1. Context

The impeller of a hydraulic machine is always specially designed for its intended application, as it is the element that first transforms hydraulic energy into mechanical energy on the turbine shaft.

Each site has its own characteristics in terms of available energy E, or net head H ≥ E/g, and exploitable flow. This diversity leads to the development of different impeller layouts for each layout, and it is in this sense that we speak of a prototype impeller for the industrial machine, because in general this impeller will be the unique specimen adapted to the site under consideration.

The term "drop" is still widely used in everyday language. On a prototype, the head varies between a maximum value and a minimum value, passing through a head that is most frequently encountered as the "nominal head". Under nominal head, we define nominal power...