Oxy-fuel combustion of propane based on rapidly mixed tubular flame technology

An inherently safe technique of rapidly mixed tubular flame combustion, with the fuel and oxidizer individually injected into a combustor, was adopted to investigate the oxy-fuel combustion of propane. The variations of flame structure and combustion stability with oxygen mole fraction were addressed. Based on propane/air combustion, it was found that the rapidly mixed combustion could obtain almost the same flame structure as that of the premixed combustion. Thereafter CO₂ was used as the diluent, and combustion tests were conducted under different oxygen mole fractions. Results illustrated that when oxygen mole fraction was no more than 0.5, a uniform and stable tubular flame can be established from lean to rich limit; by increasing oxygen mole fraction to 0.6, the laminar flame became non-uniform in structure, however, the flame was stable; by raising oxygen mole fraction to 0.7, the stable tubular flame was merely obtained at lean combustion, and oscillatory combustion appeared when the equivalence ratio of 1.0. By further increasing oxygen mole fraction, the oscillation region was expanded. The combustion range for propane/oxygen mixture diluted by N₂ and CO₂ was examined when oxygen mole fraction was no more than 0.4. It was found that the flammable range diluted by N₂ was wider than that diluted by CO₂, and the minimum oxygen mole fraction to sustain propane/oxygen combustion diluted by CO₂ was 0.18, higher than that of 0.125 diluted by N₂.