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Research Papers

Experimental Investigation of Pressure Side Flow Separation on the T106C Airfoil at High Suction Side Incidence Flow

[+] Author and Article Information
Stephan Stotz

Institute of Jet Propulsion,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: stephan.stotz@unibw.de

Yavuz Guendogdu

MTU Aero Engines AG,
München 80995, Germany
e-mail: yavuz.guendogdu@mtu.de

Reinhard Niehuis

Institute of Jet Propulsion,
Universität der Bundeswehr München,
Neubiberg 85577, Germany
e-mail: reinhard.niehuis@unibw.de

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received September 16, 2016; final manuscript received September 28, 2016; published online January 24, 2017. Editor: Kenneth Hall.

J. Turbomach 139(5), 051007 (Jan 24, 2017) (11 pages) Paper No: TURBO-16-1242; doi: 10.1115/1.4035210 History: Received September 16, 2016; Revised September 28, 2016

The objective of this work is to study the influence of a pressure side separation bubble on the profile losses and the development of the bubble in the blade passage. For the experimental investigations, the T106 profile is used, with an increased loading due to an enlarged pitch to chord ratio from 0.799 to 0.95 (T106C). The experiments were performed at the high-speed cascade wind tunnel of the Institute of Jet Propulsion at the University of the Federal Armed Forces Munich. The main feature of the wind tunnel is to vary Reynolds and Mach number independently to achieve realistic turbomachinery conditions. The focus of this work is to determine the influence of a pressure side separation on the profile losses and hence the robustness to suction side incidence flow. The cascade is tested at four incidence angles from 0 deg to −22.7 deg to create separation bubbles of different sizes. The influence of the Reynolds number is investigated for a wide range at constant exit Mach number. Therefore, a typical exit Mach number for low pressure turbines in the range of 0.5–0.8 is chosen in order to consider compressible effects. Furthermore, two inlet turbulence levels of about 3% and 7.5% have been considered. The characteristics of the separation bubble are identified by using the profile pressure distributions, whereas wake traverses with a five hole probe are used to determine the influence of the pressure side separation on the profile losses. Further, time-resolved pressure measurements near the trailing edge as well as single hot wire measurements in the blade passage are conducted to investigate the unsteady behavior of the pressure side separation process itself and also its influence on the midspan passage flow.

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Figures

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Fig. 1

The high-speed cascade wind tunnel

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Fig. 2

Profile, investigated inlet angles and measurement planes

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Fig. 3

T106A [24] and T106C Mach number distributions at design inlet angle β1=127.7 deg (i=0 deg)

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Fig. 4

Mach number distribution at different incidence angles for Re2th=200,000 and Low Tu

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Fig. 5

Mach number distribution at different incidence angles, comparison with predictions

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Fig. 6

Wake traverses at different incidence angles for Re2th=200,000 and low Tu

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Fig. 7

Integral total pressure losses at different incidence angles: (a) low Tu and (b) high Tu

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Fig. 8

Wake traverses at different incidence angles for Re2th=200,000 and high Tu

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Fig. 9

Influence of incidence angle on the integral total pressure losses for low and high Tu

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Fig. 10

Influence of Reynolds number on the pressure side separation: (a) low Tu, i=−11.7 deg, (b) low Tu, i=−17.7 deg, (c) low Tu, i=−22.7 deg, (d) high Tu, i=−11.7 deg, (e) high Tu, i=−17.7 deg, and (f) high Tu, i=−22.7 deg

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Fig. 11

Mach number distribution at different turbulence levels for i=−22.7 deg (β1=105 deg)

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Fig. 12

Wake traverses at different turbulence levels for i=−22.7 deg (β1=105 deg)

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Fig. 13

Pitot tube traverses for i=−22.7 deg (β1=105 deg) and low Tu at xax/lax=0.96: (a) total pressure loss (mean ζ and variation ζ1%,99%) and (b) turbulence intensity of dynamic pressure

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Fig. 14

Contour plots from hot wire measurements at i=−22.7 deg (β1=105 deg), Re2th=200,000, low Tu: (a) time-mean streamwise velocity, (b) velocity fluctuations and skewness, and (c) turbulence intensity

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Fig. 15

Power spectral density of velocity

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Fig. 16

Acceleration parameter along the pressure surface

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