Development of new models of performance correction factors of centrifugal pumps as a function of Reynolds number and specific speed

摘要

The performance characteristics of a small centrifugal pump having a specific speed of 20 min−1 are measured when pumping two industrial Newtonian oils of viscosities 75 and 646 cSt, at value of Reynolds number near 103. The diminishing of the performance in the case of these oils compared to water is about 50 to 80 %. It decreases with the reduction of Reynolds number. The correction factors of head, of flow rate and efficiency, are determined depending on Reynolds number, and they are compared with those obtained using the European KSB empirical method, the American method ANSI/HI and the semi-empirical method based on the analysis of power losses. For centrifugal pumps of a specific speed below 50 min−1, the fall in performance increases with the decrease of Reynolds number and specific speed. The fall in efficiency is more important than the fall of the other performance parameters. A good agreement is obtained between experimental results and predicted results using the three above mentioned methods, with the exception of the efficiency correction factor obtained by the method of power losses analysis, in the range of Reynolds numbers between 103 and 105. The expression of correction performance factors based on the Reynolds number is universal. It allows to distinguish the ranges of correction factors falls, and to know the economic limitations of the use of centrifugal pumps. A fall of head and flow rate correction factors of over 10 % occurs at values of Reynolds number below 104. But, the fall of efficiency correction factor of over 10 % occurs at values of Reynolds number below 105. To facilitate to the professionals the calculation of the performance correction factors of centrifugal pumps, new models are proposed in this study according to Reynolds number and specific speed.