EXPERIMENTAL INVESTIGATION ON HEAT TRANSFER AND PRESSURE DROP IN A RIBBED ROUGHENED LEADING EDGE COOLING CHANNEL

摘要

Walls of internal leading edge cooling channels of turbine blades are often rib roughened to augment the convective heat transfer. In this study an experimental investigation on the effect of different rib spacing on the internal heat transfer and pressure drop in an engine-similar leading edge cooling channel is presented. Square rib turbulators inclined at 45° with a constant blockage ratio of e/d_h =0.1 were mounted on two walls in a staggered arrangement. Rib pitch-to-height ratios of P/e = 5, 7.5, 10, and 15 were tested for Reynolds numbers between 20, 000 and 50, 000. A transient liquid crystal method was used to measure the heat transfer at the channel walls between the ribs. The comparison showed the highest average heat transfer for the pitch-to-height ratio of P/e = 7.5. The highest friction factor occurred for P/e = 5. Due to intense heat transfer enhancement and moderate pressure drop the rib-to-height ratio of P/e = 7.5 results in the highest thermal efficiencies for constant pumping power.