Influence of impeller outlet width on characteristic curve slope in the design of changeable flow parts of D-type pumps

The present paper focuses on study of relation between impeller outlet width and the slope of characteristic curve. In order to figure out the dependence between impeller outlet width and the slope of characteristic curve on the different operation modes the numerical simulation was used. The cause of efficiency reducing in extremely narrow and wide impellers was determined. Dependence between impeller outlet width of double-entry centrifugal pump and slope of characteristic curve was established. We have defined that changing of the impeller outlet width in some relative width range leads to achieving required characteristic curve slope with inessential efficiency drop. The study results are intended to be used during modernization of pump impellers with specific speed, which operate in groups with different initial characteristic curves. Such modernization is possible with existing pump casing and bearing compounds usage, that greatly reduces expenses on modernization and lowers pumping equipment life-cycle cost.