Vibration characteristics and strength analysis of two-stage variable-pitch axial-flow fan based on fluid-solid coupling method

Abstract

The adjustment of the rotor blade installation angle of the two-stage variable-pitch axial-flow fan affects the surface pressure characteristics, which in turn affects the vibration characteristics of the rotor blade. In this paper, the finite element model of two-stage variable-pitch axial-flow fan is first established, and then the modal analysis of blades with aerodynamic and centrifugal loads is presented. The resonance of the blade is analyzed based on the pressure pulsation frequency domain characteristics. Finally, the equivalent stress distribution under variable blade installation angles is explored. Simulation results regarding the natural frequency show that the installation angle of the moving blade has a minimal impact on the natural frequency. In contrast, the centrifugal force load significantly affects the natural frequency of the moving blade. To ensure safety, we maintain a frequency margin of over 24 % to avoid the risk of resonance. Strength analysis results indicate that the maximum equivalent stress on the first-stage and second-stage rotor blades decreases by 43.14 MPa and 45.28 MPa, respectively. This reduction is attributed to a certain centrifugal load and a slight offset in aerodynamic loading. This research can provide guidance for the vibration control and safety research of two-stage variable-pitch axial-flow fan.