Rotational Speed Research Articles

Seeding technology plays a critical role in ensuring food security and improving agricultural production efficiency. To tackle the challenges associated with seed-filling in maize mechanical precision seed-metering device during high-speed operations, a method for seed pile stratification is proposed. A mesh hole structure conducive to stratification is designed to assist seeds in passing through the mesh hole and separating from the population, thereby effectively achieving stratification and improving seed-filling performance, enabling effective filling under high-speed conditions. The mesh hole structure was designed with diamond, square, and circular configurations, with an analysis of seed screening performance revealing that the circular mesh hole structure had the highest screening efficiency. Under circular mesh hole conditions, a theoretical analysis of the seed screening process was performed, identifying key factors influencing seeding performance, such as the seed-metering disk rotational speed, mesh hole quantity, and mesh hole diameter. Theoretical calculations indicated that an initial angle of 15° and a terminal angle of 75° at the endpoint of the seeding zone yield the optimal seed screening rate. Orthogonal experiments were conducted with seed-metering disk rotational speed, mesh hole quantity, and mesh hole diameter as experimental factors. The results demonstrated that, at a maize plant spacing of 18cm and an operating speed of 273rpm (approximately 12km/h), with 5 mesh holes and a mesh hole diameter of 14mm, the qualified rate reached 89.24%, meeting the technical requirements for high-speed precision maize seeding. This study offers novel insights and a theoretical foundation for further research into mechanical high-speed precision maize seeding technology.

Abstract Piezoelectric cantilever-beam energy harvesters (PCEHs) of single degree of freedom (DOF) typically achieve maximum energy output near the natural frequency. In this work, we present a PCEH with nonlinear magnetic force as the external excitation. It is shown experimentally that the output voltage of the PCEH presents multiple local maxima as the excitation rotational speed increases, which is also confirmed by the proposed dynamic electromechanical coupling model for the PCEH. It is observed that when the excitation frequency approaches a fractional multiple of the cantilever beam's natural frequency, the nonlinear magnetic force induces superharmonic resonance in the cantilever-beam, leading to multiple local maxima in both the deflection and output voltage. We have also validated the universality of the superharmonic resonance in two types of structural configurations involving a cantilever beam and a couple of magnets. Additionally, it is demonstrated that the natural frequency and the resonant rotational speeds can be modulated by adjusting the effective mass of the piezoelectric cantilever-beam. Our designed prototype device is further integrated with external circuit for powering small electronic devices. The superharmonic resonance and the underlying mechanism observed in our work can significantly expand the effective operating frequency bands of the vibration-based energy harvesters with nonlinear excitations, offering promising solutions in fields such as wind energy harvesting and vibration energy capture.

Side-deep fertilization in paddy fields is key to improving nitrogen use efficiency (NUE) and reducing surface water pollution. However, conventional applicators are overly heavy and incompatible with paddy machinery’s limited horsepower, restricting the technology’s popularization. To solve this, this study had two core goals: develop a lightweight, low-power centrifugal distribution-type side-deep fertilizer applicator matching paddy machinery’s load and horsepower limits; design a dedicated control system to enhance fertilization uniformity and fertilizer adaptability. First, the bulk density-based fertilizer model was improved through theoretical analysis of the external grooved wheel fertilizer discharging device, and its performance was validated in bench experiments. Simultaneously, the centrifugal distribution principle was analyzed, with dispenser rotational speed and discharge rotational speed selected as key factors and uniformity across rows chosen as the response variable. The optimum rotational speed-matching and optimal speed-matching models of the dispenser and distributor were established through CCD testing. The control system of the overall machine integrated both the bulk density-based fertilizer discharge and optimal speed matching models and performed tests in the field. The results showed that the average error in total fertilizer discharge is 4.84%, with a maximum error value of 7.93%, the average coefficient of variation for fertilizer discharge across rows was 5.47%, with a maximum coefficient of variation of 7.03%. Furthermore, comparative analyses revealed that the control system adapted well to different fertilizers and maintained stability between static and dynamic tests, thereby indicating strong dynamic adaptability. Compared with other fertilizer applicators for paddy field machinery, this device offers evident advantages in terms of quality, cost, and horsepower requirements, highlighting its potential for widespread adoption.

Interlayer friction stir spot welding represents an advanced solid state joining technology, developed to manufacture both similar and dissimilar alloys. The incorporation of an interlayer material plays a pivotal role in preventing keyhole formation at the weld interface. This study utilizes experimental design to explore the joining of 304 stainless steel and 6061 aluminum alloy. Three key process parameters including tool rotation speed, plunge depth, and interlayer diameter are evaluated at three distinct levels. The findings indicate that the highest lap shear force of 3.66 kN can be attained by employing the optimized processing conditions. Microstructural studies reveal that the interlayer material is effectively integrated with the lower sheet, facilitated by the heat generated during the frictional process, resulting in a dendritic microstructure within the nugget zone. Moreover, fracture surface examinations demonstrate transgranular failure, providing insights on the mechanical behavior of the joints.

This study presents a comprehensive nonlinear dynamic analysis of a water-lubricated bearing–gear–rotor system by incorporating the effects of turbulent mixed lubrication and system damping. A dimensionless model was developed and numerically solved using the fourth-order Runge–Kutta method. The dynamic responses under various dimensionless rotational speed ratios ( s ) and damping ratios ( ξ ) were systematically investigated through bifurcation diagrams, dynamic orbits, Poincaré maps, power spectra, fractal dimension, and Lyapunov exponent analysis. The results reveal that the system exhibits chaotic behavior at low speed ratios ( s<1.2 ) and low damping values ( ξ < 0.14 ), characterized by non-periodic motion, scattered Poincaré return points, and a broad excitation spectrum. As speed or damping increases, the system transitions into periodic states, though intermittent chaos reappears within specific damping intervals. At ξ = 0.1 , all components, that is, bearing, gear, and rotor, demonstrated chaotic dynamics, as confirmed by non-integer fractal dimensions ( 2.05, 1.60, and 1.97 ) and positive Lyapunov exponents ( 0.22, 0.12, and 0.16 ). These findings highlight the complex influence of speed and damping on the stability and performance of water-lubricated systems. The results provide valuable insights for the design and control of high-performance, low-viscosity fluid-lubricated machinery operating under nonlinear and potentially chaotic conditions.

The paper presents a comparative analysis of the radial distribution of the flow velocity v (r) for the UH-60 main rotor in the basic (S₀) and modified (S₃) configurations at a rotational speed of RPM = 258. The study is aimed at identifying the relationship between the velocity profile, the thrust coefficient Cₜ, the power factor Cₚ, and the integral efficiency index FM. The analysis is based on the normalized dependencies v (r) = v (r)/ (ΩR)* and their influence on the energy balance of the system. The results show that in the S₃ configuration, the velocity redistribution along the radius leads to a decrease in induced losses by 8–10% and an increase in FM to 0.82 due to the smoothing of the velocity profile in the 0.85–1.0 R zone. The obtained dependencies are of practical importance in the design of saber-shaped blades and the optimization of rotor systems to improve the energy efficiency of new-generation rotorcraft.

To address the practical challenges in sesame cultivation such as low efficiency in manual sowing, labor-intensive and time-consuming thinning and fixing of seedlings after emergence, and the lack of suitable precision hole-seeding devices leading to issues like reseeding and missed seeding -an optimized design of a precision sesame seed metering device with a cell wheel mechanism has been developed. Key parameters of the seed metering device's critical components have been systematically optimized. Taking the rotational speed of the seed metering wheel, the number of cells, and the cell diameter as experimental factors, and using the qualified rate of seeds per hill, the reseeding rate, and the miss-seeding rate as evaluation indices, a three-factor, three-level quadratic orthogonal rotational composite design was conducted. The optimal parameter combination for the seed metering device was determined through analysis as follows: a seed metering wheel speed of 15 (r/min), 30 cells, and a cell diameter of 7 mm. Bench test results demonstrated that the qualified seed spacing rate reached 95.56%, with a reseeding rate of 2.61% and a miss-seeding rate of 1.83%, providing a design basis for the development of the socket-wheel sesame seed Metering Device.

Abstract A concept for a 2-degree-of-freedom (DOF) mobile robot is proposed, and its design and experimental study are conducted. The robot achieves linear motion along the x-axis and rotational motion along the z-axis using only two serial inertial impact devices (SIID) vibrators driven by inertial impact forces. Flexible hinge mechanisms of the 2-DOF piezoelectric robot are simulated using ANSYS Workbench by varying structural parameters. Dynamic equations are established, and a dynamic simulation model is built using MATLAB/Simulink to output performance simulations. A prototype is produced, and the drive waveform, voltage amplitude, and frequency are adjusted in experiments to study the linear movement speed, rotational movement speed, and displacement accuracy of the linear and rotational movements of the piezoelectric robot. Its 2-DOF motion performance was verified, and the results are compared with the dynamic simulation results to analyze the rationality of the model. Based on a more compact and sophisticated structural design, this concept enables the 2-DOF motion of a piezoelectric robot, providing a new technical path for the design of piezoelectric-driven multi-DOF robots and verifying the feasibility and effectiveness of the inertial configuration in terms of motion accuracy and mechanism simplification. Experimental results show that the device maintains stable performance under drive voltages ranging from 10 to 140 Vp-p. Under drive conditions of 10 V and 1 Hz, the maximum linear movement accuracy of the drive device is 0.26 μm. At 100 V and within the test frequency range, the maximum movement speed is 16.223 mm/s. Under 9 Hz conditions, the maximum operating speed is 1.06 mm/s, demonstrating excellent motion speed performance. Under driving conditions of 100 V and 11 Hz, the maximum rotational movement speed of the drive device is 11.73 μrad/s.

Stirred tanks play a pivotal role in both mechanical and chemical processes. The current study delves into its dynamics through the experimental and numerical study of the vortex shape, vortex size, and depth experimentally and numerically using the finite volume method. Two types of impellers pitched and wavy blade with different rotational speeds of 150, 250, 350, and 450 RPM were used, location on the depth and density of the vortex, flow patterns, torque values, and the amount of power consumption were observed. Theoretically, the mathematical model liquid volume (VOF) used in order to capture the gas-liquid interface, as well as the numerical model (k-ε) was used to simulate turbulent flow in the stirred tank. The obtained experimental and theoretical results showed good convergence in the values. The results showed the vortex reached the maximum depth reaching the surface of the impeller for the pitched impeller at rotation speed 450RPM, followed by the wavy impeller, where the depth of the vortexes is relatively less. In the second case, with the eccentric stirred tank, the shape and location of the vortex formation were different and less intense than in the un-baffled stirred tank. As for the amount of power consumption, the wavy impeller achieved a 40.5% reduction (1.932 W) compared to the pitched blade impeller (3.251 W) at Reynolds number 1.077×10⁵, with vortex depths of 142 mm and 185 mm, respectively, at 450 RPM. Turbulent kinetic energy analysis revealed 28.9% lower values for the wavy impeller (0.096 J/kg) compared to the pitched blade (0.135 J/kg).

Due to the limitations of traditional micropumps in terms of miniaturization and integration, ferrofluid micropumps, as emerging microfluidic driving devices, exhibit significant application potential due to their unique pumping mechanism. Research on ferrofluid micropumps can advance micro/nano technology, meet biomedical needs, and facilitate micro-electro-mechanical system (MEMS) integration. As traditional structural improvement methods struggle to meet increasingly stringent application conditions, under the action of the motion and mechanism of magnetic fluids, a new method of using neodymium magnetic ball plugs instead of traditional magnetic fluid plungers has been developed, aiming to enhance the pumping performance. In this study, the influence of the magnetic field (MF) generated by permanent magnets (PM) on the magnetic properties inside the micropump cavity was first determined. Furthermore, it was revealed in this research that the neodymium magnetic ball plug enhances the pumping flow rate and maximum pumping height of the ferrofluid plug and the pumping stability of the neodymium magnetic ball plug ferrofluid micropump is significantly improved. Additionally, the rotational speed (Rev) of the dynamic neodymium magnetic ball type magnetic fluid plug driven by the motor and the magnetic strength created by the PM are the main aspects influencing the result in this experiment.

Internal combustion engines (ICEs) face challenges in balancing efficiency and emissions. This study designed a non-crankshaft reciprocating engine (NCRE) using non-uniform rotational speed technology to optimize combustion and reduce emissions. The NCRE employs natural gas as the primary fuel, with gasoline ignition, to enhance combustion dynamics. A multi-disciplinary framework integrating non-uniform speed models, piston motion dynamics, and computational fluid dynamics (CFD) simulations was developed to analyze performance. The results show that compared with traditional engines, NCRE has improved by approximately 2% on the indicated thermal efficiency (ITE), and releases more energy, burns more thoroughly and more rapidly; nitrogen oxide emissions have been reduced, which is attributed to the improved turbulence and controlled piston movement. The design of NCRE introduces the method of non-uniform rotational speed into the engine, filling the gap caused by the piston movement in changing the airflow inside the cylinder, and providing a way to achieve an efficient and low-emission power system.

This study introduces an enhanced numerical approach for analyzing the dynamic behavior of a rotor-bearing system subjected to unbalanced excitation from a gearbox drive shaft. The Newmark-β method with the integration of a variable time-step algorithm was used, allowing the system to be solved rapidly and accurately without compromising stability. This technique enables a precise computation of displacement and torsional deformation of the rotating shaft during its operational cycle. The proposed computational model is validated against experimental data, showing deviations of displacement in normal operation below the critical speed of about 6%. A comprehensive parametric analysis is conducted to evaluate the influence of rotational speed, trial mass, and initial phase angle on the system dynamics. The findings confirm that our enhanced numerical approach yields rapid convergence and reliable predictions, making it a valuable tool for dynamic analysis of rotating systems.

This study introduces an enhanced numerical approach for analyzing the dynamic behavior of a rotor-bearing system subjected to unbalanced excitation from a gearbox drive shaft. The Newmark-β method with the integration of a variable time-step algorithm was used, allowing the system to be solved rapidly and accurately without compromising stability. This technique enables a precise computation of displacement and torsional deformation of the rotating shaft during its operational cycle. The proposed computational model is validated against experimental data, showing deviations of displacement in normal operation below the critical speed of about 6%. A comprehensive parametric analysis is conducted to evaluate the influence of rotational speed, trial mass, and initial phase angle on the system dynamics. The findings confirm that our enhanced numerical approach yields rapid convergence and reliable predictions, making it a valuable tool for dynamic analysis of rotating systems.

Robotic abrasive disc grinding is widely used for surface finishing of structural components in industries such as aerospace and automotive manufacturing, where controlling surface roughness is critical for ensuring product quality and performance. Surface roughness theoretical models play a foundational role in deepening the understanding of surface profile formation and optimizing machining processes. Despite studies in wheel and belt grinding, abrasive disc grinding-specific models are still comparatively rare. This paper addresses this gap by proposing a novel theoretical model that integrates disc machining theory with key process parameters—rotation speed, grinding force, and feed rate—to establish a quantitative relationship with surface roughness. By analysing the material removal process and surface formation mechanism, the model estimates surface roughness from both kinematic and geometric perspectives. The proposed model is validated through robotic abrasive disc grinding experiments conducted under various conditions, achieving an average absolute relative error of 7.3%, with most deviations below 10%. This theoretical model offers physical insights into the grinding process. In the future, the model could be combined with data-driven approaches to enhance generalization and accuracy, leveraging its interpretability to improve predictive performance.

This study investigated the effect of tool shape on stirring performance and wear in Friction Stir Welding (FSW) of steel using particle-based numerical simulation. Two probe shapes were analyzed: a conventional cylindrical probe and a spherical probe, which may reduce stirring area and extend tool life while maintaining joint quality. The simulation, based on particle dynamics, evaluated material behavior, rotation speed, and welding speed effects. Stirring performance was measured by material dispersion; wear was assessed using adhesive wear theory. Results showed higher stirring intensity on the advancing side (AS) than the retreating side (RS), consistent with prior experiments. Probe tip shape significantly influenced stirring. Higher rotation speed improved stirring, while higher welding speed reduced it. Tool wear peaked during the plunge phase and was greater on the RS and tool edges due to lower flow stress and increased temperature. The spherical probe showed less wear than the cylindrical one under all conditions. Wear trends matched literature: rotation speed increased wear, welding speed decreased it. Overall, the spherical tool demonstrated lower wear, especially at the probe tip, indicating its promise as a durable alternative for FSW of steel.

The transport of natural gas blended with hydrogen is a key strategy for the low-carbon energy transition. However, the influence mechanism of its thermo-physical property variations on centrifugal compressor performance remains insufficiently understood. This study systematically investigates the effects of the hydrogen blending ratio (HBR, 0–30%), inlet temperature, and rotational speed on key compressor parameters (pressure ratio, polytropic efficiency, and outlet temperature) through numerical simulations. In order to evaluate the influence of hydrogen blending on the performance and stability of centrifugal compressors, a three-dimensional model of the compressor was established, and the simulation conducted was verified with the experimental data. Results indicate that under constant inlet conditions, both the pressure ratio and outlet temperature decrease with increasing HBR, while polytropic efficiency remains relatively stable. Hydrogen blending significantly expands the surge margin, shifting both surge and choke lines downward, and consequently reducing the stable operating range by 27.11% when hydrogen content increases from 0% to 30%. This research provides theoretical foundations and practical guidance for optimizing hydrogen-blended natural gas centrifugal compressor design and operational control.

This article presents the potential of using the Modbus TCP industrial computer network in measurement tests of electrical machines and devices used in laboratory stations. The Modbus interface is the primary communication channel for most measuring equipment for reading electrical parameters, such as current, voltage, and power, as well as mechanical parameters, such as rotational speed and torque at the shaft of the tested machine. The measurement system is designed to acquire data in steady states of the electric drive assembly, where the measured parameters indicate approximately the same value. The article presents the tasks and role of the measurement system in a modern approach to collecting and processing measurement data using intelligent communication devices.

Abstract Due to their low damping and nonlinear characteristics, gas foil bearings (GFBs) are susceptible to an imbalanced amount, so accurately predicting their dynamic response is crucial. The current time-domain-based rotor orbit prediction method has two problems. First, it is computationally expensive and time-consuming. Second, the simplified model for the complex foil structure results in low accuracy. This study combines the artificial neural network method (ANN) with a novel fully aeroelastic coupling model of a multi-leaf journal foil bearing (MLJFB), which considers assembly preload, friction and the interaction between the rotor, top foil, bump foil, and sleeve, to construct a rapid prediction model for gas film load capacity. Based on this prediction model, a nonlinear rotordynamic model is developed to enable efficient estimation of nonlinear responses, including the rotor orbit. A test rig for a high-speed MLJFB was designed and built to verify the accuracy of the theoretical model. The effects of load and rotational speed on the rotor orbits were then analyzed using a combination of theoretical and experimental approaches, with the results showing good agreement. This study provides a rapid method for predicting rotor orbits, which offer a valuable reference for the efficient optimal design and practical application of MLJFB.

Due to harmful emissions from vehicles on fossil fuels, rising prices for petroleum products and natural gas, the use of electric vehicles is on the rise. The rapid growth of electric vehicle production will ultimately satisfy these problems in cities. Outside the city, it is advisable to develop intercity electric transport, primarily rail, which can significantly reduce the cost of passenger and freight transportation. The paper considers the possibility of using switched reluctance motors in the traction drives of railway locomotives to replace less efficient, outdated direct current motors. It was designed in a direct current motor housing to study the static characteristics of the switched reluctance traction motor. A simulation model of a switched reluctance motor was developed, and its static characteristics were calculated at various supply voltages and load torque when operating in traction electric drives of railway transport. A comparison of the traction, mechanical and energy characteristics of a switched reluctance motor and a direct current traction motor at different supply voltages was carried out to assess the efficiency of its application. With this approach, as with direct current motors, the supply voltage of the switched reluctance motors was regulated by changing the wiring diagram. An algorithm for controlling the switched reluctance motor through pulse-width modulation of its phase voltage to form a family of traction characteristics is proposed. The study results showed that the proposed approach to regulating the rotation speed of the switched reluctance motor allows for the formation of the required number of traction characteristics and, if necessary, for performing stepwise or smooth transitions between them to regulate the vehicle speed. The results indicate the efficiency of switched reluctance motors in direct current traction electric locomotives.

The present paper explores the micro-electrical discharge machining (µ-EDM) characteristics of high carbon high chromium (HCHCr) steel using both Sn-coated and uncoated brass electrode. The aim of the study is to assess impact of various input process parameters, such as peak current (I p; 2–4 A), pulse on time (T on: 6–8 µs), pulse off times (T off: 8–10 µs) and rotational speed of the electrode (R/S: 110–130 rev/min), which were experimentally analysed. The machining performance, analysed in terms of material removal rate (MRR), tool wear rate (TWR), frontal wear, taper angle and hole surfaces quality, was evaluated to determine the effectiveness of the electrode coating. The findings revealed that the Sn-coated electrode significantly improved process in comparison to the uncoated electrode. The MRR ranged from 1.37 to 2.47 mm3/min for uncoated electrode and from 1.63 to 2.73 mm3/min for Sn-coated electrode with the maximum enhancement of 22.36%. Similarly, the reduction in TWR is attained by up to 41.08% with Sn-coated tool. Frontal wear analysis revealed that Sn-coated electrodes maintained their tip shape much better, which led to enhanced spark concentration and energy transfer. Interestingly, the taper angles were considerably lower in the holes created with these Sn-coated electrodes, with some reductions surpassing 60%. This resulted in improved hole geometry and dimensional accuracy. The experimental analysis confirmed that peak current is the primary determinant of MRR, TWR, and hole dimensional precision. The Sn-coated brass electrodes achieve superior machining performance compared to uncoated brass electrodes in precision µ-EDM of hard tool steels.