*Hydraulic Test Circuit*

Verification tests were conducted on an open hydraulic circuit in the laboratory of fluid mechanics at the Faculty of Engineering, Czech University of Life Sciences Prague. The circuit diagram is shown in Figure 8.

The test circuit consisted of a feeding pump, a reservoir with pipes, and control and measuring devices. With this setting, the feeding pump (FP) created the hydrotechnic potential for the tested PAT and the water flowed in the direction of the blue arrows. The generator with the momentum sensor (*D*) Magtrol TMB 307/41 (accuracy 0.1%) allowed for the continuous regulation of shaft speed via the frequency converter LSLV0055s100- 4EOFNS. The water flow was measured using an electromagnetic flowmeter (*Q*) SITRANS FM MAG 5100 W (accuracy 0.5%). The pressures at *pp* and *ps* were measured by the pressure sensor HEIM 3340 (accuracy 0.5%), which was installed according to the first class accuracy requirements [23].

The hydraulic circuit described above was used for the testing of PAT variants with a head of 10 m, 20 m, and 30 m. The constant value of head was controlled by changing the speed of the feed pump by means of a frequency converter. Under these conditions,

the basic parameters were measured, from which the performance characteristics were subsequently created.

**Figure 8.** The hydraulic circuit scheme for testing PAT (Turbine variant shown in the photo): Q: flowmeter; FP: feed pump; PAT: pump as turbine; D: dynamometer; FC: frequency converter.
