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Turbulent Swirling Natural Gas Flames: Stability Characteristics, Unsteady Behavior and Vortex Breakdown

journal contribution
posted on 2023-05-16, 18:20 authored by Al-Abdeli, YM, Masri, AR
Laser diagnostic and flow visualization techniques have previously been applied to several reacting and isothermal swirling jets. Resolved flow features include the presence of vortex breakdown and unsteady behavior. As such, turbulent flames stabilized on the present (laboratory scale) burner bear similitude to those in larger (industrial) swirl combustors. With this in mind, the impact of vortex breakdown and unsteady behavior on flame stability continues to require further study. Such understanding can be gained through applying non-intrusive laser diagnostics to flow conditions covering a broad range of flame stability characteristics. This paper presents the results of one such investigation. Laser Doppler Velocimetry (LDV) measurements are acquired (along the centreline) to ascertain the presence of time periodicity and downstream recirculation. Unsteady behavior is identified through the spectra of axial velocity data whilst negative axial velocities delineate vortex breakdown. This information is augmented with observations of visible flame length and discussed in relation to established flame stability characteristics. Findings indicate that swirl numbers, over which improvements in flame stability occur, coincide with conditions leading to unsteady behavior and shorter flames. Because downstream flow reversal is not resolved at all such conditions, information available indicates flow unsteadiness is a clearer contributing factor, compared to vortex breakdown, on the observed stability characteristics. Shorter flames coupled with improvements in flame stability have significant implications on the design and operation of swirl combustors.

History

Publication title

Combustion Science and Technology

Volume

179

Issue

1-2

Pagination

207-225

ISSN

0010-2202

Department/School

School of Engineering

Publisher

Taylor & Francis

Place of publication

USA

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the physical sciences

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