HIGH-SPEED LIF-OH IMAGING OF H2-AIR TURBULENT PREMIXED FLAMES PROPAGATION IN AN OBSTRUCTED CHAMBER

This paper presents a comparative study of the effects of repeated solid obstacles on the propagation of H-2-air premixed flames. Pressure, speed of the flame front, as well as the structure of reaction zones are studied for hydrogen. Two equivalence ratios are examined for different configurations of three baffle plates and two obstacles with a square cross section having blockage ratios of either 0.24 or 0.5. Hydrogen fuel mixtures with two equivalence ratios of 0.7 and 0.8 are studied, and this is limited by excessive overpressures. The results show that the peak pressure and its rate of change can be increased by increasing the blockage ratio or by decreasing the space between successive baffles. As illustrated by the high-speed images of LIF-OH, the degree of wrinkling and contortion in the flame front increases as the blockages increase. The images also show how the flame front is relaminarized with increasing distances between the obstacles, which accounts for the pressure decrease with increasing separation. It is also found that more than one obstacle is needed to achieve a turbulent flame structure with intense corrugations.