The vigorous development of low-head hydraulic resources and tidal energy with greater stability and predictability is drawing attention to tubular turbines. However, many problems, such as incorrect unit association relationship, insufficient unit output, and severe vibration, occur frequently in tubular turbines, particularly when the water head is low. These phenomena cannot be known through model machine tests and numerical studies. Therefore, this study takes the tubular turbine with different water heads as the research object, in accordance with the actual boundary conditions. The unsteady numerical research for the prototype machine is conducted while considering the free surface in the reservoir area and water gravity. The internal flow characteristics of the tubular turbine with different water heads and the influence of free surface on its performance are analyzed. The research indicates the following: affected by the free surface and the water gravity, the pressure in the entire flow passage of the horizontal tubular turbine increases with the increase in the submerged depth. In addition, the short water diversion section allows the water flow from the reservoir area to still have a certain asymmetry before reaching the runner. During the rotation process of the runner, the surface pressure and torque of the blade have evident periodic fluctuations, and the amplitude of the fluctuations will increase significantly with the decrease in H/D₁. Moreover, in the case of small H/D₁, the amplitude of pressure pulsation in the draft tube is larger, and concentrated high-frequency pressure pulsation occurs. These factors will lead to the occurrence of material fatigue damage, unstable output, and increased vibration in low-head tubular turbines.

Pump station engineering is a water conservancy project that utilizes water pump units for energy transfer and conversion, and safe water transportation. This study ensures the safe and efficient operation of the pumping station system by taking a pump station project containing seven water pump units as the research object. Under the premise that the total water intake of the pumping station is certain, the flow distribution of the pumping station is optimized with the working flow and head as the constraint function, and the minimum operating cost as the objective function, and the required number of operating units is determined to obtain the optimal combination of flow distribution and the corresponding working flow of each operating unit. Compared with previous studies, the novel feature of this study is that a genetic algorithm is used to optimize the power-up combination and rationally distribute the flow, which can minimize the energy consumption and maximize the operation efficiency of the pumping station. Then, a genetic-algorithm-based optimization method is constructed for unit operation combination and flow distribution. The optimized combination of units is evaluated by using the uniformity of flow velocity at the inlet section of the water pump and the average deviation angle of the section as indicators. The results indicate that, when each operating unit in the pump station has the same working flow distribution, the total input power of the pump station is at maximum. As the differences increase in the working flow rates allocated to each operating unit, the total input power of the pump station decreases. Through the proposed schemes, the optimal operating combination and flow distribution of the pump station system can be achieved when the total water intake is constant, thereby enabling efficient operations and creating maximum economic and social benefits.

Tubular turbines are widely used in low water head and tidal power development due to their straight flow path, simple structure, and wide efficient area. However, the severe vibration during actual operation greatly affects the safe operation of the tubular turbine. This study performs a numerical calculation of the tubular turbine, which meets the actual machine conditions considering the free surface and water gravity; compares and analyzes the flow characteristics and pressure fluctuation spectrum characteristics in the tubular turbine under different water heads; and verifies the comparison with the actual machine test results to explore the vibration characteristics and vibration mechanism of the tubular turbine. Research results show that a large pressure difference is observed between the top and bottom of the runner chamber, and the runner needs to experience large periodic pressure fluctuations during rotation due to the combined effect of hydrostatic pressure and hydrodynamic pressure. Under different water heads, obvious flow turbulence and high turbulent kinetic energy areas are observed in the runner and draft tube due to the influence of the shape of the blade wake vortex. The vibration in the tubular turbine is mainly concentrated in the runner and draft tube and influenced by the water gravity and the runner structure of the transverse cantilever beam. The amplitude of pressure fluctuation is the largest when the frequency inside the runner is the blade passing frequency at each water head, so the maximum vibration position is located at the runner. The research results serve as a guide for the design and operation of the horizontal tubular turbine.

Pump station engineering is a water conservancy project used for long-distance water transfer, irrigation and drainage, and urban living and industrial water supply. Centrifugal pumps are one of the main pump types commonly used in pumping stations, and their operation is of considerable importance for the safety, stability, and efficient operation of pumping stations. This paper takes a large pumping station with seven centrifugal pump units as the research object and combines experimental research and numerical simulation. The axial flow velocity uniformity, average cross-sectional deviation angle, and hydraulic loss of the pump inlet section are evaluated, and the internal flow characteristics of the pump under different startup combination conditions are analyzed based on entropy generation and vorticity. This study also explores the operational performance of the pump station under different startup combination conditions, revealing the mutual influence mechanism between different startup combinations of pump stations and the internal and external characteristics of centrifugal pumps and introducing the optimal startup combination scheme for the pump station system. Research results indicate that the difference in energy loss of centrifugal pumps under different startup combinations is mainly manifested in the impeller and guide vane flow channels. For the two existing inlet flow channel structures in the pump station, the unit effectively operates when the inlet flow channel is tilted to the left. The optimal startup combination method of the pump station under different startup combinations is determined.

Hydropower unit is the compensation power generation of the energy regulating unit in wind–solar–water multi-energy complementary systems that often require the turbine to operate in a partial working condition area, thereby resulting in problems of low hydraulic efficiency and severe vibration during operation. A multi-objective and multi-condition optimization design method for Francis turbine runner based on the super-transfer approximation approach was proposed in this study. The proposed method aims to improve the hydraulic performance of the turbine, enhance and suppress the vibration of the turbine, and expand the operation range of the turbine on the basis of the actual situation given that Francis turbine frequently operates in low- and ultralow-load areas under the condition of multi-energy complementarity and continuous adjustment of operating conditions. Different operating conditions from low load to full load were selected as performance evaluation conditions. The super-transfer approximation method was used to select the weight co-efficient of water turbine operating conditions, and a multi-objective optimization function with the efficiency and cavitation performance of the water turbine as optimization objectives was constructed to ensure that the optimized water turbine can achieve the optimal performance in the full working condition range. Results showed that the pressure distribution on the blade surface of the optimized runner was uniform and the working ability was enhanced under the condition of ensuring the performance stability of optimal and rated conditions when the original runner was optimized. The hydraulic efficiency of the turbine under the low-load conditions OP1 and OP2 increased by 4.61 and 3.17%, respectively. Hence, the optimized runner is suitable for hydraulic turbines under multi-energy complementary conditions. The results of this study can provide a reference for the optimal design and operation of the turbine runner.