Rotational Speeds Research Articles

Highly Efficient Near-Infrared Light-Driven Molecular Motor Rotation Enabled by Upconversion Nanoparticles as Nanoscale Light Sources.

Powering light-driven molecular motors with visible or near-infrared (NIR) light is essential in the design of molecular machines, bringing dynamic functions to the next generation of responsive materials particularly for biological applications. However, current strategies suffer from heavy molecular substitution and low photoefficiency of excitation, limiting their practical use in bulk materials and biomolecular systems. Here, we report a general and highly efficient strategy to power NIR light-driven molecular motors via a radiative energy transfer mechanism. Taking advantage of spectrally tunable upconversion nanoparticles (UCNPs), the motors powered by continuous wave NIR light can reach photostationary states (PSS) with high efficiency, comparable to those of direct UV/visible light-driven systems, without a deaeration process needed. The concept is validated on various molecular motors with different rotary speeds, providing a general, broadly applicable principle for the future design of highly efficient NIR-powered photodynamic molecular motor systems.

Humped Flow Channel in Drum Magnetic Separator Leads to Enhanced Recovery of Magnetic Seeds in Magnetic Flocculation Process

This study examines the effect of smooth and humped flow channels on the recovery of industrial magnetic seeds in a drum magnetic separator. The results demonstrate that under varying feeding slurry quantities and drum rotational speeds, the humped channel consistently achieves higher recovery rates compared with the smooth channel, with an improvement of up to 3%. Scanning electron microscopy and vibrating sample magnetometry analyses of the samples reveal the presence of a small amount of impurities (predominantly consisting of elements, such as Al, Si, and Ti) in the industrial magnetite magnetic particles. These impurities exhibit lower magnetization, leading to reduced capture efficiency in the conventional smooth-channel drum magnetic separator. Simulations of the magnetic field, flow field, and particle trajectory indicate that the magnetic field force at the bottom of the smooth channel is only 0.6 kg2/(m·s4·A2), i.e., approximately 18 times lower than that at the roller surface. The incorporation of a humped channel shifts the impure magnetic seeds from a region with low magnetic field force to a region with higher magnetic field force, significantly enhancing the capture efficiency of the impure magnetic seeds.

A Model to Predict the Flow Rate in Single Conical Screw Extruder

Abstract A novel general model for predicting the flow rate and pressure in conical screw extruders for polymer processing has been developed, addressing a crucial need in polymer manufacturing. Based on single screw extruder flow Equations and mass conservation principles, we derived a flow rate Equation for a single conical screw, accounting for variations in screw diameter and slot depth along the length. Recognizing the significant impact of slip phenomena on flow rates, especially for energetic materials, we incorporated a slip velocity correction for non‐Newtonian fluids. This correction was based on simulations across various diameters and rotational speeds, enhancing the model's accuracy for real‐world polymer extrusion processes. The model's predictive power was validated through experimental data, yielding impressive accuracy with simulation calculation errors of 1.59% and numerical derivation errors of 7.40%. This research bridges the gap between theoretical polymer rheology and practical extrusion processes, offering a method for optimizing the design technology of single conical screws.

Investigation of the Dynamic Characteristics of Brush Seals Using a Transient Fluid-Structure Interaction Method

Abstract Brush seals operate within harsh environments within rotating machinery. They are typically exposed to high pressures and temperatures, rotor–stator relative movements, and high shaft rotational speeds leading to highly swirling inlet flow. The compliant nature of the bristle elements makes them susceptible to flow-induced vibrations, particularly associated with high levels of inlet swirl velocity. This can lead to fatigue fracture of the bristles and may also impact seal leakage. This paper establishes a two-way fluid-structure interaction (FSI) method that combines a three-dimensional transient flow model of brush seals with an analytical mechanical model of bristle deflections. This method can quickly obtain the flow field characteristics and bristle deflection of brush seals with satisfactory accuracy. Based on this method, bristle deflections under typical aerodynamic loads in operation, up to 0.4 MPa differential pressure and 200 m/s inlet swirl velocity, were investigated to understand bristle response under steady-state and transient conditions. In the absence of inlet swirl, simulated bristle axial deflections and leakage were validated against experimental measurements using an in-house seal test rig. The results for axial deflection without inlet swirl show that the bristles undergo oscillation whose amplitude quickly diminishes over time, as expected, reaching an equilibrium for the compressed bristle pack. An increase in differential pressure results in increased bristle tip oscillation displacements and longer settling times, however in all cases the settling time is of the order of milliseconds. The bristle pack center region exhibits a stratification, under conditions of fluctuating pressure and due to the inertia of the bristles themselves. This may have implications for pack stability and sealing performance, particularly when an inlet swirl is also imposed. This study shows, for the first time, that under the influence of inlet swirl, and particularly at inlet swirl velocities of 200 m/s where bristle slip is known to occur for similar pack geometries, the upstream row of bristles exhibits a circumferential displacement oscillation due to interaction between the swirling flow and bristle structure. This occurs with a characteristic frequency of 441 Hz which is of the order of the bristle natural frequency. Results indicate that a consistent oscillation amplitude is established over the simulation timescales, suggesting a typical forced vibration response. The amplitude of the bristle axial oscillation in the first row is observed to decrease when inlet swirl is applied, but the axial oscillation is sustained, occurring at a similar frequency to the circumferential oscillations but with a slight phase shift. The results also indicate that there is a substantial leakage penalty which is associated with the oscillation of the bristle upstream row, to more than double that of the stable pack. Under these conditions, bristle fretting wear and fatigue failure may be a concern, which could have significant adverse consequences for seal performance and life. Initial results show that bristle circumferential displacements do not propagate into the downstream rows. However, in the case of fatigue failure and detachment of the upstream bristle row, a progressive failure mechanism might be possible.

Nonlinear Dynamic Analysis of Temperature Characteristics in Oscillating Heat Pipes Under Radial Rotations

Radial rotating oscillating heat pipes (R-OHPs) have excellent thermal performance and great potential for application in the thermal management of rotatory machinery. However, the heat transport behavior and temperature characteristics of R-OHPs are complex, and their understanding is still limited, hence necessitating further research. In this study, thanks to an experimental investigation involving a copper R-OHP running with acetone and water, its thermal performance is evaluated, and then the temperature characteristics are analyzed by nonlinear dynamic analysis. The study reveals that the effective heat transfer coefficient of R-OHPs undergoes a notable increase with rising rotational speed, exhibiting a peak at a threshold speed value. Such a peak is present irrespectively of the working fluid, and, after exceeding the threshold, higher rotational speeds lead to a lower thermal performance. Based on nonlinear dynamic analysis, the power spectrum density of the evaporator temperature indicates a lack of dominant frequency in temperature signals, suggesting a complex behavior characterized by random oscillations of vapor slugs and liquid plugs. In order to better understand how strong the chaotic behavior is, an autocorrelation analysis was carried out, the OHP at static state has a stronger chaos than R-OHPs. The correlation dimension analysis of the evaporator temperature provides values ranging from 1.2 to 1.6, which together with the Lyapunov exponent calculations, further support an evident chaotic nature of R-OHPs.

Investigating kissing point location and solidification front in twin roll casting of steel through finite-element-based thermo-fluid models

Making thin strips directly from the melt by twin roll casting requires precise control over process parameters to obtain defect-free components. Strategically controlling the kissing point location and the solidification front can mitigate the probability of crack formation. A two-dimensional low Reynolds number k – ε turbulence model is used to identify the location of kissing point for a vertical twin roll casting process. The temperature-dependent viscosity and apparent heat capacity method is employed to imitate the flow of melt and the solidification behaviour. The effect of different roll rotational speeds (20–28 rpm) and inlet melt temperatures (1733–1813 K) on solidified shell thickness and kissing point location is explored. The formation of a laminar sub-layer near the roll surface ensures uniform temperature distribution and high Nusselt number indicates dominant convective heat transfer from the upper roll surface. The shifting of the kissing point location is obvious by increasing roll rotational speed and inlet melt temperature accompanied by reduced solidified shell thickness. A polynomial relation between these parameters offers a practical solution for optimising heat transfer efficiency with direct applicability to industrial twin roll casting operations. This insightful study provides variation in kissing point location with process variables of twin roll casting confronting various dimensionless numbers.

Reliability analysis of gear-bearing drive systems considering gear manufacturing and installation errors

Gear-bearing drive systems often exhibit manufacturing and installation errors, which can significantly affect system performance, and longevity, and increase the probability of failures. This paper focuses on the reliability analysis of gear-bearing drive systems with uncertainties in system parameters such as gear backlash and bearing clearance, caused by gear and bearing manufacturing and installation errors. First, a dynamic model of the gear-bearing drive system, incorporating coupled dynamic meshing parameters, is established. Then, the deterministic dynamic model of the system is combined with the Chebyshev interval analysis method to develop a reliability analysis model for the gear-bearing drive system with uncertain parameters. The study analyzes the variations in system natural frequencies and vibration responses due to gear quality and initial gear and bearing clearances at different deviation rates. The results indicate that at the same rotational speed and deviation rate, the initial bearing clearance has a more significant impact on the system’s dynamic characteristics compared to the initial gear clearance. At different rotational speeds and the same deviation rate, system reliability decreases with increasing average initial interference of the bearing at low speeds. At high speeds, a large bearing clearance deviation may cause abnormal fluctuations in system vibration. This method provides a prioritization of parameter control for the structural optimization and design of gear-bearing systems.

Моделирование рабочего процесса гидравлического пульсатора манипулятора лесных машин

The article studies and simulates of the working process of the hydraulic pulsator used in the manipulators of forestry machines. Manipulator units of these machines play a key role in the performance of technological operations in the preparation of areas for growing forest crops, as well as in their subsequent maintenance. To increase the effi-ciency of operations such as cutting or removing unwanted tree and shrub vegetation, removing stones, boulders and other obstacles, the modernization of manipulators is an actual direction. One of the promising ways to reduce the en-ergy intensity of the working process is the introduction of highly effective vibration effects applied to the working bod-ies of the manipulator. The analysis of modern research in the field of hydraulic pulsators has shown that the devel-opment of new designs of rotary pulsators can significantly improve the performance indicators. In the course of the work, it has been revealed that the operating parameters of the hydraulic pulsator, such as the diameter of the spool shaft and the area of the working fluid overflow hole, depend on the maximum angle of rotation of the spool shaft axis equal to 22°30′. The permissible zones of variation of geometrical parameters of the specified orifice are deter-mined. Researches have shown, that change of area of an aperture for a fluid flow in time has a direct influence on the working fluid flow rate through the rod or piston cavity of the hydraulic cylinder. The greatest time of liquid over-flow (1-1.6 s) is observed at rotational speeds of the spool shaft 10-20 rpm. It is established that for holes with diameter of 5 mm in the zone of small rotational speeds the time of absence of liquid overflow increases by 0.18-0.36 s. For high-pressure hydraulic hoses with internal diameters of 8-16 mm, most often used in forestry machinery, the maxi-mum flow rate of working fluid is 0.00101 m³/s (1.01 l/s). The results are of practical importance for improving the designs of hydraulic pulsators and increasing the efficiency of forest machine manipulators.

Influence of the velocity ratio and rotational speed on the polymer based desiccant dehumidifier

Nowadays, it’s essential to reduce our reliance on conventional air conditioning units and switch to desiccant-based dehumidifiers and air conditioners. This shift promotes sustainability, protects the environment from harmful gas emissions, and minimizes energy consumption. The current work centres on developing a polymer-based dynamic desiccant dehumidifier system. This involves studying the velocity ratios between the dehumidifier and regenerator air at various rotational speeds. Four sets of velocity ratios and four sets of rotational speeds are included in the matrix preparation. The results indicated that the system performed optimally with a velocity ratio range of 1.00 to 0.20, demonstrating improved temperature and humidity changes as well as dehumidification efficiency. In contrast, the highest velocity ratio range of 4.00 to 0.80 achieved the maximum rate of moisture removal, performance coefficient, and coefficient of mass transfer at an optimum rotational speed of 24.0 rpm. Beyond these ranges, performance declined significantly. This unit reached a maximum rate of moisture removal of 0.23 g/s, dehumidification efficiency of 83.7%, a coefficient of performance of 5.36, and a coefficient of mass transfer of 6.67 kg/m2-s.HighlightsAs the velocity ratio decreases, both efficiency & moisture removal rate increase.Dehumidification performance improves up to 24.0 rpm, and then it declines.COP values of 1.87, 3.25, 4.24, and 5.36 are achieved for VR of 1.00, 2.00, 3.00, and 4.00.Power consumption & pressure drop rise with the velocity ratio & wheel speed.Mass transfer coefficient of 6.67 kg/m2·s is obtained at 24.0 rpm & VR of 0.80.

Preparation and properties of thermoplastic starch via the synergy of ozonation and elongational stress.

Preparation and properties of thermoplastic starch via the synergy of ozonation and elongational stress.

Research on the cavitation characteristics of axial piston pump based on computational fluid dynamics models

Axial piston pumps typically operate under high-pressure and high-speed conditions, making them prone to cavitation, particularly in the piston chambers and grooves of the valve plate. When cavitation bubbles are carried into the high-pressure region by the oil flow, their collapse generates intense pressure pulsations and fluid excitation forces, which significantly affect the working stability of the pump. To study the cavitation characteristics of the axial piston pump, a computational fluid dynamics (CFD) model is developed in this paper, taking into account key flow characteristics. Meanwhile, a cavitation visualization test rig is presented to validate the effectiveness of the simulation model. By investigating the gas-phase volume fraction and jet flow velocity at different locations within the pump, generation mechanisms and dynamic characteristics of cavitation in the piston chambers, grooves, and slippers under various operating conditions are systematically revealed under various operating conditions. Moreover, comparative studies are conducted to examine the evolution of cavitation behavior under different pressures and rotational speeds. The findings elucidate the significant influences of these parameters on cavitation dynamics in axial piston pumps. This work provides a theoretical basis for developing effective strategies to suppress cavitation and enhance pump reliability.

Impeller instability based on the autocorrelation method in a centrifugal compressor

Instability behaviors significantly influence the performance and stable operating range in a centrifugal compressor, which is investigated by both experimental and numerical methods. To elucidate impeller instability characteristics, unsteady pressure signals were measured by high-response static-pressure transducers during the throttling process at various rotational speeds. Then, both the autocorrelation and spectrum methods were employed to analyze the instability process and behaviors. The results showed that during stall onset, the mean values of the autocorrelation coefficient (AC) decreased dramatically at all circumferential positions, and the root mean square values of the AC increased remarkably. The steep change in the mean value curves of the AC can be used to predict impeller stall effectively. Compressor stall was embodied by a rotating instability in the preliminary stage. The periodicity number of the AC curves in one rotor revolution varies from 2–5, corresponding to a broadband hump with 2–5 times of impeller frequency and indicating the rotating instability. The features and mechanisms of instability flow field were further discussed by unsteady simulation. Based on the clarification of relationship among the time domain periodicity behaviors, frequency spectra, and detailed flow field, the deep understanding and effective prediction for impeller instability are acquired.

Visual vibration measurement of rotating bodies with effective time–frequency characterization at constant and variable rotational speeds

Visual vibration measurement of rotating bodies with effective time–frequency characterization at constant and variable rotational speeds

Assessing Flight Angle and Rotor Speed Effects on Drying Efficiency and Power Consumption of the Centrifugal Dryer of Pelletizing Systems

This study used the Discrete Element Method (DEM) coupled with the Moving Particle Semi-implicit (MPS) method to investigate the process of drying in the centrifugal unit of a pelletizing system in polymer processing. The effects of various flight angles (10°, 45°, and 70°) and rotor speeds (1280, 1600, and 1920 rpm) on drying efficiency, polymer pellet transport, polymer pellet accumulation, and power consumption were examined. The results showed that the flight angle significantly influenced drying performance. At 1600 rpm, the 10° flight angle configuration required the least power (10.94 kW) but resulted in inefficient water separation, which led to an increase in water droplets (i.e., higher moisture content) in the upper part of the centrifugal unit and near the outlet. With a 70° flight angle, water removal was most effective, but polymer pellet transport efficiency was lower due to centrifugal forces becoming dominant. A 45° flight angle provided the best balance between drying efficiency and power consumption, requiring 16.42 kW while achieving the most efficient polymer pellet transport. Rotor speed also played a crucial role: lower speeds enhanced water removal and reduced power demand but limited throughput, whereas higher speeds facilitated centrifugal separation at the cost of increased power consumption. The optimal combination of the rotor speed and flight angle was found to be 45° at 1280 rpm, which offered an effective trade-off between drying performance and power efficiency.

EXPERIMENTAL CHARACTERIZATION OF MULTI-STAGE SPUR GEARBOX DYNAMICS UNDER VARIABLE TORQUE LOADS

This study investigates the dynamic performance of a multi-stage spur gearbox designed with a theoretical reduction ratio of 100:1. The gearbox comprises six involute spur gears on four shafts and was tested under input torque loads from 2.5 Nm to 27 Nm. Rotational speeds and torques were measured using digital tachometers (1%) and strain gauge sensors (0.5%). Output RPM ranged from 25.079 to 40.281, with an average deviation of 3.1% from the theoretical ratio. Input power varied between 0.07 W and 1.10 W, while output power ranged from 0.047 W to 0.76 W. Overall efficiency was observed between 63.9% and 87.8%, depending on load and speed. Linear regression analysis confirmed strong correlations: R2 0.854 for input-output RPM and R2 0.960 for torque transmission. These results indicate that while kinematic performance remains stable, frictional and alignment losses increase under high-load conditions. The findings contribute valuable empirical data to support the design and optimization of high-reduction gear systems for applications requiring low-speed, high-torque operation with predictable dynamic behavior.

CFD-Based Parameter Calibration and Design of Subwater In Situ Cultivation Chambers Toward Well-Mixing Status but no Sediment Resuspension

The elemental exchange fluxes at the sediment–water interface play a crucial role in Earth's climate regulation, environmental change, and ecosystem dynamics. Accurate in situ measurements of these fluxes depend heavily on the performance of marine incubation devices, particularly their ability to achieve full mixing without causing sediment resuspension. This study presents a novel parameter calibration method for a marine in situ incubation device using a combination of computational fluid dynamics (CFD) simulations and laboratory experiments. The influence of the stirring paddle’s rotational speed on flow field distribution, complete mixing time, and sediment resus-pension was systematically analyzed. The CFD simulation results were validated against existing device data and actual experimental measurements. The deviation in complete mixing time between simulation and experiment was within −9.23% to 9.25% for 20 cm of sediment and −9.4% to 9.1% for 15 cm. The resuspension tests determined that optimal mixing without sediment disturbance occurs at rotational speeds of 25 r/min and 35 r/min for the two sediment depths, respectively. Further analysis showed that the stirring paddle effectively creates a uniform flow field within the chamber. This CFD-based calibration method provides a reliable approach to parameter tuning for various in situ devices by adjusting boundary conditions, offering a scientific foundation for device design and deployment, and introducing a new framework for future calibration efforts.

Energy Efficiency and Power Transmission Analysis of a High-Ratio Gear Reduction System

This study presents the design and experimental performance evaluation of a custom-built high-ratio gear reduction system composed of four shafts and six spur gears. The gear arrangement consists of three transmission stages: 2:1 (Gear 1–2), 10:1 (Gear 3–4), and 5:1 (Gear 5–6), resulting in a total theoretical speed ratio of 1:100. The gears were manufactured with tooth counts ranging from 10 to 100 and diameters between 36 mm and 316 mm. The gearbox was tested under five different input conditions, with input rotational speeds ranging from 0.281 to 0.391 RPM and torque levels from 2.5 to 27 Nm applied at the driver shaft. RPM and torque were measured at all four shafts to evaluate transmission performance. The maximum recorded output speed at shaft 4 was 40.281 RPM, corresponding to an actual speed multiplication factor of approximately 103:1, which closely aligns with theoretical expectations. Power at each shaft was calculated using the equation P=τ⋅ω. Input power ranged from 0.07 W to 1.10 W, while output power varied from 0.047 W to 0.76 W. The system demonstrated efficiencies between 63.9% and 87.8%, with the highest efficiency observed at moderate torque inputs (6–23 Nm). Energy losses were primarily due to friction, backlash, and minor alignment deviations. The results confirm that the gearbox performs reliably and efficiently for high-ratio speed conversion applications. This configuration is suitable for systems requiring compact form, low input speed, and high output speed, such as laboratory instrumentation, automation mechanisms, or kinetic energy recovery setups.

Reliability Analysis of Tugboat’s Nozzle Structure under Propeller Induced Flow Pressure and Wave Load in Operational Conditions

Ship propellers produce thrust by transforming rotational energy from the primary engine into linear force. Ducted propellers are a widely employed propulsion device that enhances propeller efficiency through the application of the physical principles of ducts or nozzles. Research on the structural performance of nozzles is rare, despite the critical importance of preserving structural integrity during fluid-structure interaction. This paper examines the resilience of tugboat propeller fabrication under both static and dynamic fluid forces. Computational fluid dynamics (CFD) and the finite element method (FEM) are employed concurrently to assess the fluid loads and stresses within the nozzle structure at different propeller rotational speeds. The structure's reliability is assessed by integrating the stress load distribution with the propeller material's strength through a joint probability density function. This reliability model acknowledges the uncertainty of the loads exerted on the propeller construction, as well as the variability in material production. The reliability evaluation confirmed that the nozzle construction possesses a failure risk of 0.37%. The nozzle design demonstrates a reliability of 99.63% with negligible failure risk under operational settings. This result indicates that the current industry standards applied to this tugboat (BV NR467 Part B Chapter 12 Section 10) exhibit good reliability and are capable of handling operational loads effectively.

Investigation of Root Causes Analysis, Preventive Maintenance Delays & Breakdowns in Diesel Generators Using IOT Integrated Hardware & FEA Method

This study investigates the root cause of preventive maintenance in diesel generators by integrating IoT-based monitoring and Finite Element Analysis (FEA). Using an ESP8266 controller with temperature sensors, vibration sensors, and an accelerometer, real-time data is collected to analyse temperature variations, vibration occurrences, and potential misalignment effects. Additionally, FEA is performed in ANSYS for different shaft rotational speeds, evaluating frequencies with modal analysis. A 3D model is developed in CATIA to simulate modal and thermal responses, aiding in identifying breakdown causes and optimizing generator performance for enhanced reliability and lifespan.

Design and Experiment of a Multi-Row Spiral Quantitative Fertilizer Distributor

Aiming at the existing fertilizer distributor’s lack of stability of fertilizer discharge and uniformity of fertilizer discharge, which affects the precise application of fertilizer, a design and testing of a multi-row spiral quantitative fertilizer distributor was designed. The design principle and working principle of the fertilizer distributor are described, and the parameter ranges of centrifugal cone discs’ cone angle, cone disc inclination, cone disc rotation speed, etc., are determined. The Elementary Discrete Element Method (Referred to as EDEM in the following) simulation analysis software was adopted to carry out the simulation analysis of the fertilizer discharge process of the fertilizer discharger, to study the influence of each parameter on the fertilizer discharge performance and the optimal combination parameters of the fertilizer discharger. Taking the coefficient of variation for the consistency of fertilizer application amount among rows and the coefficient of variation for the consistency of fertilizer application amount within the same row as the evaluation indicators, and taking the cone angle of the centrifugal cone disk, the cone disk inclination angle, and the cone disk rotational speed as the test factors, multi-factor and multi-level experiments were carried out. The simulation test results show that the optimal parameter combination of the fertilizer discharger is the rotational speed of the centrifugal cone disk at 95 r/min, the cone angle of the cone disk at 16.7°, and the blade inclination angle of the cone disk at 2.7°. Using potassium sulphate compound fertilizer as the test material, the bench test on the fertilizer discharge performance and adaptability of the fertilizer distributor when the speed of centrifugal cone discs was 30~110 r/min was carried out to verify the fertilizer discharge performance of the fertilizer distributor. The results of the validation test showed that the coefficient of variation for the consistency of fertilizer application amount among rows of fertilizer distributor at different rotational speeds was lower than 4.25%, the coefficient of variation for the consistency of fertilizer application amount within the same row was lower than 3.21%, which meets the requirement of fertilizer discharge quality. The research provides technical support for enhancing the performance of fertilizer distributors and achieving precise fertilizer application, thereby playing an active role in improving fertilization efficiency and promoting sustainable agricultural development.