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Research Papers

A Low Pressure Turbine at Extreme Off-Design Operation

[+] Author and Article Information
Martin Lipfert

e-mail: lipfert@ila.uni-stuttgart.de

Stephan Staudacher

Institute of Aircraft Propulsion Systems,
University of Stuttgart,
Pfaffenwaldring 6,
Stuttgart D-70569, Germany

Markus Brettschneider

MTU Aero Engines GmbH,
Dachauer Strasse 665,
Munich D-80995, Germany

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 11, 2013; final manuscript received July 26, 2013; published online October 25, 2013. Editor: Ronald Bunker.

J. Turbomach 136(3), 031018 (Oct 25, 2013) (9 pages) Paper No: TURBO-13-1149; doi: 10.1115/1.4025592 History: Received July 11, 2013; Revised July 26, 2013

In a cooperative project between the Institute of Aircraft Propulsion Systems and MTU Aero Engines GmbH, a two-stage low pressure turbine with integrated 3D airfoil and endwall contouring is tested. The experimental data taken in the altitude test-facility study the effect of high incidence in off-design operation. Steady measurements are covering a wide range of Reynolds numbers between 40,000 and 180,000. The results are compared with steady multistage CFD predictions with a focus on the stator rows. A first unsteady simulation is taken into account as well. The CFD simulations include leakage flow paths with disk cavities modeled. Compared to design operation the extreme off-design high-incidence conditions lead to a different flow-field Reynolds number sensitivity. Airfoil lift data reveals changing incidence with Reynolds number of the second stage. Increased leading edge loading of the second vane indicates a strong cross channel pressure gradient in the second stage leading to larger secondary flow regions and a more three-dimensional flow-field. Global characteristics and area traverse data of the second vane are discussed. The unsteady CFD approach indicates improvement in the numerical prediction of the predominating flow-field.

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References

Figures

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Fig. 1

Meridional view of the ATRD-Rig annulus

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Fig. 2

Airfoil pressure distribution of NGV1. Experimental results as indicated; steady CFD results indicated with (- -) for ReV1 = 40 k; (- ·) for ReV1 = 75 k; (…) for ReV1 = 100 k; (-) for ReV1 = 180 k: (a) ReV1 = 40 k – experiment; (b) ReV1 = 40 k to 180 k – off-design only.

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Fig. 3

Airfoil pressure distribution of NGV2. Experimental results as indicated; steady CFD results indicated with (- -) for ReV1 = 40 k; (- ·) for ReV1 = 75 k; (…) for ReV1 = 100 k; (-) for ReV1 = 180 k: (a) ReV1 = 40 k – experiment; (b) ReV1 = 40 k to 180 k – off-design only.

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Fig. 4

Comparison of steady and time averaged unsteady airfoil pressure distribution: (a) NGV1 off-design – ReV1 = 75 k; (b) NGV2 off-design – ReV1 = 75 k

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Fig. 5

Stage degree of reaction against Reynolds number; lines indicate steady CFD results: (- ·) off-Des.;St.1; (- ··) off-Des.;St.2; (-) design;St.1; (- -) design St.2

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Fig. 6

Normalized isentropic efficiency against Reynolds number; lines indicate steady CFD results, (-): design; (- -): off-design

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Fig. 7

Normalized turbine capacity against Reynolds number

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Fig. 8

Blockage factor at NGV exit against Reynolds number

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Fig. 9

Radial distribution of circumferential average loss coefficient ζ of NGV2: (a) ReV1 = 75 k – off-design to design; (b) off-design Reynolds lapse - experiment

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Fig. 10

NGV2 flow field distortion at design (left) and off-design operation: (a) design – ReV1 = 40 k – experiment; (b) off-design – ReV1 = 40 k – experiment

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