Gas turbine fuel flexibility: pressurized swirl flame stability, thermoacoustics, and emissions

Power generation gas turbine manufacturers and operators are tasked increasingly with expanding operational flexibility due to volatility in global gaseous fuel supplies and increased renewable power generation capacity. Natural gas containing high levels of higher hydrocarbons (e.g. ethane and propane) is typical of liquefied natural gas and shale gas, two natural gas sources impacting gas turbine operations, particularly looking forward in the United Kingdom. In addition, hydrogen-blending into existing natural gas infrastructure represents a potential energy storage opportunity from excess renewable power generation, with associated combustion impacts not fully appreciated. This thesis aims to address the specific operational problems associated with the use of variable gaseous fuel compositions in gas turbine combustion through a combination of experimental and numerical techniques, with a focus on natural gas blends containing increased levels of higher hydrocarbons and hydrogen. Parametric experimental combustion studies of the selected fuel blends are conducted in a new fully premixed generic swirl burner at elevated ambient conditions of temperature and pressure to provide representative geometry and flow characteristics typical of a can-type industrial gas turbine combustor. New non-intrusive diagnostic facilities have been designed and installed at Cardiff University’s Gas Turbine Research Centre specifically for the characterization of the influence of fuel composition, burner geometry, and operating parameters on flame stability, flame structure, thermoacoustic response, and environmental emissions. Experimental measurements are supported through the use of numerical chemical kinetics and acoustic modelling. Results from this thesis provide an experimental validation database for chemical kinetic reactor network and CFD modelling efforts. In addition, it informs gas turbine manufacturers on potential burner design modifications for future fuel flexibility and provide enhanced empirical tools to power generation gas turbine operators for increased operational stability, reduced environmental impact, and increased utilization