Effects of Bulk Flow Pulsations on Film Cooling From Spanwise Oriented Holes

Abstract

Experimental results are presented which describe the effect of bulk flow pulsations on film cooling from a single row of spanwise oriented holes. The film coolant is injected from the holes with 35 degree inclination angles and 90 degree orientation angles. Static pressure pulsations are produced by rotating vanes made of an array of six shutter blades, which are extended across the span of the exit of the wind tunnel test section. The free-stream velocity is in the form of near-sinusoidal variation and peak-to-peak amplitude is 11%. Changing two parameters which are time-averaged blowing ratio (M = 0.5, 1.0, 2.0) and frequency (f = 0, 36 Hz) gives the corresponding coolant Strouhal numbers in the range from 0 to 3.6. Time-averaged and phase-averaged temperature distributions are measured in spanwise/normal planes, and the adiabatic film cooling effectiveness is evaluated from the adiabatic wall temperature distributions. The results show that the imposed free-stream velocity pulsations generate static pressure difference variations between the plenum chamber and free-stream. These static pressure pulsations result in periodic variation of injectant flow rate and spanwise momentum which cause dramatic alterations in film coolant distributions, trajectories and corresponding adiabatic film cooling effectiveness distributions downstream of injection holes.