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

Experimental Studies of Cavity and Core Flow Interactions With Application to Ultra-Compact Combustors

[+] Author and Article Information
David L. Blunck

Air Force Research Laboratory,
Wright-Patterson AFB, OH 45433
e-mail: david.blunck@oregonstate.edu

Dale T. Shouse

Air Force Research Laboratory,
Wright-Patterson AFB, OH 45433
e-mail: dale.shouse@us.af.mil

Craig Neuroth

Air Force Research Laboratory,
Wright-Patterson AFB, OH 45433
e-mail: craig.neuroth@us.af.mil

Amy Lynch

Air Force Research Laboratory,
Wright-Patterson AFB, OH 45433
e-mail: amy.lynch.1@us.af.mil

Timothy J. Erdmann, Jr.

Innovative Scientific Solutions Inc.,
Dayton, OH 45459
e-mail: timothy.erdmann.3.ctr@us.af.mil

David L. Burrus

Innovative Scientific Solutions Inc.,
Dayton, OH 45459
e-mail: david.burrus.1.ctr@us.af.mil

Joseph Zelina

GE Aviation,
Evendale, OH 45241
e-mail: joseph.zelina@ge.com

Daniel Richardson

NRC Research Associate,
Wright-Patterson AFB, OH 45433
e-mail: daniel.richardson.26.ctr@us.af.mil

Andrew Caswell

Spectral Energies, LLC,
Dayton, OH 45431
e-mail: andrew.caswell.2.ctr@us.af.mil

1Now with the School of Mechanical, Industrial, and Manufacturing Engineering at Oregon State University.

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received December 19, 2013; final manuscript received January 17, 2014; published online March 26, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(9), 091505 (Mar 26, 2014) (8 pages) Paper No: GTP-13-1457; doi: 10.1115/1.4026975 History: Received December 19, 2013; Revised January 17, 2014

Reducing the weight and decreasing pressure losses of aviation gas turbine engines improves the thrust-to-weight ratio and improves efficiency. In ultra-compact combustors (UCC), engine length is reduced and pressure losses are decreased by merging a combustor with adjacent components using a systems engineering approach. High-pressure turbine inlet vanes can be placed in a combustor to form a UCC. In this work, experiments were performed to understand the performance and associated physics within a UCC. Experiments were performed using a combustor operating at pressures in the range of 520–1030 kPa (75–150 psia) and inlet temperature equal to 480–620 K (865 R–1120 R). The primary reaction zone is in a single trapped-vortex cavity where the equivalence ratio was varied from 0.7 to 1.8. Combustion efficiencies and NOx emissions were measured and exit temperature profiles were obtained for various air loadings, cavity equivalence ratios, and configurations with and without representative turbine inlet vanes. A combined diffuser-flameholder (CDF) was used to study the interaction of cavity and core flows. Discrete jets of air immediately above the cavity result in the highest combustion efficiencies. The air jets reinforce the vortex structure within the cavity, as confirmed through coherent structure velocimetry of high-speed images. The combustor exit temperature profile is peaked away from the cavity when a CDF is used. Testing of a CDF with vanes showed that combustion efficiencies greater than 99.5% are possible for 0.8 ≤ Φcavity ≤ 1.8. Temperature profiles at the exit of the UCC with vanes agreed within 10% of the average value. Exit-averaged emission indices of NOx ranged from 3.5 to 6.5 g/kgfuel for all test conditions. Increasing the air loading enabled greater mass flow rates of fuel with equivalent combustion efficiencies. This corresponds to increased vortex strength within the cavity due to the greater momentum of the air driver jets.

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References

Figures

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Fig. 1

Illustration of UCC (top) and conventional combustor (bottom) integrated into an engine [7]

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Fig. 2

UCC (side view) with CDF-2 with turbine inlet vanes above the cavity. (a) Photograph of top view of experimental arrangement. (b) Illustration of side view of combustor where air driver jets and inlets are shown in blue, fuel injectors in green, and effusion cooling in red.

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Fig. 3

UCC (side view) with CDF at the inlet to the combustor and turbine inlet vanes removed. Air from driver jets and inlets is shown in blue, fuel injectors are shown in green, and effusion cooling in red.

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Fig. 4

Illustration of steps used to quantify vortex strength: (a) false color image of flame luminosity from high-speed movie showing location of air jets in blue, fuel injector in green, and effusion cooling in red; (b) representative gas velocities within combustor cavity based on coherent structure velocimetry; (c) magnitude-independent velocities; (d) magnitude-independent vorticity map showing location of vortex center, and (e) magnitude-dependent vorticity map and sample region used to find average vorticity value

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Fig. 5

Combustion efficiency and normalized vortex strength as a function of cavity equivalence ratio for the top (Pa1top), middle (Pa1middle), bottom (Pa1bottom), and bottom and middle (Pa2b + m) rows of passages open on CDF

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Fig. 6

Emission indices of NOx for experiments corresponding to combustion efficiencies reported in Fig. 7

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Fig. 7

Normalized exit temperature profiles for testing with different rows of holes on CDF open

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Fig. 8

Combustion efficiency (colored contours) as cavity air loading and cavity equivalence ratio were varied for configurations with bottom row of air jets open along the CDF (Pa1bot). The three panels correspond to different inlet areas of the driver jets in the cavity.

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Fig. 9

Combustion efficiency for three air loadings and bottom row of holes on CDF open

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Fig. 10

Emission indices of NOx for three air loadings and bottom row of holes on CDF open (E1.x)

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Fig. 11

Combustion efficiency as a function of cavity equivalence ratio for the Pa1bot CDF, the CDF-2, and the CDF-2 with vanes configurations

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Fig. 12

Normalized exit temperature profile for testing with the Pa1bot CDF, the CDF-2, and the CDF-2 with vanes configurations

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