Search Results (178)

To address the problems of low crushing efficiency and uneven distribution in traditional straw crushing and returning machines for cotton stalk return operations in Xinjiang, a vertical straw crushing and returning machine with large and small dual-blade discs was designed, adapted to Xinjiang’s cotton planting model. The machine employs a differentiated configuration of large and small blade discs corresponding to four and two rows of cotton stalks, respectively, effectively reducing tool workload while significantly improving operational efficiency. A simulation model of the crushing and returning machine was developed using the discrete element method (DEM), and a flexible cotton stalk model was established to systematically investigate the effects of machine forward speed, crushing blade rotational speed, and knife tip-to-ground clearance on operational performance. Single-factor simulation experiments were conducted using crushing qualification rate and broken stalk drop rate as evaluation indicators. Subsequently, a multi-factor orthogonal field experiment was designed with Design-Expert software (13.0.1.0, Stat-Ease Inc, Minneapolis, MN, USA). The optimal working parameters were determined to be machine forward speed of 3.5 m/s, crushing blade shaft speed of 1500 r/min, and blade tip ground clearance of 60 mm. Verification tests demonstrated that under these optimal parameters, the straw crushing qualification rate reached 95.9% with a broken stalk drop rate of 15.5%. The relative errors were less than 5% compared to theoretical optimization values, confirming the reliability of parameter optimization. This study provides valuable references for the design optimization and engineering application of straw return machinery. Full article

Wingtip devices like winglets and other types have been created to improve the aerodynamic efficiency of aircraft based on minimizing the induced drag of tip vortices. This study aims to investigate the aerodynamic characteristics of these devices at low Reynolds numbers. In the present study, the models of a basic non-swept tapered wing and a wing with arc-shaped wingtips are examined. For this purpose, the basic model is equipped with replaceable tips with different geometries. The measurements are performed in a low-speed wind tunnel at a Reynolds number of around 100,000. The analysis of the collected data shows that the best aerodynamic characteristics have a configuration with a 45-degree dihedral angle at the tips of the wing. These results can be used in the conceptual design of small unmanned aerial vehicles (UAVs) to improve their performance in terms of range and endurance. Full article

This study investigated the performance of Savonius hydrokinetic turbine blades through three-dimensional computational fluid dynamics simulations conducted at a fixed tip speed ratio of 0.87. A multi-factor experimental design was employed to construct 45 V-shaped rotor blade models, systematically examining the effects of a V-angle (30–140°) and straight-edge length (0.24 L–0.62 L) on hydrodynamic performance, where L = 25.46 mm (the baseline length of the straight edge). The results indicate that, as the V-angle and the straight-edge length vary independently, the performance of each blade first increases and then decreases. At TSR = 0.87, the maximum power coefficient (C_P) of 0.2345 is achieved by the blade with a 70° V-Angle and a straight edge length of 0.335 L. Pressure and velocity field analyses reveal that appropriate geometric adjustments can optimize the high-pressure zone on the advancing blade and suppress negative torque on the returning blade, thereby increasing net output. The influence mechanisms of the V-angle and straight-edge length variations on blade performance were further explored and summarized through a comparative analysis of the vorticity characteristics. This study established a detailed performance dataset, providing theoretical and empirical support for V-shaped rotor blade design studies and offering engineering guidance for the effective use of low-flow hydropower. Full article

As a vital oil and cereal crop in China, soybean requires efficient and low-loss harvesting to ensure food security and sustainable agricultural development. However, pod-shattering losses during soybean harvesting in Xinjiang remain severe due to low pod moisture content and poor mechanical strength, while existing studies lack a systematic analysis of the interaction mechanism between reeling devices and pods. The current research on soybean harvester headers predominantly focuses on conventional rigid designs, with limited exploration of flexible reel mechanisms and their biomechanical interactions with soybean pods. To address this, this study proposes an optimization method for low-loss harvesting technology based on mechanical-crop interaction mechanisms, integrating dynamic simulation, contact mechanics theory, and field experiments. Texture analyzer tests revealed pod-shattering force characteristics under different compression directions, showing that vertical compression exhibited the highest shattering risk with an average force of 14.3271 N. A collision model between the spring tooth and pods was established based on Hertz contact theory, demonstrating that reducing the elastic modulus of the spring tooth and increasing the contact area significantly minimized mechanical damage. Simulation verified that the PVC-nylon spring tooth reduced the maximum equivalent stress on pods by 90.3%. Furthermore, the trajectory analysis of spring-tooth tips indicated that effective pod-reeling requires a reel speed ratio (Δ) exceeding 1.0. Field tests with a square flexible spring tooth showed that the optimized reel reduced header loss to 1.371%, a significant improvement over conventional rigid teeth. This study provides theoretical and technical foundations for developing low-loss soybean harvesting equipment. Future work should explore multi-parameter collaborative optimization to enhance adaptability in complex field conditions. Full article

In this paper, the aerodynamic performance of an improved hybrid vertical-axis wind turbine is investigated, and the performance of the hybrid turbine at high tip–speed ratios is significantly enhanced by adding a spoiler at the end of the inner rotor. The improved design increases the average torque coefficient by 7.4% and the peak power coefficient by 32.4%, which effectively solves the problem of power loss due to the negative torque of the inner rotor in the conventional hybrid turbine at high TSR; the spoiler improves the performance of the outer rotor in the wake region by optimizing the airflow distribution, reducing the counter-pressure differential, lowering the inner rotor drag and at the same time attenuating the wake turbulence intensity. The study verifies the validity of the design through 2D CFD simulation, and provides a new idea for the optimization of hybrid wind turbines, which is especially suitable for low wind speed and complex terrain environments, and is of great significance for the promotion of renewable energy technology development. Full article

The fuel produced through water electrolysis is non-toxic and clean, and the water propulsion system offers low cost and easy integration with other systems. This study investigates the pulse operating characteristics of a water electrolytic chemical propulsion engine using microwave ignition technology. A high-speed camera captured flame images, while a spectrometer and pressure sensor were used for data quantification. Three peak gas pressure points were selected for data analysis. The experimental results revealed that the flame color changes at different combustion stages, starting white and turning blue at the flame tip during stable combustion. Combustion pressure fluctuated between −0.53 kPa and 765 kPa, with an average of ≈32 kPa, showing a rapid pressure rise followed by smooth decay. At all three operating points, the thrust was small (0.38 N, 0.37 N, and 0.35 N), but after the third operating point, thrust increased significantly to 2.25 N, an enhancement of 508.1%. Spectral data indicated that the combustion products included H, O, and N atoms. This study is the first to investigate the pulsed conditions of a direct microwave ignition system and provide insights into its operating characteristics. The system will be optimized in the future. Full article

For crop protection, electrostatic spraying technology significantly improves deposition uniformity and pesticide utilization through the “wraparound-adsorption” effect of charged droplets. However, existing electrostatic nozzles using hydraulic atomization suffer from low charge-to-mass ratios due to unclear principles for optimizing electrode parameters. To this end, this study designs and evaluates a novel air-assisted hydraulic-atomization hollow-cone electrostatic nozzle. First, the air-assisted hollow-cone nozzle was designed. High-speed imaging was then employed to obtain morphological parameters of the liquid film (length: 2.14 mm; width: 1.96 mm; and spray angle: 49.25°). Based on these parameters, an electric field simulation model of the electrostatic nozzle was established to analyze the influence of electrode parameters on the charging performance and identify the optimal parameter combination. Finally, feasibility and efficiency evaluation experiments were conducted on the designed electrostatic nozzle. The experimental results demonstrate that cross-sectional dimensions of the electrode exhibit a positive correlation with the surface charge density of the pesticide liquid film. In addition, optimal charging performance is obtained when the electrode plane coincides with the tangent plane of the liquid film leading edge. Based on these charging laws, the optimal electrode parameters were determined as follows: 2.0 × 2.0 mm cross-section with an electrode-to-nozzle tip distance of 3.8 mm. With these parameters, the nozzle achieved a droplet charge-to-mass ratio of 4.9 mC/kg at a charging voltage of 3.0 kV. These charged droplets achieved deposition coverages of 12.19%, 5.72%, and 5.91% on abaxial leaf surfaces in the upper, middle, and lower soybean canopies, respectively, which is a significant improvement in deposition uniformity. This study designed a novel air-assisted hollow-cone electrostatic nozzle, elucidated the optimization principles for annular induction electrodes, and achieved improved spraying performance. The findings contribute to enhanced pesticide application efficiency in crops, providing valuable theoretical guidance and technical references for electrostatic nozzle design and application. Full article

Wind turbine blades are prone to icing in cold environments, which leads to decreased aerodynamic performance, increased power loss, and even endangers the safe and stable operation of wind turbines. Electric heating anti-deicing method is the most effective solution because of its flexible control, rapid response, and high deicing efficiency. However, in the process of blade high-speed rotation, the complex flow field effect significantly affects the blade heat transfer performance, which leads to the problems of high energy consumption, low heat utilization, and uneven heating of traditional electric heating anti-icing/deicing methods, limiting their application effect in complex working conditions. Based on the physical mechanism and heat exchange characteristics of electric heating deicing of wind turbine blades, a coupled flow–heat transfer numerical model suitable for complex flow field conditions was constructed in this study, aiming to realize the dynamic simulation of the global temperature field and the phase transition process of ice sheets under different heating modes. Furthermore, the deicing efficiency characteristics of continuous heating and cyclic heating modes were compared and analyzed. The blade tip section of a Sinoma87.5 was taken as the experimental object, and the deicing experiment of blade by electric heating was carried out under artificial ice-covering laboratory conditions. The simulation and experimental results show that the deicing process by electric heating can be divided into three typical stages: initial temperature rise, stagnation, and rapid temperature rise. Under the influence of incoming flow conditions, the temperature rise of the front stagnation point region lags behind that of the windward side, and the steady-state peak temperature is lower. Compared with the cyclic heating mode, the continuous heating mode can enter and cross the stagnation period more quickly. The peak steady-state temperature of the continuous heating mode is 24.2 °C, and the deviation from the simulation result is only 2.8 °C, which is within the acceptable error range, effectively verifying the reliability of the numerical calculation model established. Full article

Because of their distinctive toroidal blade configuration, toroidal propellers can improve propulsion efficiency, reduce underwater noise, and enhance blade stability and strength. In recent years, they have emerged as an extremely promising novel underwater propulsion technology. To investigate their working mechanism, a geometric model of the toroidal propeller was initially established, and an unsteady numerical calculation model was constructed based on the sliding mesh technique. Subsequently, with the E779A conventional propeller as the research subject, the numerical model was verified, and a grid independence test was accomplished. Thereafter, the hydrodynamic performance of the toroidal propeller under diverse advance coefficients was analyzed based on the numerical model, and open water characteristic curves were established. Eventually, the surface pressure distribution, velocity field, and vorticity field of the toroidal propeller under various working conditions were studied. The outcomes demonstrate that the toroidal propeller attains the maximum propulsion efficiency at high advance coefficients, possesses a broad range of working condition adaptability, and is more applicable to high-speed vessels. At low advance coefficients, the toroidal propeller exhibits a relatively strong thrust performance, with the thrust generated by the front propeller being greater than that generated by the rear propeller, and the pressure peak emerges at the leading edge of the transition section of the front blade. The analysis of the velocity field indicates that its acceleration effect is superior to that of the conventional propeller. The analysis of the vorticity field reveals that the trailing vortices shed from the leading edge of the transition section of the front propeller merge and develop with the tip vortices, resulting in a more complex vortex structure. This research clarifies the working mechanism of the toroidal propeller through numerical simulation methods, providing an important basis for its performance optimization. Full article

As the utilization of wind energy continues to expand as a prominent renewable energy source, the application of Darrieus Vertical Axis Wind Turbine (VAWT) technology has expanded significantly. Various passive modification methods have been developed to enhance efficiency and optimize the aerodynamic performance of the rotor through blade modifications. This study presents passive modification method utilizing Kline–Fogleman (KF) blades which incorporate step-like horizontal slats along the trailing edge. Through Computational Fluid Dynamics (CFD) simulations, this study evaluates ten distinct KF blade configurations, varying in step length and depth, with steps positioned on the inner side, outer side, and both sides of the airfoil. The results indicate that the KF blade with a shorter step on inner side, 20%$c$ in length and 2%$c$ in depth, enhances the average power coefficient ($C_p$) by 19% compared to the rotor with a clean blade. However, when horizontal slats are incorporated on both sides of the blade, with dimensions of 50%$c$ in length and 5%$c$ in depth, $C_p$ decreases by 33% compared to the clean blade. This reduction occurs across both low and high tip speed ratio (TSR) ranges. It has been observed that the presence of a high-pressure zone of 200 Pa at the trailing edge disrupts the aerodynamic performance when the KF blade is in the upwind region between the azimuth angles of 45° and 135°. Full article

This study presents an advanced hybrid energy management system (EMS) designed for isolated microgrids, aiming to optimize the integration of renewable energy sources with backup systems to enhance energy efficiency and ensure a stable power supply. The proposed EMS incorporates solar photovoltaic (PV) and wind turbine (WT) generation systems, coupled with a battery energy storage system (BESS) for energy storage and management and a microturbine (MT) as a backup solution during low generation or peak demand periods. Maximum power point tracking (MPPT) is implemented for the PV and WT systems, with additional control mechanisms such as pitch angle, tip speed ratio (TSR) for wind power, and a proportional-integral (PI) controller for battery and microturbine management. To optimize EMS operations, a novel hybrid optimization algorithm, the JSO-GJO (Jellyfish Search and Golden Jackal hybrid Optimization), is applied and benchmarked against Particle Swarm Optimization (PSO), Bacterial Foraging Optimization (BFO), Artificial Bee Colony (ABC), Grey Wolf Optimization (GWO), and Whale Optimization Algorithm (WOA). Comparative analysis indicates that the JSO-GJO algorithm achieves the highest energy efficiency of 99.20%, minimizes power losses to 0.116 kW, maximizes annual energy production at 421,847.82 kWh, and reduces total annual costs to USD 50,617,477.51. These findings demonstrate the superiority of the JSO-GJO algorithm, establishing it as a highly effective solution for optimizing hybrid isolated EMS in renewable energy applications. Full article

This paper presents a numerical study of the optimization of the geometric parameters of a four-bladed Darrieus vertical-axis wind turbine (VAWT) with a NACA 0021 aerodynamic profile. The aim of the study was to increase the aerodynamic efficiency of the turbine by selecting optimal values of the rotor diameter and blade chord length. The Taguchi method using an orthogonal array was used as an optimization method, which reduced the number of necessary calculations from 77 to 20 while maintaining the reliability of the analysis. CFD modelling was performed in the ANSYS 2022 R2 Fluent software environment based on a two-dimensional non-stationary model, including a full rotor revolution and an analysis of the steady-state mode for the twentieth cycle. As a result of the analysis, the optimal parameters were determined: rotor diameter D = 3 m and chord length c = 0.4 m. Additionally, for the selected configuration, the numerical model was validated by constructing the dependence of the power coefficient Cp on the tip speed ratio λ in the range from 0.2 to 2.8. The maximum value of Cp was 0.35 at λ = 2.2, which is an increase of ~64% compared to the least efficient rotation mode in the considered range of λ. The obtained results allow us to conclude that the Taguchi method can be used in combination with CFD modelling for fast and accurate optimization of the aerodynamic parameters of low-power wind turbines. Full article

Vertical-axis wind turbines (VAWTs) offer key advantages such as independence from wind direction, low manufacturing costs, and reduced noise levels, making them highly suitable for urban and offshore wind energy applications. Among various VAWT designs, the J-shaped VAWT demonstrates improved energy capture at low and medium tip speed ratios (TSRs) compared to symmetrical blade VAWTs, which has garnered increased interest in recent years. However, the mechanisms by which J-shaped blades enhance VAWT performance remain insufficiently explored. In this paper, the high-resolution three-dimensional Improved Delayed Detached Eddy Simulation was employed to investigate the evolution and interaction of complex vortex systems in J-shaped and symmetrical blade VAWTs at varying TSRs, aiming to deepen the understanding of J-shaped blade effects on wind turbine aerodynamic performance. The results indicate that the tip vortex plays a role in inhibiting flow separation, while the J-shaped blade generates a stronger tip vortex, conferring upon it an advantage in suppressing flow separation and delaying dynamic stall. Additionally, the smaller pressure differential between the root and tip of the J-shaped blade reduces cross-flow on the blade surface, thereby reducing susceptibility to flow separation. Therefore, as the blade enters the dynamic stall region at low and medium TSRs, the J-shaped blade achieves a higher lift coefficient than the symmetrical blade, yielding greater torque, and enhancing wind energy utilization. Full article

Unmanned aerial vehicles (UAVs) have emerged as practical and potentially advantageous tools for scientific investigation and reconnaissance of planetary surfaces, such as Mars. Their ability to traverse difficult terrain and provide high-resolution imagery has revolutionized the concept of exploration. However, operating drones in the Martian environment presents fundamental challenges due to the harsh conditions and the different atmosphere. Aerodynamic challenges include low chord-based Reynolds number flows and the presence of dust particles, which can accumulate on the airfoil surface. This paper investigates the accumulation of dust on cambered plates with 6% and 1% camber, suitable for the type of flow studied. The analysis is conducted for Reynolds numbers of around 20,000 as a result of dimension restrictions, assuming a wind speed ranging from 12 to 14 m/s. Computational simulations are performed using a 2D C-type mesh in ANSYS Fluent, employing the $\gamma$-Re SST turbulence model. Dust particle modeling is achieved through the Discrete Phase Model (DPM), with one-way coupling between phases. The accumulation of particles is monitored over a 6-month period with monthly intervals, and the airfoil is set at a 0° angle of attack. A deposition model, developed using user-defined functions in Fluent, considers particle–airfoil interaction and forces acting on particles. Results indicate a decrease in airfoil performance for negative angles of attack due to geometric changes, particularly due to accumulation on the bottom side near the tip. The discussion includes potential model enhancements and future research directions arising from the assumptions made in this study. Full article

This study successfully achieved the in situ synthesis of carbon nanotubes (CNTs) on aluminum powder substrates through rotating chemical vapor deposition (R-CVD) using nickel-based catalysts with acetylene as the carbon source. Through systematic parameter optimization, we elucidated the effects of catalyst loading, synthesis temperature, reaction duration, reactor rotation speed, and carrier gas ratio on the morphology, crystallinity, and yield of CNTs. Comprehensive characterization employing transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD) demonstrated that R-CVD enables low-temperature synthesis (480 °C) of CNTs with enhanced crystallinity, improved yield, and uniform distribution, exhibiting superior performance compared to conventional CVD methods. Our analysis revealed two concurrent growth mechanisms on aluminum substrates: the tip-growth and base-growth modes, wherein the proportion of the base-growth mechanism exhibited significant temperature dependence. The present work establishes an innovative strategy for the low-temperature fabrication of high-performance CNT-based composite materials. Full article