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Are the pump impeller blades mainly of two types: cylindrical and twisted? What are the main differences in their uses? What do people usually see, and in what type of pumps is it used? Is there anyone expert who can explain this? Urgently needed! ! Urgent! Urgent! Urgent! ! ! :P
This post was last edited by 3983596_FPPZ on 2018-9-25 at 17:00. 1. Considerations regarding fluid flow: In typical centrifugal pumps, the angle of the twisted blades allows them to conform to the laws of fluid flow at different diameters of the impeller, aligning with the direction and speed of the fluid flow. This results in less turbulence and impact of the fluid between the blades within the flow channel, thereby enabling higher pump efficiency. 2. Local comparison: Twisted blades cause significant crowding in the impeller inlet area, which is detrimental to suction ； At the impeller outlet, excessive twisting can result in an overly small angle between the blades and the shroud, leading to excessive crowding. 3. Whether at the inlet or outlet, an increased contact area between the twisted blades and the liquid leads to greater frictional losses between the liquid and the blades, resulting in lower mechanical efficiency; however, compared to its advantages, this issue can be ignored. 4. Casting considerations: It is more difficult to cast impellers with twisted blades compared to those with straight blades, as it is challenging to demold the twisted blades. The angle between the blades and the cover plate is small, the blades overlap significantly, which hinders the flow of molten iron and leads to casting defects. 5. Applications: Impellers with narrow flow channels and low specific speed generally have straight blades, or the inlet is twisted while the blades are straight near the outlet ； In high specific speed impellers with wide flow channels for large flow rates, the blades are generally twisted, which enables higher efficiency. Generally, twisted blades offer a significant efficiency advantage over straight blades; twisted blades are widely used, while straight blades are employed only in certain specially designed pumps or under specific operating conditions. All the above comparisons are relative; for pumps with specific structures and operating conditions, flexible selection is possible.
High-speed pumps mostly have straight blades； Those with a low specific speed are mostly cylindrical ； Centrifugal pumps with a medium to high specific speed typically use twisted blades; these blades can reduce the load on the blades, improve the suction performance of the pump, enhance its resistance to cavitation, and result in higher efficiency.