Stabilization performances and mechanisms of a diffusion-like vortex-tube combustor for oxygen-enriched combustion

The stabilization performance and mechanisms in a diffusion-like vortex-tube combustor is investigated for oxygen-enriched combustion. The stability limit, flame configuration, and pressure fluctuation are investigated under various conditions. Results show that a diffusion-like flame structure is established in the combustor and the nonpremixed peculiarity becomes more prominent with the increase of oxygen mole fraction. The steady combustion can be achieved in the range of global equivalence ratio 0.01 to 1.0 with a low-pressure fluctuation amplitude always less than 1300 Pa, indicating a good combustion stability of this combustor. Additionally, the stabilization mechanism is discussed from the time matching and velocity matching. Based on the axial fuel entry method, the Damkohler number (Da) is always less than 1.0 as a whole, which is the principal reason for the tubular flame shape and the steady combustion procedure in this vortex-tube combustor. The intensified combustion under oxygen-enriched combustion can increase the flame speed, and subsequently reduce the mixing quality and make the yellow flame more visible. Besides, the temperature distribution and the flow field structure can explain the corrugation and deformation of the flame front under oxygen-enriched conditions.