Centrifugal Fans - Impeller Designs
Howden supplies centrifugal fans with five basic blade shapes, and a number of impeller configurations. The final choice of impeller design will depend on the aerodynamic duty and the operating conditions. Our experienced engineers work with customers to determine the optimum solution for a particular application.
Backward inclined, backward curved blades
A highly efficient design of impeller. Its inherent strength means that in addition to handling air, it can be used with gases containing moderate amounts of erosive particles and at high temperatures. It can carry liners and hard surfacing, if required.
Backward inclined, flat plate blades
An efficient and strong shape, this design is a cost-effective alternative to the backward curved design but with flat plate blades instead of curved. This results in a slightly lower efficiency, compensated by the easier fitting of liners.
Backward inclined, forward curved blades
Also termed radial tipped blades, this design reduces the potential for dust build-up on the underside of the blades in applications with moderate amounts of gas-borne dust.
Backward inclined, aerofoil blades
Aerofoil bladed impellers are most commonly used in applications handling large volumes at low pressures. This highly efficient design of fan is used in clean air or with gases containing small amounts of erosive particles.
Forming a rotor which is essentially a large paddle wheel, this design results in a relatively inefficient fan with a power consumption higher than that using the much more common backward inclined blade. Its inherent mechanical strength and resistance to wear mean it is generally used when high quantities of abrasive dust are present in the gas stream, or when very high gas temperatures are expected.
Single or double inlet
A double inlet impeller consists of two single inlet impellers back to back on the shaft sharing a common backplate, providing almost double the flow of a single inlet fan. The selection of a double inlet fan results in a smaller diameter, faster (and perhaps cheaper) machine compared to the single inlet alternative.
Single or multiple stage
A multi-stage fan consists of two or more impellers mounted on the same shaft. The air or gas flow passes through each one in turn, with a consequent increase in pressure.