The Experimental and Kinetic Study on Ignition Characteristics of n-Butane/Oxygen-Enriched Air Mixtures in a Heated Meso-Channel

Oxygen-enriched combustion is expected to be introduced into small scale to improve the characteristics of micro- or meso-scale combustion. To fully understand the advantages of oxygen-enriched combustion, the ignition characteristics of n-butane/oxygen-enriched air mixtures are studied by the experimental and numerical methods in a heated quartz tube with an inner diameter of 5 mm. The experimental results show that the oxygen enrichment level, equivalence ratio, and flow rate have an important influence on the ignition temperature of the mixed gas in the tube. The ignition temperature decreases with the increasing oxygen enrichment and is strongly affected by oxygen concentration at higher equivalence ratio and lower oxygen enrichment level. In the meanwhile, higher equivalence ratio and lower flow velocity also significantly reduce the ignition temperature in the experimental cases. Furthermore, the increase in the oxygen enrichment level significantly enhances the effect of the equivalence ratio on the ignition temperature while higher flow velocity slightly weakens the effect. The numerical results show that oxygen enrichment is beneficial to the production of OH radicals in pre-ignition period and significantly promotes the oxydehydrogenation reactions of intermediates.