ABSTRACT
FIGURE 11.1 Flame impingement normal to a cooled target. (Adapted from C.E. Baukal, L.K. Farmer, B. Gehhart, and I. Chan, 1995 Int. Gas Research Conf., Vol. II, D.A. Dolenc, Ed., Government Institutes, Rockville, MD, 2277-2287, 1996.)
are caused by the hypersonic flow impact velocities that ionize the highly shocked atmospheric gases.2 Subsequent studies have since investigated the heat fluxes attainable using high-intensity combustion, with pure oxygen instead of air, to increase metal heating and melting rates.' Highintensity impinging jet flames have been used in recent years to produce synthetic diamond coatings by chemical vapor deposition.' Supersonic-velocity, high-intensity flames have been used in a process known as thermal spallation. In this process, the impinging jet bores through rock by causing it to fragment, due to the large thermal stresses arising from the high heat fluxes on a cold surface.' This may be more rapid and economical than traditional mechanical rock drilling, depending on the rock type. High-velocity flames impinging on structural elements have been used to simulate large-scale fires caused by ruptured piping in the chemical process industry.' Low-intensity impinging flame jets have been used in safety research to quantify the heating rate caused by buoyant fires impinging on walls and ceilings.' Eibeck et al. (1993) studied the impact of pulse impinging flames on the heat transfer to a target.' Zhang and Bray (1999) studied the effects of the burner nozzle exit velocity and the distance between the impinging flame and a water-cooled plate positioned directly above the burner nozzle exit.9 As shown in Figure 11.2, five different flame shapes were identified: (1) ring flame, (2) conic flame, (3) disc flame, (4) envelope flame, and (5) cool central core flame.
