Development of low-noise and large-air flow rate bionic serrated blades for multi-blade centrifugal fans in heat pump dryers

A heat pump dryer usually adopts a centrifugal fan with multi-blades for generating large flow rate of air, but faces the problem of high aerodynamic noise. The application of bionic serrated blades instead of straight-edged blades in fans is a promising way for reducing the aerodynamic noise while keeping the air flow rate. The objective of this study is to develop low-noise and large-air flow rate bionic serrated blades by establishing prediction formulas of air flow rate and aerodynamic noise. The prediction formulas for bionic serrated blades are derived from existing flow rate and noise equations for straight-edged blades, and are extended to bionic serrated blades by maintaining the invariance of the radial projected area between the two types of blades. The relative errors between the predicted values and experimental values for the air flow rate and noise are ±4.0% and ±2.5% respectively. Based on the predicted formulas, the optimal values of serrated parameters are determined for blade design. The effects of designed blades are validated, and the results show that the noise of the fan with the designed blades is reduced by 2.1 dB(A) at the same air flow rate, compared to the original fan with straight-edged blades. The noise reduction and air flow rate maintenance are attributed to the serrated edges of the designed blades breaking down large vortices into uniformly distributed small ones, which mitigates pressure fluctuations and energy loss in the airflow field. • Application of bionic serrated blades for low noise and large air flow rate is studied. • A method for rapidly designing bionic serrated blades is presented. • Serration height and spacing are key parameters in design of bionic serrated blades. • Noise of fan with the designed bionic serrated blades is reduced by 2.1 dB(A).