Design and Research for a Gas–water Separator for Pump Cavitation Testing

In open-type cavitation tests, pump inlet air bubbles affect the accuracy of cavitation margin measurements. To improve the accuracy of these measurements, a novel gas–water separation device for pump cavitation testing was designed in this study based on the principle of multiphase flow separation. This device could effectively remove unintended air bubbles. Through numerical simulations and experimental studies, we characterized the internal flow field features and quantified how the inner cylinder length-to-diameter ratio governed the separation efficiency and pressure drop, finding an optimal length-to-diameter ratio of 2.5 for maximum gas removal. The shape of the inner cylinder and the outlet structure was optimized, and the large curvature (LC) structure minimized a pressure loss of 314.6 Pa while maximizing the separation efficiency to 89.66%. The degrees of influence exerted by the internal cylinder diameter at the bottom, the internal cylinder inclination, and the internal cylinder height on the separation performance of the LC structure were investigated through orthogonal tests. The bottom diameter of the internal cylinder was found to have the most significant influence. These results offer practical guidance for enhancing cavitation-test accuracy and informing the optimal design of gas–water separators.