Applications of Fuel/Oxidizer-Flexible Premixed Combustion in Gas Turbines

Manufacturers of gas turbines have modified their combustion systems to usage of lean premixed combustion (LPM) somewhat different from the more traditional non-premixed combustion in order to control pollutant emissions, namely CO and NOx. One of the greatest developments in LPM combustion for considerable NOx emission control is the Dry Low NOx (DLN) combustor. However, DLN combustors struggle to separate CO2 from the exhaust stream in order to lessen the carbon footprint of gas turbines. This is especially true while running at low load (near blowout). The operations of CO2 separation and capture from the exhaust stream can be made simpler by modifying the combustors to handle oxy-fuel flames (oxidizer flexibility) rather than the typical air–fuel flames. This will allow for complete emission control. However, due to the high CO2 concentrations inside the combustor, oxy-fuel combustion technology has a number of unique difficulties, such as slowed reaction rates, decreased combustion efficiency, and a constrained operating range for stable flames. The idea of fuel flexibility is proposed, focusing primarily on syngas and hydrogen-enriched combustion, to increase the operability, regulate the emissions, and advance the turndown percentage of oxy-fuel combustors. As a result, this chapter goes into great length about fuel/oxidizer-flexible premixed combustion for clean power production in gas turbine assemblies, supported by experimental and numerical research. To achieve this goal of maintaining steady flames with ultra-low emissions even at very low part loads, various burner designs are introduced. The performance of the combustor under stratified oxy-syngas circumstances is given particular attention, which is prompted by the growing demand for this technology in combined cycle power plants. Several focused investigations on oxidizer/fuel-flexible combustion, in various burner schemes, for gas turbine combustion assembles are introduced after a brief on hydrogen-enriched combustion for gas turbines applications. For the purpose of investigation of the combustion behavior and stability features of such flames experimentally and numerically, the first study takes into account theoretical hydrogen-enriched oxy-methane flames of CH4/H2/O2/CO2 in a premixed dry-low-emission (DLE) combustor with swirl. The investigation emphases on how the combustible mixture’s hydrogen portion (HF), oxygen portion (OF), and bulk velocity at inlet (Uin) affect the flames’ stability and combustion properties. This study reports several unique flame characteristics for potential use in gas turbines with regulated emissions. In order to further explore the combustion properties, flame stability, flame macrostructure of oxy-methane-hydrogen (H2-CH4-O2-CO2) flames in the same premixed swirl-stabilized combustor model of gas turbine, a second study is given. Both experimentally and numerically, the impacts of equivalency ratio, inlet swirl number and Reynolds number inlet on stability and combustion characteristics were investigated. The stabilization parameters and macrostructure of oxygen-enriched air-propane (C3H8/O2/N2) and premixed oxy-propane (C3H8/O2/CO2) flames are then compared in two thorough studies in a model dry-low-emissions (DLE) gas turbine combustor at fixed inlet velocity and over ranges of oxygen fraction and equivalence ratio. In the most recent study, an enhanced turndown oxy-fuel micromixer combustor with hydrogen enrichment for use in the emission-free Allam power is shown.