Experimental investigation of meridional velocity and circulation in axial-flow impeller outlet

In order to investigate the meridional velocity and circulation distribution in axial-flow impeller outlet, the measuring device was designed to measure a series of high efficiency axial flow pump models. A miniature five-hole spherical probe based on flow around a sphere the principle was used to measure the meridional velocity and circulation in axial-flow impeller outlet in multi-conditions. The experimental results show that meridional velocity distribution in axial-flow impeller outlet is parabolic flow pattern in optimal conditions. The maximum meridional velocity is located in the middle of blade, while meridional velocity decreases near the hub and flange region. Non-linear circulation distribution occurs in the flow field of impeller outlet, the circulation curve is relatively flat in the central of blade, while it reduces to about 0.8 times near hub and increases to about 1.2 times near tip. The measurement data of axial velocity and circulation is synthesized polynomial equations, which will provide reference for the axial-flow impeller hydraulic design.