PIV analysis of the internal flow in a Venturi injector

The capability of fertilizer suction of a Venturi injector depends on the vacuum pressure at the throat portion, where cavitation occurs due to the high negative pressure. In this paper, the internal flow in a Venturi injector was observed by using PIV technique and comparing with high speed photography experiment and numerical simulation. The results showed that the increase of suction flow rate would have an impact on the main internal flow, causing the bubbles in the cavitating flow field to the upper side of the diffusion portion. In the experiment, it was found that, under the inlet pressures of 0.3 MPa, 0.35 MPa, and 0.4 MPa, when suction flow rate was greater than 1 m³/h, the reflux phenomenon occurred obviously in the rear of the diffusion portion close to the wall; when suction flow rate was less than 1 m³/h, the reflux phenomenon was not found in all scenarios. Velocity fields are measured in internal flow from the throat portion to the diffusion portion of Venturi injector. It also showed that, the cavitation had a great impact on velocity field, when the cavitation gradually aggravated, the high velocity field was found in the rear of the diffusion portion influenced by the energy generated in the cavitation collapse.