Extinction of a stagnation-point diffusion flame at reduced gravity

The extinction limits of a diffusion flame in the stagnation-point boundary layer of a solid fuel in mixed-, natural-, and forced-convective flows are determined numerically. The flow is characterized by a mixed-convection stretch rate and a densimetric Froude number. The results depend primarily on stretch rate and only slightly on Froude number. The computed results show that in addition to the familiar blowoff limit, which occurs at large stretch rate, an extinction limit due to radiative heat loss from the fuel surface is found at very low stretch rate. These two extinction boundaries merge to define a fundamental low oxygen limit. The difference of this oxygen limit for forced and buoyancy-driven flows is found to be slight. (Author)