Continuous High Speed Cascade Wind Tunnel S-1
The modification of the S1 wind tunnel into a large scale cascade facility was made possible by replacing the 90 deg elbow following the diffuser by a cascade test section. The cylindrical rear part of the diffuser acts as a settling chamber for the cascade test section. It is fitted with wire meshes and honeycombs to ensure homogeneous flow conditions.
The figure above shows the main elements of the cascade test section. The mainframe is a welded construction screwed to 2 circular 1,175 mm diameter end plates that replace the two flanges of the original elbow. Nozzle blocs ensure a smooth transition from the circular 1,010 mm diameter settling chamber to the rectangular cascade entrance. The upper and lower tunnel walls are movable. The cascade entrance height can be changed from maximum 650 mm down to a minimum of 375 mm. The width of the entrance duct and therewith of the blade height is 225mm.
The cascade ensemble is made up of the desired number of full blades plus two end blocs at the extremities of the cascade. These end blocs allow an easy assembly of the cascade blades between the two rectangular side walls. The test section set-up allows testing of turbine and compressor cascades from axial inlet to about 55 degree inlet angle. A rotating disk, equipped with bars can be installed upstream of the cascade to generate periodic wakes impinging on the airfoils with a correct, engine simulated, velocity triangle. The flow Reynolds number, based on blade chord length, typically ranges from 80.000 to 300.000, at high subsonic regime. These values are typical of low pressure turbine operating conditions. Pneumatic and fast response pressure and angle measurements combined with hot film sensors allow a detailed and time resolved blade wall behavior and global performance definition.