Hydrogen-enriched methane combustion in a swirl vortex-tube combustor

The hydrogen-enrichment combustion performance was investigated numerically by employing methane mixed with different volume proportions of hydrogen, wherein a vortex-tube combustor was employed to achieve a steady combustion process. Results show that this combustion technique indicates good adaptability to hydrogen-enrichment combustion together with an ultra-steady combustion process. The lean stability limit is always within 0.15, which decreases further with the increase of hydrogen content, whilst the amplitude of pressure fluctuation op is always within 500 Pa with a uniform flame front. The generated non-premixed property flame structure can guarantee a high concentration of components in the reaction zone, which im-proves the local concentration of species and yields a large stability limit. The strong vortex flow can decrease the local flow velocity to inhibit flame blow-out and yield a large tangential velocity component. The high com-bustion intensity generates a large density gradient. The large density gradient and large tangential velocity promote the laminarization of the flow, resulting in a large Richardson number Ri* that is always much greater than 1.0. The laminarization of the flow field provides good aero-dynamic and thermo-dynamic stability. Further, the thermo-acoustic coupling is ultra-weak as well, and therein the Ra(x) is always smaller than 0.0024, indicating good flame-dynamic stability. In summary, the resultant good aero-dynamic, thermo-dynamic, and flame-dynamic stabilities of this vortex-tube combustor are the principal reasons for the super-steady hydrogen -enrichment combustion.