Measurement of kinematically unstationary separated flows
Abstract
The development of flow separation between the hub wall and the blade suction side in an axial compressor annular cascade is examined with several measurement techniques. The flow was first assumed to be stationary; separation could be estimated with flow visualization and pneumatic pressure measurements on lateral walls and blade surfaces were carried out for evaluating flow losses in the cascade. Measurements at airfoil surfaces with hot wire probes and hot film sensors gave information about the development of the blade boundary layer. The influence of the unstationary flow on the development of airfoil boundary layers and the separation at the hub with dependence of the aerodynamic loading is studied. Cylindrical bars were used instead of a real blading in order to obtain typical wakes without potential interactions between rotor and stator. Experimental examinations similar to the one described for the steady flow were carried out. It is found that flow losses increase in the airfoil boundary layer while they drop to the hub separation. By and large, the total losses are found to be lower with unsteady flow.
- Publication:
-
Tech. Univ. Berlin, Experimental Methods in Separated Flows
- Pub Date:
- 1991
- Bibcode:
- 1991tube.rept...15P
- Keywords:
-
- Boundary Layer Flow;
- Boundary Layers;
- Compressors;
- Flow Measurement;
- Separated Flow;
- Turbulent Flow;
- Unsteady Flow;
- Calibrating;
- Compressor Blades;
- Compressor Rotors;
- Hot-Wire Anemometers;
- Reynolds Stress;
- Turbomachinery;
- Velocity Measurement;
- Fluid Mechanics and Heat Transfer