Experimental Investigation of Flame and Emission Characteristics of Hydrogen-Enriched Natural Gas MixturesAn...

The hydrogen-natural gas blending is proving to be a viable route toward the decarbonization of the city gas distribution (CGD) network in India. In this research work, a full-scale experimental testbed is introduced that has high-pressure hydrogen storage, a programmable logic controller, mass flow controllers, a static gas-mixing manifold, hydrocarbon filtration, and a moisture absorber, as well as multimaterial pipelines (galvanized iron, medium-density polyethylene pipe, and carbon steel) used in the Indian CGD infrastructure. To study the flame structure, thermal efficiency, heat flux, gas consumption, and stability of operation in the CGD simulated conditions. The experiments were performed using 0-30% hydrogen mixtures in methane. Gradual increase in hydrogen enrichment changed the flame from a typical blue flame of methane to a bluish-purple high-temperature profile, and the flame remained stable with the enrichment of the hydrogen up to 25% without flashback or instability, and at 30%, minor instability was observed. Maximum values of the highest heat flux (22,489-22,763 W/m²) were obtained at 18-25% blends of hydrogen, which implied shorter heating time and faster combustion rates. The analysis of emissions indicated a consistent decrease in carbon monoxide (CO), from 112 to 38 ppm, and in carbon dioxide (CO₂), from 8.9% to 6.1%. Additionally, with a 0-30% enrichment of hydrogen (H₂), there was an increased formation of nitrogen oxides (NO _x ) due to higher temperatures. The 25% hydrogen mixture exhibited the best combination of high heat flux, uniform flame geometry, and low gas consumption, while also achieveing the highest (12.6%). These findings illustrate that 18-25% hydrogen is the best blending range of domestic burners in the CGD system, which has better combustion efficiency, less emission intensity, and can blend with available confirmation of the hydrogen-enriched natural gas as a short-term decarbonizing measure of the CGD infrastructure in India.