Comparative experimental study of flame–wall interaction for hydrogen and methane

This paper presents measurements of flame–wall interaction (FWI) of thermodiffusive instability (TDI) cells in lean hydrogen–air flames ( Φ = 0 . 34 − 0 . 4 ) using a V-flame burner with a temperature-controlled wall. A clear separation between an upstream stable flame and a downstream onset of TDI cells enables a detailed investigation of their wall interaction. The lean H 2 flames exhibit strong differential diffusion effects due to their low Lewis number ( L e ≈ 0 . 37 ). For comparison, a methane flame ( Φ = 0 . 75 ) at the same Reynolds number ( R e ub = 6000 ) is used, as CH 4 lacks TDIs ( L e ≈ 1 ). Flame topology and wall quenching were investigated using 10 Hz OH planar laser-induced fluorescence (PLIF) from two perspectives, capturing both global behaviour and local FWI. Results show that TDI cell onset moves upstream with increasing equivalence ratio, consistent with reduced flame thickness and steeper spatial gradients. Increasing equivalence ratio also results in steeper angles for both the upstream stable and downstream TDI portions of the flame. The locally increased reactivity of TDI cells leads to significantly smaller quenching distances compared to stable flames. However, TDI cell quenching is highly stochastic due to the stochastic nature of cell formation and wall interaction. This produces a broad flame–wall distance distribution skewed toward larger distances, contrasting with the normally distributed quenching distances of stable CH 4 flames. Consequently, the stochastic behaviour of lean H 2 flames suggests that TDI cell quenching is best defined by the 1st percentile of the positively skewed distance distribution. • Comparison of thermodiffusively unstable premixed lean hydrogen/air flames and thermodiffusively stable methane/air flames interacting with cold walls in a side-wall quenching configuration. • First experimental evidence of the non-stationary thermodiffusive instability cells causing a spatial distribution of flame–wall interaction events.