Laminar premixed hydrogen flame transfer functions: Comparison between flow solvers and transport models

Abstract

The computation of flame transfer functions (FTFs), which characterize the flame response to acoustic fluctuations, is of central importance to the assessment of thermoacoustic stability. Hydrogen is an important carbon-free fuel to ensure sustainable power production in gas turbines. Since hydrogen possesses different reactivity and thermo-diffusive characteristics in comparison to natural gas, the nominal flame structure is different from natural gas, and therefore it also exhibits different dynamics. In the context of computing hydrogen flames, the non-unity Lewis numbers call for transport models that consider the enhanced molecular diffusion of hydrogen. This article answers an open question of how present-day computational fluid dynamics (CFD) solvers and transport models perform in the calculation of flame dynamics. Computations of FTFs of laminar premixed hydrogen flames are performed using OpenFOAM, ANSYS Fluent, S3D DNS code, and the AVBP solver. These solvers encompass the spectrum of numerical schemes and transport models used in computational combustion. Transport models taking into account the enhanced molecular diffusion of hydrogen are used in each solver. The results show that despite using similar transport models and identical chemical mechanisms, quantitative differences in the laminar flame speed, mean flame shapes, and the FTFs are seen between the solvers. However, the qualitative features of the FTF remain the same and the quantitative differences in terms of the root-mean-square error metric are within $15\mathrm{\%}$ in gain and $6\mathrm{\%}$ in phase. However, with transport models, larger quantitative differences in the phase of the FTF are observed.