Rotor Size Research Articles

Discussion on bending-torsion behavior of long wind turbine blades

In recent years there has been a tendency to increase the size of wind turbine rotors, particularly when considering offshore applications, leading to more capacity for energy extraction from wind. However, there are many engineering challenges to that. Blades become very long, surpassing lengths of 100 meters, and are usually very flexible, which claims a geometrically nonlinear model for evaluation of their structural behavior. In this context, the present work employs an enhanced structural solver to evaluate the behavior of very flexible wind turbine blades. The blades are modeled as beams. Large displacements and finite rotations are assumed to model the kinematics by employing the geometrically-exact theory. To establish a relationship between generalized internal loads and generalized strains we adopt a linear constitutive model such that one can take results from BECAS, directly. This can handle torsion-bending constitutive coupling for a general position of the beam axis, conveniently. The developed solver was used to study general operational conditions, assuming distinct pitch angles for the blade considering the scenario of the wind turbine. The present work brings discussions on the structural behavior, such as internal loads distributions along the blade spam in numerical simulations. The focus is given to the analysis of bending and torsion moments, discussing their aspects when considering such a long and flexible blade in operational conditions.

A Comparison of a Three Blade and Five Blade Wind Turbine in Terms of the Mechanical Properties Using the Q-Blade Software

يمكن لتوربينات الرياح المنتشرة في مزارع الرياح على نطاق المرافق أن تدعم تلبية رغبات الطاقة المستقبلية وتقليل انبعاثات ثاني أكسيد الكربون عن طريق تقليل متطلبات الطاقة من الوقود الأحفوري. مع ارتفاع درجة حرارة الهواء على مدار اليوم، تزداد سرعة الرياح بسبب تدرجات درجة الحرارة، والتي تنتج تدرجًا في الكثافة / الضغط، مما يؤدي إلى حركة الهواء التي تواجهها توربينات الرياح. اعتمادًا على تضاريس الأرض، يمكن أن تواجه الرياح وتوجه في الوديان بين التلال وفوقها حيث تتدفق وتتبع منحنيات الأرض. تنتج هذه التضاريس زيادة في سرعة الرياح في القمم والتلال. في هذا العمل، تم تصميم شفرة دوار توربينات الرياح الأفقية الصغيرة للعمل في ظل سرعة الرياح المنخفضة، باستخدام برنامج (Q-Blade). استنادًا إلى نظرية عنصر الشفرة (BEM). مع الجنيح NACA3712. تم استخدام دوار ثلاثي الشفرات ودوار بخمس شفرات بناءً على نوع التوربين وحجم الدوار لتوليد الطاقة الميكانيكية من طاقة الرياح. تم إجراء مقارنة وتحليل قوة التوربين ومعامل القدرة ومعامل عزم الدوران عند سرعة رياح منخفضة ((1m/s-8m/s وتم الحصول على نتائج دقيقة للغاية. وجد أن أفضل أداء يمكن أن يعمل فيه دوار توربيني ثلاثي الشفرات بقدرة توربينية تبلغ (955W) كما تم الحصول على قدرة التوربين ((582W للدوار خماسي الشفرات. وجد أن تصميم توربينة رياح أفقية صغيرة بخمس ريش أفضل من التوربين بثلاث ريش ومناسب للعمل في المناطق ذات سرعة الرياح المنخفضة وبكفاءة عالية مقارنة بحجم التوربين.

Improving cross-axis wind turbine performance: A Lab-scale investigation of rotor size and blades number

Horizontal and vertical-axis wind turbines have long been used to generate electricity in open areas by utilizing horizontal wind flow. Under certain conditions, for example in multi-storey building areas, wind flows not only from horizontal but also vertical directions. Therefore, this research aims to develop a new turbine model known as a cross-axis to capture wind flow from horizontal and vertical directions around multi-storey buildings. Design, production, testing, and performance analysis are carried out in this project. The model is designed with a rotor diameter of 700 mm which has 5 vertical blades and 10 horizontal blades with a total height of 600 mm which is divided into two configurations, upper and lower. Performance analysis was carried out using a wind tunnel in a conditioned laboratory both in loaded and unloaded conditions. The output power of the wind turbine is measured using an electric dynamometer. The no-load test was applied to determine the time required to move from non-rotating to constant rotation at different speeds and horizontal blade angles. Meanwhile, the load test is used to determine the power coefficient at various speeds, horizontal blade pitch angles, and loads. The research results show that the time required to move from a non-rotating speed to a constant speed is influenced by the wind speed and the blade pitch angle. The power coefficient was also observed to be influenced by wind speed, blade pitch angle, and load. Furthermore, the shortest time to reach a constant rotation speed is around 20 seconds at a wind speed of 7.6 m/s and a blade pitch angle of 25°. The maximum power coefficient of the wind turbine was obtained at 5.2% at a wind speed of 7.6 m/s, blade pitch angle of 25°, and tip speed ratio of 0.5.

Real-time hybrid test method for floating wind turbines: Focusing on the aerodynamic load identification

Since the development of floating wind turbine (FWT) shows a rapid trend towards larger capacity and larger rotor size, the traditional full-model basin test method has encountered limits. Especially the balance between the wind generation system (WGS) size and scale ratio of the model FWT system. Under such circumstances, the hybrid model test method provides the possibility to improve the FWT model test. In the hybrid model test method, the original physical model system is divided into physical subsystem and numerical subsystem, and the data acquisition and process module between the 2 subsystems plays an important role. In this paper, a framework of real-time hybrid test (RTHT) system is setup firstly, which combines physical model wind turbine and motion platform. The damping modification to the corresponding numerical code is applied to improve the motion calculation accuracy. Delay implementation is employed to avoid motion divergence. Then a simulation loop is setup in numerical environment to study the identification of aerodynamic load. The influence of identification accuracy to the RTHT result is analyzed. Lastly, the dual-accelerometer method of aerodynamic load identification is employed in the proposed RTHT system. Decay tests and irregular wave only tests are carried out to validate the aerodynamic load identification method. The capability and potential of the RTHT method of floating wind turbine model test is preliminary proved in the work of this paper.

Solid-State NMR 13C sensitivity at high magnetic field

Sensitivity is the foundation of every NMR experiment, and the signal-to-noise ratio (SNR) should increase with static (B0) magnetic field, by a proportionality that primarily depends on the design of the NMR probe and receiver. In the low B0 field limit, where the coil geometry is much smaller than the wavelength of the NMR frequency, SNR can increase in proportion to B0 to the power 7/4. For modern magic-angle spinning (MAS) probes, this approximation holds for rotor sizes up to 3.2 mm at 14.1 Tesla (T), corresponding to 600 MHz 1H and 151 MHz 13C Larmor frequencies. To obtain the anticipated benefit of larger coils and/or higher B0 fields requires a quantitative understanding of the contributions to SNR, utilizing standard samples and protocols that reproduce SNR measurements with high accuracy and precision. Here, we present such a systematic and comprehensive study of 13C SNR under MAS over the range of 14.1 to 21.1 T. We evaluate a range of probe designs utilizing 1.6, 2.5 and 3.2 mm rotors, including 24 different sets of measurements on 17 probe configurations using five spectrometers. We utilize N-acetyl valine as the primary standard and compare and contrast with other commonly used standard samples (adamantane, glycine, hexamethylbenzene, and 3-methylglutaric acid). These robust approaches and standard operating procedures provide an improved understanding of the contributions from probe efficiency, receiver noise figure, and B0 dependence in a range of custom-designed and commercially available probes. We find that the optimal raw SNR is obtained with balanced 3.2 mm design at 17.6 T, that the best mass-limited SNR is achieved with a balanced 1.6 mm design at 21.1 T, and that the raw SNR at 21.1 T reaches diminishing returns with rotors larger than 2.5 mm.

Development of a portable small wind turbine for integration into a mobile cooling technology

In this study, a small wind turbine prototype was developed to provide electric power for a mobile cooling unit The aim of this study was to design and develop a 600-W small wind turbine that can generate electric energy to power a mobile cooling unit used for the storage of fruits and vegetables, mainly for the benefit of smallholder farmers. Smallholder farmers suffer from high postharvest losses, approximated at 50%, some of which can be avoided by using efficient low-cost cooling units, rather than open transport. Cooling slows down the metabolic rate which consequently extends the produce's shelf life and prevents spoilage, allowing farmers to provide high-quality produce to the market. This could potentially increase the farmers’ monetary returns. The study was conducted in KwaZulu-Natal on the road that stretches between Pietermaritzburg and Estcourt. The wind turbine is made of a 600-mm-diameter rotor with three PVC blades, a permanent magnet synchronous generator, a bridge rectifier, a 230-V AC inverter and a battery for energy storage. The wind turbine was tested against three vehicle speeds of 60, 80, and 100 km h−1, and the two opening levels, level 1 at 45∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} and level 2 at 80∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ$$\\end{document} relative to the louvre mechanism frame. The results of this study revealed that the power generated by the wind turbine is greatly influenced (p < 0.001) by both the vehicle travelling speed and louvre opening level. The power output of 113.4, 159.6 and 210.0 W per hour was observed for the vehicle speeds of 60, 80 and 100 km h−1, respectively, on louvre opening level 1. The power output of 142.8 W h−1, 268.8 W h−1 and 294.0 W h−1 were observed for a wind speed of 60 km h−1, 80 km h−1, and 100 km h−1, respectively, on Louvre opening level 2. This shows that higher wind speeds (vehicle speeds) produce high-power output which accounts for the small size of the wind turbine rotor. A maximum power coefficient of 0.49 was achieved for this study. The wind turbine can generate the power required to run a cooling technology to a limited extent, thus must have a backup power supply from the diesel engine or be used in a hybrid system.

Multiscale-simulation method for the wear behaviour of planetary journal bearings in wind turbine gearboxes

Wind energy is one of the most important renewable energy sources. To maintain competitiveness wind energy needs to be cost effective. Increasing the performance of wind turbines can help to reduce the total cost of wind energy. The power output can be increased by an increase in turbine rotor size since the power increases disproportionately with the rotor diameter. The increase in rotor size inherently comes with an increase in overall wind turbine size to cope with the increasing loads. Since the nacelle weight cannot be increased without limitation, e.g. due to the effect on the tower and costs, an increase in power density is necessary. The usage of journal bearings instead of rolling bearings for the application in planetary gearboxes in wind turbines is one way to increase the power density and reliability of the drivetrain. When designed and operated correctly, journal bearings have a longer service lifetime than rolling bearings. Wear simulations aid in the design of journal bearings. This work presents a simulation method for the wear prediction of planetary journal bearings in wind turbine gearboxes. The method is validated with measurements on a component test rig. The transfer to the wind turbine gearbox is shown by means of simulation.

Hierarchical sensitivity study on the aeroelastic stability of the IEA 15 MW reference wind turbine

Increased rotor size and blade flexibility are leading to new stability characteristics for current and future wind turbines. Numerical aeroelastic models are an essential tool to understand these new mechanisms and to design next-generation wind turbines suitably. A comprehensive understanding of how model input parameters influence the stability analysis will enhance the confidence in these simulations. This article presents a study on the sensitivity of uncertain parameters on aeroelastic stability predictions of the IEA 15 MW turbine model in HAWCStab2. It uses a hierarchical approach to handle the large number of investigated model parameters. Relevant uncertainties are identified through one-at-a-time and elementary effects analyses first. The remaining parameters are fed into a variance-based uncertainty quantification (UQ), that employs polynomial chaos expansion representations as surrogates for a full nonlinear description of the sensitivities. A robust post-processing of the stability analysis results is the main challenge of the presented methodology, but it is shown how the UQ process can still be used to explore the parameter space effectively. The presented study shows that the structural blade properties have the highest sensitivity and that a set of relatively small parameter variations can lead to unstable behavior of the reference model.

Low-Voltage High-Frequency Lamb-Wave-Driven Micromotors.

By leveraging the benefits of a high energy density, miniaturization and integration, acoustic-wave-driven micromotors have recently emerged as powerful tools for microfluidic actuation. In this study, a Lamb-wave-driven micromotor is proposed for the first time. This motor consists of a ring-shaped Lamb wave actuator array with a rotor and a fluid coupling layer in between. On a driving mechanism level, high-frequency Lamb waves of 380 MHz generate strong acoustic streaming effects over an extremely short distance; on a mechanical design level, each Lamb wave actuator incorporates a reflector on one side of the actuator, while an acoustic opening is incorporated on the other side to limit wave energy leakage; and on electrical design level, the electrodes placed on the two sides of the film enhance the capacitance in the vertical direction, which facilitates impedance matching within a smaller area. As a result, the Lamb-wave-driven solution features a much lower driving voltage and a smaller size compared with conventional surface acoustic-wave-driven solutions. For an improved motor performance, actuator array configurations, rotor sizes, and liquid coupling layer thicknesses are examined via simulations and experiments. The results show the micromotor with a rotor with a diameter of 5 mm can achieve a maximum angular velocity of 250 rpm with an input voltage of 6 V. The proposed micromotor is a new prototype for acoustic-wave-driven actuators and demonstrates potential for lab-on-a-chip applications.

An aero-structure-acoustics evaluation framework of wind turbine blade cross-section based on Gradient Boosting regression tree

Under the rapid development of wind turbines, the rotor size has substantially increased in recent years. To meet the key design criteria, finding a trade-off between aerodynamic, structure and noise (ASN) impact becomes a challenging problem. The blade cross-section is the basic element of the blade, its outer contour is the airfoil profile that produces aerodynamic loads as well as noise, and the inner part is the supporting composite material that provides enough stiffness to balance the loads. Modifying local blade sections can adjust the rotors’ overall performance. However, in the work of blade-combined ASN optimization, the iterative process using traditional numerical simulation methods becomes extremely heavy. In this study, a sustainable database is created based on a large number of calculations of aerodynamic, structural and noise attributes at various cross-sections. Then a platform named AFML (Airfoil machine learning) for simultaneously predicting the comprehensive performance of the cross-section is constructed by using the integrated Gradient Boosting Regression Tree algorithm. Results show that the prediction accuracy of AFML is acceptable even for unseen inflow conditions. By calling the pre-trained AFML, ASN data of the cross-section can be immediately obtained, and the blade shape and inner structure can be updated quickly.

An approach for cost and configuration optimization of horizontal axis wind turbine (HAWT)

In addition to the environmental advantage of wind turbines, the modern wind turbine design is aiming to become more competitive by minimizing the cost of energy (COE). When evaluating any change to the design of a wind turbine, it is critical that the designer evaluates the impact of the design change on the system cost and performance. A typical problem when start a wind turbine design project is to determine the optimum configuration and operation parameters to minimize COE. In this article an optimization approach is adopted using COE as objective function with the rotor size, power rating and rated rotational velocity (RPM) as design variable. The cost of energy model of the National Renewable Energy Laboratory (NREL) is adopted with modifications to include the main components load level effects on the COE. An aerodynamic blade design is developed and used as base for evaluating the rotor performance. The blade is scaled to present different rotor size and operating conditions for each power rating. Analysis tool is developed to consider coupled interactions between power rating and the rotor size. The Blade Element Momentum (BEM) technique is used to evaluate the effect of configuration and operational conditions on the wind turbine load levels and the expected annual energy production (AEP). These are used as inputs for the proposed COE model in addition to main parameters presenting the manufacturing technology and site conditions. The COE model is based on several elements such initial capital cost (ICC), balance of station (BOS), operations and maintenance (O&amp;M), levelized replacement cost (LRC), AEP and design load levels. A pattern search technique is adopted for the optimization and the approach is illustrated by means of a principle test examples for two types of turbines platform one for low wind onshore site and another for high wind offshore site.

Using acoustic emission for condition monitoring of the main shaft bearings in 4-point suspension wind turbine drivetrains

ABSTRACT The continuous growth of wind power technology makes condition monitoring of wind turbine components crucially important for their operational efficiency. The main shaft bearings in wind turbines have been identified as one of the most critical components in the system, especially with the ongoing increase in rotor size and weight. This increase made the 4-point suspension drivetrain more preferable. In this study, we present a novel approach for condition monitoring of the main shaft bearings in a 2 Megawatt wind turbine with 4-point suspension drivetrain using primarily acoustic emission (AE). The focus was on the analysis of time and frequency domains of the AE signal, where the dominant frequency of each AE hit was identified and plotted back in the time domain to create the so-called dominant frequency map in specific time intervals for each bearing. A comparison between the two dominant frequency maps of the two bearings gives valuable insights into the condition of the two bearings. The distinctive nature of the dominant frequency bands in the dominant frequency maps presented promising potential for this method. The presented method is straightforward and can be automated and then integrated into a planned predictive maintenance programme for this wind turbine.

Effects of blade torsion on IEA 15MW turbine rotor operation

The increase in the size of wind turbine rotors in recent decades necessitates investigations into aeroelastic behavior and its influence. This work proposes the computational modeling and the subsequent dynamic study of the rotor of the IEA Wind TCP Task 37 reference wind turbine of 15MW, considering different torsional stiffness and wind speed conditions. Sensitivity studies regarding the wind conditions and the torsional stiffness of the blades on the overall operation were carried out. It was verified that at nominal wind speed, the original torsional stiffness led to a reduction in the thrust on the rotor, the flapwise displacement at the blade tip, and the peaks of flapwise curvature at the blade root compared to the amplified stiffness. Referring to different wind speeds, simulations using the original torsion stiffness revealed a considerable decrease in generator torque with the expected in the high wind speed region, in contrast to the amplified stiffness. It is also noteworthy that the peak shaving process is affected by the amplified blade torsional stiffness, as it can lead to excessive adjustments due to smaller cut regions and thrust values. Consequently, a new pitch curve was proposed, taking into account the desired generator torque.

Scaling Challenges for Conical Plain Bearings as Wind Turbine Main Bearings

Wind energy is an important renewable energy source. Rotor main bearings are critical components of wind turbines since a faulty main bearing leads to downtime and high repair costs. Operational expenditures amount to 32% of wind energy costs. The use of plain bearings as main bearings can potentially reduce these costs. Plain bearings with segmented sliding elements can be repaired up-tower without dismantling the drivetrain, as damaged segments can be exchanged individually. One such segmented plain bearing design is the conical plain bearing design called FlexPad. For the FlexPad, proof of concept was achieved for the 1 MW range during previous studies. Modern wind turbines—especially for offshore deployment—have increased in size significantly compared with their predecessors. The goal of current studies is to transfer the FlexPad design towards a main bearing unit at a market relevant scale of 8.5 MW. In this work, the identified scaling challenges are presented. A FlexPad model scaled to the 8.5 MW range is presented to illustrate the challenges. The bearing load components, such as radial forces and torque, increase on different scales with increasing rotor size leading to changed load characteristics with increasing size. Increased rotor weight and bearing diameters result in an increase in the breakaway torque required to start turbine rotation. This breakaway torque can exceed the torque generated by the turbine at starting wind speeds. The generally increased loads necessitate stiffer sliding segments leading to the increased weight of the segments, which hampers the ability to easily exchange segments.

A techno‐economic assessment and optimization of Dumat Al‐Jandal wind farm in Kingdom of Saudi Arabia

AbstractOne major criterion in the selection of wind farm location is the cost of energy (COE). COE is the cost of producing 1 kWh electric energy on an annual basis. Mathematical model of COE includes site‐specific constants (such as reference height, mean wind speed, shape factors, wind shear coefficient, average temperature, and turbine altitude) and wind turbine parameters (such as maximum power coefficient, total loss of energy, cut‐in/cut‐off wind speed, rated wind speed, rated power, and the fix charge rate). In this work, we evaluate the COE of an onshore wind farm located at Dumat Al‐Jandal (Saudi Arabia) according to the hub height and rotor size. The 99 Vestas turbines can be mounted at a hub height ranging from 105 to 166 m with available rotor diameters of 105, 112, 117, 126, 136, 150, 155, or 163 m. Particle swarm optimization with a normal distribution is used to optimize the COE. Results show that COE is varying around the average value of $0.029335/kWh by ±$0.00021/kWh. The minimum COE was achieved with a rotor diameter of 150 m at hub height of 105 m. COE increases with the increase of hub height. At 105 m‐hub height, COE is almost the same, with a variation of 0.03% (It ranges between $0.029125/kWh and $0.029133/kWh). COE is more sensitive to rotor size than hub height. This investigation revealed that the COE estimation is in a range of 39%–48% greater than that announced COE by the developing project consortium.

Effect of the vertical wake deflection on the response of a 12MW semisubmersible FWT

The need to understand the interaction of floating wind turbines operating in the marine boundary layer with other surrounding turbines is of increasing importance as wind farms and rotor sizes get larger. For low wind speed conditions, the wake deflects upwards due to the floating wind turbine built-in rotor tilt and the platform pitch angle. Furthermore, based on field data from the North Sea, a convective atmosphere is likely to occur, especially for lower wind speeds. It is therefore key to understand the combined effect of meandering, wake deflection and atmospheric stability for low wind speed conditions on the floating wind turbines in a wind farm.In this work, to account for atmospheric stability, data from large-eddy simulation (LES) for a 7.5m/s wind speed scenario and three atmospheric stability conditions, are used as input to FAST. Farm to study the effect of the wake deflection upwards on a 12 MW semisubmersible placed 8 rotor diameters (D) downwind of a stationary wind turbine. Three built-in shaft tilt angles cases are considered for the fixed upwind turbine: 12°, 6° and no tilt angle. The main effects of the wake deflection are on the power output of the floating wind turbine in the wake, and on the tower top yaw moment. For stable conditions, the mean tower top yaw moment increases by more than three times. The findings of this work contribute to the investigation of the wake deflection as a control strategy to minimize wake losses in floating wind farms.

Modification, Simulation and Demonstration of Laboratory Scale Pelton Turbine for Waterfall Hydropower Plant

To demonstrate the concepts of using waterfall hydropower to generate energy, a Mini-Laboratory Pelton Turbine (MLPT) was designed and simulated. The principle of energy conversion from potential energy of water at high elevation to kinetic energy at lower elevation through gravity fall was used. To achieve relative continuity of supply as in waterfall, a centrifugal pump was used to deliver water into a set of three reservoirs positioned at different heights. Water from the reservoirs through pipes of different diameters was used to drive the pelton Wheel turbine. A pipe matrix that allows combination of water from two or three sources at different heights and different pipe diameters was designed to demonstrate principle of conservation of flow at a junction. In the laboratory scale design, a power of 750 W was targeted. The required flow rates from different heights of reservoirs to deliver the power were used to establish nozzle diameters, rotor size, rotational speeds and power coupling ratios. A simulation of the model was conducted with different heights, pipe diameters and flow combinations using pipe matrix, were conducted using Matlab Simulink environment. The results showed that the velocity of flow under gravity increases with height of water and the force and torque associated with the flow rate increase with flow area and height of water. The sum of flows from matrix pipes was always found to be conserved with a variance of 0.27. For water heights of 7, 9 and 11 m, the nozzle diameter was found to be 19.0, 25.4, and 38.1 mm and the corresponding jet velocities were 11.2, 12.5, and 13.8 m/s. The flow rates for the scenarios were 0.0026, 0.0046 and 0.0103 m3/s. The optimum wheel diameter was 313 mm with a power coupling of 5.6:1. Compared to other models [27, 35] from the direct use of jets from pumps, the results have similar characteristics and geometric profiles. The average velocity is lower but, flow rate is higher due to the influence of larger cross sectional area. Thus, it is possible to produce the same power output using lower pressure heads when flow rate is optimized using nozzle diameter to compensate loss in velocity. Such systems can be used to harness most of the low head waterfall in Nigeria. However, the possibility of harnessing waterfalls to generate electricity for low energy demand such as recreation centers and farm settlements is faced with problem of hard-to-reach water source due to topographic complexities.

A FEM-Based Comparative Study of the Effect of Rotor Bar Designs on the Performance of Squirrel Cage Induction Motors

Induction motors (IM) are the most frequently used type of motor in the industry. The number of rotor slots, bar geometry, and conductivity of bar material have a strong impact on the torque profile and efficiency characteristics of induction motors. This study focused on investigating the effect of different rotor bar designs on motor performance by the finite element method (FEM). The IMs have been designed using the same stator core, winding, and core lengths. The total rotor bar cross-section areas are also fixed throughout all designs. In addition to the change in the number of rotor bars and geometry, the effect of copper and aluminum bar materials on motor performance was also investigated, both for single and double-layered squirrel-cage structures. The results of the study indicate that the starting torque of the motor in a 36/30-slot aluminum single-cage structure was obtained as 96.26 Nm, while the starting torque of a 36/46-slot aluminum double-cage structure was found to be 115.34 Nm. It is also found that the starting torque of the initial design can be increased by up to 19.82% by changing only the rotor bar numbers and material with the same stator and rotor size. The efficiency of the motors was determined as 86.6% for both designs. In addition to efficiency, the output torque ripple has been decreased to 2.63, which equals a 67.32% decrease in the ripple of the initial design. The improved design has an approximately 8 °C lower T2 due to better cooling performance as a result of a higher number of rotor slots.

Development and validation of a mathematical model for evaluating shear-induced damage of von Willebrand factor

PurposeTo develop a mathematical model for predicting shear-induced von Willebrand factor (vWF) function modification which can be used to guide ventricular assist devices (VADs) design, and evaluate the damage of high molecular weight multimers (HMWM)-vWF in VAD patients for reducing clinical complications. MethodsMathematical models were constructed based on three morphological variations (globular vWF, unfolded vWF and degraded vWF) of vWF under shear stress conditions, in which parameters were obtained from previous studies or fitted by experimental data. Different clinical support modes (pediatric vs. adult mode), different VAD operating states (pulsation vs. constant mode) and different clinical VADs (HeartMate II, HeartWare and CentriMag) were utilized to analyze shear-induced damage of HMWM-vWF based on our vWF model. The accuracy and feasibility of the models were evaluated using various experimental and clinical cases, and the biomechanical mechanisms of HMWM-vWF degradation induced by VADs were further explained. ResultsThe mathematical model developed in this study predicted VAD-induced HMWM-vWF degradation with high accuracy (correlation with experimental data r2 > 0.99). The numerical results showed that VAD in the pediatric mode resulted in more HMWM-vWF degradation per unit time and per unit flow rate than in the adult mode. However, the total degradation of HMWM-vWF is less in the pediatric mode than in the adult mode because the pediatric mode has fewer times of blood circulation than the adult mode in the same amount of time. The ratio of HMWM-vWF degradation was lower in the pulsation mode than in the constant mode. This is due to the increased flushing of VADs in the pulsation mode, which avoids prolonged stagnation of blood in high shear regions. This study also found that the design feature, rotor size and volume of the VADs, and the superimposed regions of high shear stress and long residence time inside VADs affect the degradation of HMWM-vWF. The axial flow VADs (HeartMate II) showed higher degradation of HMWM-vWF compared to centrifugal VADs (HeartWare and CentriMag). Compared to fully magnetically suspended VADs (CentriMag), hydrodynamic suspended VADs (HeartWare) produced extremely high degradation of HWMW-vWF in its narrow hydrodynamic clearance. Finally, the study used a mathematical model of HMWM-vWF degradation to interpret the clinical statistics from a biomechanical perspective and found that minimizing the rotating speed of VADs within reasonable limits helps to reduce HWMW-vWF degradation. All predicted conclusions are supported by the experimental and clinical data. ConclusionThis study provides a validated mathematical model to assess the shear-induced degradation of HMWM-vWF, which can help to evaluate the damage of HMWM-vWF in patients implanted with VADs for reducing clinical complications, and to guide the optimization of VADs for improving hemocompatibility.

3D-Printable centrifugal devices for biomolecular solid state NMR rotors

The advent of magic angle spinning (MAS) rates exceeding 100 kHz has facilitated the acquisition of 1H-detected solid-state NMR spectra of biomolecules with high resolution. However, challenges can arise when preparing rotors for these experiments, due to the physical properties of biomolecular solid samples and the small dimensions of the rotors. In this study, we have designed 3D-printable centrifugal devices that facilitate efficient and consistent packing of crystalline protein slurries or viscous phospholipids into 0.7 mm rotors. We demonstrate the efficacy of these packing devices using 1H-detected solid state NMR at 105 kHz. In addition to devices for 0.7 mm rotors, we have also developed devices for other frequently employed rotor sizes and styles. We have made all our designs openly accessible, and we encourage their usage and ongoing development as a shared effort within the solid state NMR community.