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

The Effect of Confinement on the Structure and Dynamic Response of Lean-Premixed, Swirl-Stabilized Flames

[+] Author and Article Information
Alexander J. De Rosa

Turbulent Combustion Lab,
The Pennsylvania State University,
University Park, PA 16802
e-mail: Alexander.DeRosa@stevens.edu

Stephen J. Peluso

Turbulent Combustion Lab,
The Pennsylvania State University,
University Park, PA 16802
e-mail: sjp249@psu.edu

Bryan D. Quay

Turbulent Combustion Lab,
The Pennsylvania State University,
University Park, PA 16802
e-mail: bdq100@psu.edu

Domenic A. Santavicca

Turbulent Combustion Lab,
The Pennsylvania State University,
University Park, PA 16802
e-mail: das8@psu.edu

1Corresponding author.

2Present address: Stevens Institute of Technology, Castle Point on Hudson, Hoboken, NJ 07030.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 6, 2015; final manuscript received August 31, 2015; published online November 24, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(6), 061507 (Nov 24, 2015) (10 pages) Paper No: GTP-15-1235; doi: 10.1115/1.4031885 History: Received July 06, 2015; Revised August 31, 2015

The effect of flame–wall interactions on the forced response of a lean-premixed, swirl-stabilized flame is experimentally investigated by examining flames in a series of three combustors, each with a different diameter, and therefore a different degree of lateral confinement. The confinement ratios tested are 0.5, 0.37, and 0.29 when calculated using the diameter of the nozzle relative to the combustor diameter. Using both flame images and measured flame transfer functions (FTFs), the effect of confinement is investigated and generalized across a broad range of operating conditions. The major effect of confinement is shown to be a change in flame structure in both the forced and unforced cases. This effect is captured using the parameter Lf,CoHR/Dcomb, which describes the changing degree of flame–wall interaction in each combustor size. The measured FTF data, as a function of confinement, are then generalized by Strouhal number. Data from the two larger combustors are collapsed by multiplying the Strouhal number by the confinement ratio to account for the flow expansion ratio and change in convective velocity within the combustor. Trends at the transfer function extrema are also assessed by examining them in the context of confinement and by using flame images. A change in the fluctuating structure of the flame is also seen to result from an increase in confinement.

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Figures

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Fig. 1

Test section geometry

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Fig. 2

Comparison of projection flame images in three different diameter combustors (images shown to scale): (a) 0.11 m, (b) 0.15 m, and (c) 0.19 m

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Fig. 3

Illustration of the image processing procedure: (a) projection (line-of-sight) image, (b) emission image (deconvoluted projection image), and (c) revolved image (r-weighted emission image). Operating condition: 25 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.6 in the 0.11 m diameter combustor.

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Fig. 4

Axial heat release profile (AHR), FWHM measurement overlaid. Operating condition: 25 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.6.

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Fig. 5

Example heat release rate index image. Operating condition: 25 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.6 in the 0.11 m diameter combustor at 120 Hz modulation.

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Fig. 6

Time-averaged, radially weighted, deconvoluted chemiluminescence flame structure comparison for three combustor sizes: (a) 0.11 m diameter combustor, (b) 0.15 m diameter combustor, and (c) 0.19 m diameter combustor. Operating condition: 22.5 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.65.

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Fig. 7

Flame structure parameters under variable confinement. (a) Flame CoHR coordinates. The location of the combustor wall is indicated by the dashed lines. (b) FWHM plotted against flame length/combustor diameter. (c) Percentage of total heat release in the near-wall region as a function of the flame length divided by combustor diameter.

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Fig. 8

Transfer function gain and phase data for the three difference combustor sizes. Operating condition: 22.5 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.65.

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Fig. 9

Measured transfer function data for all test conditions

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Fig. 10

Collated flame transfer function gain and phase normalized by Strouhal number

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Fig. 11

Trends in FTF extrema with the flame length/combustor diameter parameter: (a) initial gain maximum, (b) second gain maximum, and (c) first gain minimum

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Fig. 12

Collated FTF gain and phase normalized by Strouhal number multiplied by confinement ratio

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Fig. 13

Heat release rate index images for the second gain maximum condition: (a) 0.11 m diameter combustor, (b) 0.15 m diameter combustor, and (c) 0.19 m diameter combustor. Operating condition: 25 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.6.

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Fig. 14

Heat release rate index image for a flame in the 0.11 m diameter combustor at 350 Hz. Operating condition: 25 m/s inlet velocity, 5% forcing, 473 K preheat, and Φ = 0.6.

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