A new configuration of wind tunnel and some experience with an annular cascade for transonic flow conditions

A new type of wind tunnel was developed to investigate experimentally the transonic flow in annular cascades. The test rig permits variations of the medium velocities and flow angles in the test section, as well as of the velocity and flow angle distributions over the channel height. Flow measurements were made in a transonic turbine cascade with a small aspect ratio (H/S = 0.19). A comparison between the profile Mach numbers measured on the outer wall of the test section and in the middle of the channel shows a fairly good agreement on the pressure side, but a greater deviation is found on the suction side of the blade. This is due to the clearance flow. By attaching end plates to the tip of the blades, the clearance flow was reduced. In this case, the difference between the measured profile Mach numbers in the middle of the channel and on the outer wall was also reduced. The flow velocity in the cascade with end plates, compared to the case without end plates, increases in the case of identical upstream conditions.