Regarding impeller calculations
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Suppose a centrifugal pump is tested and it is found that its head and flow rate are higher or lower than the rated values; in such a case, the impeller needs to be reshaped. What is the formula for this calculation? For example, a certain centrifugal pump has a rated head of 46.7 meters and a flow rate of 215 cubic meters, with an impeller diameter of 356 mm. Upon testing, the actual head and flow rate were found to be 49.7 meters and 221 cubic meters respectively, which are above the rated values. How should the impeller be redesigned in this case?
1 Find a book on pump theory and use the principle of similarity for the conversions. 2 During the cutting process, both flow rate and head will change
For pumps with a low specific speed, it can be calculated as (D2/D1)*(D2/D1) = (Q2/Q1)*(Q2/Q1) = H2/H1. For pumps with a medium to high specific speed, D2/D1 = Q2/Q1 = H2/H1
You must be wrong; the flow rate and head under testing can’t both be higher than the rated values.