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Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Vortex Breakdown in Swirling Fuel Injector Flows

[+] Author and Article Information
Adrian Spencer, James J. McGuirk

Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough, Leicestershire LE11 3TU, U.K.

Kris Midgley

 Renault F1 Team Ltd, Enstone, Oxfordshire, OX74EE U.K.j.j.mcguirk@lboro.ac.uk

J. Eng. Gas Turbines Power 130(2), 021503 (Jan 22, 2008) (8 pages) doi:10.1115/1.2799530 History: Received May 01, 2007; Revised July 04, 2007; Published January 22, 2008

It is well known that the process of vortex breakdown plays an important role in establishing the near-field aerodynamic characteristics of fuel injectors, influencing fuel/air mixing and flame stability. The precise nature of the vortex breakdown can take on several forms, which have been shown in previous papers to include both a precessing vortex core (PVC) and the appearance of multiple helical vortices formed in the swirl stream shear layer. The unsteady dynamics of these particular features can play an important role in combustion induced oscillations. The present paper reports an experimental investigation, using particle image velocimetry (PIV) and hot-wire anemometry, to document variations in the relative strength of PVC and helical vortex patterns as the configuration of a generic fuel injector is altered. Examples of geometric changes that have been investigated include: the combination of an annular swirl stream with and without a central jet; variation in geometric details of the swirler passage, e.g., alteration in the swirler entry slots to change swirl number, and variations in the area ratio of the swirler passage. The results show that these geometric variations can influence: the axial location of the origin of the helical vortices (from inside to outside the fuel injector), and the strength of the PVC. For example, in a configuration with no central jet (swirl number S=0.72), the helical vortex pattern was much less coherent, but the PVC was much stronger than when a central jet was present. These changes modify the magnitude of the turbulence energy in the fuel injector near field dramatically, and hence have an important influence on fuel air mixing patterns.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Datum fuel injector geometry

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Figure 2

Modular fuel injector geometry

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Figure 3

Overall flow structure; datum injector (a) with fuel jet; (b) without fuel jet

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Figure 4

Radial RMS profiles; (top) with central jet; (bottom) no central jet

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Figure 5

Turbulence kinetic energy contours; (top) with central jet; (bottom) no central jet

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Figure 6

PDF of spatial attachment point of swirl cone

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Figure 7

PSD of axial velocity in swirlstream shear layer (top) with central jet; (bottom) no central jet

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Figure 8

Conditionally averaged velocity vectors in r−θ plane at x∕Ds=0.0; (top) with central jet; (bottom) no central jet

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Figure 9

Instantaneous velocity vectors in r−θ plane at x∕Ds=2.65, no central jet

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Figure 10

Angular location of swirl pattern aerodynamic center at x∕Ds=2.65, no central jet

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Figure 11

PSD in modular injector, Case 1, x∕Ds=0.27; α1=30deg

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Figure 12

PSD in modular injector, Case 1; various slot angles

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Figure 13

Velocity vectors, modular injector, Case 1; α1=30deg

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Figure 14

Velocity vectors, modular injector, Case 1; (top) α1=20deg; (bottom) α1=10deg

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Figure 15

Velocity vectors and k contours, modular injector, Case 6; α1=30deg

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Figure 16

PSD for modular injector, Case 6; various slot angles

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