Search Results (636)

To address the problems of excessive transportation width, limited operational flexibility, and insufficient adaptability to uneven seedbed conditions of wide-width cotton film-mulching seeders, this study designed a horizontal-folding cotton wide-width film-mulching seeder. The overall structure and operating principle of the machine are described, and the results of theoretical analyses conducted on the key components, including the folding frame, parallel four-bar profiling mechanism, and hydraulic system, to determine their critical structural parameters are reported. The static and modal characteristics of the folding frame under road transportation conditions were investigated using the finite element analysis method. Under the fully loaded condition, the maximum stress of the folding frame was 102.52 MPa, and the maximum deformation was 1.7857 mm. The first six natural frequencies of the folding frame ranged from 15.734 to 39.681 Hz. The modal analysis results indicate that the natural frequencies of the folding frame are separated from the main excitation frequencies considered in this study, suggesting a low resonance risk under the investigated operating conditions. An ANSYS–ADAMS rigid–flexible coupled model of the folding frame was established to analyze its dynamic behavior during field operation. The location of the maximum loading point of the folding frame and the stress variation curves of the rocker arm during operation were obtained. The maximum load at the hinged joint between the driving rocker arm and the suspension frame was 4.27 × 10⁴ N, while the maximum loads at the middle position of the driving rocker arm and the hinged joint between the driving rocker arm and the auxiliary frame were 2.78 × 10⁴ N and 1.48 × 10⁴ N, respectively. Using a multi-channel strain signal acquisition system, the stress variations at critical points of the folding frame under field deployment operation conditions were experimentally measured. The finite element analysis results were compared with the experimental measurements. The results showed that under both road transportation and field operation conditions, the stress variation trends obtained from the experimental measurements were consistent with those from the finite element analysis, verifying the reliability of the folding frame. Field test results indicated that the folding cotton wide-width film-mulching seeder achieved a missing-hole rate of 2.28%, a single-seed rate of 95.7%, a qualified hole spacing rate of 97.12%, a damage rate of 0.11%, a qualified rate of seeding depth beneath the plastic film of 95.86%, a longitudinal elongation rate of the plastic film of 5.17%, a qualified rate of light-exposure surface width of 91.64%, a plastic film light-exposure surface flattening rate of 98.88%, a qualified rate of soil-covering thickness at the film edge of 95.94%, and a qualified rate of soil-covering width at the film edge of 97.74%. All measured performance indicators met the requirements of relevant national and industrial standards. Full article

Hydro-mechanical coupling governs the stability of tunnel surrounding rock in soft-rock strata. Mudstone-type soft rocks exhibit abrupt strength loss and time-dependent large deformation under groundwater infiltration, posing severe threats to construction safety and long-term service performance. Most existing studies focus on oven-dry and fully saturated end-members, leaving continuous mechanical data across the unsaturated-saturated spectrum scarce, and the quantitative correlation between macroscopic mechanical degradation and microstructural damage remains poorly constrained. This study investigates mudstone intervals from the Baoshishan Tunnel in western Yunnan, where frequent groundwater-related support failures have been recorded. A series of laboratory tests, including uniaxial compression, triaxial compression, and triaxial creep tests, are performed on specimens prepared at six saturation levels ranging from oven-dry to fully saturated. Hydraulic property tests and microstructural analyses (SEM, MIP, XRD) are conducted complementarily to characterize water sensitivity and track pore-structure evolution. The derived degradation relationships are validated against 20 valid rounds of advanced geological prediction (AGP) records. Results show that full saturation reduces uniaxial compressive strength by 62–71%, and cohesion degrades far more significantly than the internal friction angle. The steady-state creep rate increases nonlinearly with rising saturation, while long-term strength follows an exponential decay trend. Hydration swelling of clay minerals and subsequent formation of a connected pore network are identified as the dominant micro-mechanisms driving macroscopic degradation. On this basis, a full-process degradation model, macro-micro damage correlation equations, and a composite water sensitivity index (WSI) are established. The findings provide a quantitative basis for surrounding rock classification revision, support timing optimization, and groundwater control in the Baoshishan Tunnel and similar soft-rock tunnels. Full article

Conventional valve-controlled hydraulic excavator boom drive systems suffer from low energy conversion efficiency and severe throttling losses. To address this issue, this paper proposes a pump-controlled digital hydraulic drive system based on a Direct Energy Recovery Digital Pump (DERDP). The DERDP integrates hydraulic pumping and boom potential energy recovery within a single unit, enabling both energy recuperation and precise flow regulation. An AMESim simulation model of the system is developed and validated against experimental measurements from a dedicated hardware-in-the-loop test bench. Using the validated model, the operational characteristics are investigated under varying boom load pressures, pump displacement fractions, and motor displacement fractions; the drive and energy recovery efficiencies are systematically evaluated across different operating conditions. Simulation results show that the accumulator stores 2834 J per lowering cycle and releases 2756 J per lifting cycle, reducing motor energy consumption from 5413 J to 2317–2903 J. The system-level energy recovery efficiency reaches 50–60%. These findings offer practical guidance for implementing digital hydraulic solutions in construction machinery. Full article

This study develops a design procedure for electromechanical regenerative dampers using recorded damper stroke, velocity, and force from city, highway, country, and rough-road driving. The signals are converted into directional force, mechanical-power, energy-coverage, and operating-duty requirements. Motor size, gear ratio, lever ratio, power-network limits, packaging, and reflected inertia are screened, and 12 V and 48 V configurations are selected separately. Force tracking is checked with a prescribed-motion actuator model, and the selected designs are compared with a hydraulic reference in a quarter-car model under paired ISO Class B/80, C/60, and D/40 km/h inputs. The design points include 0.4 kW at 0.30 m/s, 0.6 kW for continuous-load screening, and 2.3 kW for 95% mechanical-energy coverage per damper. On the selected Class D/40 km/h input, the interface-force NRMSE is 52.3% for the 12 V configuration and 23.5% for the 48 V configuration. This is a comparison of two complete system designs, and prototype validation remains necessary. Full article

This paper presents the development and field evaluation of the Horty AutoHammer system for semi-automatic driving of orchard support posts, integrating a mobile carrier, post handling mechanisms, a pile-driving mast, a positioning system and multi-actuator control. The system is semi-automatic: post handling on the conveyor is performed by the operator, the driving sequence runs automatically, and an obligatory operator confirmation of position and angles precedes driving, so the results characterize the operator–machine system. Acceptance testing was conducted at four locations in the Masovian Voivodeship. A balanced experiment comprised 120 work cycles (4 locations × 2 process variants × 15 replicates), the variants differing in post type and target depth. Process variant significantly affected complete cycle time and productivity (p < 0.001); location and the interaction did not (p > 0.05). The end-post cycle was on average 5.91 s longer and depth error did not differ between variants (p = 0.106). All observations met the ±3 cm driving-depth criterion as recorded by the machine’s own measuring chain, with a maximum absolute error of 2.6 cm, and mean productivity exceeded 20 posts·h⁻¹. Driving depth was not verified independently of that chain and the horizontal position of the posts was not quantified; both are to be addressed separately. Full article

The large-scale integration of intermittent renewable energy has increased operating-condition transitions in pumped storage hydropower plants, thereby raising the probability of successive load rejection (SLR) and associated hydraulic transient risks. To mitigate the severe low draft tube pressure (DTP) commonly induced by SLR, this study proposes installing a tailwater connection pipe (TWCP) between the draft tubes of adjacent units. The mitigation mechanism and performance are investigated through theoretical modeling and three-dimensional numerical simulations. Results show that the first load-rejecting unit (FLRU) enters the reverse-pump region prematurely and effectively behaves as a normal-rotation pump. This accelerates the discharge reduction in the subsequent load-rejecting unit (SLRU), drives its operating point deeper into the reverse-pump region, and substantially worsens its minimum DTP. With the TWCP, the head difference drives compensating flow from the FLRU to the SLRU, alleviating transient water shortage, reducing discharge and pressure discrepancies between the two tailwater systems, and improving local turbulent flow. The mitigation effect is sensitive to structural parameters: a larger pipe diameter increases flow capacity, while installation closer to the pump-turbines increases the driving head difference. Both measures enhance DTP mitigation, whereas the TWCP has little influence on steady-state flow conditions. Full article

Improving energy efficiency while maintaining accurate force and displacement control is a key requirement for servo deep-drawing die-cushion systems. Electro-hydraulic actuators (EHAs), which combine the high power density of hydraulic transmission with the controllability of electric drives, provide an effective approach for improving the dynamic performance and energy efficiency of metal-forming equipment. This paper investigates the control and energy-efficiency characteristics of an EHA applied to a servo deep-drawing die-cushion system, with particular emphasis on the working mechanism of its hydraulic system, the AMESim-Simulink co-simulation control strategy, and the energy-efficiency distribution characteristics. Firstly, an electro-hydrostatic actuator (EHA) model composed of a permanent magnet synchronous motor, a fixed-displacement pump, valve block unit, accumulator, and single-rod double-acting hydraulic cylinder is established. The power flow relationship of the system in the four-quadrant working condition is analyzed, and the flow distribution characteristics of the main oil circuit, supplementary oil circuit, and bypass branch are studied. Secondly, a joint simulation platform is built based on AMESim and Simulink to achieve bidirectional coupling between the hydraulic actuator and the motor drive control system. In the speed control loop, the traditional PI and fuzzy PI control strategies are compared; in the position control loop, the PID control and sliding mode control strategies are simulated and analyzed. The results show that the fuzzy PI control has better dynamic regulation ability under load torque and speed step change conditions, which can reduce speed overshoot and shorten the regulation process; the position-control results under a step-displacement command show that the sliding-mode controller improves the transient response and steady-state tracking accuracy compared with the conventional PID controller. Finally, the system’s four-quadrant energy efficiency, motor efficiency, pump volumetric efficiency, and mechanical efficiency are analyzed from the perspective of energy conversion. The results show that the system efficiency is affected by load, actuator speed, motor speed, and pump pressure difference, and the efficient working area is mainly distributed in the medium-high speed and moderate load range. Full article

Efficient stimulation of heterogeneous sandstone reservoirs requires a comprehensive understanding of cross-layer hydraulic-fracture propagation and its controlling mechanisms. Taking the Jurassic Lianggaoshan Formation in the Sichuan Basin as the geological prototype, 300 mm cubic artificial specimens containing coarse-, transitional-, and fine-grained cycles were prepared by sequential layered casting and tested using large-scale true-triaxial hydraulic fracturing. The coupled effects of interlayer and vertical stress differences on cross-layer fracture propagation were investigated. Under the tested conditions, increasing the interlayer stress difference from 2 to 6 MPa changed the fracture response from continuous, nearly vertical penetration through all depositional cycles to fracture arrest and pronounced diversion along the interface, forming a T-shaped branch and producing large-amplitude sawtooth pressure fluctuations. At a vertical stress difference of 2 MPa, the fracture was arrested at the upper interface, accompanied by extensive lateral diversion and asymmetric downward deflection, whereas a vertical stress difference of 6 MPa enabled continuous penetration through all three depositional cycles and produced a characteristic stepwise pressure response. These contrasting behaviors indicate that cross-layer fracture propagation is governed by competition between the vertical driving force and interfacial resistance. The stepwise pressure response observed during successful cross-layer penetration is consistent with a cyclic mechanism involving inferred fracture-tip blunting, net-pressure accumulation, interfacial breakthrough and reinitiation, and local pressure release. The results provide a mechanistic basis for understanding hydraulic-fracture propagation across heterogeneous depositional interfaces in multicyclic sandstone reservoirs. Full article

Rainfall and fluctuations in reservoir water levels are critical external factors influencing the stability of landslides along reservoir banks. This study investigates the Yetan Primary School landslide, which serves as a representative example of a metamorphic rock landslide influenced by reservoir conditions in Shiyan City. We quantitatively investigate the evolutionary characteristics of slope seepage and stress responses by integrating GNSS field monitoring data (2021–2025) with FLAC3D numerical simulations. The analysis encompasses five distinct working conditions, including groundwater level rises of 1 m, 3 m, and 5 m, as well as periodic fluctuations in reservoir water levels ranging from 236 m to 242 m. The results indicate that rainfall is the dominant triggering factor for the landslide, with monitoring data revealing two stages of stepwise deformation that are synchronized with heavy rainfall, and a maximum average displacement rate of 0.302 mm/d. Simulation results show that when the groundwater table rises by 1 m, 3 m, and 5 m, the maximum displacement at the landslide front is 0.51 m, 1.26 m, and 2.63 m, respectively, with the plastic zone extending from the front to the rear, exhibiting a composite failure mode characterized by front traction and rear thrust. The drawdown of the reservoir water level (from 242 m to 236 m) generates outward hydrodynamic pressure, resulting in a displacement of 12.8 cm at the front, which is greater than the 2.7 cm observed during the rise. However, the impact of reservoir water alone on overall stability is limited. Landslide instability can be attributed to a coupling mechanism of ‘easily sliding metamorphic rock—hydraulic driving (water-rock softening + hydrodynamic pressure)’: rainfall triggers the composite failure of front traction and rear thrust, while fluctuations in reservoir water level primarily exacerbate deformation at the front. This study provides theoretical guidance for the early warning and prevention of similar landslides in the metamorphic rock region of northwestern Hubei Province. Full article

Conventional Continuously Variable Transmissions (CVTs) employ mechanically driven hydraulic oil pumps that operate continuously with the engine, resulting in unnecessary power consumption, reduced transmission efficiency, and limited flexibility in hydraulic pressure regulation. To overcome these limitations, this paper proposes a novel electric oil pump (EOP)-based CVT controlled by a Pulse Width Modulation (PWM)-based Proportional–Integral (PI) speed tracking controller. The proposed system replaces the conventional mechanically driven pump with an independently controlled EOP, enabling hydraulic pressure generation according to the instantaneous transmission demand. A comprehensive model of the EOP-CVT system was developed in MATLAB/Simulink and evaluated using the four European driving cycles (ECE 15, EUDC, EUDC for low power vehicles, and NEDC). The simulation results demonstrate high-speed tracking performance, with a tracking accuracy of more than 99.7%, maximum mean absolute error of 0.19 km/h, and maximum overshoot of 3.28%, while the max settling time was 2.18 s. The CVT ratio range was 0.4–2.4, and the EOP maximum speed was 3344 rpm. Compared with the conventional pump, the proposed EOP requires 47% less energy. These results demonstrate the potential of independently controlled EOP operation to reduce simulated hydraulic power demand while maintaining accurate vehicle-speed tracking, providing a practical foundation for further experimental validation and advanced transmission control. Full article

Polders are typical semi-artificial and human-dominated ecosystems widely distributed in the middle and lower reaches of the Yangtze River Basin. They serve as important sinks and sources of nitrogen (N) and phosphorus (P) in agricultural watersheds. Long-term intensive human intervention substantially alters the hydrological and biogeochemical processes of polder ecosystems, resulting in complex and uncertain effects on water quality that remain insufficiently understood. This study conducts a systematic literature review and narrative synthesis of evidence on N and P transport in polders across the middle–lower Yangtze River plain. The evidence is derived from field monitoring, plot experiments, and numerical simulations. The review focuses on the spatiotemporal patterns of nutrient variation, sink–source conversion functions of ditches and small ponds, drivers of nutrient loss, and current research bottlenecks under artificial sluice-pump regulation. The synthesized results indicate that polders exhibit a distinctive nutrient transport pattern characterized by dispersed in situ retention under conventional water management and concentrated pulse export during drainage events. Artificial sluice-pump operation drives episodic nutrient export throughout the crop growth period, imposing persistent pressure on the water quality of downstream rivers and lakes. N and P transformations are jointly controlled by natural hydrological fluctuations and human activities. Within agricultural lands of polders, fertilizers account for 73.3% of total nitrogen inputs and 87.9–93.5% of total phosphorus inputs. Crop harvesting and regulated drainage constitute the two dominant pathways for nutrient export. Hydraulic regulation prolongs water residence time in polder ditches and ponds, resulting in retention efficiencies of 52–65% for allochthonous N and P. However, seasonal flooding and waterlogging can induce sediment hypoxia and endogenous nutrient release, thereby causing secondary internal pollution and increasing the eutrophication risk of adjacent receiving water bodies. Three major research gaps are identified: insufficient long-term continuous multi-indicator monitoring data, limited model applicability for simulating human-regulated hydrology–nutrient coupling, and poorly defined critical thresholds for polder sink–source functional reversal. This regional systematic review advances the understanding of human–hydrology–nutrient coupling mechanisms in Yangtze River polder systems. It also provides targeted theoretical support for agricultural non-point source pollution mitigation and water environment management in floodplain agricultural areas. Full article

To address the unclear fracture propagation behavior and the insufficient understanding of the influence mechanisms of fracturing parameters during the hydraulic fracturing of deep coalbed methane reservoirs in the Yan’an Gas Field, Well JY1 in the No. 8 coal seam of the Benxi Formation in Block N was selected as the study object. An integrated three-dimensional geomechanics–fracture propagation model coupling geomechanical conditions, cleat characteristics, and fracture propagation was established. Fracture propagation simulations were conducted under different injection rates, fluid volumes per stage, and proppant volumes per stage. The results indicate that when main fractures intersect with cleats, they may exhibit deflection, branching, or direct crossing. Increasing the injection rate enhances the driving force at the fracture tip and improves the penetration capability of main fractures. Increasing the fluid volume improves fracture coverage and inter-cluster connectivity. Increasing the proppant volume contributes to greater residual fracture width, higher proppant placement concentration, and improved fracture conductivity. An injection rate of 19–21 m³/min, a fluid volume per stage of 2500–2700 m³, and a proppant volume per stage of 280–320 m³ provide a favorable balance between fracture network development and effective proppant support under the studied reservoir conditions. Full article

Electric pump-fed liquid rocket engines require coordinated propellant delivery under coupled hydraulic, electrical, actuator, and thermal constraints. This study develops an integrated reduced-order model of a dual-channel electric pump-fed propellant system, including the battery and DC bus, power converters, two independently driven motor–pump units, hydraulic feed lines, control valves, combustion chamber, and thermal states. A hierarchical constrained multi-criteria supervisory controller is formulated to regulate chamber pressure, oxidizer-to-fuel mixture ratio, feed-channel coordination, electrical loading, and thermal response. Performance is compared with a conventional PI controller and an enhanced PI configuration incorporating feedforward and disturbance compensation under nominal, degraded, long-duration, and constraint-active scenarios. Relative to the baseline PI controller, the proposed controller reduced the startup pressure peak from 2.64 to 2.32 MPa, pressure RMSE from 0.016 to 0.006 MPa, and mean branch synchronization error from 0.112 to 0.028 MPa. The minimum battery voltage increased from 87.0 to 90.4 V, while the peak motor current decreased from approximately 88 to 65 A. In the 1800 s thermal case, the maximum fuel-drive temperature decreased from approximately 104 to 74 °C. Numerical verification and comparison with published experimental benchmarks supported the physical plausibility and equilibrium-scale behavior of the reduced-order model, while differences in absolute transient time scales limit its use for quantitative prediction of hardware transient dynamics. The results indicate improved coordinated control within the investigated operating envelope and support the use of the framework for comparative system-level assessment and preliminary design of small-class electric-pump propulsion systems. Full article

This article discusses the development of a control system for an electric propellant pump for a light-lift launch vehicle. The relevance of this work stems from the need to create compact and energy-efficient propellant supply systems capable of ensuring stable operation within the weight, size, and energy resource constraints of onboard equipment. The research object is presented as a single electromechanical-hydraulic system comprising an electric drive, a pump unit, a hydraulic circuit, and a digital control system. A mathematical model of the electric pump unit is developed, its numerical parameterization is performed, and a cascade control structure with a feedforward channel is proposed. A series of computational experiments are conducted, including an analysis of transient processes during pressure target changes, a study of the system’s response to hydraulic disturbances, and a robustness assessment under parameter uncertainty. It is established that the proposed control system provides higher response speed, a smaller integral control error, and better resistance to external disturbances compared to a classical cascade PI structure. The obtained results confirm the potential of the proposed approach for electric pump units for fuel supply of ultra-light launch vehicles. Full article

The start-up process of a siphon vertical axial-flow pump is accompanied by rapid internal-flow reconstruction, transient hydraulic loading and unsteady rotor response, which directly affect the operational stability of the pump system. In this study, the unsteady internal flow evolution and rotordynamic characteristics of a siphon vertical axial-flow pump during start-up were investigated using a transient numerical method with dynamic rotational-speed updating. The instantaneous impeller speed was solved based on a torque-balance equation considering motor driving torque, hydraulic resistance torque and rotor inertia, and the angular-velocity boundary condition of the rotating domain was updated at each time step through a custom UDF routine. The numerical model was validated against model-test data, and good agreement was obtained for both pump head and efficiency. Based on the validated model, the flow-angle distribution, vortex stretching term, blade-surface pressure, rotor mechanical response, radial-force time–frequency characteristics and blade-loading variation were analyzed. The results show that the internal flow in the main pump section evolves from a strongly unsteady swirling state to an axially dominated quasi-steady state. In the early stage, obvious pre-swirl, local backflow and strong vortex stretching occur near the impeller inlet, blade-tip clearance and impeller–guide-vane interaction region. With increasing rotational speed and flow rate, the disordered vortical structures are gradually suppressed, and the internal flow becomes more organized. The rotor response exhibits clear stage-dependent characteristics, and the radial force is more sensitive to local flow instability than the axial force and torque. Continuous wavelet transform and variational mode decomposition further indicate that the radial-force signal is dominated by low-frequency transient excitation in the early stage, while medium- and high-frequency modulation components appear in the later stage. This study reveals the coupling mechanism between transient internal-flow evolution and rotor dynamic response during pump start-up, providing guidance for improving the start-up stability of siphon vertical axial-flow pump systems. Full article