Influence of Upstream and Downstream Stator Blades on the Rotor Blade Flutter Characteristics

One of the important issues in turbomachinery flutter analysis is the intra-row interaction effects. The present work is aimed at a systematic research of the adjacent rows effects on aerodynamic damping. Three models, the isolated rotor, the IGV-rotor and the rotor-stator model, are performed to identify the upstream and downstream stator effects on the rotor blade. It is found that the aerodynamic damping from the stage flutter simulations are quite different from that from isolated rotor. In addition, the mixing-plane method is also applied to calculate the stage flutter characteristics and its accuracy of flutter predictions is compared with the time-marching method. It is indicated that the main difference of aerowork density between MP and TM is in the tip area, and in some cases the result from MP method can be misleading. Furthermore, study with different axial gaps illustrates that there is a nonmonotonic relationship between the rotor blade aerodynamic damping and the gap in the rotor-stator model, while the rotor blade aerodynamic damping monotonically increases with the gap in the IGV-rotor model.