Jet impingement cooling in rotating coolant passages of gas turbine blades

Jet impingement cooling was studied in a simulated rotating gas turbine blade, focussing the effects of Coriolis and centrifugal forces on new impingement-cooling configurations. The experiments were performed on two test models, namely two-pass rotating rectangular channel and one-pass rotating rectangular channel. Rotation-induced Coriolis and centrifugal forces deflected the jets away from the walls and caused characteristically different flow and heat transfer patterns in the impingement channels.;The first section of this dissertation studied impingement cooling in rotating two-pass rectangular channels. Jet Reynolds numbers and rotation numbers varied from 4 x 103 to 1 x 104 and 0 to 0.0133, respectively. Rotation-induced Coriolis and centrifugal forces decreased the Nusselt number values 20 and 25% in the impingement channels and turn region, respectively. Nusselt number values in the turn region were 60% higher when compared with those in the impingement channels for higher flow rates.;The second section investigated the effect of angled ribs (45-deg) in non-rotating and rotating impingement-cooled blades. Secondary flow produced by angled ribs and rotation interacted with each other and developed a new heat transfer pattern that is different from those produced by angled ribs or by rotation alone. As the jet Reynolds number increased from 4 x 103 to 1 x 104, the ratios of channel averaged ribbed-to-smooth surface Nusselt numbers increased from 13 to 47% for the nonrotating test. For the rotating test, however, these ratios changed from 9 to 44% as the jet Reynolds number increased. Rotation decreased the Nusselt number values up to 20% in the ribbed impingement channels.;The final section measured heat transfer coefficients in rotating one-pass rectangular channel under low jet velocities. Low jet velocities provided inadequate cooling and generated low heat transfer rates under non-rotating condition. This design could not simulate the flow and heat transfer conditions of an impingement-cooled high temperature gas turbine blade. Rotation generated strong secondary flow and enhanced the heat transfer rate from the walls. As rotation speed increased from 325 to 650 rpm at Rej = 1.6 x 104, the ratio of rotation to non-rotation Nusselt numbers increased from 1.3 to 2.5.