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

Flame Structure Effects at High G-Loading

[+] Author and Article Information
Jacob D. Wilson, Christopher J. Damele

Air Force Institute of Technology,
Wright-Patterson AFB, OH 45433

Marc D. Polanka

Air Force Institute of Technology,
Wright-Patterson AFB, OH 45433
e-mail: Marc.Polanka@afit.edu

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 5, 2014; final manuscript received March 3, 2014; published online May 2, 2014. Editor: David Wisler.

J. Eng. Gas Turbines Power 136(10), 101502 (May 02, 2014) (8 pages) Paper No: GTP-14-1068; doi: 10.1115/1.4027128 History: Received February 05, 2014; Revised March 03, 2014

Previous research has been conducted showing significant benefits on combustion efficiency and stability by creating high gravity-loaded combustion environments. Ultracompact combustor systems decrease the size and weight of the overall engine by integrating the compressor, combustor, and turbine stages. In this system, the core flow is split and a portion is routed into a circumferential direction to be burned at a high equivalence ratio. Fuel and air are brought into the cavity and combusted in a high g-loaded environment driven by air injection. Computational research showed that the hole diameter of the air injection jets are directly related to g-loading within the cavity. An experimental rig was built where the air injection rings could be changed to contain one of three different jet hole diameters to verify this result. The smallest air injection diameter achieved the highest g-loading in the cavity, which is consistent with the computational fluid dynamics (CFD) results. However, the flame stability within the cavity was affected by the air injection jet becoming too large or too small for a particular equivalence ratio. Video taken at 8000 Hz was used to capture the flame structure, revealing that the flame was not stable even before lean blow out conditions were achieved. Additionally, the direction that the air jets swirled in the cavity was found to have an impact on the combustion dynamics. When flow swirled counterclockwise and impacted the suction side of the turbine vane, the cavity had a more uniform fully developed flow field, as opposed to the pressure side impact. Finally, liquid fuel testing was done to test the atomization and mixing of JP-8 in a g-loaded environment. The results showed that increasing the cavity g-load increased the residence time the fuel stayed in the cavity.

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Fig. 1

Representative UCC setup (above) compared to a typical combustor (below) [3]

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Fig. 2

Stability limits of the AFRL UCC test rig [6]

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Fig. 3

Relationship between the cavity air jet diameter, velocity, and tangential velocity [3]

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Fig. 4

AFIT full annulus UCC test rig

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Fig. 5

Migration flow path for CW (left) and CCW (right)

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Fig. 6

Camera and mirror positioning (left) and mirror visualization (right)

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Fig. 7

Cavity driver rings with different air injection diameters

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Fig. 8

CW (left) and CCW (right) instantaneous flame intensities

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Fig. 9

CW (left) and CCW (right) averaged flame intensities (50 frames)

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Fig. 10

Lean blow out for a constant core flow of 3.24 kg/min

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Fig. 11

Average flame intensity (50 frames each) with decreasing equivalence ratio

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Fig. 12

G-loading data for 3.24 kg/min core and ϕ = 1.76




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