There are two styles of stages for the range of flow rates in which ESPs operate.
The first is a radial stage.
The impeller is shown in Fig. 4
and the diffuser in Fig 5
Its geometry has the flow entering the impeller or diffuser parallel to the axis of the shaft and exiting perpendicular to the shaft, or in a "radial" direction. They are sometimes referred to as "pancake" or "mushroom" stages, respectively, because of the impellers’ flat shape and the diffusers’ mushroom-shaped downthrust pedestal. A cross-sectional schematic of a radial stage is shown in Fig. 6
The second is a mixed-flow stage; a typical impeller is shown in Fig. 7
, and the diffuser is shown in Fig. 8
. Its geometry has the flow exiting the impeller at an angle less than 90° to the shaft. A graphic of this flow path is shown in Fig. 9
. Generally, this angle changes from near perpendicular to near axial, as the design flow rate of the stage increases for a particular-diameter unit. This relationship is shown in Fig. 10 .