<p>The transient effect of unsteady wakes on film cooling effectiveness using a fast response pressure sensitive paint (PSP) is studied.&nbsp; Testing was performed in a five passage low speed wind tunnel using five times scaled versions of typical high pressure blades (axial chord of 17 cm).&nbsp; To accurately capture the response of the fast PSP, with a response rate of 1000 Hz, a high speed camera with accompanying software was used to collect the data.&nbsp; The test blade being studied includes three separate rows of film cooling holes on its leading edge as well as two separate rows on both the suction and pressure surfaces.&nbsp; The blowing ratios studied include 0.4, 0.8 and 1.2 with a density ratio of 1.0 at each blowing ratio.&nbsp; Upstream unsteady wakes are produced by a spoked wheel type wake generator with rods of 9.3 cm in diameter.&nbsp; The wake generator produces Strouhal numbers of 0.1 and 0.3 while the wind tunnel inlet mainstream Reynolds number is held at a constant value of 300,000 for every test case. &nbsp;The Strouhal number cases of 0.1 and 0.3 are compared with a clean wind tunnel case (Strouhal number of 0) at each blowing ratio.&nbsp; An unsteady wake in the mainstream immediately upstream of the test blade has the effect of reducing the overall film cooling effectiveness on the leading edge and suction areas of the blade compared to no wake results. This phenomenon is primarily due to an increase in the local turbulence at the location of each wake as it passes over the surface of the blade.&nbsp; The results in this paper confirm the overall time averaged reduction in film cooling effectiveness with the addition of an unsteady wake while providing more detailed information on the transient response of the film cooling effectiveness as the wake moves across the surface of the blade.&nbsp; The transient results in this paper are presented in the form of film cooling effectiveness RMS values.&nbsp; The results show that film cooling effectiveness RMS values follow the same general trends as film cooling effectiveness values in relation to Strouhal numbers. The RMS values increase on the leading edge region of the blade and decrease on the suction side of the blade with an increase in Strouhal number.&nbsp; The pressure side of the blade shows little change in both film cooling effectiveness and film cooling effectiveness RMS values when increasing the Strouhal number.</p>

Analysis of Film Cooling Effectiveness on a Gas Turbine Blade With An Unsteady Wake Using Fast Response Pressure Sensitive Paint

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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