The flow in the axial-flow compressor is intrinsically very unsteady due to the rotor-stator interaction. Additional unsteadiness can be further introduced of the cascade blades vibrate through flutter phenomenon. In this dissertation, the mechanism of unsteady potential interaction and wake interaction wake interaction in the rotor-stator stage flow of axial-compressor is numerically investigated in two dimension. Different cascade stagger angles and loading ratios are considered. Vibration of cascade blades is also considered to study the aerodynamic effect of reduced frequency, amplitude, and the various bending and torsional modes of vibration.
The numerical method consists of moving-grid finite volume method and the FEM-FVM blending techniques. The unsteady motion of computational grid can then be efficiently treated either by block motion of moving grid sliding at the surface of stationary grid system or by the deformable grid installed at the local, limited buffer layer between two nondeformable grid systems, one for the FVM region and the other for the FEM region. For the simplified test flow cases, the flows solved for the moving cascade either by the moving-grid FVM or by the deformable buffer grid technique well compared with the stationary-grid results for the fixed cascade blades with different but equivalent incident flow angles.
In the stator-rotor flow, the potential interaction caused by the motion of downstream rotors travelled upstream only up to the position of choking Shock wave at the stators. The inviscid wake interaction, on the other hand, caused by the stators travelled downstream to the whole rotors, causing subharmonic fluctuation in the force components of rotors. For the unsteady transonic cascade flow around vibration blades, suction side of the blades again had limited region where disturbance waves could not penetrate further. Uniform as well as paired plunging vibration of blades were considered for the bending mode, and pitching vibration of blades was considered for the torsional mode. The shock wave dynamics, the force and moment fluctuations, and effect of vibration parameters to the flow structure are presented in detail in the main text.
