Performance enhancement of swirl-assisted distributed combustion with hydrogen-enriched methane

Effect of hydrogen addition to methane fuel on the performance of swirl-assisted distributed combustion was studied at 5.72 MW/m3-atm thermal intensity using different hydrogen-enrichment (at 0, 10, 20, and 40%) to methane fuel and CO2 and N2 as the flowfield diluents. High-speed chemiluminescence imaging performed (without spectral filtering) exhibited a gradual increase of chemiluminescence intensity along with gradually narrowing of the flame shape for both swirl and distributed combustion with increase in hydrogen-enrichment from increased reactivity in flame brush. Fluctuations of pressure (p ') and heat release (q ') were signals showed the existence of a peak in swirl combustion indicating the possibility of thermo-acoustic coupling. This peak mostly diminished in distributed combustion. Investigation of fluctuation with the proper orthogonal decom-position exhibited no prominent structures in distributed combustion. Measurement of lean blowoff equivalence ratios (phi LBO) at different combustion conditions showed extended phi LBO in distributed combustion indicating wider operational limits in distributed combustion. The NO emission increased in conventional swirl combustion while it consistently decreased in distributed combustion even at increased H2 enrichment to methane fuel. The exhaust CO2 gradually decreased with increase in H2 enrichment for both swirl and distributed reaction zones at constant thermal intensity. Reduced pollutants emission with hydrogen enrichment was also observed with air preheats in the range of 373-573 K to support distributed combustion for gas turbine conditions.