Experimental investigation of novel gas turbine combustion concepts operating with CO2 vitiated air

In the upcoming years, the continuous growth in energy demand will push the energy productions towards more sustainable and efficient solutions. Future stringent regulations and the technologies adopted will drive the greenhouse gases emissions abatement and limit the negative effect on climate change. 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 has not yet found a practical application due to its expensive and complex installation that hardly ever justifies the emissions reduction when compared to already established Dry Low NOx combustion technologies. EGR becomes an interesting option in gas turbine 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 novel lean premixed burner for industrial gas turbine applications was studied at ambient pressure in a reactive singlecup test rig. The burner was fed with methane and first characterised in standard air conditions in terms of emissions and stability limits at different operating conditions. The flame position and shape were studied through OH* chemiluminescence imaging, while the burner flow field was analysed thanks to PIV measurements. The effects of CO2 addition on the flame were then investigated at different oxidant oxygen molar fraction decreasing 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 windows. The collected 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. The present work provide a significant contribution to a better understanding of the driving phenomena, proving the importance of dedicated experimental investigations throughout the burner design process.