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Research Papers

The Application of Low-Profile Vortex Generators in an Intermediate Turbine Diffuser

[+] Author and Article Information
C. Santner

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austriacornelia.santner@tugraz.at

E. Göttlich

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austriaemil.goettlich@tugraz.at

A. Marn, J. Hubinka, B. Paradiso

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria

J. Turbomach 134(1), 011023 (Jun 01, 2011) (9 pages) doi:10.1115/1.4003718 History: Received October 27, 2010; Revised January 22, 2011; Published June 01, 2011; Online June 01, 2011

The demand of further increased bypass ratios for turbofan engines will lead to low pressure turbines with larger diameter and lower rotational speed in conventional high-bypass aeroengine architectures. Due to that, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at a larger diameter without any severe loss generating separation or flow disturbances. To reduce costs and weight this turbine duct has to be as short as possible. This results in superaggressive (very high diffusion) S-shaped geometries where the boundary layers are not able to withstand the strong adverse pressure gradient, which results in flow separation. This paper describes the flow through a fully separated duct as a baseline configuration. In a next step the influence of passive flow control devices onto this separation has been investigated. Therefore, low-profile vortex generators were applied within the first bend of this S-shaped intermediate turbine diffuser in order to energize the boundary layer and further reduce or even suppress the occurring separation. This configuration was investigated downstream a transonic turbine stage. Measurements were performed by means of five-hole-probes, static wall pressure taps, and oil flow visualization at the duct endwalls. For a better understanding of the flow behavior the vortex generators were also investigated in a two-dimensional rectangular S-shaped duct using the same Mach number level. Results showed that the vortex generators reduce the separation in the 2D-duct but have no distinct influence on the separation within the turbine duct due to wakes as well as strong secondary flow effects.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

(a) Meridional section of the 3D-duct with probe measurement planes, (b) blade counts and profiles, and (c) definition of nondimensional duct length l/hexit,blade=1.67

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Figure 2

3D-model of the 2D-duct design with outer duct contour at the bottom and the modified inner contour at the top

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Figure 3

(a) Counter-rotating low-profile VGs’ arrangement and geometries, corresponding values see Table 3, and (b) theoretical, suggested, and realized section of the VGs from left to right

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Figure 4

2D-duct with suggested position for VGs from Chalmers at the outer duct

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Figure 5

Annular duct with applied VGs at the outer duct contour

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Figure 6

Instrumentation of the 2D-duct with total pressure rake at the (a) duct inlet and (b) exit, (c) total temperature rake 83 mm upstream duct inlet, and static pressure taps

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Figure 7

Distribution of the static pressure rise coefficient along the outer contour of the 2D-duct

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Figure 8

Oil flow visualization at the outer duct contour in the 2D-duct without VGs

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Figure 9

Oil flow visualization at the outer duct contour in the 2D-duct with VGs

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Figure 10

Distribution of the static pressure rise coefficient along the outer (casing, OD) and inner duct contour (hub, ID) of the annular S-shaped duct with and without VGs

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Figure 11

Oil flow visualization at the casing for the ITD without VGs

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Figure 12

Oil flow visualization at the casing for the ITD with VGs

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Figure 13

Oil flow visualization at the hub for the ITD without VGs

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Figure 14

Oil flow visualization at the hub for the ITD with VGs

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Figure 15

Total pressure loss production

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