Research Papers

A Global Approach to Turbomachinery Flow Control: Passage Vortex Control

[+] Author and Article Information
Matthew J. Bloxham

e-mail: mbloxham@gmail.com

Jeffrey P. Bons

e-mail: bons.2@osu.edu
Department of Aerospace Engineering,
The Ohio State University,
2300 West Case Road,
Columbus, OH 43235

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received March 11, 2013; final manuscript received April 23, 2013; published online September 26, 2013. Assoc. Editor: David Wisler.

J. Turbomach 136(4), 041003 (Sep 26, 2013) (9 pages) Paper No: TURBO-13-1036; doi: 10.1115/1.4024686 History: Received March 11, 2013; Revised April 23, 2013

A flow control scheme was implemented in a low-pressure turbine cascade that simultaneously mitigated profile and endwall losses using midspan vortex generator jets (VGJs) and endwall suction. The combined system had an approximate zero-net mass flux. During the design, a theoretical model was used that effectively predicted the trajectory of the passage vortex using inviscid results obtained from two-dimensional computational fluid dynamics (CFD). The model was used in the design of two flow control approaches: the removal and redirection approaches. The emphasis of the removal approach was the direct application of flow control along the passage vortex (PV) trajectory. The redirection approach attempted to alter the trajectory of the PV with the judicious placement of suction holes. A potential flow model was created to aid in the design of the redirection approach. The model results were validated using flow visualization and particle image velocimetry (PIV) in a linear turbine cascade. Detailed total pressure loss wake surveys were measured while matching the suction and VGJ mass flow rates for the removal and redirection approaches at ReCx = 25,000 and blowing ratio, B, of 2. When compared with the no control results, the addition of VGJs and endwall suction reduced the wake losses by 69% (removal) and 68% (redirection). The majority of the total pressure loss reduction resulted from the spanwise VGJs, while the suction schemes provided modest additional reductions (<2%). At ReCx = 50,000, the endwall control effectiveness was assessed for a range of suction rates without midspan VGJs. Area-averaged total pressure loss reductions of up to 28% were measured in the wake at ReCx = 50,000, B = 0, with applied endwall suction (compared to no suction at ReCx = 50,000), at which point the loss core of the PV was almost completely eliminated.

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Fig. 1

Representation of the passage vortex system by Langston et al. [3]

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Fig. 2

Schematics of the L1A cascade and VGJ orientation

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Fig. 3

Schematics of splitter plate hole pattern (a) and the removal (b) and redirection (c) approach hole patterns

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Fig. 4

The computational domain and boundary conditions used to solve the inviscid flow field (top). The inviscid static pressure contour (bottom-left) and streamline (bottom-right) results obtained from fluent.

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Fig. 5

Theoretical model particle path predictions for initial velocities of 0.5Uin (black vectors) and 0.75Uin (gray vectors)

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Fig. 6

The percent reduction of angle deviation as a function of the number of active holes and total suction rate. The vertical dashed line denotes the number of suction holes used in the redirection study.

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Fig. 7

Theoretical model velocity vector fields with and without endwall control (redirection approach)

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Fig. 8

Overlay of PIV (black vectors) and model velocity vectors (grey vectors) for Γ = 0 and 0.7 (SR = 29%)

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Fig. 9

Turbine cascade schematic of the total pressure data location

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Fig. 10

Total pressure loss wake surveys with (right) and without (left) steady VGJ actuation. ReCx = 25,000, SR = 0. (PTinPT)/ (PTinPSin).

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Fig. 11

Total pressure loss wake surveys. Baseline (top), removal approach (bottom left), and redirection (bottom right). ReCx = 25,000, SR = 9.7%, B = 2. (PTin – PT)/(PTinPSin).

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Fig. 12

Total pressure loss wake surveys. Baseline (top), removal approach (bottom left), and redirection approach (bottom right). ReCx = 50,000, SR = 11.3%, B = 0. (PTinPT)/(PTinPSin).

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Fig. 13

Normalized PT losses for the removal and redirection approaches at ReCx = 25,000 and 50,000. (PTinPT)/(PTinPT)SR=0.




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