The higher the efficiency of the centrifugal fan, the better. When the efficiency is as high as possible, in order to meet the required flow, total pressure and other requirements, the calculation of the geometrical dimensions of the fan flow channel is called aerodynamic calculation, generally called its dynamic calculation.

Through aerodynamic calculation, the geometric size of the centrifugal fan flow channel can be determined, which can be converted into the percentage of the impeller diameter and its relative size can be obtained. The geometrical figure of the centrifugal fan drawn with this relative size (including the thickness of each part) is called the aerodynamic sketch of the centrifugal fan. The aerodynamic sketch is a geometric figure shared by the same type of ventilator.