An experimental investigation on the rapidly mixed type tubular flame combustion under high oxygen mole fractions

An inherently safe technique of rapidly mixed type tubular flame combustion has been experimentally examined to extend it to high oxygen concentrations including pure oxygen. Fuel and oxidizer are separately injected into cylindrical burner through four tangential slits. Oxygen is gradually added into air to increase oxygen mole fraction in the oxidizer, and three cases with oxygen mole fractions of 0.684, 0.842 and 1.0 are investigated with two different burners. Stable tubular flame is established at lean condition, while oscillatory combustion becomes dominant at large equivalence ratio. The stable tubular flame range in equivalence ratio shrinks with an increase of slit width from 1 to 2 mm owing to reduced injection velocity and anchored diffusion flame. With an increase of flow rate hence increased injection velocity, the mixing of fuel and oxygen is enhanced, resulting in a slightly expansion of tubular flame range, especially for the case of slit width of 2 mm where the diffusion flame has been inhibited at low equivalence ratio.