2.2.6. Sizing of the Volute

The diameter of the water cutter (*d*3) is obtained considering that it must be slightly higher (about 5%) than the external diameter of the impeller. This is necessary to avoid interference due to machine vibrations. The following dimensioning criterion [38] is adopted:


The geometry relating to the exit section of the volute (*A*4) is obtained through the value of the average speed in the volute. It is expressed as a function of a parameter *Kv*, obtained from a statistical diagram as the specific speed varies.

The procedure used is as follows:

$$K\_v = \frac{\upsilon\_{volutte}}{\sqrt{2gH\_m}}\tag{43}$$

$$A\_4 = \frac{Q}{K\_v \sqrt{2gH\_m}}\tag{44}$$

$$b = h\_{\mathbb{D}} = \sqrt{A\_4} \tag{45}$$

A square geometry was assumed for the exit section of the volute (*A*4).
