Effect of Film Cooling on Entropy Noise Generation in a Stator Blade Row

In this study the effect of film cooling on entropy wave attenuation and indirect entropy noise generation was investigated in a subsonic stator blade row with a leading edge, pressure side, and suction side cooling geometry. The investigation was conducted on a small blade mid-span section (in a linear cascade arrangement), using a three dimensional unsteady Reynolds-averaged Navier-Stokes simulation approach. A planar entropy wave was injected at the inlet for a range of frequencies from 200 Hz to 1000 Hz. Additionally, the compact model by Cumpsty and Marble was extended to account for a cooling flow. Results show that for an increase in coolant mass flow rate of 3.4%, the entropy noise increases by about 12% for the transmitted pressure wave, while the reflected pressure wave increases by about 9%. This is attributed to the change in convective acceleration in the blade passage. The film cooling was found to have a minor effect in promoting the entropy wave attenuation. The extended compact model was capable of capturing both the entropy wave attenuation and increase in the acoustic transfer function due to film cooling.