For many years, there has been interest in evaluating the effect of density differences between the coolant and the freestream in terms of the cooling effectiveness.  Numerous experiments have been conducted with different cooling gases or different temperature gases to evaluate the effect of the density ratio.  With little agreement on the best way to scale the density ratio effect, it has become commonplace for some researchers to insist upon matching the density ratio for experimental work.

However, the density is not the only property that differs between the various coolant gases used in experiments, and it is certainly not the only property difference between the coolant and the freestream in actual engines.  In the present work, we isolate the effects of these ancillary properties by conducting film cooling experiments with two carefully selected and conditioned coolant gases with identical densities but other property differences, most significantly specific heat.  Through measurements of the adiabatic effectiveness from a film cooling hole on a leading edge model, we are able to show that the specific heat effect is just as important as the density effect, providing more evidence that effects in prior research attributed to density differences, are actually a combination of density and other property differences.


The Effects of Specific Heat and Viscosity on Film Cooling Behavior

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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