COMBINED EFFECTS OF PERFORATED BLOCKAGES AND PIN FINS IN A TRAILING EDGE INTERNAL COOLING DUCT

Pin fin arrays and perforated blockages are both important methods for gas turbine trailing edge cooling. Perforated blockages result in higher heat transfer coefficients with larger pressure loss penalty. For enhanced heat transfer with medium pressure loss, we installed a perforated blockage at the inlet of pin fin arrays and studied the combined effects between impingement and pin fin. Heat transfer coefficients were measured with the transient liquid crystal method and the lumped capacitance model. Flow field was investigated using the RNG k-epsilon model. Six configurations with different flow area ratio, hole distribution and hole aspect ratio were examined at duct Reynolds number between 9,000 and 20,000. The results reveal that under impingement condition, Nusselt number for the first two rows of pin fins near the stagnation point is 2-3 times larger than the baseline case without impingement. The most important parameter for heat transfer and friction loss is the area ratio. The average Nusselt number increases 20%-50% with impingement, and the friction factor increases 4-20 times. Heat transfer and friction loss for the combined configurations satisfy the correlation Nu=0.1766Re(0.702)f(0.188).