Characteristics of Premixed Ammonia/Methane/Air Blends as an Alternative Fuel in a Swirl-Stabilized Gas Turbine Combustor Under Varying Pilot Percentage

Abstract

Alternative low carbon fuel blends are a promising way towards clean energy transition in the transportation and power generation sectors. In this work, the objective was to study the combustion characteristics of one such low carbon fuel blend (premixed Ammonia, Methane and Air) in a swirl stabilized Gas Turbine Can Combustor under varying % of pilot fuel flow (= 8 % to 10 % of the main fuel flow rate) at atmospheric pressure conditions. Pure Methane was used as the pilot flame which helped in the ignition and stabilization of the main flame and was kept on throughout the experiment. Different volume % of Ammonia and Methane blends were analyzed (starting from 10 to 50 % Ammonia in the fuel blend and the rest being Methane) at Reynolds number of the incoming air ~ 50000, and at equivalence ratio = 0.6 and 0.7. Characteristics such as Combustor liner wall heat load and flame stability were studied using the Infrared Thermography technique and High-Speed flame imaging respectively. Additionally, both carbon and NOx emission trends were estimated for selected cases using the CONVERGE CFD software under steady state conditions incorporating the RANS RNG k-ε and SAGE modeling techniques. Among all cases, wall heat load was observed to be the least for the 50 % Ammonia-50 % Methane case and for cases under reduced pilot %. Also, under reduced pilot %, flames were mostly unstable wherein the manifestation of instabilities at equivalence ratio = 0.6 and 0.7 were markedly different from one another.