Combustion modelling for the flame–wall interaction of thermodiffusively unstable hydrogen/air flames

Flame–wall interaction (FWI) of lean premixed hydrogen/air flames is critical in wall-bounded combustors, where thermodiffusive instabilities strongly influence quenching. To capture these effects efficiently in realistic configurations, reduced-order combustion models such as flamelet tabulation are desirable, as they lower resolution requirements and computational cost. In this study, advanced flamelet manifolds incorporating a mixture-averaged species diffusion model and thermal diffusion are developed to represent the FWI of thermodiffusively unstable lean hydrogen/air flames. A central challenge is the simultaneous capture of intrinsic instabilities and heat losses, each complex in itself. Separate manifolds addressing these effects are first introduced, providing the foundation for joint manifolds that capture both simultaneously. In this context, the choice of flamelet databases is examined by comparing freely propagating flames with exhaust gas recirculation, commonly used in flamelet modelling to represent enthalpy variations, with one-dimensional head-on quenching (HOQ) flames, which are essential for accurate prediction of wall heat flux and pollutant formation in hydrocarbon flames. The models are evaluated through both a-priori and a-posteriori analyses across increasingly complex configurations, culminating in the HOQ of a thermodiffusively unstable flame, where both instability and quenching must be captured simultaneously. Results show excellent agreement with reference simulations using detailed chemistry, accurately reproducing key features of the flame front, thermochemical state and global flame properties such as consumption speed and quenching wall heat flux. This marks a key advance in modelling hydrogen combustion and provides a robust foundation for studying safety-critical phenomena such as flame flashback linked to near-wall flame propagation.