As gas turbine inlet temperatures can nowadays reach values as high as 1800°C in modern engines, vanes and blades have to be efficiently cooled to operate without failure. Internal cooling can provide the large forced convection heat transfer rates which are needed in the airfoil inner surfaces to prevent the metal from overheating. Long narrow channels, in single or multi-pass arrangements, are provided inside the vanes and blades for this purpose.
The LC1-LC3 facilities are designed to reproduce these configurations in order to investigate the aerodynamic and thermal characteristics of these highly turbulent flowfields. The test section simulates a gas turbine cooling passage with an approximate scale factor of 20. It has a length of 1 m and a cross-section of 50 x 50 mm2. The walls are made of plexiglass. A wooden duct and a bell-shaped entrance precede this test section. This arrangement provides a channel length to hydraulic diameter ratio of 29 which is representative of nozzle guide vane values. A centrifugal blower aspirates air at atmospheric pressure and ambient temperature through the test section in order to reproduce a wide range of Reynolds numbers (104 to 8 x 104). The test section is heated by a resistive foil in order to generate a uniform wall heat flux boundary condition. Various turbulence promoter configurations (ribs) can be installed on one or several walls to enhance the local heat transfer.
Wall temperature measurements are performed with the help of liquid crystals and infrared thermography in order to obtain detailed local heat transfer coefficient distributions. In addition, dense wall static pressure measurements provide information on the friction factor. Finally, flow visualization, LDV, PIV, hot wire anemometry and cold wire thermometry techniques are used to characterize the different velocity and temperature characteristics of the flow in these complicated passages.