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Research Papers

Steady Vortex-Generator Jet Flow Control on a Highly Loaded Transonic Low-Pressure Turbine Cascade: Effects of Compressibility and Roughness

[+] Author and Article Information
Chiara Bernardini

Department of Mechanical
and Aerospace Engineering,
The Ohio State University,
2300 West Case Road,
Columbus, OH 43235
e-mail: bernardini.3@osu.edu

Stuart I. Benton

Department of Mechanical
and Aerospace Engineering,
The Ohio State University,
2300 West Case Road,
Columbus, OH 43235
e-mail: benton.53@osu.edu

John D. Lee

Department of Mechanical
and Aerospace Engineering,
The Ohio State University,
2300 West Case Road,
Columbus, OH 43235
e-mail: lee.30@osu.edu

Jeffrey P. Bons

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

Jen-Ping Chen

Associate Professor
Department of Mechanical
and Aerospace Engineering,
The Ohio State University,
201 W 19th Avenue,
Columbus, OH 43210
e-mail: chen.1210@osu.edu

Francesco Martelli

Professor
Department of Industrial Engineering,
University of Florence,
via di S. Marta, 3,
Firenze, Italy
e-mail: francesco.martelli@unifi.it

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 3, 2014; final manuscript received July 16, 2014; published online August 26, 2014. Editor: Ronald Bunker.

J. Turbomach 136(11), 111003 (Aug 26, 2014) (11 pages) Paper No: TURBO-14-1111; doi: 10.1115/1.4028214 History: Received July 03, 2014; Revised July 16, 2014

A new high-speed linear cascade has been developed for low-pressure turbine (LPT) studies at The Ohio State University. A compressible LPT profile is tested in the facility and its baseline performance at different operating conditions is assessed by means of isentropic Mach number distribution and wake total pressure losses. Active flow control is implemented through a spanwise row of vortex-generator jets (VGJs) located at 60% chord on the suction surface. The purpose of the study is to document the effectiveness of VGJ flow control in high-speed compressible flow. The effect on shock-induced separation is assessed by Mach number distribution, wake loss surveys and shadowgraph. Pressure sensitive paint (PSP) is applied to understand the three dimensional flow and shock pattern developing from the interaction of the skewed jets and the main flow. Data show that with increasing blowing ratio, the losses are first decreased due to separation reduction, but losses connected to compressibility effects become stronger due to increased passage shock strength and jet orifice choking; therefore, the optimum blowing ratio is a tradeoff between these counteracting effects. The effect of added surface roughness on the uncontrolled flow and on flow control behavior is also investigated. At lower Mach number, turbulent separation develops on the rough surface and a different flow control performance is observed. Steady VGJs appear to have control authority even on a turbulent separation but higher blowing ratios are required compared to incompressible flow experiments reported elsewhere. Overall, the results show a high sensitivity of steady VGJs control performance and optimum blowing ratio to compressibility and surface roughness.

Copyright © 2014 by ASME
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References

Figures

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Fig. 1

Transonic cascade schematic

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Fig. 2

Transonic cascade operating map

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Fig. 3

Machis distribution CFD/experiments comparison: Machin 0.43, Re 8.5· × 105

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Fig. 4

Machis distribution: smooth surface, Machin 0.43

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Fig. 5

Shadowgraph: smooth surface, Machin 0.43

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Fig. 6

Wake loss coefficient: smooth surface, Machin 0.43

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Fig. 7

Integral wake loss coefficient: Machin 0.43

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Fig. 8

Machis distribution: rough surface, Machin 0.43

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Fig. 9

Shadowgraph: rough surface, Machin 0.43

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Fig. 10

PSP Machis distribution: rough surface, Machin 0.43

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Fig. 11

PSP Mach number ensemble-average distributions over four hole pitches for nine different blowing ratios: rough surface, Machin 0.43

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Fig. 12

Traces of Mach number distribution from PSP at locations shown in Fig. 11. Dashed–dotted line: z/D = −3.33; bold line: z/D = 0; dotted line: z/D = 3.3. Rough surface, Machin 0.43.

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Fig. 13

Machis distribution: rough surface, Machin 0.20

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Fig. 14

Integral wake loss coefficient and jet Mach number: rough surface, Machin 0.20

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Fig. 15

Shadowgraph: rough surface, Machin 0.20

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Fig. 16

PSP Machis distribution: rough surface, Machin 0.20

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Fig. 17

PSP Machis ensemble average distributions over four pitches for seven different blowing ratios: rough surface, Machin 0.20

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