Quenching and Propagation of Premixed n-Hexane/Air Laminar Flames in Parallel-Plate Narrow Slits

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ABSTRACT This study investigates flame-arresting performance in parallel-plate slits, critical for preventing aircraft fuel tank explosions via ventilation systems. Employing an integrated experimental and numerical approach with n-hexane as an aviation fuel surrogate, laminar premixed flame quenching and flashback propagation under standard conditions (T = 353 K − 393 K, P 0 = 0.65–1.05 atm, and ϕ = 0.8–1.4) were characterized. High-speed imaging was used to capture laminar flame quenching and flashback propagation within parallel-plate slits, revealing that the flame flashback propagated in the form of comet-shaped flame fronts. The flame propagation through the narrow slits (enclosed duct) is categorized into three phases: i) flow resistance-induced recirculation, ii) oscillatory flame stabilization, and iii) quenching and flashback. Experiments quantified the quenching distances for n-hexane/air premixed flame. Crucially, pressure measurements within the elongated enclosed duct confirmed significant pressure accumulation (1.16 ± 0.03 times initial pressure) during flame propagation toward the slits, a key factor enabled by our optimized experimental platform utilizing this effect for efficient quenching behavior analysis. Numerically, a validated skeletal n-hexane mechanism, derived via Chemkin reduction for computational efficiency, was implemented in ANSYS Fluent for 2D simulations of flame propagation in parallel slits. Comparative analysis demonstrated close agreement between predicted and measured quenching distances, confirming the model’s predictive capability for quenching behavior. This work provides fundamental insights into the quenching characteristics and flashback dynamics of premixed n-hexane/air flames in narrow parallel slits, directly informing the design and evaluation of flame arrestors for enhanced aviation fuel tank safety.