperature exceeds the limiting homogeneous nucleation temperature, and explosive evaporation of the water film follows. There is also the possibility of a shock wave in the liquid adjacent to a cavity in the combustion mixture of hydrogen and air during its combustion. The maximum pressure in such a pressure wave in the liquid is 2–3 times higher than the maximum explosion pressure.