Abstract
At three flow conditions (0.8Qd, 1.0Qd, and 1.2Qd), the centrifugal pump cavity with front inducer was expanded at 0°, 90°, 180°, and 270°, and a flow path analysis of the axial cross section at the four angles was performed. This revealed that the circumferential and radial velocities of the liquid in the pump cavity along the same angle at different radii follow an axial and radial variation law to different degrees. The pump cavity center axial liquid velocity component along the radial distribution at different angles was analyzed, and liquid pressure in the pump cavity along the radial distribution was numerically analyzed from different points of view. The mean pump cavity pressure was plotted along the radial distribution curve, and a detailed numerical calculation of the axial force of the centrifugal pump and pump cavity was developed. The influence of flow conditions on the liquid flow mechanism and axial force characteristics in the pump cavity was thoroughly discussed. The results showed that liquid flow in the centrifugal pump cavity with the front inducer is mainly restricted by the main flow of the volute. The liquid eddy current in the pump cavity is mainly concentrated near the volute and the hub at 90° and 180° angles, and the higher the flow rate, the larger is the area of the side vortex of the impeller-cover plate, and the smaller is the area of the side vortex of the pump-cover plate. When the flow rate increases, the flow direction of the eddy current at the same angle in the pump cavity remains unchanged, but when the flow rate becomes too high, the flow direction of the eddy current at the same angle in the pump cavity changes. When the range of circumferential and radial partial velocities decreases, the rotational angular velocity increases, and the pressure decreases. At low flow rate, the larger the area of the volute corresponding to the pump cavity, the higher the speed becomes. The axial force in the pump cavity is the most important factor determining the axial force of the centrifugal pump.
Highlights
The axial force of a centrifugal pump is one of the most important factors affecting its service life and stable operation [1,2,3]
Another experimental study [9, 10] according to traditional theory assumed that the liquid in the pump cavity obeyed the flow-velocity calculation formula for axial force, but this did not tally with the actual test results
The pump cavity fluid-flow characteristic has a direct impact on the force on the centrifugal pump impeller cover plate, and this cover-plate force is a major component of axial force [11, 12]
Summary
The axial force of a centrifugal pump is one of the most important factors affecting its service life and stable operation [1,2,3]. Salvadori [7] performed a CFD numerical simulation of a multistage centrifugal pump and pointed out that to calculate the centrifugal pump axial force accurately, a detailed analysis of the flow characteristics of the fluid on the side of the impeller cover-plate cavity must be included. Matsui [8] used a numerical simulation method to model the back and side cavity flow in a centrifugal pump impeller to study the effects of axial force on hydraulic performance. Another experimental study [9, 10] according to traditional theory assumed that the liquid in the pump cavity obeyed the flow-velocity calculation formula for axial force, but this did not tally with the actual test results. A detailed analysis of the fluid flow mechanism and axial force characteristics in the cavity of a centrifugal pump is of great significance to calculating and balancing the centrifugal pump axial force
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