10. Aerothermal Investigation of a Turbine Cooling Channel with U-Bend

The performance of the modern aeroengines is highly dependent on the turbine inlet gas temperature. However, the turbine inlet temperatures of the today’s engines are already beyond the material structural limits. Hence, the turbine section must be cooled down to acceptable levels. Various types of cooling methods like internal cooling, film cooling, impingement cooling, etc. are typically applied to the gas turbine blades. Current research focuses on experimentally and numerically investigating the thermal performance of a two-pass channel. A rectangular cross-section tunnel with two passages and a U-turn section that mimic the modern gas turbine cooling configurations was investigated. The ribs with square cross section are located on the bottom wall of both passages. The ambient air is sucked to the wind tunnel by using a blower. The bottom wall of the test section was heated by a foil heater which generates uniform heat flux. The experiments were conducted at Reynolds number of 20,000. Finally the Nusselt number was computed based on the heater power, the surface temperature, and the mainstream temperature. The results were compared with the smooth wall configuration. Experimental results are compared with the numerical analysis to come up with a suitable turbulence model. Experimental results show that the heat transfer decays along the first pass and increases at the turning for smooth and ribbed cases. The effect of turning remains through the second passage. In terms of turbulence model performance, Rke model predicts better at the first pass; besides, in the turning part and the second pass, v2f and low Re YS models perform better.