Stability analysis of thermodiffusively unstable counterflow lean premixed hydrogen flames
A. Porcarelli (TU Delft - Flight Performance and Propulsion)
Pasquale Eduardo Lapenna (Sapienza University of Rome)
Francesco Creta (Sapienza University of Rome)
I. Langella (TU Delft - Flight Performance and Propulsion)
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Abstract
This study investigates the effect of increasing strain rate on thermodiffusively unstable, lean premixed hydrogen flames in a 2D counterflow configuration through detailed-chemistry numerical simulations for the first time. The analysis of transient flame dynamics without imposed perturbations reveals that a steady-state flame front is achieved only when the strain rate exceeds a certain threshold. Below this threshold, the curved flame tips exhibit an unstable sequential onset and suppression pattern. When subjected to a range of perturbation wavelengths, the flame front exhibits an exponentially increasing wavelength over time, driven by the flame-tangential velocity component, with the applied strain rate acting as the amplification factor. It is shown that any perturbation is damped at sufficiently high applied strain rate conditions after a transient phase. At these high strain regimes, the growth rate transient follows a characteristic onset that depends uniquely on the initial perturbation wavelength and exhibits a linear dependence on the applied strain rate.
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