Abstract
The transient effect of unsteady wakes on film cooling effectiveness using a fast response pressure sensitive paint (PSP) was studied. Testing was performed in a five passage, low speed wind tunnel using a scaled-up high pressure, blade profile. The blowing ratios studied include 0.4, 0.8 and 1.2 with a density ratio of 1.0 at each blowing ratio. Upstream unsteady wakes were produced by a spoked wheel type wake generator. The wake generator produced Strouhal numbers of 0.1 and 0.3 while the wind tunnel inlet mainstream Reynolds number was held at a constant value of 300,000 for every test case. 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, presented in the form of film cooling effectiveness RMS values. 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. 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.
