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ISSN Online: 2377-424X

ISBN Print: 0-89116-559-2

International Heat Transfer Conference 8
August, 17-22, 1986, San Francisco, USA

SCALING PARAMETERS IN FILM−COOLING

Get access (open in a dialog) DOI: 10.1615/IHTC8.2190
pages 1271-1276

Аннотация

This paper reports on an experimental and analytical investigation into the parameters which govern the process of film-cooling, a technique used in cooling gas turbine engine components. In this environment, the coolant injection temperature is considerably less than the mainstream gas temperature, giving rise to density gradients in the flowfield. In the past, experimental data has been acquired mainly at injection-to-mainstream density ratios close to unity. The effects of injection are then characterised using the injection-to-mainstream mass flux ratio. However, this parameter does not adequately incorporate the effect of changes in injection-to-mainstream density ratio.
Experiments performed in the present study suggest that, for three injection geometries over a range of injection-to-mainstream temperature ratios and injection rates, the momentum flux ratio is the correct scaling parameter for injection flows where no gross separation of the injection flow occurs from the surface. This is classed as "weak injection". For "strong injection", where the injection jets penetrate into the freestream, the velocity ratio is more successful. Using these results, parameters are proposed which scale heat transfer data for all injection rates and downstream distances, allowing data obtained at conditions unrepresentative of the gas turbine engine to be correctly interpreted in order to predict heat transfer loads in the engine. A theoretical justification for the use of these parameters is also presented.