Centrifugal fan is also fastidious in design. First of all, the blade type should be reasonably selected: at a certain speed, the pressure coefficient of the backward impeller is small, then the impeller diameter is larger, and its efficiency is higher; for the forward impeller, the opposite.
The overall dimension of the volute of the centrifugal fan shall be as small as possible. For the high-specific-speed fan, the shortened worm shape can be adopted, and the standard worm shape is generally used for the low-specific-speed fan. In order to reduce the size of the spiral case, the outlet speed of the spiral case can be selected to be larger than that of the fan inlet speed. At this time, the outlet diffuser is used to improve the static pressure value.
The blade outlet angle is one of the main geometric parameters to be selected first when the centrifugal fan is designed. For ease of application, we classified the blade as: the rear curved blade (water pump type), the rear curved arc blade, the rear bent straight blade, the rear curved wing blade, the radial outlet blade, the radial straight blade, the front curved blade and the strong front curved blade.
In centrifugal fans, increasing the number of impeller blades increases the theoretical pressure of the impeller because it reduces the effect of relative vortex. However, an increase in the number of blades will increase the friction loss of the impeller channels. Therefore, for each impeller, there is an optimal number of blades. Determine the number of blades, sometimes based on the experience of the designer.www.jnblower.com