Forward-curved double-inlet centrifugal fans are widely used production equipment with straightforward operating principles. Nevertheless, diversified operating requirements continuously drive the upgrading and optimization of such fans. To meet various production demands, multiple improved variants of forward-curved double-inlet centrifugal fans have been developed on the basis of traditional models.

When the blades of this type of fan interact with airflow, aerodynamic forces are generated. These forces excite blade vibration at a specific frequency; once resonance occurs between the excitation force and structural vibration, severe equipment failures may be triggered. To effectively prevent such accidents, it is necessary to calculate the magnitude of the excitation force and optimize material properties accordingly.

For fans in operation, the primary sources of excitation frequency include the number of inlet ducts, the number of outlet ducts, blade count of the rotating forward-curved double-inlet centrifugal fan, and impeller rotational speed. During operation, the excitation frequency of the fan shall be calculated and compared with the fan’s natural vibration frequency.

The natural frequency of a single blade is inherently determined by its material characteristics. The overall natural vibration frequency of the forward-curved double-inlet centrifugal fan can be derived by taking the square root of the sum of the square of individual blade natural frequency and the product of dynamic frequency coefficient and the square of rotational frequency. Among these parameters, the dynamic frequency coefficient is related to the included angle between the blade vibration plane and the impeller plane, while the fan rotational frequency is governed by the rotating speed of blades.

After calculation, the fan operating rotational speed is compared with its natural vibration frequency to obtain the resonance avoidance margin, which serves as a safety evaluation indicator for fan manufacturing.