Research Of Structural Parameters Impact On Performance Of Non-overload Centrifugal Pumps

Non-overload centrifugal pump is a kind of pump that the shaft power curve hasextreme value, means that the shaft power of the pump is less or equal to the ratedpower of the electromotor in full flow （from the zero-flow to the full-flow）. Thereshould be a multiple of the relationship between the maximal axle power and the ratedaxle power in order to decrease the rated power of the electromotor in actual use. Inorder to achieve non-overload performance, ensure the reliability of pump operation,domestic and foreign experts and scholars have had some study on the highly efficientnon-overload centrifugal pump. On the basis of the precedent researches, therelationship between the design parameters and the performance of the non-overloadcentrifugal pump is researched by calculating the theoretical formula. The maincontent is as follows:1. According to the formula for the ratio K of the maximal axle power to therated axle power of the non-overload centrifugal pumps, the ratio K was the functionof specific speed, impeller outlet angle and number of blades by calculating theformula in certain conditions (the outlet width of blade fit the empirical formula ofthe low specific speed centrifugal pump:b₂=00003752D₂n_s^1.15, this condition can bechanged). Programs are wrote and the three-dimensional image of the ratio K andcontours about specific speed and impeller outlet angle of the ratio K under differentnumber of blades were drawn based on the function by using software MATLAB.2. Three different specific speed non-overload centrifugal pumps A （n_s=62）, B（n_s=53）, C （n_s=58） are designed based on the above function and the contours. Thewhole flow passage of the pumps is built using Pro/E, meshed using GAMBIT andsolved using FLUENT.3. The different specific speed pump A, B, C are non-overload, and the powerspare coefficient gained by numerical simulation agree with the given power sparecoefficient of the pump A and B; but the pump C is different by numerical simulation.The reason of the error is that the outlet width of blade of the pump C does not fit theassumed condition (b₂=00003752D₂n_s^1.15) of calculating the above function.4. Non-overload centrifugal pump which the power spare coefficient fit thedesign requirements can be designed successfully by the function deduced in thepaper if it’s guaranteed that the outlet width of blade fit the empirical formula(b₂=00003752D₂n_s^1.15), when pumps are designed. For the low specific speed non-overload centrifugal pump designed by other methods, the power sparecoefficient of it can be calculated accurately by the function deduced in the paper ifits design parameters meet the conditions (b₂=00003752D₂n_s^1.15).5. The example shows that the method mentioned in the paper can make thedesign of non-overload centrifugal pumps successfully and quickly, which can avoidthe blindness in choosing the impeller outlet angle with the traditional method.