The main part of the industrial centrifugal ventilator, its geometry, number of blades, size and manufacturing precision have a great impact on the performance, the impeller will be effectively static and dynamic balance correction to ensure the smooth rotation of the fan. According to the direction of the blade outlet, the impeller is divided into three types: forward, radial and backward. The top of the blade of the forward impeller is inclined toward the direction of rotation of the impeller. The top of the blade of the radial impeller is radial, and is divided into a straight blade type and a curved blade; the tip of the blade of the backward impeller is inclined to the opposite direction of the rotation of the impeller.
The pressure generated by the forward impeller in the industrial centrifugal fan is the largest. In the case of a constant flow rate and number of revolutions, the required impeller diameter is the smallest, and its efficiency is generally low when operating, and the backward impeller is reversed. The pressure generated is the smallest, the required impeller diameter is the largest, and the efficiency is generally high; the radial impeller is between the two. The profile of the blade is the simplest with straight blades, and the airfoil blades are the most complex.
In order to make the blade surface have a suitable velocity distribution, industrial centrifugal ventilators generally use curved blades, such as arcs of equal thickness. The impeller usually has a cover disk to increase the strength of the impeller and reduce gas leakage between the blade and the casing. The connection of the blade to the cover plate is welded or riveted. The welding impeller has a light weight and a smooth flow path. The impellers of low and medium pressure small centrifugal fans are also cast in aluminum alloy.