The invention discloses a method and device for determining the size of an
impeller of a fan, and relates to the field of
wind power. The method comprises the steps that feature parameters of wings and the
trunk of a
flying fish and size parameters of blades of the
impeller are determined; constructing a mapping relationship between the feature parameters and the size parameters, and determining a to-be-corrected size of the blade based on the mapping relationship; determining the working performance of the
impeller based on the to-be-corrected size; and when the working performance of the impeller is optimal, the final size of the blades is determined. The wings and the
trunk of the
flying fish have better hydrodynamic performance, so that a theoretical conversion formula from a
flying fish model to an impeller model is established by extracting the body characteristic parameters of the flying fish, the thickness distribution and the angle distribution of the flying fish body structure are combined to carry out bionic mapping, and the generation of
noise and the pneumatic loss are inhibited from the source. Meanwhile, various factors are considered, and when the working performance is optimal, the final size of the blade is determined, so that the impeller designed based on the method is more reliable.