Effects of Wall Admittance Changes on Aeroelastic Stability of Turbomachines

In the present investigation a kind of new lifting surface model has been suggested based on the application of generalized Green’ sfunction theory anddoubleFouriertransformation technique, which issuitableforsupersonic cascadewithsubsonicleading-edgelocus.Thetheoreticalanalysisshowsthatthechangeofwallboundarycondition not only affects the eigenvalues of the system but also the eigenfunction normalizing factor in comparison with a rigid boundary condition, and it is these variations that affect the e ow and acoustic e eld. On the other hand, through the present numerical simulation the change of wall admittance leads to very remarkable effects on both the lift and moment coefe cients, which will determine whether a nonrigid wall has a positive effect on suppressing blade e utter or not. This means that if one aims at suppressing cascade e utter by use of a nonrigid wall one of the best ways is to e nd soft wall with a controllable acoustic admittance. Nomenclature Aab = periphery of a blade Ab = upper or lower surface of a blade b = blade semichord CFqi, CFa i = imaginary part of blade lift coefe cient CFqr, CFa i = real part of blade lift coefe cient CMqi, CMa i = imaginary part of blade moment coefe cient CMqr, CMa r = real part of blade moment coefe cient H = height from the hub to the tip side h = height from the hub to the tip side in the transformed space h1 = stagger distance, measured parallel to chord h2 = gap distance, measured normal to chord i = p i 1 kb