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J. Kosel, et al.
Fig. 2. Experimental setup scheme for the developed cavitation (A) and supercavitation (B).
Hygrosens DRTRAL-10 V-R16B pressure probe (uncertainty of ± 0.2%). The fl ow rate was measured using the Buerkert SE32 fl owmeter (uncertainty of ± 1%). Sample temperature was monitored by a re- sistance temperature sensor Pt100 (uncertainty of ± 0.2 K), installed directly into the reservoir. In the experimental setup the installed heat exchanger was cooled by an external fan with ambient air, preventing any heating of the treated sample above 30 °C. The stator was made of transparent acrylic glass due to visualization and functioned as a cover. High-speed visualization was performed using Photron SA-Z, which enables recording with 20,000 frames per seconds at full resolution (1024 × 1024 pixels) and can go up to 2.100,000 fps at reduced re- solution. For the present case visualization was performed with 75,000 fps at resolution of 512 × 465 pixels. The illumination was performed with high intensity LED, focused into the observed area from the same
liquid in the tangential direction. The narrow gap between the rotor and the stator and sharp edges cause high shear stress and consequently intense pressure pulsations resulting in cavitation formation (Fig. 3). In the case of the two teeth rotor there is enough space between the teeth so that a large and stable cavitation cavity forms behind each tooth, which resembles a supercavitation cavity (Fig. 3B). Each entire fl owof the 2 L sample through the treatment chamber is de fi ned as one cavi- tation pass. Both rotors were made of stainless steel and both stators were made of a transparent acrylic glass and these also functioned as a cover. Both materials used are inert and don ’ t allow for any chemical reactions between the sample liquid and the machine. Measurements of the local system pressure ( P L ), were conducted upstream of the treatment chamber (on the suction side) using the
Fig. 3. Scheme of the treatment chamber of the rotation generator. The rotor and stator pairs used for developed cavitation and supercavitation are presented under A and B, respectively. Both rotors are rotating in a counter clockwise fashion where water is entering in the axial direction through the stator before exiting in the radial direction. Under C the geometry of a Venturi constriction is presented. Angles are indicated by α (8°), β (10°) and γ (30°).
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