As an important overcurrent component in a waterjet propulsion system, the inlet passage is used to connect the propulsion pump and the bottom of the propulsion ship. e anticavitation, vibration, and noise performance of the waterjet propulsion pump are significantly affected by the hydraulic performance of the inlet passage. e hydraulic performance of the inlet passage directly affects the overall performance of the waterjet propulsion system, thus the design and optimization method of the inlet passage is an important part of the hydraulic optimization of the waterjet propulsion system. In this study, the hydraulic characteristics of the inlet passage in the waterjet propulsion system with different flow parameters and geometric parameters were studied by a combination of numerical simulation and experimental verification. e model test was used to verify the hydraulic characteristics of the waterjet propulsion system, and the results show that the numerical results are in good agreement with the test results. e numerical results are reliable. e hydraulic performance of the inlet passage is significantly affected by the inlet velocity ratio.ere is a certain correlation between the hydraulic performance of the inlet passage and ship speed, and the hydraulic performance of the inlet passage is limited by ship speed. e geometric parameters of the best optimization case are as follows: the inflow dip angle α is 35°, the length L is 6.38D 0 , and the upper lip angle is 4°. e optimal operating conditions are the conditions of IVR 0.69-0.87.

Sampling fluids from the small-diameter deep pipeline is a challenging problem. In this paper, a very simple, piezoelectric-actuated inertial pump (PIP) is developed using a bionic valve to solve these problems. The PIP consists of simple components, including a cantilever beam piezoelectric actuator, a hard tube, and a bionic valve made of silicone. The fluid is driven by the inertial force generated in the vibration process of the tube. A new bionic valve inspired by a heart valve has been designed which has the advantages of small flow resistance and large flow area. The authors described the working principle of PIP in detail, established the flow characteristics model of the bionic valve, and used COMSOL Multiphysics to analyze the characteristics of the bionic valve. By comparing the response characteristics of the bionic valve with different tilt angles, the optimal Angle was obtained. Finally, the experimental and simulation results were compared, and the basic performance of PIP was tested. The experimental results showed that: When the tilting angle was 45° and the valve hole diameter was 6 mm, when the voltage was 98 V and the frequency was 24.5 Hz, the maximum output flow of the piezoelectric pump was 170.25 ml/min.

Unsteady numerical simulation and visual experiment are used to reveal the formation mechanism of the roof-attached vortex (RAV) on the roof of the closed sump of a pumping station. The results show that RAVs mainly occur between the pump device and the rear wall of the closed sump. In the 10th period of impeller rotation, there are 2 RAVs at the roof. V1 (Vortex 1 in numerical simulation) is located directly behind the water pump unit, and V2 (Vortex 2 in numerical simulation) is close to the right wall. Significantly, the vorticity intensity at the V1 vortex core increases with the rotation of the impeller. Vtest1 (Vortex 1 in test) and Vtest2 (Vortex 2 in test) are two RAVs observed in the experiment, which are highly consistent with the unsteady numerical simulation V1 and V2. Comparing the vorticity intensity of the roof, rear wall, and sidewall, it can be seen that the maximum vorticity intensity on the roof is more significant than that on the rear wall and both sides of the wall. The roof is more likely to induce vortex. When the RAVs on the roof occur, the pressure in the middle of the bell mouth is lower than that on the sidewall, and the velocity is higher. At 2/5 T, the blade is in the low-pressure zone. The velocity distribution uniformity and velocity weighted average angle at the bell mouth also decreased. The RAVs enter the pump after being generated, which is the most harmful to the safe and stable operation of the pump. The study can provide theoretical guidance for the optimal design of the closed sump.

The hydraulic performance of an inlet duct directly affects the overall performance of a waterjet propulsion system. Key parameters for the hydraulic optimization of the inlet duct are explored using the computational fluid dynamics (CFD) technology to improve the hydraulic performance of the waterjet propulsion system. In the CFD simulation and experiment, an inlet duct with different flow and geometric parameters is simulated. By comparing grid sensitivity and different turbulence models, a suitable grid size and a turbulence model are determined. The comparison between the numerical simulation and the experiment shows that the numerical results are reliable. The results of the calculation and analysis of different speed cases show that the ship speed affects the efficiency of the waterjet propulsion system. In particular, the system efficiency increases first and then decreases with an increase in the ship speed. Under the conditions of constant ship speed and rotational speed, the influence of the length and dip angle of the inlet duct on the waterjet propulsion system is investigated using a single factor method. The results show that the dip angle has an obvious effect on the hydraulic performance of the inlet duct, and an extremely small angle of inclination will lead to poor flow patterns in the inlet passage. When the length is approximately six times the inlet duct outlet diameter, and the dip angle is 30°-35°, the hydraulic performance of the waterjet propulsion pump system is satisfactory.

In order to understand the influence of blade angle on the hydraulic characteristics of a shaft tubular pumping device, the energy characteristics, cavitation characteristics, runaway characteristics, and pressure pulsation of the tubular pumping device under different blade angles were studied by a model test. Comparing the efficiency of the best efficiency point of the pumping device under different blade angles, it can be seen that when the blade angle is +4°, the efficiency of the best efficiency point of the pumping device is the lowest, 74.10%. When the blade angle is −4°, the efficiency of the best efficiency point of the pumping device is the highest, 79.75%. Comparing the cavitation characteristics of the pumping device under different blade angles, it can be seen that when the blade angle is −4°, the overall cavitation performance of the pumping device is the best. When the design head point is deviated, the NPSHav (Net positive suction head available) of the pump will increase. At the same blade angle, the runaway speed increases with the increase in head. The runaway speed of the prototype pump decreases with the increase in blade angle. When the blade angle is −6°, the runaway speed of the prototype pump is the largest, which is not conducive to the safe operation of the pumping station. When the blade angle is −4°, the variation law of pressure pulsation is small, and there is no abnormal pulsation. The tubular pumping device has satisfactory hydraulic performance, high efficiency, cavitation, and runaway characteristics. Therefore, the shaft tubular pumping device has wide application prospects under ultra-low head, and we recommend prioritizing it in low-head pumping stations.