Abstract：In Venturi injector, the critical cavitation caused by large pressure difference will result in poor fertigation uniformity. Experimental investigation was conducted to study the cavitation phenomenon of DN25 Venturi injector. For seven different inlet pressure values, the changes of suction flow rate were measured under different pressure differences between inlet and outlet. The strain values on the enternal surface of throat and diffusion portions were detected by dynamics strain indicator. Stan-dard deviations of the strain values were calculated to analyze the relationship between the suction flow rate and the internal characteristics of the cavitating flow. The results show that critical cavitation occurs in Venturi injector when inlet pressure is below 0.20 MPa. As inlet pressure exceeds 0.20 MPa, the critical maximum pressure difference has linear relationship with inlet pressure, and critical cavitation occurs in Venturi injector. When inlet pressure is larger than the critical maximum pressure diffe-rence, the variation curves of strain standard deviation versus pressure difference appear to be “M”, where three inflection points of “M” are linear with inlet pressure, respectively.
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