Numerical Investigation of Super-Adiabatic Flame Temperature in Multislot Turbulent Premixed Hydrogen Flames

Applying hydrogen as a fuel holds great potential for facilitating the aviation industry’s transition to carbon neutrality. In hydrogen premixed combustion, differential diffusion (DD) between thermal and mass diffusivity, and preferential diffusion (PD) among species lead to super-adiabatic flame temperature (SAFT), which results in local hot spots and may worsen NOx emission. This study investigates the SAFT characteristics of turbulent [Formula: see text] premixed flames produced by a multislot nozzle, which serves as a representative configuration of multihole combustors widely employed in hydrogen-fueled gas turbines. Numerical investigations were conducted across a wide range of conditions, including operating pressure, unburnt gas temperature, global equivalence ratio, and inlet velocity. The SAFT characteristics were analyzed using the Reynolds-Averaged Navier-Stokes (RANS)-based turbulent model coupled with the Eddy Dissipation Concept (EDC) combustion model. SAFT is found to concentrate in the near-field region of the nozzle exit where the flame is positively stretched, resulting in the average normalized temperatures up to [Formula: see text], i.e., [Formula: see text] higher than the adiabatic flame temperature at the nominal equivalence ratio. This is consistent with the findings in laminar counter-flow flame with positive stretch, where DD and PD lead to increased hydrogen content and SAFT. For the first time, a power-law scaling has been identified that quantifies SAFT in multislot nozzles, where turbulent viscosity is found to be the sole parameter determining SAFT.