Christian Herwerth, Michael Pfreuntner, Hannah Kaiser, Herbert Pfeifer
Abstract: To validate a CFD modeling approach for the assessment of the combustion efficiency in partially premixed acetylene/air flames, this study integrates experimental and numerical methods to investigate flame structure, flow field characteristics, and heat transfer behaviour. Measurements of the global heat flux and stagnation pressure, alongside OH* chemiluminescence imaging, are employed to analyse the primary and secondary oxidation front of flames with high heat release rates in the primary oxidation. The experimental setup includes a water-cooled calorimeter with a capillary bore for static pressure extraction and a UV-sensitive camera with a bandpass filter to capture averaged OH* intensity. These results are compared to CFD simulations using the Flamelet-Generated-Manifold (FGM) and Reynolds-Stress-Model (RSM) frameworks. While the experimentally determined combustion efficiency is reproduced sufficiently for practical applications, the CFD model fails to predict the characteristic heat transfer maximum observed at a firing rate/Reynolds number specific torch-to-target distance. Conversely, the stagnation pressure is accurately captured across all flame configurations. The OH* imaging reveals flame quenching near the flame/wall interface at low burner-to-target distances, attributed to curvature-induced strain and cold wall effects—phenomena not adequately represented in the current CFD model. These discrepancies significantly impact the heat transfer predictions, specifically for low torch-to-target distances with an impinged primary reaction front. Future work should incorporate diffusion flamelets rather than premixed flamelets to explore their sensitivity to strain and scalar dissipation rates to enhance the fidelity of heat transfer modelling in similar flame impingement systems.
Keywords: Experimental heat transfer, numerical heat transfer, partially- premixed combustion, turbulent impinging flame jets, turbulence-chemistry-interaction, Flamelet-Generated-Manifold, Reynolds-Stress-Model, Stagnation Pressure, OH* chemiluminescence, Flame Quenching and Extinction
Date Published: December 16, 2025 DOI: 10.11159/jffhmt.2025.045
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