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

Short Helical Combustor: Dynamic Flow Analysis in a Combustion System With Angular Air Supply

[+] Author and Article Information
B. Ariatabar

Institute of Thermal Turbomachinery,
Karlsruhe Institute of Technology (KIT),
Kaiserstr. 12,
Karlsruhe 76131, Germany
e-mail: ariatabar@kit.edu

R. Koch, H.-J. Bauer

Institute of Thermal Turbomachinery,
Karlsruhe Institute of Technology (KIT),
Kaiserstr. 12,
Karlsruhe 76131, Germany

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 July 17, 2016; final manuscript received August 15, 2016; published online October 26, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(4), 041505 (Oct 26, 2016) (8 pages) Paper No: GTP-16-1344; doi: 10.1115/1.4034688 History: Received July 17, 2016; Revised August 15, 2016

A novel gas turbine combustor is investigated by means of a global flow analysis. Its main feature is the helical arrangement of the burners, which allows the utilization of the high angular momentum of the flow from compressor, so that the length of the flame tube and the number of NGV can be reduced. The concept was studied in Ariatabar et al. (2016, “Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor With Angular Air Supply,” ASME J. Eng. Gas Turbines Power, 138(3), p. 031503) based on similarity considerations and a kinematic assessment of the simulated flow in various combustor models. For the best configuration found in the previous work, the exit mean flow angle was lower than the half of its initial value at the combustor inlet. The reason for this unwanted decay of the initial high angular momentum flux was not clear. In the present work, the underlying physics of the strong reduction of the mean flow angle is elucidated by analysis of the integral balance equation of angular momentum. It is shown that the flow in the vicinity of the burners is governed by inertial forces associated with an asymmetric pressure distribution on the sidewall and the combustor dome. The friction and turbulent mixing phenomena are found to have marginal effects on the flow pattern. To compare mean flow quantities of different combustor designs, a physically consistent averaging method is introduced, which can also be applied to a conventional combustor to assess different swirl configurations regarding the resulting flow pattern, mixing performance, and total pressure loss.

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References

Figures

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Fig. 1

Schematic illustrations of the investigated SHC types ((a) and (b)). Evaluation planes and the coordinate system in SHC (c).

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Fig. 2

Time-averaged field of Ux,β on A–A planes. The arrow indicates the stable high Ux,β zone at the midspan of the flame tube in the 14DA45-DA6.

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Fig. 3

Time-averaged fields of Ux and isolines of flow angle (top) and temperature (bottom) at the SHC exit (E–E plane). Arrows indicate the vortex systems and the resulting flow motion. Dashed lines indicate the periodic boundaries.

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Fig. 4

Contour plots of Ux,β on C–C planes. Black isolines refer to Ux,β/U0 = 0, white to Uz,β/U0 = 0.2, and gray to Uz,β/U0 = –0.2. Arrows show the direction of Uz,β.

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Fig. 5

Successive control volumes (CV1–CV20) for the integral balance of the angular momentum in SHC. Dashed–dotted lines are representative control volumes, dashed lines are cyclic boundaries, and dotted lines are inlets and the combustor outlet.

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Fig. 6

Development of different terms of conservation law of the angular momentum for nonreacting flow in the SHC as defined in Eq. (2). Lin,0 refers to initial angular momentum of an L07SA45-SA1. Solid lines: Lout, dashed lines: Lp, and dashed–dotted lines: Lτ.

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Fig. 7

Top: Development of different terms of conservation law of the angular momentum for reacting flow in the SHC as defined in Eq. (2). Lin,0 refers to initial angular momentum of an L07SA45. Solid lines: Lout, dashed lines: Lp, and dashed–dotted lines: Lτ. Bottom: Schematic illustration of a double annular SHC. Fp,sw and Fp,dome indicate the asymmetric pressure reaction forces induced by the sidewall and combustor dome.

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Fig. 8

Contour plots of the relative pressure at the walls of 14DA45-DA6. Isolines refer to (p−p0/0.5ρ0U02)=0.35.

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Fig. 9

Mean flow angle α¯ and its standard deviation σα at the SHC exit. Mass-weighted average (mass) and consistent averaging method (cons) proposed in the present work.

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Fig. 10

(a) Evaluation planes Ai at the inlet and Ao at the outlet of the turbine. (b) The Cartesian and cylindrical coordinate systems at the turbine inlet plane. Dashed lines refer to cyclic boundaries, and dashed–dotted lines to contour of the control volume at the turbine inlet.

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