Air Model Testing To Determine Entrance Flow Fields
The designer of the centrifugal pump impellers requires knowledge of the velocity flow field entering the impeller for several reasons. These include an assurance that a reasonably uniform field exists, that the leading edge vane angles are matched to the flow field, and that the amount of prerotation affects the pump head. Some velocity distributions resulting from various inlet configurations can be calculated by various techniques. However, since these techniques assume mostly axisymmetric, nonviscous flow under ideal conditions, the real velocity distribution caused by side inlets truly remains unknown until an experimental program is instituted to probe the flow field and quantitatively describe the velocity distribution. The experimental technique of determining entrance flow fields of pumps having side inlets as opposed to axial inlets is described in this paper. The procedure of building models of the flow path preceding the impeller and testing these models with air as the working fluid is discussed. A description of how the flow field is probed with three-dimensional velocity probes to quantitatively “map out” the full 360 degrees velocity flow field, as well as flow visualization procedures to qualitatively give insight into the flow patterns is described in detail. A case history of the influence of the inlet flow on NPSH tests follows the discussion of the experimental methods.
Silvaggio, Joseph A. (1984). Air Model Testing To Determine Entrance Flow Fields. Turbomachinery Laboratories, Department of Mechanical Engineering, Texas A&M University. Available electronically from