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Research Papers

# Flow Statistics and Visualization of Multirow Film Cooling Boundary Layers Emanating From Cylindrical and Diffuser Shaped Holes

[+] Author and Article Information
Justin Hodges

Center for Advanced Turbomachinery and
Energy Research,
Laboratory for Turbine Aerodynamics,
Heat Transfer and Durability,
University of Central Florida,
Orlando, FL 32816
e-mail: Justin.Hodges@ucf.edu

Craig P. Fernandes

Center for Advanced Turbomachinery and
Energy Research,
Laboratory for Turbine Aerodynamics,
Heat Transfer and Durability,
University of Central Florida,
Orlando, FL 32816
e-mail: Fernandes.Craig@knights.ucf.edu

Erik Fernandez

Center for Advanced Turbomachinery and
Energy Research,
Laboratory for Turbine Aerodynamics,
Heat Transfer and Durability,
University of Central Florida,
Orlando, FL 32816
e-mail: Erik.Fernandez@ucf.edu

Jayanta S. Kapat

Center for Advanced Turbomachinery and
Energy Research,
Laboratory for Turbine Aerodynamics,
Heat Transfer and Durability,
University of Central Florida,
Orlando, FL 32816
e-mail: Jayanta.Kapat@ucf.edu

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received October 6, 2018; final manuscript received October 23, 2018; published online January 21, 2019. Editor: Kenneth Hall.

J. Turbomach 141(6), 061005 (Jan 21, 2019) (14 pages) Paper No: TURBO-18-1283; doi: 10.1115/1.4041867 History: Received October 06, 2018; Revised October 23, 2018

## Abstract

The research presented in this paper strives to exploit the benefits of near-wall measurement capabilities using hotwire anemometry and flowfield measurement capabilities using particle image velocimetry (PIV) for analysis of the injection of a staggered array of film cooling jets into a turbulent cross-flow. It also serves to give insight into the turbulence generation, jet structure, and flow physics pertaining to film cooling for various flow conditions. Such information and analysis will be applied to both cylindrical and diffuser shaped holes, to further understand the impacts manifesting from hole geometry. Spatially resolved PIV measurements were taken at the array centerline of the holes and detailed temporally resolved hotwire velocity and turbulence measurements were taken at the trailing edge of each row of jets in the array centerline corresponding to the PIV measurement plane. Flowfields of jets emanating from eight staggered rows, of both cylindrical and diffuser shaped holes inclined at 20 deg to the main-flow, are studied over blowing ratios in the range of 0.3–1.5. To allow for deeper interpretation, companion local adiabatic film cooling effectiveness results will also be presented for the geometric test specimen from related in-house work. Results show “rising” shear layers for lower blowing ratios, inferring boundary layer growth for low blowing ratio cases. Detachment of film cooling jets is seen from a concavity shift in the $u′rms$ line plots at the trailing edge of film cooling holes. Former rows of jets are observed to disrupt the approaching boundary layer and enhance the spreading and propagation of subsequent downstream jets. Behavior of the film boundary layer in the near-field region directly following the first row of injection, as compared to the near-field behavior after the final row of injection (recovery region), is also measured and discussed. The impact of the hole geometry on the resulting film boundary layer, as in this case of cylindrical verses diffuser shaped holes, is ascertained in the form of mean axial velocity, turbulence level ($u′rms$), and length scales profiles.

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## References

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## Figures

Fig. 1

Isometric sectional view of wind tunnel [6]

Fig. 2

Diffuser shaped film cooling hole geometry (Φ1 = Φ2 = 14 deg, AR = 2.66)

Fig. 3

Top and side view of cylindrical geometry with hotwire testing locations

Fig. 4

Particle image velocimetry experimental setup

Fig. 5

Uncertainty in velocity magnitude for M = 0.5

Fig. 6

Average axial velocity contours acquired using PIV for M = (a) 0.3, (b) 0.5, (c) 0.7, (d) 1.1, and (e) 1.3 (cylindrical film cooling array)

Fig. 7

Momentum thickness calculations for cylindrical and diffuser shaped film cooling holes

Fig. 8

Cylindrical, M = 0.30; spatially resolved η

Fig. 9

Average velocity profiles for M = 0.3, 0.5, and 0.7, 1.0, and 1.2 obtained with hotwire (cylindrical holes)

Fig. 10

Average velocity profiles for M = 0.3, 0.5, and 0.7, 1.0, and 1.2 obtained with hotwire (diffuser holes)

Fig. 11

Average velocity profiles for M = 1.0, obtained with hotwire for both diffuser and cylindrical holes

Fig. 12

Nondimensionalized u′rms profiles plots for M = 0.3, 0.5, 0.7, 1.0, and 1.2 obtained with hotwire (cylindrical holes)

Fig. 13

Nondimensionalized u′rms profiles for M = 0.3, 0.5, 0.7, 1.0, and 1.2 obtained with hotwire (diffuser holes)

Fig. 14

Integral length scales profiles for M = 0.3, 0.5, 0.7, 1.0, and 1.2 obtained with hotwire (cylindrical holes)

Fig. 15

Integral length scales profiles for M = 0.3, 0.5, 0.7, 1.0, and 1.2 obtained with hotwire (diffuser holes)

Fig. 16

Average velocity profiles following the first row of holes obtained with hotwire (cylindrical holes)

Fig. 17

Average velocity profiles following the first row of holes obtained with hotwire (diffuser holes)

Fig. 18

Average velocity profiles following the last row of holes obtained with hotwire (cylindrical holes)

Fig. 19

Average velocity profiles following the last row of holes obtained with hotwire (diffuser holes)

Fig. 20

Cylindrical, M = 0.79; spatially resolved η

Fig. 21

Cylindrical, M = 1.23; spatially resolved η

Fig. 22

Diffuser, M = 0.5; spatially resolved η

Fig. 23

Diffuser, M = 1; spatially resolved η

Fig. 24

Diffuser, M = 1.5; spatially resolved η

## Errata

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