Relationship between the number of impeller stages, head, and outlet pressure in multi-stage pumps
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I have a multi-stage pump with 10 stages. The outlet pressure of this pump does not meet the design requirements – the designed pressure is 2.58 MPa with a head of 390 meters, whereas the actual pressure is only around 2.0 MPa. Additionally, the pump experiences significant vibration. I plan to modify this pump by replacing it with another model. The manufacturer’s solution involves thickening the original shaft, adding an inducer wheel at the inlet, and reducing the number of pump stages from 10 to 7. According to the calculations, the expected outlet pressure will be 2.6 MPa, with a head of 390 meters. What puzzles me is: why can the outlet pressure increase even when the impeller is reduced?
Has only the shaft been thickened, or has the impeller been reduced in size? Are there no other changes? Please explain in detail! Has it been successfully tested in operation?
The pre-induction wheel can increase the suction pressure at the pump inlet. The head of the pump is directly related to the inlet pressure, and it serves to boost the pressure of the fluid as a whole
In my humble opinion: The working principle of a centrifugal pump: Euler’s law； The number of stages in the pump and its rotational speed are the key parameters that determine the capacity increase of a centrifugal pump ； It says here that the number of stages in the centrifugal pump has been reduced ； The overall performance of the pump still needs to be improved, which indicates that its rotational speed has increased significantly ； The induction wheel is added to prevent cavitation at the pump inlet when operating at high speeds ； At the same time, there are also some benefits to adding features. . The single-stage efficiency of a multi-stage pump can be understood using the concept of specific speed. The original poster can look up the calculation formula. .
To add an impeller, it is necessary to thicken the pump shaft. The impeller can increase the pump’s net positive suction head as well as its head capacity; however, a single impeller results in a lower relative head. Has the diameter of the impeller or the thickness of the flow channels also changed?
Understood; the rotational speed remains unchanged, the shaft has become thicker and the impeller diameter has increased
The head h is approximated as h = v²/2g, where v is the linear velocity at the outer circumference of the impeller. The square of the linear velocity. With the rotation speed remaining unchanged, an increase in diameter leads to an increase in the head per stage; therefore, the number of stages was reduced from 10 to 7