COMBUSTION DIAGNOSTICS AND EMISSIONS MEASUREMENTS OF A NOVEL LOW NOX BURNER FOR INDUSTRIAL GAS TURBINE OPERATED WITH CO2 DILUTED METHANE/AIR MIXTURES

While the employment of Exhaust Gas Recirculation (EGR) is a well-established technique in Internal Combustion Engines to limit NOx emissions, its adoption in Gas Turbine engines hasn't yet found a practical application due to its expensive and complex installation that doesn't justify the emissions reduction when compared to already established DLN combustion technologies. EGR becomes an interesting option in GT engines considering the possibility of increasing the CO2 content of the exhaust gases to improve the efficiency of Carbon Capture and Storage (CCS) units. However, the decrease in oxygen content of the combustion air is extremely challenging in terms of combustion stability and therefore of engine operability. In the present work, a low NOx burner was studied at ambient pressure in a reactive single burner test rig. The burner was fed with methane and characterised in terms of emissions and stability limits at different operating conditions. In addition, the flame position and shape were studied through OH* chemiluminescence imaging together with the flow field thanks to PIV measurements. The effects of CO2 addition on the flame were then investigated at different EGR increasing levels, highlighting the impact of the oxygen content on the combustion reaction intensity. Variations in emissions and burner stability limits in terms of maximum sustainable CO2 content were also studied, to detail the burner operating window. Data have been thoroughly analysed to gather information on the burner behaviour to support the design of new technical solutions capable of ensuring both proper flame stability and low CO and NOx emissions.