Combustion Characteristics of Premixed Ammonia/Methane/Air Blends as an Alternative Fuel in a Swirl-Stabilized Gas Turbine Can Combustor Sustained Using a Pilot Flame

Abstract

The present research work investigated the combustion characteristics of lean premixed ammonia/methane/air flames in an atmospheric pressure swirl-stabilized gas turbine can combustor. The study focused on characteristics such as flame structure, flame stability, combustor liner wall heat load and emissions. Different volume % of ammonia–methane (0–50% ammonia, the rest being methane) blends were considered at an equivalence ratio = 0.6 and at Reynolds number ~50,000 where the flame was sustained using a 10% methane pilot flame. High-speed flame luminosity imaging was carried out to study characteristics such as flame structure and flame stability. Infrared thermography technique was used to simultaneously measure both outer and inner liner wall temperatures and to estimate the liner wall heat load. For studying emissions, steady-state numerical modeling was carried out using the converge cfd 3.0 software where both isothermal and adiabatic cases were studied; The latter comprised the entire volume fraction range of ammonia. Particle image velocimetry data were used to validate the numerical model. From the study, ammonia/methane/air flames were found to exhibit increased flame–turbulence interaction compared to the pure methane–air flame. Flame instability and flame extinction were observed in the 50% ammonia–50% methane flame in the downstream section of the combustor away from the pilot flame and along the combustor wall unlike the other flame cases. Compared to the combustor wall heat load in the pure methane–air flame, in ammonia/methane/air flames, the combustor wall heat load was found to be reduced by ~10% to 40% for various cases. In addition, NOx emissions for ammonia/methane/air flames were found to be less under isothermal wall conditions as compared to adiabatic wall condition because of unburnt fuel.