Modeling local flows in “dictating” sections at the inlet of a centrifugal pump impeller

Abstract

When developing new centrifugal pump designs, engineers calculate the main parameters of the equipment at the design stage, including the expected flow characteristics of the pumped medium in its various zones. Given the above, it should be noted that the actual flows occurring in the suction and discharge cavities during the operation of the developed unit closely match those predicted in the design. At the same time, the flow characteristics in the boundary zones between the discharge and suction cavities are generally not examined in detail, remaining a kind of “blank spot”. This is due to the practical impossibility of measuring all spatial velocity components of the pumped medium in these zones. Attempts to describe the flow patterns in these areas by extrapolating data on local flow currents recorded at a certain distance upstream in the suction pipe are, with a high degree of probability, insufficiently justified. Nevertheless, the partially realized capability to monitor changes in the main flow of the pumped liquid caused by volumetric leakage at the impeller inlet near the front clearance seal of the centrifugal pump made it possible to qualitatively register the observed effect and obtain approximate numerical values. Given the difficulty of determining the directions and numerical parameters of individual flows, modeling local flows in “dictating” sections at the centrifugal pump impeller inlet is proposed based on data previously cited in several well-known sources but not yet used for similar modeling purposes. The “dictating” sections, which are of considerable research interest, are defined as the boundary zones between the discharge and suction cavities of the centrifugal pump. In view of the above, this paper presents an analytical study based on data previously reported in several established sources. Since these sources contain a significant amount of verified information, it is appropriate to use it to substantiate the occurrence of obvious and regular, yet insufficiently studied, processes within pump systems.