The cam-type hydrogen circulating pump offers advantages such as rapid startup, high efficiency, a wide range of applicable working conditions, and a compact structure. As key equipment in proton exchange membrane fuel cells, it typically enhances delivery efficiency by increasing the compression ratio. Hydrogen in proton exchange membrane fuel cells has stringent temperature requirements. Excessively high or low temperatures can affect the state of the internal hydrogen medium, and reduce the kinetic performance of the internal chemical reactions. Two-lobe and three-lobe cycloidal cam-type hydrogen circulating pumps were designed with cycloid-arc combined profiles. Based on numerical simulation methods, dynamic mesh technology was employed to simulate the internal flow field to obtain the flow field distribution patterns within the working cavity. Subsequently, the internal working process, pressure distribution, force conditions, and temperature distribution at various monitoring points inside the working cavity were analyzed. Analyses were conducted on the two-lobe and three-lobe cycloidal cam pumps under compression ratios of 1.2, 1.3, and 1.4. By utilizing the constructed theoretical model and thermodynamic theory, the variation patterns of internal temperature under different compression ratios were investigated. The results indicate that, under identical working conditions, the radial force of the two-lobe cycloidal cam rotor exceeds that of the three-lobe cycloidal cam rotor. As the rotor rotates, the temperature at the rotor outlet varies periodically with the rotor profile. As the compression ratio increases, the temperature at the rotor outlet also rises. Each suction and discharge process of the rotor causes a fluctuation in outlet temperature, and the system's expansion power, technical power, and shaft power increase correspondingly.

To investigate the impact of the number of turbine impeller blades on pressure pulsation during the transient process of the pumped storage unit, a one-dimensional-three-dimensional coupled flow calculation method was employed to numerically simulate the guide vane closure process after the pump was powered off in pumped storage units equipped with 9-blade and 11-blade impellers, respectively. A comprehensive computational domain was established, encompassing upstream/downstream water pipelines, volute, fixed guide vanes, movable guide vanes, runner, and discharge pipe. The DDES turbulence model was used to solve the unsteady flow inside the pump-turbine system. The short-time Fourier transform method was applied to perform time-frequency analysis characterization on the pressure pulsation signals at each measuring point, and the influence mechanism of the change in the number of blades on pressure pulsation was revealed by combining the internal flow field characteristics. The results demonstrate that the water thrust fluctuation amplitude of the 11-blade impeller in pump braking mode is significantly lower than that of the 9-blade impeller, with a marked reduction in the component intensity in the blade-free zone. Increasing the number of blades can effectively suppress backflow at the high-pressure outlet of the impeller, improve the flow dynamics in the blade-free zone, and attenuate the water thrust during the guide vane closure process. With the increase in the number of blades, the rotor-stator interaction frequencies of the impeller-guide vane shift from 9fn and 18fn to 11fn and 22fn (where fn denotes rotational frequency). The above research results can provide a reference for the rational selection of the number of turbine blades in pumped storage units.

To investigate the influence of the opening angle of the bidirectional flow component on fluid flow behavior and pump hydraulic performance in a multistage centrifugal pump with symmetrical impeller arrangement, a four-stage vertical multistage centrifugal pump was taken as the research object. A three-dimensional CFD method validated by experimental data was employed to conduct a parametric study on the inlet angle (50°,60°, and 70°) and outlet angle (60°,70°,and 80°) of the bidirectional flow component, in order to analyze its operating law and influence mechanisms. The variations in pump head and efficiency under different opening angles were analyzed, with particular attention paid to the pressure distribution, velocity characteristics, turbulent kinetic energy, and vortex evolution in the inlet region. The results indicate that the inlet angle has a significant influence on pump performance. Under low-flow conditions, a smaller inlet angle is beneficial for suppressing inlet flow separation, whereas a larger inlet angle improves flow capacity under high-flow conditions. Under rated conditions, =60° is the optimal angle. By contrast, the outlet angle exhibits a relatively weaker effect on pump performance. As the inlet angle deviates from an appropriate range, the pump head increases to some extent. However, turbulent kinetic energy and vortex structures in the inlet region are significantly intensified, leading to reduction in flow stability, and thus exacerbating local energy loss. The research results can provide a theoretical basis for the rational design of the geometric parameters of bidirectional flow components in multistage centrifugal pumps with symmetrical impeller arrangement.

To enhance the hydraulic performance of large-scale low-lift two-way flow passage pump devices, the influence of the suspension heights of the outlet diffuser pipe and the water guide cone on the hydraulic performance of the pump device was studied by using an elliptical-line design approach for the diffuser section. By varying the suspension heights and of the diffuser and the water guide cone, both separately and simultaneously ( and are nondimensionalized by the axial-flow pump impeller diameter ), 21 different schemes were designed. Combined with hydraulic performance indicators such as velocity distribution uniformity and entropy production analysis, the influence of the outlet diffuser section suspension height on the hydraulic performance of the pump device was revealed. The research results show that when only the diffuser suspension height is changed, appropriately increasing improves velocity uniformity and reduces energy dissipation in the diffuser. At , the hydraulic efficiency of the pump device reaches its maximum of 73.46%. When the diffuser suspension height is fixed, appropriately reducing the suspension height of the water guide cone increases the hydraulic efficiency of the pump device. At , the hydraulic efficiency of the pump device reaches its peak, and further reduction leads to a decrease in efficiency. When the relative height between the diffuser and the water guide cone is kept constant, a higher suspension height of both components results in better hydraulic performance. When and , the hydraulic efficiency of the pump device reaches its maximum of 72.93%. Comprehensive comparison shows that the suspension height of the diffuser has a significant effect on the efficiency of the two-way flow passage pump device.

In hydro-wind-solar hybrid power generation systems, mixed-flow turbines are required to operate over a broader load range and greater operational flexibility. To mitigate the pressure pulsations within the draft tube under low-load conditions, a three-dimensional full flow path numerical simulation of a giant mixed-flow turbine was conducted using the DES turbulence model. The analysis focused on the vortex rope characteristics within the draft tube at 37.8% load and the internal mechanism of pressure pulsation suppression by draft tubes with wave-shaped generatrix and two different protrusion heights were analyzed. The results indicate that the wave-shaped generatrix draft tube can truncate wall vortices and improve the flow state at the draft tube inlet, significantly reducing the amplitude of the pressure pulsations on the draft tube wall, with a maximum reduction of 25.00%. Additionally, it suppresses upstream-propagating pressure pulsations caused by the wall-attached vortices. Due to the increased energy loss caused by the geometric modification of the draft tube, the efficiency decrease remains within 0.73 percentage point. Moreover, the study shows that units equipped with wave-shaped generatrix draft tubes exhibit faster attenuation of pressure pulsation amplitude due to the rotor-stator interaction at the draft tube inlet wall, with a maximum reduction reaching 69.98%.

To improve the suction performance of a jet pump, the inlet flare profile of the throat inlet was optimized based on the centrifugal pump impeller flow channel design method. Three sets of comparative schemes were constructed by controlling the smoothness of the curve of the flow channel centerline and the cross-sectional area variation curve. Numerical simulations were performed to compare the internal flow field, velocity distribution, pressure distribution and vorticity characteristics, to reveal the influence of the flow profile on the flow characteristics and energy loss inside the pump. An experimental test platform was built to verify the simulation results through field measurements. The results show that the optimized throat inlet flare profile can significantly improve the internal flow pattern inside the pump, reduce local flow losses and vortex dissipation, effectively lengthen the jet core region and expand the low-pressure zone, thereby enhancing the suction capacity. Scheme 2, with the smoothest cross-sectional area variation curve achieves the optimal performance, increasing the absorbed liquid flow rate by 16.16% compared to the prototype and by 15.78% in experimental measurements. The errors between simulation and experiment are less than 2%, verifying the accuracy of this proposed design method. The smoother the flow channel profile, the more effectively it can suppress flow separation and reduce energy loss. The relevant conclusions can provide reliable methods and theoretical support for the structural optimization and performance improvement of jet pumps.

To investigate the influence of trash rack clogging on the internal flow characteristics within the inlet passage of a pumping station, a CFD numerical simulation method was conducted based on the RNG turbulence model to analyze the water flow within the inlet passage of an axial-flow pump. The flow pattern, pressure distribution, vortex distribution, turbulent kinetic energy, and flow velocity uniformity of the vertical axial-flow pump unit at the inlet cross-section were studied under four different clogging schemes. The results show that trash rack clogging leads to a severely uneven velocity distribution at the inlet passage entrance: a low-velocity region forms in the clogged area, while high-velocity regions appear in the surrounding unclogged areas. The maximum flow velocity increases from 1.38 m/s under the unclogged condition of Scheme 1 to 1.89 m/s under Scheme 4. Clogging also causes a significant reduction in the cross-sectional water pressure. Due to the clogging, the flow pattern becomes turbulent, generating complex vortex structures mainly concentrated in the clogged areas, and the number of vortices increases with the clogged area. As the clogging amount increases, the turbulent kinetic energy increases, and the flow velocity uniformity decreases from 56% under the unclogged condition to a minimum of 45%, representing a reduction of 11 percentage points. The research results can provide a theoretical basis for the design, operation, and maintenance of trash racks in pumping stations, and have certain academic value and theoretical significance.

A piezoelectric ceramic actuator was used to apply sinusoidal vibration excitation to the jet, and a vibration-controlled electrostatic micro-jet atomization characteristic test platform was established. High-speed imaging technology was used to study the morphological change law of anhydrous ethanol simple jet mode under external vibration. By analyzing the length of the stable segment of the jet, the influence of different vibration parameters on micro-jet stability was explored. The results indicate that the applied vibration intensifies the transition of the electrostatic micro-jet from varicose instability to whipping instability, accelerates the transition from whipping instability to whipping-assisted bifurcation changes, expands the range of whipping-assisted bifurcation occurrence, and increases the voltage required for the occurrence of dendritic fragmentation. As the vibration frequency increases, the length of the stable section of the jet continues to decrease, and the whipping instability morphology is more significantly affected by the change in vibration frequency than the flexural morphology. At , the decrease in the stable section length of the whipping morphology is 83.2%. As the vibration amplitude increases, the length of the micro-jet stable segment gradually shortens. The flexural and whipping morphologies decrease by 44.4% and 64.6%, respectively, compared to the no-vibration condition when the vibration amplitude is 7.5 μm. The length of the stable segment of the whipping morphology is more easily influenced by changes in vibration amplitude.

To improve the aggregate properties of municipal solid waste incineration bottom ash (bottom ash) and the strength of bottom ash concrete, a water quenching process was adopted to treat the bottom ash, the influence of water quenching treatment on the properties, mineral composition, and hydraulic properties of bottom ash aggregate was analyzed. Experimental tests were designed for bottom ash and water-quenched bottom ash concrete with three water-to-binder ratios (0.2, 0.4, 0.6) and three sand replacement rates (0%, 50%, 100%). The basic mechanical properties of bottom ash and water-quenched bottom ash concrete were studied, and a quantitative relationship formula for the mechanical properties of water-quenched bottom ash fine aggregate concrete was established. The results reveal that after water quenching treatment, the bulk density and apparent density of the water-quenched bottom ash increases to some extent, and the water absorption and crushing index values decrease significantly. The water quenching treatment significantly reduces the crystallinity of bottom ash and improves its potential hydraulic properties. The toxic substance leaching from the water-quenched bottom ash meets the limits specified in the national standard. The compressive strength and splitting tensile strength of water-quenched bottom ash concrete are higher than those of bottom ash fine aggregate concrete but slightly lower than those of natural sand concrete under the same mixing conditions. Due to the potential hydraulic properties of water-quenched bottom ash, the long-term (90-180 d) strength growth rate of its concrete is higher than that of bottom ash fine aggregate concrete and ordinary natural sand concrete. The quantitative relationship formula established using the Poly2D function for water-quenched bottom ash fine aggregate concrete has a high correlation coefficient.

In order to explore the influence of temperature on the mechanical properties of pisha sandstone cement soil (PSCS), unconfined compressive strength tests and GDS dynamic triaxial tests were performed on PSCS with 7% cement content under ambient temperatures of 20, 0, -5, -10, and -15 ℃. Based on the stress-strain curves from the unconfined compressive strength test, the effect of temperature on the compressive strength of PSCS was analyzed from the perspective of energy absorption. Concurrently, the dynamic response characteristics of PSCS under cyclic load were studied through GDS dynamic triaxial test, focusing on the evolution law of mechanical properties and energy dissipation mechanism of the material in the temperature range of -15 ℃ to 20 ℃. The results show that the peak stress is negatively correlated with temperature. Compared with the peak stress at room temperature (20 ℃), the peak stress at 0, -5, -10, and -15 ℃ increases by 65.87%, 90.46%, 163.60%, and 229.38%, respectively. The peak strain displays a significant inflection near the phase transition temperature threshold (-5 ℃). The pre-crack energy, the crack energy absorbed during compression, and the post-crack energy absorbed in compression all show an increasing trend with decreasing temperature, and the total energy absorption value at -15 ℃ increased by 515.62% compared to that at 20 ℃. Under constant amplitude cyclic loading, as the temperature decreases, the dynamic elastic modulus of PSCS progressively increases, whereas the damping ratio and cumulative plastic deformation gradually decrease. Additionally, compared to the room temperature group under constant-amplitude cyclic loading, the average dynamic elastic modulus at 0, -5, -10, and -15 ℃ increases by 63.7%, 88.1%, 96.8%, and 103.0%, respectively.

The dynamic response characteristics of hydropower units during load shedding directly affect the safe and stable operation of the hydropower station. Traditional studies have been mainly focused on the use of deterministic theories and models, without fully considering the impact of parameter uncertainties during actual operation. In response to this issue, a modeling method for unit systems based on interval uncertainty analysis was developed and solved using Monte Carlo simulation to reveal the propagation characteristics of unit parameter uncertainties on system responses and to evaluate the system reliability performance of typical parameters under different uncertainty levels. The results show that the uncertainties of upstream and downstream water levels, the unit's flywheel torque, and the inflow/outflow coefficients of the surge tank have a significant impact on the dynamic response of the unit. Moreover, the coupling effect of multiple uncertain parameters can greatly amplify the uncertainty of the system output response, and may even cause the system to exceed the reliability control limits. These relevant research results enrich the modeling and analysis system for the load-shedding transient process of hydropower units, and provide theoretical and technical guarantee for the safe and stable operation of hydropower units.

To investigate the effects of deep subsurface irrigation on soil water storage, fruit yield, and quality in citrus orchards in hilly red soil regions, an experiment was conducted in a typical citrus orchard in Jiangxi Province. The experiment included three irrigation depths: D1 (25 cm), D2 (50 cm), and D3 (100 cm); three irrigation levels: W3 (full irrigation upper limit of 100% field capacity), W2 (mild deficit irrigation, 75% of W3), and W1 (severe deficit irrigation, 50% of W3), resulting in a total of nine treatments. The results show that D2W2 treatment (50 cm irrigation depth combined with mild deficit irrigation) creates a stable moist zone in the 0-120 cm soil layer that effectively covers the main root zone of citrus (0-80 cm). The root zone water storage under this treatment increases by 8.74% and 16.43% compared to D1W2 and D3W2 treatment, respectively. This treatment also achieves the highest yield per plant (58.13 kg/plant), the highest sugar content (15.93%), the lowest acidity (0.46%), and the optimal sugar-acid ratio (34.63). D2W1 treatment has the highest irrigation water use efficiency at 11.15 kg/m³, which is slightly higher than that of D2W2 treatment (11.03 kg/m³). TOPSIS comprehensive evaluation indicates that D2W2 treatment is the optimal irrigation mode with the highest score. The study recommends promoting a deep irrigation mode with a 50 cm depth combined with mild water deficit in citrus orchards in hilly red soil regions to synergistically achieve water conservation, yield increase, and quality improvement.