Rotodynamic pumps - Operating mode

The article "Rotodynamic pumps" is the subject of several articles:

• – [BM 4 300] Presentation. Description ;

• –[BM 4 302] How it works ;

• – [BM 4 303] Similarity and design of centrifugal pumps ;

• – [BM 4 304] Propeller pump project ;

• – [BM 4 306] Special mechanical problems ;

• – [BM 4 308] Operations ;

• – [BM 4 314] Cavitation resistance of rotodynamic pumps.

The subjects are not independent of each other. Readers may need to refer to other articles.

The flow inside a turbomachine is always highly complex. It is unsteady and three-dimensional, i.e. it depends on time and three space variables. Without prior simplification, it can neither be analyzed by simple means of calculation, nor even described or explained by ordinary means of communication.

The flow is therefore represented by fictitious quantities. At a given point, the pressure and velocity components considered are time-averaged values. On a given surface, for example at the outlet of a centrifugal impeller, the pressures and velocities considered are values averaged over the entire surface.

We reason as if the flow were uniform and depended on a single space variable. In the case of flow in a purely centrifugal pump, this space variable is the radius.

The simplified theory also assumes that the flow...