Predicting flashback limits in H_2 enriched CH_4/air and C_3H$_8/air laminar flames

• Published in: Combustion and flame Vol. 258; no. 2
• Main Authors: Flores-Montoya, Enrique, Aniello, Andrea, Schuller, Thierry, Selle, Laurent
• Format: Journal Article
• Language: English
• Published: Elsevier 2023
• Subjects: Engineering Sciences; Reactive fluid environment; Flashback; Non-equidiffusive Fuels; Fuel Flexible Burners; Preferential Diffusion; Hybridization Strategies
• ISSN: 0010-2180
• DOI: 10.1016/j.combustflame.2023.113055

The influence of hydrogen blending on the flashback limit of dihedral premixed laminar flames stabilized on a slit burner is investigated via two-dimensional direct numerical simulations with conjugate heat transfer and detailed chemistry. Flashback limits are determined for CH$_4$/H$_2$/Air and C$_3$H$_8$/H$_2$/Air mixtures with hydrogen contents ranging from 0 % to 100 % and varying fuel-to-air ratios adjusted according to the iso–Tad and the iso–δT hybridization strategies. The analysis reveals the existence of two different f lashback regimes and a critical effective Lewis number for the fuel mixture, Le$_c$ = 0.5, controlling the switch from one regime to the other. Simulations are also used to explore the dynamics of flames during flashback in these two regimes. They show that for mixtures above the critical effective Lewis number, flashback is symmetric whereas for mixtures below the critical value, an asymmetric flame propagation is observed through the burner slit. These results highlight the impact of preferential diffusion on the stabilization mechanism of hydrogen fuel blends