Cavitation is a common phenomenon and continues to be a primary concern in the fields of hydraulic machinery. To provide a reference for cavitation flow and cavitation performance improvement, this paper presents the experimental study on the cavitation flow structures of the water-jet pump. High-speed photography technology is used to capture the cavitation flow structures and reveal the physical process of cavitation evolution in the water-jet pump. Cavitation–vortex interaction was further explored by numerical simulations. By extracting 24 m/s water velocity isosurface and analyzing the water superficial velocity on the isosurface, the flow characteristics in the high-velocity fluid area under different cavitation stages are revealed. Then, by analyzing the vortex structure on the isosurface, the main factors affecting the development of the vortex structure on the high-velocity fluid area are summarized.

Non-uniform inflow at the inlet of a reactor coolant pump generates performance variations, such as in the head, efficiency, cavitation, and vibrations. The three-dimensional velocity and pressure for non-uniform inflow are reconstructed via time-resolved tomographic particle image velocimetry to evaluate its effect on the reactor coolant pump. Five volume velocity fields were reconstructed through the multiplicative algebraic reconstruction technique, which constitutes the entire non-uniform flow field. The statistics of the velocity fields were used to study the non-uniform inflow characteristics. The non-uniform inflow contains two large-scale vortices in the form of counter-rotating vortex pairs. The influence of non-uniform inflow on the performance of the pump may be caused by the non-uniform pressure field. For power fluctuations during reactor operations, this non-uniform pressure distribution may generate a low-pressure region on the impeller, which induces cavitation. The non-uniform inflow shown by inhomogeneous vectors was evaluated statistically through the turbulent kinetic energy, which represents the velocity variance in each direction. For a constant head, the non-uniformity of the flow field increased with the flow rate, and the scale of small-scale turbulent vortices decreased. With proper orthogonal decomposition analysis, 90% of the energy region and flow structures were dominated by the previous 412 modes. Furthermore, the temporal modes 1, 2, 3, 100, 200, and 400 show that the frequency of large-scale eddy turnover was about 6.6–13.2 Hz. However, the large-scale eddy could be characterized within the first mode of the spatial distribution.

Cavitation can cause noise in the water-jet pump. If cavitation occurs in the water-jet pump, the hydraulic components in the pump are prone to erosion. The surface erosion reduces energy delivery efficiency and increases maintenance costs. The decline in pump performance will lead to the instability of the entire energy system. In this paper, the cavitation flow structure of the water-jet pump is studied by the method of numerical simulation and experiment, which provides a reference for the prediction and improvement of cavitation. Based on the closed test platform, in order to reveal the physical process of cavitation evolution, high-speed photography is used to capture the complex cavitation flow phenomenon in the pump. After that, the cavitation vortex structure was further explored by numerical simulation. Through the simulation of the impeller blade tip leakage flow and the Tip Leakage Vortex Cavitation (TLVC) characteristics under different cavitation conditions, the flow mechanism of the impeller blade tip leakage flow and the separation vortex induced by the cavitation region under different cavitation conditions were revealed. The main factors affecting the development of the cavitation wake vortex structures were summarized.

In order to analyze the pump shaft stability of multistage centrifugal pump during the closed-valve start-up process, the transient internal fluid field and structural field during the closed-valve start-up process of the TDM 35-140 × 13 segmental multistage centrifugal pump are solved by transient fluid-solid coupling. The transient deformation and vibration velocity of the pump shaft are analyzed. It is found that the maximum deformation amount of the third stage impeller and the pump shaft cylindrical contact surface (N = 7 node area) during the whole closed-valve transition start-up process is the largest. The maximum deformation in the region where the nodes 1 ≤ N ≤ 10 are significantly greater than that in other regions. In the 11 ≤ N ≤ 19 node, with the node position coordinate value N increasing, the maximum deformation amount is continuously decreasing. During the entire closed-valve transition start-up process, the vibration speed of the pump shaft fluctuates drastically. In the node of 1 ≤ N ≤ 19, with the node position coordinate value N increasing, the maximum vibration velocity first increases and then decreases. The maximum vibration speed at N = 11 nodes is higher than that of all other nodes.