High-head water pump is the most widely used general-purpose machinery, and it is also a large consumer of electricity and energy. Therefore, improving the efficiency of the pump itself and the efficiency of the pump are of great importance to energy conservation.
High-lift water pump
Ways to improve the efficiency of the high-lift pump itself:
1. The blade extends and thins toward the suction port, so that the liquid is acted on by the blade earlier, which can reduce the outer diameter of the impeller, increase the length of the streamline in the blade passage, and reduce relative diffusion; If the Et area is too small, the corner of the intersection between the blade inlet and the blade cover becomes smaller, which increases the hydraulic friction loss and squeezes the inlet flow path, which is detrimental to cavitation and efficiency.
2. The ratio of the exit and the inlet area of the flow path between adjacent blades is controlled within the range of 1.0 to 1.3 to reduce the diffusion loss. If the ratio is greater than 1.3, the flow channel will diffuse seriously and the efficiency will decrease.
3. The larger the hydraulic radius of the flow channel, the better. Make the blade inlet section as close to a square as possible to reduce friction loss. Known by hydraulics, the ratio of the cross-section area to the wet circumference is called the hydraulic radius, that is, the hydraulic radius is once the cross-section. Area/wet week. A large wet circumference means that the contact area between the liquid and the wall surface is large. When the flow channel section is changed from an approximate square to a long and narrow rectangle, it essentially allows the liquid to flow through the gap of the long and narrow section, so the resistance must be large.
4. Due to the large hydraulic loss of the curved diffuser, most of the diffuser sections that are slightly curved and close to a straight line are now used. For the anti-guide vane, its inlet angle and position in the circumferential direction should be combined with the flow out of the diffusion section. The principle is to form a continuous flow channel to avoid the inlet section of the anti-guide vane from being too narrow. Otherwise, eddy current and impact loss will be caused at the entrance of the anti-guide blade.
5. For multi-stage pumps, pre-rotation is added to the impeller inlet (the exit angle of the anti-guide vane is less than 90.) to reduce the relative speed of the impeller inlet while reducing the relative velocity spread. When the exit angle of the anti-guide vane is less than 90. When the water flow enters the impeller, the pre-swirl is generated. 1≠0.
6. The pre-rotation caused by the exit angle of the anti-guide vane has a greater impact on the characteristics of the next stage impeller. In order to make the 1Vul term in the theoretical head formula Ht-U2Vu2-"lVul" zero, the anti-guide vane The exit angle of 90 should be selected. , Which can eliminate the rotation component for the final guide vane. However, experiments have proved that this is not good for efficiency and obtaining a stable performance curve, especially for some low specific speed pumps, in order to obtain a reduced characteristic curve, the outlet angle of the anti-guide vane should be selected to be less than 90 degrees, usually 60 degrees to 80 degrees . The two ends of the blade should be thinner to avoid impact and eddy current loss.
The cross section of the blade flow path:
7. Increase the width of the impeller outlet and reduce the absolute speed of the impeller outlet, thereby reducing the hydraulic loss in the pressurized water chamber.
8. Cut the impeller outlet obliquely, reduce the length difference between front and rear streamlines, or choose different blade outlet angles for different streamlines, so as to reduce the pressure difference between the front and rear cover plate streamlines and reduce the secondary return flow of the outlet.
9. Increase the throat area of the pressurized water chamber. When the original design area is small, the flow will not be blocked.
Reduce mechanical and friction losses
①The mechanical friction loss caused by bearings and fillers is generally small, and has little effect on efficiency. The mechanical friction loss of the packing seal is larger than that of the mechanical seal. It is better if the mechanical seal can be used.
②Improve the surface finish of the impeller and guide vane runner. If possible, it is best to use a hand-held grinding wheel or other tools to polish the surface of the runner, so that the hydraulic friction loss will be significantly reduced.
③The friction loss of the disc between the front and rear cover plates of the impeller and the liquid is proportional to the 5th power of the outer diameter of the impeller. Choosing a larger blade exit angle can reduce the outer diameter of the impeller, thereby reducing the friction loss of the disc. The friction loss of the disc is closely related to the surface roughness, and the outer wall of the impeller cover should be as smooth as possible. Properly reducing the gap between the impeller cover and the guide vanes can also reduce the friction loss of the disc.
reduce leakage:
Appropriately reduce the gap of each part or lengthen the gap between the seals and adopt labyrinth seals to increase the leakage resistance and reduce the volume loss.
Leakage in the pump occurs at the impeller and seal ring, between the multi-stage pump stages, the axial force balance device, etc.
