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RESEARCH PAPERS: Forced Convection

Film-Cooling Efficiency in a Laval Nozzle Under Conditions of High Freestream Turbulence

[+] Author and Article Information
Valery P. Lebedev, Vadim V. Lemanov

Kutateladze Institute of Thermophysics, Russian Academy of Sciences, Siberian Division, 630090, Lavrent'ev Ave., 1, Novosibirsk, Russia

Victor I. Terekhov

Kutateladze Institute of Thermophysics, Russian Academy of Sciences, Siberian Division, 630090, Lavrent'ev Ave., 1, Novosibirsk, Russiaterekhov@itp.nsc.ru

J. Heat Transfer 128(6), 571-579 (Nov 11, 2005) (9 pages) doi:10.1115/1.2188508 History: Received July 16, 2005; Revised November 11, 2005

In the present work we experimentally examined the effect of enhanced freestream turbulence on the film-cooling efficiency in an axisymmetric supersonic nozzle. A considerable reduction in the film-cooling efficiency was observed with increasing level of flow turbulence, both in the subsonic and supersonic parts of the Laval nozzle. For instance, an increase in the freestream turbulence number from 0.2% to 15% resulted in more than twofold deterioration of film-cooling efficiency. A similar decrease of film-cooling efficiency was also observed under off-design flow conditions. At the same time, the increase in the freestream turbulence number had almost no effect on the recovery factor and on the distribution of static pressure over the length of the nozzle. The Kutateladze-Leont'ev asymptotic theory of gas cooling films was used to generalize the experimental data for nozzle flows with allowance for flow nonisothermality, compressibility, longitudinal pressure gradient, and high freestream turbulence number.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

(a) Schematic of the test section: 1—turbulizer, 2—convergent part of the settling-chamber, 3—partition, 4—injection chamber, 5—fairing, 6—test section, 7—thermal insulation, and 8—thermocouples; (b) turbulence generators (T in (a)); (c) geometry of the Laval-nozzle contour

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Figure 2

(a) Profile of flow velocity in the main-flow boundary layer at the slot exit plane, (b) profile of flow velocity in the main-flow boundary layer in the universal coordinates, and (c) distribution of streamwise velocity fluctuations in the main-flow boundary layer

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Figure 3

Degeneration of turbulence in the convergent part of the nozzle and in the cylindrical pipe

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Figure 4

Distribution of flow velocity, Mach number, acceleration factor, and velocity gradient over the length of the nozzle

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Figure 5

Effect of Mach and turbulence numbers on the distribution of recovery factor in the nozzle

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Figure 6

Effect of initial turbulence on the film-cooling efficiency in the nozzle

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Figure 7

Effect of freestream turbulence on the film-cooling efficiency in the cylindrical pipe and in the Laval nozzle

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Figure 8

Distribution of wall pressure (a) and temperature (b) along the nozzle in off-design regimes (symbols—experimental data, line—predicted data): open symbols—Tu0=0.2%, full symbols—Tu0=15%, line—data predicted by the model assuming one-dimensional isentropic expansion of the flow

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Figure 9

Effect of freestream turbulence number on the film-cooling efficiency in the Laval nozzle under off-design conditions

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Figure 10

Film cooling in the nozzle flow: Comparison between experimental and predicted data

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Figure 11

Generalization of experimental data on the film-cooling efficiency in nozzle flows

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