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Gas Turbines: Combustion, Fuels, and Emissions

The Impact of Compressor Exit Conditions on Fuel Injector Flows

[+] Author and Article Information
C. L. Ford1

J. F. Carrotte, A. D. Walker

Department of Aeronautical and Automotive Engineering,  Loughborough University, Loughborough, LE11 3TU United Kingdom

1

Corresponding author.

J. Eng. Gas Turbines Power 134(11), 111504 (Sep 28, 2012) (9 pages) doi:10.1115/1.4007025 History: Received June 18, 2012; Revised June 21, 2012; Published September 28, 2012; Online September 28, 2012

This paper examines the effect of compressor generated inlet conditions on the air flow uniformity through lean burn fuel injectors. Any resulting nonuniformity in the injector flow field can impact on local fuel air ratios and hence emissions performance. The geometry considered is typical of the lean burn systems currently being proposed for future, low emission aero engines. Initially, Reynolds-averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) predictions were used to examine the flow field development between compressor exit and the inlet to the fuel injector. This enabled the main flow field features in this region to be characterized along with identification of the various stream-tubes captured by the fuel injector passages. The predictions indicate the resulting flow fields entering the injector passages are not uniform. This is particularly evident in the annular passages furthest away from the injector centerline which pass the majority of the flow which subsequently forms the main reaction zone within the flame tube. Detailed experimental measurements were also undertaken on a fully annular facility incorporating an axial compressor and lean burn combustion system. The measurements were obtained at near atmospheric pressure/temperatures and under nonreacting conditions. Time-resolved and time-averaged data were obtained at various locations and included measurements of the flow field issuing from the various fuel injector passages. In this way any nonuniformity in these flow fields could be quantified. In conjunction with the numerical data, the sources of nonuniformities in the injector exit plane were identified. For example, a large scale bulk variation (+/−10%) of the injector flow field was attributed to the development of the flow field upstream of the injector, compared with localized variations (+/−5%) that were generated by the injector swirl vane wakes. Using this data the potential effects on fuel injector emissions performance can be assessed.

Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Rich (a) / lean (b) burn combustor geometries

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Figure 2

CFD models: prediffuser fed (a), plenum fed (b) (showing total velocity contours)

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Figure 3

Dump cavity flow field with stream-traces; indicating the flow captured by the fuel injector passages

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Figure 4

Injector captured stream-tubes with different inlet profiles: plenum (a), test profile (b), axisymmetric (OGV wake removed) (c), flat (idealized) (d)

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Figure 5

Fully annular test facility cross section

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Figure 6

Rotor exit and OGV exit profiles (nondimensionalized by local plane average)

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Figure 7

OGV exit contours (single OGV sector, viewed looking downstream)

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Figure 8

Prediffuser exit contours—nondimensional velocity (injector sector, viewed looking downstream)

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Figure 9

Prediffuser exit

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Figure 10

Injector exit velocity contours (mains, viewed looking downstream)

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Figure 11

Radial averaged circumferential flow distributions at injector exit (mains)

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Figure 12

Comparison of predicted and measured circumferential flow nonuniformity

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Figure 13

Predicted circumferential flow nonuniformity for various inlet configurations

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Figure 14

Predicted circumferential flow nonuniformity with and without OGV wakes (injector pilot passages)

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Figure 15

Turbulence intensity contours with location of spectra

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Figure 16

Injector exit plane frequency spectra (measured)

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