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

Simulating Bluff-Body Flameholders: On the Use of Proper Orthogonal Decomposition for Combustion Dynamics Validation

[+] Author and Article Information
Ryan Blanchard

Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: rpberlin@vt.edu

A. J. Wickersham

Mem. ASME
Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: ajwick17@vt.edu

Lin Ma

Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: linma@vt.edu

Wing Ng

Fellow ASME
Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: wng@vt.edu

Uri Vandsburger

Virginia Polytechnic Institute and State University,
100S Randolph Hall,
Blacksburg, VA 24061
e-mail: uri@vt.edu

1Corresponding author.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 12, 2014; final manuscript received March 25, 2014; published online July 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(12), 121504 (Jul 02, 2014) (10 pages) Paper No: GTP-14-1154; doi: 10.1115/1.4027558 History: Received March 12, 2014; Revised March 25, 2014

Contemporary tools for experimentation and computational modeling of unsteady and reacting flow open new opportunities for engineering insight into dynamic phenomena. In this article, we describe a novel use of proper orthogonal decomposition (POD) for validation of the unsteady heat release of a turbulent premixed flame stabilized by a vee-gutter bluff-body. Large-eddy simulations were conducted for the same geometry and flow conditions as examined in an experimental rig with chemiluminescence measurements obtained with a high-speed camera. In addition to comparing the experiment to the simulation using traditional time-averaging and pointwise statistical techniques, the dynamic modes of each are isolated using proper orthogonal decomposition (POD) and then compared mode-by-mode against each other. The results show good overall agreement between the shapes and magnitudes of the first modes of the measured and simulated data. A numerical study of into the effects of various simulation parameters on these heat release modes showed significant effects on the flame's effective angle but also on the size, shape, and symmetry patterns of the flame's dynamic modes.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Large-eddy simulation from current work of nonreacting flow around a bluff body. The alternating shedding pattern in the bluff-body's wake can be seen from pattern of the vorticity isosurfaces.

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Fig. 2

Schematic of a bluff-body stabilized premixed flame showing the recirculation of combustion products from the bluff-body's wake into the shear layer where it mixes and ignites the unburned fuel and air mixture

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Fig. 3

Envelope of section inlet temperature and Mach number limitations from facility constraints

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Fig. 4

Schematic of experiment showing the three sections of the rig and the locations of the fuel injection, vee-gutter flameholder, and windows

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Fig. 5

Transparent view of CAD model of the test section showing the two side windows and top window relative to the location of the vee-gutter flameholder

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Fig. 6

Isometric view of dimensions of the domain used in the LES models based on the width of the flameholder w = 3.05 cm and an included angle of 70 deg

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Fig. 7

Plan view dimensions of the domain used in LES models

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Fig. 8

Illustration of flame's heat release imaged to simulate the line-of-sight integrated chemiluminescence imaged in the experiment

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Fig. 9

Illustration of relative sizes and locations of sampling planes relative to the flameholder: 100 × 100 CFD sample grid points (blue) compared to the effective viewing area for the chemiluminescence measurements

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Fig. 10

Line-of-sight mean heat release fields as measured by chemiluminescence (left) and LES (right)

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Fig. 11

Line of sight rms heat release fields as measured by chemiluminescence (left) and LES (right)

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Fig. 12

Contours of the dominant POD modes of chemiluminescence (left) and the projection integral of heat release in the LES model (right). The Strouhal numbers of these modes were 0.24 and 0.29, respectively.

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Fig. 13

Comparison between mode shapes of the second-most energetic pair of modes showing chemiluminescence data on the left and the baseline LES model on the right. The Strouhal numbers of these modes matched closely between experiment and simulation giving Str = 0.64 and Str = 0.63, respectively.

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Fig. 14

Contours of a low-frequency, low-energy mode revealed during POD of the chemiluminescence (left) and LES data (right). The spectra of these modes' POD coefficients showed peaks at Str = 0.037 and Str = 0.036, respectively.

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Fig. 15

Comparison between the dominant modes of the baseline LES model as determined by the line-of-sight-integrated heat release across the full width of the test section (left) and the local heat release at the midplane (middle) and near-wall (right) sampling locations

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Fig. 16

Dominant POD modes of the baseline simulation (left) and simulation with periodic sidewalls (right)

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Fig. 17

Illustration of the geometry modification to understand the effect of the boundary layer on the flame's dynamics. The baseline geometry is shown on the left and the extended geometry is shown on the right.

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Fig. 18

Comparison between dominant POD modes of baseline simulation (left) and simulation with thicker boundary layer (right)

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