Influence of Cross-Flow Induced Swirl and Impingement on Heat Transfer in an Internal Coolant Passage of a Turbine Airfoil

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Abstract Detailed heat transfer distributions are presented inside a two-pass coolant channel with crossflow-induced swirl and impingement. The crossflow is generated from one coolant passage to the adjoining coolant passage through a series of straight or angled holes along the dividing wall. The communicating holes provide for the flow turning from one passage to another typically achieved in a conventional design by a 180° U-bend. The holes direct the flow laterally from one passage to another, and depending on the injection angle, cause impingement and generate swirl. The heat transfer enhancement in the second pass is achieved by the combination of impingement and crossflow-induced swirl. Heat transfer distributions are presented on the sidewalls of the passages. Three different hole configurations are tested for three flow channel Reynolds numbers (Re = 10000–50000). The hole configurations were varied by angle of delivery and location on the divider wall. A transient liquid crystal technique is applied to measure the detailed heat transfer coefficient distributions inside the passages. Results for the three hole supply cases are compared with the results from the traditional 180° turn passage. Results show that the new feed system, from first pass to second pass using crossflow injection holes, produces significantly higher Nusselt numbers on the second pass walls. The enhancement is as high as 7–8 times greater than obtained in the second pass for a channel with a 180° turn. The additional pressure drop (rise in friction factor) caused by flow through the crossflow holes is compensated by the significant heat transfer enhancement obtained by the new configuration.