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Research Papers

Effects of Periodic Unsteady Inflow on Film Cooling and Heat Transfer on Highly Loaded High Pressure Turbine Blades With Flow Separation

[+] Author and Article Information
Reinaldo A. Gomes

Research Assistant
e-mail: reinaldo.gomes@unibw.de

Reinhard Niehuis

Professor
Member of ASME
e-mail: reinhard.niehuis@unibw.de
Institute of Jet Propulsion,
University of the German Federal
Armed Forces Munich,
Neubiberg 85577, Germany

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the Journal of Turbomachinery. Manuscript received February 21, 2013; final manuscript received February 27, 2013; published online September 26, 2013. Editor: David Wisler.

J. Turbomach 136(2), 021014 (Sep 26, 2013) (9 pages) Paper No: TURBO-13-1028; doi: 10.1115/1.4023957 History: Received February 21, 2013; Revised February 27, 2013

Film cooling experiments were run at the high-speed cascade wind tunnel of the University of the Federal Armed Forces Munich. The investigations were carried out on a linear cascade of highly loaded turbine blades. The main targets of the tests were to assess the film cooling effectiveness and the heat transfer in zones with main flow separation. The previous cascade was designed to have a large zone with flow separation on the pressure side starting at the leading edge and reaching up to approximately half of the axial chord. This cascade was changed for a new design with a larger pitch to chord ratio in order to set the focus on flow separation on the suction side. This increased pitch forces a massive separation on the suction side due to strong shocks. The flow separation is controlled with aid of vortex generating jets in order to reduce the total pressure loss caused by it. Film cooling is provided on the suction side upstream of the vortex generating jets. The measurements comprise of blade loading, profile loss, adiabatic film cooling effectiveness, and heat transfer coefficient under two Mach numbers at a Reynolds number of 390,000. In a previous publication detailed results with homogeneous inflow where shown. Now, the focus is set on the effects of periodic unsteady wakes resulting from bars moving upstream of the cascade. These moving bars create a periodic unsteady inflow similar to the interaction between stator and rotor in the machine. It is shown how these wakes have significant influence on the heat transfer in the acceleration region of the suction side and affect the adiabatic film cooling effectiveness upstream of the shock.

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Figures

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Fig. 1

The high-speed cascade wind tunnel

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Fig. 2

Wake generator setup

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Fig. 3

Schematic of the test section and cascade instrumentation (not to scale)

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Fig. 4

Definition of the geometric data on the cascade (not to scale)

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Fig. 5

Blade with film cooling and AJVG rows (not to scale)

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Fig. 6

Velocity and turbulence level downstream of the wake generator for Ma2,s=0.87;Re2,s=390,000

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Fig. 7

Isentropic profile Mach number distribution without film cooling and AJVG for two operation points

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Fig. 8

Isentropic Mach number distribution on the rear suction side of the blade for Ma2,s=0.87;Re2,s=390,000;ptc/pt1=1.03

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Fig. 9

Isentropic Mach number distribution on the rear suction side of the blade for Ma2,s=0.95;Re2,s=390,000;ptc/pt1=1.03

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Fig. 10

Thermodynamic losses with steady and periodic unsteady inflow

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Fig. 11

Heat transfer coefficient on the suction side for Ma2,s=0.87;Re2,s=390,000

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Fig. 12

Heat transfer coefficient on the suction side for Ma2,s=0.95;Re2,s=390,000

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Fig. 13

Adiabatic film cooling effectiveness on the suction side for Ma2,s=0.87;Re2,s=390,000

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Fig. 14

Adiabatic film cooling effectiveness on the suction side for Ma2,s=0.95;Re2,s=390,000

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Fig. 15

Temperature difference ratio on the suction side for Ma2,s=0.87;Re2,s=390,000

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Fig. 16

Temperature difference ratio on the suction side for Ma2,s=0.95;Re2,s=390,000

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