A Blade Resonance Prediction Using Fluid-Structure Interaction Calculation Method and Comparison With the Test

In this study, nozzle-wake resonance of a low-speed axial fan blade is numerically analyzed, and compared with the test. The numerical method is fluid-structure interaction (FSI) calculation, which combines unsteady structural FEM and unsteady CFD. Instantaneous blade surface pressure distribution is calculated by CFD, which is used as a boundary condition of unsteady FEM. Blade response is then calculated by FEM, and the deformation of the blade is transferred to CFD. Advantage of this method is that it can include the effects of real geometry, blade/vane arrangement, operating conditions, etc. Aerodynamic damping is also included. In this study commercial codes are used for both CFD and FEM. On the other hand, the authors have built a test rig of low-speed two-stage axial fan, specially designed for this study. The second stage rotor (2R hereafter) blades are intentionally designed to have a resonance of 1st bending mode near design speed. Vibratory stress, amplitude, and unsteady surface pressure of 2R blades were measured. Comparison of measurement and calculation revealed the potential of FSI method. Though there were some discrepancies between prediction and measurement, the blade response was reasonably explained by lift fluctuation estimated from blade surface pressure.Copyright © 2009 by ASME