The impeller is the heart of a centrifugal fan. Different working environments and conditions place different requirements on the impeller type. Based on the blade angle at the impeller outlet, impeller types can be divided into three categories: forward-curved, radial, and backward-curved.
Forward-curved blades: The blade outlet angle β2 > 90°, resulting in higher outlet air pressure but lower efficiency. Forward-curved blades tend to accumulate impurities and scale between the impeller blades. They are widely used in areas with moderate airflow but high requirements. The blades are generally narrower and more numerous. Common forward-curved fan models include the 9-19 series and 9-26 series high-pressure fans.
Radial blades: The blade outlet angle β2 = 90°. Radial blades have a simple structure and low production cost, with parameters between forward-curved and backward-curved types. However, their efficiency is lower. Due to their resistance to scaling, they are widely used in mines and environments with high dust content.
Backward-curved blades: The blade outlet angle β2 < 90°. This type of impeller has a large air volume and low pressure, but very high efficiency. In China, centrifugal fans with general backward-curved impellers can achieve an efficiency of 80%-90%, so they are widely used. Moreover, due to their non-fouling characteristics, they are widely used in the fields of power, metallurgy, chemical industry, and building materials.