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Research Papers: Jets, Wakes, and Impingment Cooling

Experimental Investigation of Film-Cooling Effectiveness of a Highly Loaded Turbine Blade Under Steady and Periodic Unsteady Flow Conditions

[+] Author and Article Information
Ali Nikparto

Turbomachinery Performance and
Flow Research Lab,
Texas A&M University,
3123 TAMU,
College Station, TX 77840
e-mail: nikp11@tamu.edu

Meinhard T. Schobeiri

Oscar Wyatt Professor
Turbomachinery Performance and
Flow Research Lab,
Texas A&M University,
3123 TAMU,
College Station, TX 77840
e-mail: tschobeiri@tamu.edu

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received April 29, 2016; final manuscript received December 11, 2016; published online March 15, 2017. Assoc. Editor: George S. Dulikravich.

J. Heat Transfer 139(7), 072201 (Mar 15, 2017) (13 pages) Paper No: HT-16-1236; doi: 10.1115/1.4035651 History: Received April 29, 2016; Revised December 11, 2016

This paper describes the experimental investigations of film-cooling effectiveness on a highly loaded low-pressure turbine blade under steady and unsteady wake flow conditions. The cascade facility in Turbomachinery Performance and Flow Research Lab (TPFL) at the Texas A&M University was used to simulate the periodic flow condition inside gas turbine engines. Moving wakes, originated from upstream stator blades, are simulated inside the cascade facility by moving rods in front of the blades. The flow coefficient is maintained at 0.8 and the incoming wakes have a reduced frequency of 3.18. A total of 617 holes on the blade are distributed along 13 different rows. Six rows cover the suction side, six other rows cover the pressure side, and one last row feeds the leading edge. Each row has a twin row on the other side of the blade with exact same number of holes and arrangement (except for leading edge). They both are connected to the same cavity. Coolant is injected from either sides of the blade through cavities to form a uniform distribution along the span of the blade. Film-cooling effectiveness under periodic unsteady flow condition was studied using pressure-sensitive paint. Experiments were performed at Reynolds number of 150,000 and blowing ratio of one, based on equal mass flux distribution. Experimental investigations were performed to determine the effect of flow separation and pressure gradient on film-cooling effectiveness. Moreover, the effect of impinging wakes on the overall film coverage of blade surfaces was studied. It was found that heat transfer coefficient (HTC) and film-cooling effectiveness (FCE) in majority of regions behave in opposite ways. This can be justified from turbulence intensity and velocity fluctuation point of view. Also, unsteady wakes imposed on top of film injection have opposite effects on suction and pressure side of the blade. This is more clearly seen in region near leading edge.

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Figures

Grahic Jump Location
Fig. 1

Turbine cascade test section at TPFL with components and adjustable test section as described in Refs. [11], [22], [2729], [34], and [36]

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Fig. 2

Heat transfer blade covered with liquid crystal sheet [11]

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Fig. 3

Film-cooled blade covered with PSP inside the test facility (top) and the cross section of the blade (bottom)

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Fig. 4

Data-acquisition system

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Fig. 5

Pressure-sensitive paint calibration curve

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Fig. 6

Static pressure coefficient distribution around the blade

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Fig. 7

Velocity profiles at different streamwise locations on the suctions side of the blade (top left) and velocity fluctuation magnitude at the same streamwise locations on the suction side of the blade (top right). Heat transfer coefficient and film-cooling effectiveness for entire span of the blade (bottom).

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Fig. 8

Film-cooling effectiveness contours of unsteady wake flow condition (top) and steady (bottom) for the entire span of the blade at turbulence intensity of 1.9% and Ω of 3.18

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Fig. 9

Ensemble-averaged velocity contours at t/τ = 0.25, 0.5, 0.75, and t/τ = 1 for Ω of 3.18: (a) Ω = 3.18, t/τ = 0.25, (b) Ω = 3.18, t/τ = 0.50, (c) Ω = 3.18, t/τ = 0.75, and (d) Ω = 3.18, t/τ = 1.0

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Fig. 10

Ensembled-averaged turbulence intensity contours at t/τ = 0.25, 0.5, 0.75, and t/τ = 1 for Ω of 3.18: (a) Ω = 3.18, t/τ = 0.25, (b) Ω = 3.18, t/τ = 0.50, (c) Ω = 3.18, t/τ = 0.75, and (d) Ω = 3.18, t/τ = 1.0

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