Advantages and disadvantages of forward-curved, backward-curved, and radial impellers.
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Could someone tell me the advantages and disadvantages, as well as the areas of application, for forward-curved, backward-curved, and radial impellers? Thank you
The last edit to this post was made by comperj001 on 2016-2-24 at 18:53. The forward or backward curvature of the blade depends on the installation angle β2 at the blade outlet; when β2 is 90°, it indicates a forward-curving blade； β2 = 90° for radial blades. With all other conditions unchanged, the larger β2 is, the higher the pump’s head. As β2 increases, the flow channels between the blades become more curved and shorter, the diffusion angle of the flow channels between adjacent blades increases, and hydraulic losses rise. The larger β2 is, the more likely a maximum will appear in the middle of the H-Q curve, resulting in a hump-shaped curve; such a performance curve is an inherent factor contributing to unstable operation of the pump. From an operational perspective, β2 is preferred
Then why are ordinary pumps usually of the backward-curving type?
Currently, the impellers of centrifugal pumps almost always use backward-curving blades (β2=20%~30%). The characteristic of backward-curving impellers is that as the head increases, the flow rate decreases accordingly. Therefore, the relationship curve between the flow rate Q and the shaft power N is a relatively gentle upward curve, allowing the motor to operate effectively within a range of limited power variations~~
Common centrifugal pumps have backward-curving blades, and their head curve decreases as the flow rate increases. The impellers of constant-pressure tangent fire pumps are radial in design, arranged radially around the axis of rotation; their characteristic is that the head curve is essentially a straight line.
Multi-blade centrifugal fans generally have forward-curving blades, while centrifugal pumps generally have backward-curving blades. It has low back-bending loss, high efficiency, and is less prone to hump formation.