AN INVESTIGATION OF PILOT-ASSISTED PREMIXED AMMONIA/METHANE/AIR BLENDS AS ALTERNATIVE FUELS IN A SWIRL-STABILIZED GAS TURBINE COMBUSTOR

Abstract

In this work, the gas turbine combustor liner wall temperatures, wall heat load, and flame stability characteristics of swirl-stabilized, premixed ammonia (NH₃)/methane (CH₄)/air flames were investigated in an atmospheric pressure can combustor rig equipped with an industrial swirl burner. The volume percentages of NH₃ and CH₄ gases in the main fuel blend were varied from 10% to 60%, and a 10% C4 pilot flame was used to ignite and stabilize the main flame. In all cases, the Reynolds number and equivalence ratio were set to 50,000 and 0.65, respectively. The Infrared Thermography technique was used to measure the liner wall temperatures, and estimate the liner wall heat load. Additionally, the effect of increasing the NH₃ volume percentage on the overall flame stability was qualitatively studied using a high-speed camera. The results showed that the liner wall heat load decreased as the NH₃ volume percentage increased, with approximately 25% reduction observed in the 60% NH₃ case compared to the 10% NH₃ case. Stable flames were obtained up to 50% NH₃, beyond which instabilities were observed in the form of oscillations with repetitive extinction and reignition occurring in the downstream portion of the flame. However, the pilot flame continued to sustain the upstream portion of the main flame, rendering the crown of each flame stable. Three-dimensional steady-state numerical simulations were carried out wherein the simulations revealed that unburnt fuel at the exhaust and outer recirculation zones increased as the NH₃ volume percentage increased in the fuel blend.