Rotational Speed Research Articles

The influence of ambient temperature on exhaust emissions during cold start in the homologation test

The cold start phase in an ICE is susceptible to changing environmental conditions, especially ambient temperature. The work aimed to analyse the influence of different thermal conditions on the concentration of pollutants and operating parameters of the drive unit during a cold start. The tests were conducted on a chassis dynamometer at various ambient temperatures. The same homologation cycle was used in both cases, allowing direct comparison of results. The concentrations of HC, CH₄, CO₂ and NOx were recorded, as well as the basic operating parameters of the engine: coolant temperature, rotational speed, load and throttle position. Based on empirical data, mathematical models describing the influence of ambient temperature on the dynamics of emissions and stabilisation of engine operation were developed. Relationships were identified that allow for assessing the time to reach steady-state conditions as a function of starting temperature. The results of the analysis provide the basis for developing a start control strategy in climatically variable conditions. They can support the development of adaptive emission control systems compliant with current and future legal standards.

A numerical modelling approach to predict material flow and defect formation in refill friction stir spot welded joints

Abstract In this study, a fully coupled thermomechanical model of the refill friction stir spot welding process was developed using the coupled Eulerian–Lagrangian technique. The model was used to simulate joining of AA2024-T3 sheets with different welding times of 3 s and 1.5 s, and a fixed rotational speed of 2000 rpm. Model outputs of welding temperature, equivalent plastic strain, void content, and material flow were validated against experimental welds produced using the same welding parameters. Welding temperatures were accurately predicted for both welding times throughout the plunging stage yet overestimated during the refill stage compared with thermocouple measurements. Simulated regions of high plastic strain were found to correlate well with regions of higher grain refinement in experimental welds. Internal tunnel-like defects were predicted by the model in the shoulder plunge region; these predictions were validated by equivalent defects found in the microstructures of experimental welds. Stop-action analysis of experimental welds was used to validate the model’s ability to accurately capture material flow during the refill stage. This provides a valuable insight into refill flow behaviour and the formation mechanism of the internal tunnel defects, indicating that volume ratio is an important parameter for future study.

Experimental investigation of combined size and shape segregation in binary mixtures of cylindrical particles with varying aspect ratios in a rotating drum

ABSTRACT This study systematically investigates the segregation mechanisms and dynamic behaviors of binary mixtures composed of spherical and non-spherical cylindrical particles with varying aspect ratios in rotating drums. The results reveal that the aspect ratio of cylindrical particles significantly influences segregation behavior. Particles with low aspect ratios promote stronger segregation due to the size-driven percolation of smaller spheres into the core region of the granular bed. In contrast, large aspect ratio particles exhibit enhanced interlocking interactions, which reduce bed porosity and suppress percolation, thereby substantially decreasing segregation intensity. The dynamic angle of repose increases with both particle aspect ratio and rotational speed, showing a strong linear correlation with granular temperature. As the rotational speed increases, the mean particle velocity is effectively enhanced, which in turn promotes mixing performance; however, the overall impact remains relatively minor.

Inner ring defect frequency deviation of ball bearings induced by slipping effect under starved lubrication

The vibration response of locally defective ball bearings is closely related to their lubrication conditions. In this paper, the interaction within the system under starvation conditions is considered, and a dynamic model of lubricant-deficient inner ring defective deep groove ball bearing is established, and the accuracy of the model is verified by experiments. The results show that the slipping behavior of the bearing leads to a deviation between the cage speed and the theoretical value, which modulates the inner ring failure frequency. And the increase in the lack of lubricant significantly increases the friction force, which leads to the increase in the cage rotational speed, and ultimately leads to the decrease in the inner ring failure frequency. At the same time, the increase in rotational speed makes the slipping phenomenon more severe, leading to an increase in the deviation rate of the inner ring failure frequency at the same level of starvation. The results of the study are useful for fault diagnosis and condition monitoring of related equipment.

Hydrophobic PVDF‐Based Electrospun Nanofibrous Membranes: Design Criteria Fabrication and Resistance to Long‐Term Hydrodynamic Operation

ABSTRACTThe mechanical integrity of electrospun nanofiber membranes (ENMs) under operational conditions may limit their application in membrane contactors. This study integrated the electrospinning (ESP) with heat treatments to enhance nanofiber integrity in polyvinylidene fluoride (PVDF) ENMs. The impact of ESP parameters on the properties of the resulting ENMs was explored, including polymer dope flow rate (1.0–1.2 mL h−1), tip‐to‐collector distance (TCD, 12–18 cm), and needle size (20–22 Ga), along with collector type (flat or rotary drum), needle motion (static or moving at 10 cm s−1), and collector rotation speed were assessed. Heat treatment was evaluated at 130°C–170°C for 1–15 h. The optimized ENM exhibited a 134° ± 5° water contact angle, 200 ± 50 μm thickness, and 3.10 ± 0.02 mg cm−2 surface density. It was fabricated using a 1.20 mL h−1 polymer dope flow rate, 12 cm TCD, and a static 20 Ga needle during an 8‐h ESP session with a rotary collector, followed by treatment at 150°C under 70 Pa for 6 h. It endured over 800 h under high hydraulic stress (21 L h−1 water flow), outperforming a commercial PVDF membrane and highlighting its potential for long‐term operation in gas–liquid membrane contactor applications.

PENGEMBANGAN ALAT PEMIPIL CENGKEH DI KABUPATEN KOLAKA

This study aimed to design and test a clove threshing machine to increase post-harvest efficiency for local farmers in Kolaka Regency. The development process involved prototype design and two phases of field testing to evaluate capacity, rotational speed, separation performance, and screening system effectiveness. In Trial 1, the machine featured a 3–5 kg hopper capacity and a low RPM, producing 1 kg of separated cloves per minute (60 kg/hour) with a separation rate of 75% clove buds and 25% stems. In Trial 2, with a 10–15 kg hopper and higher RPM, output increased to 2.5 kg per minute (150 kg/hour), with improved separation efficiency of 90% buds and only 10% stems. The screening system was also improved from a flat, non-inclined vibrating setup in Trial 1 to a 10-degree inclined fixed tray in Trial 2, further enhancing separation quality. These results demonstrate that the improved machine significantly increases productivity and separation efficiency, making it a viable appropriate technology solution for smallholder clove farmers facing labor constraints and economic shifts due to industrialization.

Analysis of Friction Torque Characteristics of a Novel Ball–Roller Composite Turntable Bearing

Traditional three-row roller YRT turntable bearings exhibit high friction torque during operation, which limits their performance in high-precision and high-response applications. To address this issue, a novel ball–roller composite turntable bearing is proposed that effectively reduces friction torque while maintaining a high load capacity. A mechanical model based on statics is established, and the Newton–Raphson method is employed to calculate the contact load. The formation mechanism of friction torque is analyzed, and a corresponding computational model is developed and validated using experimental data. The effects of axial load, eccentricity, overturning moment, rotational speed, and axial clearance on friction torque are systematically studied. Results indicate that friction torque increases with these parameters. Axial clearance has a significant influence, and an optimal clearance value between the balls and rollers is determined. Additionally, a reasonable range for the raceway curvature radius coefficient is proposed. When the numerical ratio of balls to rollers is 1, the bearing exhibits optimal friction performance. Among various roller crowning strategies, logarithmic crowning yields the best results. This study provides a theoretical basis and technical support for the optimized design of ball–roller composite turntable bearings.

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.

Development of a novel regime map for fabric motion in rotating horizontal drum of a household cloth dryer

Moisture evaporation from clothes in household tumble dryers is significantly affected by the motion of fabric within the rotating horizontal drum. This study experimentally investigated fabric motion under varying operational conditions to develop a regime map. The effects of fabric quantity, initial moisture content (MC), drum rotation speed, and the presence of lifters on the drum wall were systematically examined. In the drum without lifters (DWOL), four dominant motion regimes were identified: slip, rolling, falling, and centrifuging. In contrast, the drum equipped with lifters (DWL) exhibited three motion patterns: rolling, falling, and centrifuging. A Gaussian mixture model (GMM) was employed to quantitatively classify these fabric motion regimes. Additionally, information entropy analysis was utilized to determine the transition boundaries between different motion states. Based on these analyses, regime maps were constructed for both drum configurations. These maps provide valuable insights for predicting fabric motion patterns and can support the optimization of drying performance in household dryers.

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.

Multi-response optimization of process parameters for weld performances during underwater friction-stir welding of dissimilar aluminum alloys AA6063-T6 and AA5083-H32

This study investigates the multi-response optimization of process parameters in welding for superior welds performance in welds for AA6063-T6 and AA5083-H32 aluminum alloys. Underwater friction stir welding (UFSW) emerges as a promising technique, offering improved mechanical properties through accelerated cooling rates. The response surface methodology coupled with desirability function analysis was used to optimizing three key process parameters are tool rotational speed, welding speed, and plunge depth. The objective is to simultaneously maximize tensile strength, minimize weld defects, and improve corrosion resistance. Experimental results show that at a weld speed of 17 mm/min and 1400 rpm, the maximum ultimate tensile strength (UTS) of 267 MPa occurs at a 2° tilt angle, while the highest yield strength (YS) of 226.04 MPa is observed at a 1° tilt. Optimal elongation (12.72%), impact energy (18.29 J), and microhardness (102.03 VHN) occur at a 2.5° tilt angle. Analysis of Variance (ANOVA) reveals that spindle speed has a significant impact on UTS, yield stress YS, impact energy, and microhardness, whereas tilt angle predominantly affects elongation. The microhardness profile indicates higher values in stir zone (SZ) and thermo-mechanical affected zone (TMAZ) zones compared to the heat-affected zone (HAZ) and base metal (BM), emphasizing distinct material property variations across weld regions.

Fabrication of magnetic manganese ferrite-loaded sugar cane bagasse/peanut peel biochar adsorbents for the adsorptive removal of phosphorus from aqueous solution

Adsorption has the potential to be a highly effective and selective method for recovering and adsorbing phosphate from wastewater and water, which can serve as secondary sources of phosphorus. The objectives of this study were to synthesize manganese ferrite (MF) nanoparticles which are fabricated and studied alone and loaded on sugar cane bagasse and peanut peels biochar (BC) adsorbents (Mn@Fe3O4@BC) by in-situ growth method, which in turn applied to evaluate their capabilities for phosphorus adsorption from aqueous solutions. Batch experiments were conducted to determine the optimum adsorption conditions for different process parameters such as pH, adsorbent dose, and initial phosphorus concentration. The maximum phosphorous removal efficiency using MF, MFBCb, and MFBCp was obtained at adsorbent doses 0.2 and 0.3 g/L, and initial phosphorous concentrations of 20, 40, and 60 mg/L, respectively. The optimum retention time was obtained at 120 min for MF and MFBCb, and 150 min for MFBCp. The optimum rotation speed and temperature were 120 rpm and 25 °C for all adsorbents. The maximum removal efficiencies obtained are 98.5% and 99% for MF and MFBCs, respectively. Different characterization analyses; including SEM, EDX, and FTIR; were applied to investigate surface morphology, elemental composition, and chemical properties of the adsorbents before and after the adsorption process. Adsorption kinetics, isotherms, capacity, mechanisms, and thermodynamic studies were studied to evaluate the adsorption process. And finally, adsorbents were regenerated using their magnetic properties and a second successive adsorption cycle was evaluated showing promising results for MFBC adsorbents which can affect the expected costs of the adsorption process.

The Development of an Air Suction Precision Seed-Metering Device for Rice Plot Breeding

To address the lack of specialized seeding equipment and low manual seeding efficiency in rice plot breeding, this study developed an air suction precision seed-metering device for rice plot breeding, featuring automatic seed-switching and seed-clearing functions controlled by an STM32 microcontroller. Firstly, based on morphological analysis and MATLAB image processing, an active contour method was used to construct a suction hole model. Secondly, to meet the non-contaminated switching requirements between rice varieties, an electrically controlled seed-switching and seed-clearing mechanism was developed based on QR code-based precise recognition and positioning. Using 10 rice varieties as experimental materials, performance tests were conducted. The results showed that the seed-switching mechanism had single and cumulative errors under 0.4°, and the seed-clearing rate reached 100% with an average clearing time below 0.88 s. At a rotational speed of 20 r·min−1 and negative pressure of 3200 Pa, seed-filling performance was optimal for all rice varieties. Among them, the rice variety Nayou 6388 exhibited the best seed-filling performance, with a 0.8% missing seed rate, 97.6% single and double seed rate, and 1.6% multiple seed rate. In double-row coordinated tests, each seed-metering device independently completed seed switching and maintained synchronized operation, meeting agronomic requirements for accurate seed switching/clearing and precision seed filling in rice plot breeding.

Dynamic analysis of prismatic auxetic trigonometric rotating blades integrated by GNPs-reinforced layers

This study presents a comprehensive investigation into the free vibration behavior of rotating prismatic sandwich blades with linearly varying thicknesses. The blade structure features an auxetic core and graphene nanoplatelet (GNP)-reinforced composite face sheets. Various GNP dispersion patterns—uniform and functionally graded—are considered along the blade height. Due to the anisotropic and spatially varying nature of the material reinforcement, stress transformation techniques are applied at specific angles to determine the effective material properties. The governing equations of motion are derived using Hamilton’s principle and the variational approach, incorporating the effects of geometric nonuniformity and material gradation. These equations are numerically solved using the generalized differential quadrature method (GDQM), a high-accuracy numerical technique suitable for such complex systems. Parametric studies are conducted to examine the influence of transformation angle, GNP distribution pattern, auxetic geometry, rotational speed, and structural geometry on the natural frequencies. The results provide valuable insights for the optimized design of high-performance rotating structural components.

A Study on the Transient Flow Characteristics of Pump Turbines Across the Full Operating Range in Turbine Mode

The transient operation of pump turbines generates significant flow-induced instabilities, prompting a comprehensive numerical investigation using the SST k − ω turbulence model to examine these instability effects throughout the complete operating range in turbine mode. This study specifically analyzes the evolutionary mechanisms of unsteady flow dynamics under ten characteristic off-design conditions while simultaneously characterizing the pressure fluctuation behavior within the vaneless space (VS). The results demonstrate that under both low-speed conditions and near-zero-discharge conditions, the VS and its adjacent flow domains exhibit pronounced flow instabilities with highly turbulent flow structures, while the pressure fluctuation amplitudes remain relatively small due to insufficient rotational speed or flow rate. Across the entire turbine operating range, the blade passing frequency (BPF) dominates the VS pressure fluctuation spectrum. Significant variations are observed in both low-frequency components (LFCs) and high-frequency, low-amplitude components (HF-LACs) with changing operating conditions. The HF-LACs exhibit relatively stable amplitudes but demonstrate significant variation in the frequency spectrum distribution across different operating conditions, with notably broader frequency dispersion under runaway conditions and adjacent operating points. The LFCs demonstrate significantly higher spectral density and amplitude magnitudes under high-speed, low-discharge operating conditions while exhibiting markedly reduced occurrence and diminished amplitudes in the low-speed, high-flow regime. This systematic investigation provides fundamental insights into the flow physics governing pump-turbine performance under off-design conditions while offering practical implications for optimizing transient operational control methodologies in hydroelectric energy storage systems.

Design and Performance Verification of a Novel Eccentric Rotational Cutting Tool for Removal of Vascular Calcification Tissue

Cardiovascular disease is the leading cause of human mortality, and calcified tissue blocking blood vessels is the main cause of major adverse cardiovascular events (MACE). Rotational Atherectomy (RA) is a minimally invasive catheter-based treatment method that involves high-speed cutting of calcified tissue using miniature tools for removal. However, the cutting forces, heat, and debris can induce tissue damage and give rise to serious surgical complications. To enhance the effectiveness and efficiency of RA, a novel eccentric rotational cutting tool, with one side comprising axial and circumferential staggered micro-blades, was designed and fabricated in this study. In addition, a series of experiments were conducted to analyze their performance across five dimensions: tool kinematics, force, temperature, debris, and surface morphology of the specimens. Experimental results show that the force, temperature and debris size of the novel tool were well inhibited at the highest rotational speed. For the tool of standard clinical size (diameter 1.25 mm), the maximum force is 0.75 N, with a maximum temperature rise in the operation area of 1.09 ℃. Debris distribution followed a normal distribution pattern, with 90% of debris measuring smaller than 9.12 μm. All tool metrics met clinical safety requirements, indicating its superior performance. This study provides a new idea for the design of calcified tissue removal tools, and contributes positively to the advancement of RA.

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.

Discrete Element Method Modeling of an Extrusion Process with Recirculation for Dry Manufacturing of Lithium‐Ion Battery Electrodes

Herein, a computational modeling study is reported to enhance the understanding of the solvent‐free extrusion process employed to produce filaments for the 3D printing of lithium‐ion battery electrodes. This study is supported by a newly developed dynamic, 3D‐resolved numerical model, designed as a methodological framework to explore mesoscopic particle dynamics in a twin‐screw extruder (TSE). Based on the discrete element method, this granular model accounts for the main features of the TSE, allowing the simulation of several recirculation cycles and extrusion of active material, carbon additive, and binder mixtures. This study also discusses how different electrode material formulations, material injection sequences, twin‐screw rotation speeds, and residence time in the extruder barrel affect the microstructure and particle distribution of the extruded filament. Finally, parameters including the porosity, tortuosity factor, effective diffusivity, and electrical conductivity of the filament microstructures are calculated.

Control of an autonomous wind energy conversion system based on doubly fed induction generator supplying a non-linear load

Introduction. Nowadays, many researches are being done on wind turbines providing electrical energy to a stable power grid by via a doubly fed induction generator (DFIG), but the studies on the autonomous networks are rare, due the difficulty of controlling powers often close to the nominal power of the generator. Goal. This paper presents a variable speed constant frequency (VSCF) autonomous control system to supply isolated loads (linear or non-linear). The main objective is the design of an effective strategy to reduce harmonic currents induced via the non-linear loads such as rectifier bridge with 6 diodes. The novelty of the work consists in study of system composed of a DFIG providing energy by his stator to a stand-alone grid. It uses a static converter connected to the rotor allowing operation in hypo and hyper synchronism. A permanent magnet synchronous machine (PMSM) connected to a wind turbine supplies this converter, that is sized proportionately to the variation range of the necessary rotational speed. In the case of linear loads there is no problem, all desired parameters are well controlled but in the non-linear loads case such as rectifier bridge with 6 diodes there is the harmonic problem. For this purpose, to reduce this harmonic, the proposed solution is the installation of a LC filter. Methods. The DFIG is controlled to provide a constant voltage in amplitude and frequency independently of the grid load or the drive turbine speed. This command is vector control in a reference related to the stator field. The stator flux is aligned along the d axis of this landmark allowing thus the decoupling of the active and reactive stator powers of DFIG. The DFIG is controlled by an internal control loop of rotor flux and an external control loop of output stator voltage. We present also the control of the PMSM and the DC bus of the converter. The PMSM is controlled by an internal control loop of the current and an external control loop of the continuous bus of the converter according to its nominal value. The control system of wind generator based on the maximum power point tracking and the control of bus continuous at output rectifier knowing that the non-linear loads introduce high harmonic currents and disrupt the proper functioning of the system. The installation of a LC filter between the stator and the network to be supplied reduce harmonics. Results. Simulation results carried out on MATLAB/Simulink show that this filter allows obtaining a quasi-sinusoidal network voltage and it also has the advantage of a simple structure, a good efficiency and a great performance. This proves the feasibility and efficiency of the proposed system for different loads (linear or non-linear). Practical value. This proposed system is very performing and useful compared to others because it ensures the permanent production of electricity at VSCF to feed isolated sites, whatever the load supplied (linear or non-linear), without polluting the environment so that the use of wind energy is very important to reduce the greenhouse effect. References 34, figures 9.

Development, construction, and validation of a ship propeller test rig for open-water testing

ABSTRACT This work presents the development and validation of a test rig for open-water propeller testing, designed for use in the towing tank at the University of Applied Sciences Emden/Leer. The goal was to create a cost-efficient, modular, and precise system capable of measuring thrust, torque, and rotational speed. The propeller is based on the Wageningen B-series and manufactured using additive techniques with varying layer heights. To assess the structural behaviour, a truss support structure was designed and analyzed using both FEM tools and analytical methods, including Castigliano's theorem for stiffness verification. Several sets of repeated measurements were carried out under submerged (in-water) and dry (bench) conditions; the resulting data were used to derive correction factors that compensate for system-related losses. The flow behaviour around the test rig was observed at increasing propeller speeds, revealing vortex formation and turbulence at higher rpm. Validation against Wageningen reference data showed mean absolute relative errors of approximately 11% for torque, 10% for power, and 18% for thrust in the operative range (300–500 rpm). The test rig thus delivers reliable and reproducible data for further research in hydrodynamics and propulsion efficiency.