Colorless distributed combustion effects on hydrogen-enriched methane fuels combustion in a laboratory-scale combustor

Abstract

This research explores the burning of methane fuel enriched with hydrogen in a distributed mode within a laboratory-scale combustor. The objective is to improve the combustion efficiency of these fuels by incorporating hydrogen enrichment. However, it is evident that hydrogen enrichment increases flame temperature. Therefore, the application of colorless distributed combustion (CDC), an advanced combustion technique that controls flame temperature by slowing down reaction rates, is proposed to achieve ultralow emissions and a uniform temperature with an expanded combustion flame. To achieve this goal, a Computational Fluid Dynamics (CFD) code was employed to model hydrogen-enriched methane fuels. The findings suggest that the introduction of hydrogen enrichment raises flame combustion temperatures from around 1625 K to 1654 K when up to 20 % H2 is present in the fuel. This temperature elevation correlates with a rise in the anticipated levels of NOX within the combustion chamber. As the oxygen percentage decreases, the flame expands, and flame temperatures, for instance, for fuel containing 20 % H2, decrease from around 1654 K to 1359 K at 15 % O2. Consequently, NOX levels in the combustion chamber drop from approximately 565 ppm to values below 0,98 ppm. The distributed regime demonstrates the capability to mitigate the increases in temperature and emission levels associated with hydrogen, thereby suggesting that hydrogen-enriched gas turbines could operate within broader flammability limits.