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Research Papers

Development of a Turning Mid Turbine Frame With Embedded Design—Part I: Design and Steady Measurements

[+] Author and Article Information
Emil Göttlich

e-mail: emil.goettlich@tugraz.at

Franz Heitmeir

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

1Currently at Whittle Laboratory, Department of Engineering, University of Cambridge.

2Currently at Dipartimento di Macchine, Sistemi Energetici e Trasporti, Universita di Genova.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received August 21, 2013; final manuscript received October 20, 2013; published online January 2, 2014. Assoc. Editor: Rolf Sondergaard.

J. Turbomach 136(7), 071008 (Jan 02, 2014) (9 pages) Paper No: TURBO-13-1194; doi: 10.1115/1.4025949 History: Received August 21, 2013; Revised October 20, 2013

The paper presents a new setup for the two-stage two-spool facility located at the Institute for Thermal Turbomachinery and Machine Dynamics (ITTM) of Graz University of Technology. The rig was designed in order to simulate the flow behavior of a transonic turbine followed by a counter-rotating low pressure (LP) stage like the spools of a modern high bypass aeroengine. The meridional flow path of the machine is characterized by a diffusing S-shaped duct between the two rotors. The role of turning struts placed into the mid turbine frame is to lead the flow towards the LP rotor with appropriate swirl. Experimental and numerical investigations performed on the setup over the last years, which were used as baseline for this paper, showed that wide chord vanes induce large wakes and extended secondary flows at the LP rotor inlet flow. Moreover, unsteady interactions between the two turbines were observed downstream of the LP rotor. In order to increase the uniformity and to decrease the unsteady content of the flow at the inlet of the LP rotor, the mid turbine frame was redesigned with two zero-lifting splitters embedded into the strut passage. In this first part of the paper the design process of the splitters and its critical points are presented, while the time-averaged field is discussed by means of five-hole probe measurements and oil flow visualizations. The comparison between the baseline case and the embedded design configuration shows that the new design is able to reduce the flow gradients downstream of the turning struts, providing a more suitable inlet condition for the low pressure rotor. The improvement in the flow field uniformity is also observed downstream of the turbine and it is, consequently, reflected in an enhancement of the LP turbine performance. In the second part of this paper the influence of the embedded design on the time-resolved field is investigated.

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Figures

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Fig. 1

Two-stage—two-spool facility at the ITTM and measurement section

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Fig. 2

Pressure taps position at the hub and casing endwalls

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Fig. 3

Plane C—five-hole probe measurements at the duct inlet (view from downstream)

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Fig. 4

Static pressure measurements within the strut passage

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Fig. 6

Plane E—five-hole probe measurements at the LP rotor inlet flow (view from downstream)

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Fig. 7

Embedded design concept: schematization of the strut secondary vortex suppression and splitter vortex generation mechanisms

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Fig. 8

Plane F—five-hole probe measurements at the LP rotor exit flow (view from downstream). L3 loss core due to the strut passage vortex. L4 trace of the splitter B wake.

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Fig. 9

Losses through the duct for baseline and embedded design setups

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