Impact of Fuel Injection System on the Performance of an Industrial Burner With Hydrogen Piloting Operated With Simulated Exhaust Gas Recirculation

Exhaust gas recirculation (EGR) can be exploited to increase the CO2 content at the exhaust of gas turbines (GTs), in order to improve the efficiency of carbon capture systems. The lower oxygen level leads to challenging conditions for the combustion process, resulting in high CO and unburned hydrocarbon emissions and the possible onset of thermoacoustic instabilities. To mitigate these effects and expand the combustor's operational range, pilot flames can be employed to stabilize the combustion process, with localized hydrogen injections further enhancing reactivity. In this demanding and complex environment created by EGR, fuel injection strategy is crucial in the flame stabilization mechanism, and many design parameters come into play. The present work illustrates the results of an extensive screening performed in a single-cup atmospheric test rig at the THT Lab of the University of Florence, with EGR conditions simulated with CO2 addition in the combustion air. In particular, six different configurations of a dry low NOx industrial burner have been tested, varying the arrangement and geometry of the pilot jets, and the premix fuel injection mode. Burners' performance has been compared in terms of CO emissions, lean blow-out (LBO) limits, and dynamic behavior, and OH* chemiluminescence imaging has also been employed to investigate the flame structure. The results point out that, for the investigated configuration, the occurrence of thermoacoustic instabilities is, together with CO emissions, the main limiting factor, but benefits have been observed with hydrogen addition, and promising configurations will be further tested in engine-like conditions.