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

Short Helical Combustor: Concept Study of an Innovative Gas Turbine Combustor 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

D.-A. Negulescu

Senior Fellow
Aerothermal Systems,
Rolls-Royce Deutschland Ltd. & Co. KG,
Eschenweg 11,
Dahlewitz 15827, 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 14, 2015; final manuscript received August 4, 2015; published online September 22, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(3), 031503 (Sep 22, 2015) (10 pages) Paper No: GTP-15-1291; doi: 10.1115/1.4031362 History: Received July 14, 2015; Revised August 04, 2015

An innovative design of a gas turbine annular combustor is investigated analytically and numerically. Its principal feature is the helical arrangement of the burners around the turbine shaft. Hence, a shorter combustor with lower aerodynamic losses and cooling air demand might be realized. A generic model of the combustor is developed and analyzed by means of a parametric study. Scaling laws for the geometry of the flame tube and the burners are derived. Thereby, the relevant similarity parameters for fluid flow, combustion, and heat transfer are maintained constant. Subsequently, nonreacting and reacting flow regimes of selected design variants are numerically investigated. It is shown that a double annular (DA) configuration with a tilting angle of β = 45 deg, where circumferentially adjacent swirls are corotating and radially are counter-rotating, is the superior design in terms of (1) maintaining the relevant similarity rules, (2) size and location of the recirculation zones and swirl flames, and (3) flow pattern at the combustor exit. The deflection angle of the nozzle guide vanes (NGV) as well as the axial length of such a short helical combustor (SHC) could be reduced by approximately 30%.

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Fig. 1

Schematic comparison of SHC and conventional combustor. (Reproduced with permission from Rolls-Royce.)

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Fig. 2

Generic conventional annular combustor and the equivalent SHC model

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Fig. 3

Schematic of the RCC and selected SHC types. Gray circles correspond to the actual burner diameter dβ and hatched one to dmax.

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Fig. 4

Top: parametric study using L0 scaling law. Burner confinement ratio Δ as function of parameters: SA or DA, number of segments Nseg, and tilting angle β. Note that the curves of L0-7SA and L0-14DA are coincided. Bottom: liner heat transfer similarity parameters as function of tilting angle.

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Fig. 5

Possible swirl directions in SA and DA SHC

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Fig. 6

The CFD domain of the L0-14DA45 SHC type with illustration of the imposed swirl profiles at the inlet (right). The perpendicular evaluation planes A–A, B–B, and C–C at arbitrary positions (left).

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Fig. 7

Time-averaged field of Ux. C–C planes located normal to burner axis at a distance xc−c/d=0.7, where Lsidewall/d=1.6. Arrows indicate the swirl cores, dashed–dotted lines the cross-sectional stagnation, black contour lines the zero Ux, solid lines the sidewall, and dashed lines the cyclic boundaries.

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Fig. 8

Time-averaged field of the Ux in circumferential planes (B–B). Arrows illustrate the intensity of the swirl cores.

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Fig. 9

Time-averaged field of the Ux in longitudinal planes (A–A). The P1–P3 indicate the evaluation planes for calculation of the mean flow-angle α and it standard deviation σα. They are located parallel to the combustor exit plane.

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Fig. 10

Bar-diagram shows the mass flow weighted average of the flow-angle (left bar) and its standard deviation (right bar) for SHC types DA4-10. The evaluation planes P1–P3 are located in combustor exit nozzle parallel to the exit plane.

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Fig. 11

Exit flow pattern of selected SHC configurations. Contour plots show field of Uax and isolines the flow-angle of two adjacent segments.

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Fig. 12

Time-averaged field of Ux (a) and temperature (b) for reacting flow. Arrows point the high Ux zone out. Contour lines in (a) correspond to Ux = 0. Additional contour lines in (b) correspond to progress variable θ = 0.5, i.e., the flame front.

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Fig. 13

Field of Uax and isolines of flow-angle at the SHC exit for DA4 and DA6 types, each one segment. Dashed–dotted lines indicate the form and place of high Ux zone, which are similar to those of near burner regions.

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Fig. 14

Flow-angle and its standard deviation for reacting flow in SHC

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Fig. 15

Angular momentum flow from inlet to exit of DA4,6 reacting (left). Time-averaged field of the pressure at the walls (right). High stagnation pressure at the sidewall, indicated by dashed ellipse, imposes a force on the flow in circumferential direction and reduces the angular momentum.




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