Combustion Characterization of an Industrial Gas Turbine Combustor for Low Emissions Applications Fed with Natural Gas/Hydrogen Blends

Recently, the use of lean-premixed combustion systems in gas turbines for power generation has led to consistent emissions reduction. Nevertheless, swirl burners can be prone to flashbacks and to a non-negligible increase in emission levels when operated with blends of natural gas and hydrogen. In this scenario, the use of 3D-CFD analysis can contribute to the redesign of both the combustor and the injection system for the lifetime extension of existing power plants. In this work, a 5 MW annular combustor is investigated with a set of numerical simulations performed with the ANSYS FLUENT solver. This research follows a previously performed study on the injection system for the same machine. An in-house routine developed in MATLAB exploits the species profiles and velocity field obtained from the thorough characterization of the injector, thus allowing for a loosely-coupling of the two systems. Thus, the number of elements necessary to describe the combustor domain is reduced without any loss of information. The procedure is initially validated for the natural gas case by comparing the numerical results to both the performance tests performed by EthosEnergy Italia SpA and the evidence of deterioration observed in the injection system. Then, the effects of hydrogen blending are analyzed in detail in terms of temperature distributions and emissions. The obtained results provide some retrofitting guidelines in the field of hydrogen usage for this type of machine.