Boundary layer flashback of H2/Air premixed flames in a swirling flow around a central body

IF 5.8 2区工程技术 Q2 ENERGY & FUELS

Combustion and Flame Pub Date : 2025-03-25 DOI:10.1016/j.combustflame.2025.114123

Justin Bertsch , Thierry Poinsot , Nicolas Bertier

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引用次数: 0

Abstract

Fast and thin premixed hydrogen flames can lead to flashback scenarios which are unusual, especially for swirled configurations. Flashback can occur far from all walls, in the bulk flow, if the flow speed is less than the flame speed: this is a scenario which is usually avoided by increasing flow rates. However, flashback can also occur near walls where the flow speed goes to zero. Injector walls boundary layers always contain a zone where the local flow speed is less than the flame speed, even if the bulk flow velocity is large. The size of this zone is controlled by the velocity gradient at the wall which is the classical parameter used to predict flashbacks in boundary layers.

In this study, flashback of lean hydrogen–air flames is computed using DNS (Direct Numerical Simulation)(flame resolved). Without swirl, results are compared and validated against experimental measurements and usual flashback criteria based on wall velocity gradient. DNS are also performed with swirl in a sector of an annular chamber, providing maps of flashback occurrence as function of swirl number and wall velocity gradient. Results show that swirl enhances flashback propensity and that thermodiffusive effects must be accounted to build a flashback criteria, indeed very lean H

_{2}

flames flashback for flow speeds higher than expected.

Novelty and significance

Almost all injection systems designed for hydrogen face a new, key issue in terms of operability: flashback. This study presents for the first time an analysis of the combined effects on flashback of the velocity gradients at the wall and of swirl. DNS of a swirling flow around a central body are performed and flashback maps are produced in a (swirl-velocity gradient) diagram of direct use for systems injecting lean premixed hydrogen–air mixtures.

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来源期刊

Combustion and Flame 工程技术-工程：化工

CiteScore

9.50

自引率

20.50%

发文量

631

审稿时长

3.8 months

期刊介绍： The mission of the journal is to publish high quality work from experimental, theoretical, and computational investigations on the fundamentals of combustion phenomena and closely allied matters. While submissions in all pertinent areas are welcomed, past and recent focus of the journal has been on: Development and validation of reaction kinetics, reduction of reaction mechanisms and modeling of combustion systems, including: Conventional, alternative and surrogate fuels; Pollutants; Particulate and aerosol formation and abatement; Heterogeneous processes. Experimental, theoretical, and computational studies of laminar and turbulent combustion phenomena, including: Premixed and non-premixed flames; Ignition and extinction phenomena; Flame propagation; Flame structure; Instabilities and swirl; Flame spread; Multi-phase reactants. Advances in diagnostic and computational methods in combustion, including: Measurement and simulation of scalar and vector properties; Novel techniques; State-of-the art applications. Fundamental investigations of combustion technologies and systems, including: Internal combustion engines; Gas turbines; Small- and large-scale stationary combustion and power generation; Catalytic combustion; Combustion synthesis; Combustion under extreme conditions; New concepts.