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Research Papers

# Effect of Upstream Step on Flat Plate Film-Cooling Effectiveness Using PSP

[+] Author and Article Information
Akhilesh P. Rallabandi, Joshua Grizzle

Department of Mechanical Engineering, and Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843-3123

Je-Chin Han1

Department of Mechanical Engineering, and Turbine Heat Transfer Laboratory, Texas A&M University, College Station, TX 77843-3123jc-han@tamu.edu

1

Corresponding author.

J. Turbomach 133(4), 041024 (Apr 26, 2011) (8 pages) doi:10.1115/1.4002422 History: Received January 20, 2010; Revised February 19, 2010; Published April 26, 2011; Online April 26, 2011

## Abstract

The effect of a step positioned upstream of a row of film-cooling holes on the film-cooling effectiveness is studied systematically using the steady state pressure sensitive paint technique. The upstream step effect is studied on four separate hole geometries: simple angled (axial angle of 30 deg) and compound angled (axial angle of 30 deg and compound angle of 45 deg) and cylindrical and fan-shaped film-cooling holes. Each plate considered has seven holes, each hole 4 mm in diameter. The plates with cylindrical holes have a spacing of 3 diameters (12 mm) between the centers of two consecutive holes while the fan-shaped holes have a spacing of 3.75 diameters (15 mm). Three different step heights ($12.5%d$, $25%d$, and $37.5%d$) are studied. The effect of the width of the step is also studied; the distance of the step upstream of the hole and the positioning of the step downstream of the film-cooling hole. Four separate blowing ratios are reported for all tests: $M=0.3$, $M=0.6$, $M=1.0$, and $M=1.5$. All studies have been conducted with a mainstream of 25 m/s velocity at an ambient temperature of $22°C$. Results indicate an increase in film-cooling effectiveness in the region near the hole due to the upstream step for all the plates considered. This increase due to the step is found to be most significant in the case of compound angled cylindrical holes and least significant in the case of simple angled fan-shaped holes.

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## Figures

Figure 1

(a) Experimental setup used for the PSP tests and (b) schematic of the equipment used to measure local pressure using PSP

Figure 2

Hole geometries tested: (a) cylindrical simple angled, (b) cylindrical compound angled, (c) fan-shaped simple angled, and (d) fan-shaped compound angled

Figure 3

Principle of pressure measurements using PSP

Figure 4

Calibration curve for pressure sensitive paint

Figure 5

Effect of upstream step height (h) on cylindrical simple angled holes: (a) M=0.6 and (b) M=1.5

Figure 6

Effect of upstream step height (h) on cylindrical compound angled holes: (a) M=0.6 and (b) M=1.5

Figure 7

Effect of upstream step height (h) on fan-shaped simple angled holes: (a) M=0.6 and (b) M=1.5

Figure 8

Effect of upstream step height (h) on fan-shaped compound angled holes: (a) M=0.6 and (b) M=1.5

Figure 9

Cylindrical simple angled holes: spanwise averaged effectiveness showing the effect of step height h on film-cooling effectiveness for four different blowing ratios

Figure 10

Cylindrical compound angled holes: spanwise averaged effectiveness showing the effect of step height h on film-cooling effectiveness for four different blowing ratios

Figure 11

Fan-shaped simple angled holes: spanwise averaged effectiveness showing the effect of step height h on film-cooling effectiveness for four different blowing ratios

Figure 12

Fan-shaped compound angled holes: spanwise averaged effectiveness showing the effect of step height h on film-cooling effectiveness for four different blowing ratios

Figure 13

The effect of step width (w) on the film-cooling effectiveness: spanwise averaged plots

Figure 14

The effect of step position (du) on the film-cooling effectiveness: spanwise averaged plots

Figure 15

The effect of downstream step (dd=0) on the film-cooling effectiveness: spanwise averaged plots

Figure 16

(a) Definitions of various parameters. The area considered for reporting spanwise averages is shaded. (b) Simple angle (α) and compound angle (β) definitions used in the current work.

Figure 17

Comparison of current results with similar tests available in literature. All holes are compound angled and details of each experiment are listed in Table 3.

Figure 18

Schematic of effect of upstream step on film-cooling effectiveness by entrapping the coolant in recirculation zone formed immediately downstream of the step: (a) effect of step height h and (b) effect of distance of the upstream step from leading edge of hole du

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