Numerical study on blade un-running design of a transonic fan

A novel iterative method is presented for turbomachinery blade un-running design with a fluid-structure coupled method. The effect of aerodynamic and centrifugal loads on blade deflections is considered in the process. Starting with a blade definition designed by an aerodynamic method, the procedure predicts a manufacturing blade profile, and computes blade deflections due to aerodynamic and centrifugal loads. The manufacturing blade profile is corrected accounting for the difference between the target blade shape and the newly deformed shape. The calculation of blade deflection due to aerodynamic loads simulates the interaction of fluid/structure at each time step, thus it is capable of accounting for the nonlinear aerodynamic contributions due to the blade deforming. In the aerodynamic domain, time accurate unsteady Reynolds averaged Navier-Stokes equation is solved in order to simulate the effect of blade deflections on the flow fields. The blade deflection is computed by solving structure dynamic equations with aerodynamic forces as boundary conditions. The information exchanges at each time step by an innovative projection-interpolation procedure with shape functions in order to transfer information between non-matching surface grids in the aerodynamic and structure domains. The method is used to predict the manufactured blade profile of NASA rotor 67 transonic fans, the predicted blade profile and the twist angle of the blade at various spans is presented. The results show that the proposed method for blade un-running design predicted more accurate manufactured fan blade shapes.