Visualisation of isothermal large coherent structures in a swirl burner

Valera Medina, Agustin ORCID: https://orcid.org/0000-0003-1580-7133, Syred, Nicholas and Griffiths, Anthony John 2009. Visualisation of isothermal large coherent structures in a swirl burner. Combustion and Flame 156 (9) , pp. 1723-1734. 10.1016/j.combustflame.2009.06.014

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Abstract

Lean premixed combustion using swirl flame stabilisation is widespread amongst gas turbine manufacturers. The use of swirl mixing and flame stabilisation is also prevalent in many other non-premixed systems. Problems that emerge include loss of stabilisation as a function of combustor geometry and thermo-acoustic instabilities. Coherent structures and their relationship with combustion processes have been a concern for decades due to their complex nature. This paper thus adopts an experimental approach to characterise large coherent structures in swirl burners under isothermal conditions so as to reveal the effects of swirl in a number of geometries and cold flow patterns that are relevant in combustion. Aided by techniques such as Hot Wire Anemometry, High Speed Photography and Particle Image Velocimetry, the recognition of several structures was achieved in a 100 kW swirl burner model. Several varied, interacting, structures developed in the field as a consequence of the configurations used. New structures never observed before were identified, the results not only showing the existence of very well defined large structures, but also their dependency on geometrical and flow parameters. The PVC is confirmed to be a semi-helical structure, contrary to previous simulations performed on the system. The appearance of secondary recirculation zones and suppression of the vortical core as a consequence of geometrical constrictions are presented as a mechanism of flow control. The asymmetry of the Central Recirculation Zone in cold flows is observed in all the experiments, with its elongation dependent on Re and swirl number used.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Engineering
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Uncontrolled Keywords:	Swirling flows; Large coherent structures; Precessing vortex core (PVC); Recirculation zone (RZ)
Publisher:	Elsevier
ISSN:	0010-2180
Last Modified:	17 Oct 2022 10:33
URI:	https://orca.cardiff.ac.uk/id/eprint/8424

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