Laboratory Study of Premixed H₂-Air and H₂-N₂-Air Flames in a Low-Swirl Injector for Ultra-Low Emissions Gas Turbines

The objective of this study is to conduct laboratory experiments on low-swirl injectors (LSIs) to obtain the basic information for adapting LSI to burn H₂ and diluted H₂ fuels that will be utilized in the gas turbines of the integrated gasification combined cycle coal power plants. The LSI is a novel ultralow emission dry-low NO_x combustion method that has been developed for gas turbines operating on natural gas. It is being developed for fuel-flexible turbines burning a variety of hydrocarbon fuels, biomass gases, and refinery gases. The adaptation of the LSI to accept H₂ flames is guided by an analytical expression derived from the flow field characteristics and the turbulent flame speed correlation. The evaluation of the operating regimes of nine LSI configurations for H₂ shows an optimum swirl number of 0.51, which is slightly lower than the swirl number of 0.54 for the hydrocarbon LSI. Using particle image velocimetry (PIV), the flow fields of 32 premixed H₂-air and H₂–N₂-air flames were measured. The turbulent flame speeds deduced from PIV show a linear correlation with turbulence intensity. The correlation constant for H₂ is 3.1 and is higher than the 2.14 value for hydrocarbons. The analysis of velocity profiles confirms that the near field flow features of the H₂ flames are self-similar. These results demonstrate that the basic LSI mechanism is not affected by the differences in the properties of H₂ and hydrocarbon flames and support the feasibility of the LSI concept for hydrogen fueled gas turbines.