Studies Of Methane And Methane-Air Flames Impinging On A Cold Plate

Jet-impingement heating is of interest because it offers, potentially, a method of increasing convectiveheat-transter rates. The impinging jet may be high-velocity combustion products or an actual flame. In the latter case, convection vivre may enhance the heat-transfer rate. The work reported here is concerned with the impingement of a methane-diffusion flame and a premixed methane-air flarne on a cold steel plate. The dominant feature of both flames was the presence of a cool central core of unreacted gas which impinged on the plate (nozzle-plate distance/burner diameter = 10–16). This caused the area of the plate around the stagnation point to be cooler than the maximum temperature which was achieved at some distance away. The heat flux through the plate followed a similar pattern. A nozzle-Reynoldsnumber increase extended the zone of influence of this cool central core. A special feature of the diffusion flame was the series of rings of “visible eddies” observed in the wall-jet region. Temperature measurements taken in the premixed flame showed that, as well as the cool core, there was also a small, very-high-temperature region whose temperatures approached the theoretical same temperature. The measurements were at too low a temperature to indicate whether convectior vivre enhanced the heat-transfer rate but the heat-transfer coefficient did not decrease with distance from the stagnation point as with nonreacting jets. The coefficient was bigher in the wall-jet region than in the impingement region due to the effect of the cool, central core.