Characteristics of Combustion and Heat Transfer of Premixed Flat Flames with Heat Loss Stabilized in a Stagnation Flow.

Abstract

The effects of the temperature of the stagnation surface (surface temperature),the Lewis number of the deficient reactant and preheating of the unburned gas on the characteristics of premixed flat flames with heat loss stabilized in the stagnation flow were numerically examined in order to utilize the heat from the flame effectively and to develop a new type of domestic burners and heaters. Then, the characteristics of convective heat transfer to the stagnation surface from the flame were discussed. (1) With an increase in the surface temperature T ω and in the preheat temperature of the unburned gas T e , and with a decrease in the Lewis number Le, the flame temperature at the same value of the first Damkohler number D I is increased. (2) The heat flux utilized from the flame at the near limit of extinction is increased with an increase in T e , and with a decrease in Le and T ω (3) The characteristics of heat transfer to the stagnation surface in the case in which the premixed flat flame is stabilized in the stagnation flow are superior to those in the stagnation flow in which only the burned gas flows. (4) In order to increase the heat flux utilized from the premixed flat flame stabilized in stagnation flow, it is necessary to maintain higher flame temperature and to stabilize the flame near the stagnation surface. Therefore, preheating of the unburned gas and use of the premixed gas with Le< 1.0 are effectual in improving characteristics of heat transfer to the stagnation surface.