Maximum Rotational Speed Research Articles

Theoretical investigation and optimization of rotation sensing in the new photonic crystal gyroscope based on the Sagnac effect using nonlinear photonic resonators

In this research, the angular rotation speed in a passive photonic gyroscope based on the combination of side nanoring resonators and compensating waveguides has been analyzed by creating nonlinear effects in the control factors of the rings using the Sagnac effect. This structure consists of a central waveguide, two identical square resonators, and an almost U-shaped waveguide. The U-shaped waveguide causes coupling between the two resonators in a counterclockwise (CCW) mode. In this structure, a phase shift has been created in the output from the interference of two clockwise (CW) and CCW waves inside the resonators, and according to this phase shift and the central wavelength, the angular rotation speed has been estimated. In the proposed design of the gyroscope, by managing the nonlinear effects in the radius and refractive index (RI) of the coupling and inner rods, we have been able to control the changes in power, phase, and wavelength of the output from the device. With the increase in the intensity of power, the output power has an increasing slope at first, and at the point of creating a nonlinear effect in the sensor, the output power slope decreases. Also, this nonlinear effect directly affects the output phase of the structure. The maximum angular rotation speed in this gyroscope was [Formula: see text]/s. By changing the RI of the inner rods from 3.2 to 3.7, the maximum output-to-input power ratio changes from 0.38 W/[Formula: see text]m2 to 0.75 W/[Formula: see text]m2. By changing the radius of the coupling rods from 93 nm to 97 nm, the maximum power ratio decreases from 0.78 W/[Formula: see text]m2 to 0.55 W/[Formula: see text]m2. The field distribution profile and photonic bandgap in this gyroscope have been analyzed using the finite-difference time-domain (FDTD) and plane-wave expansion (PWE) methods, respectively. Also, the gyroscope has a footprint of 163.5 [Formula: see text]m2.

The relationship between the shape of SPARC rotation curves to the galactic mass model: a chi-square test of independence

Rotation curves of galaxies are strongly related to dark matter and baryonic matter. The gravitational attraction of baryonic matter, e.g., stars and gas, is the dominant force in the inner regions of galaxies, and its distribution determines the shape of the inner rotation curve. In contrast, the outer regions of galaxies are dominated by the gravitational force of dark matter, which is thought to be distributed in a spherical halo around a galaxy. Since the ratio of rotational speed in the inner regions and maximum rotational speed (η rot) is related to the shape of the galaxy rotation curve, it might be a significant association between this ratio and each combination of matters, or the mass models. Specifically, for dark matter, we assume the Navarro-Frenk-White (NFW) profile. This study explores the use of SPARC data (Spitzer Photometry and Accurate Rotation Curves) and categorizes shapes of galaxy rotation curves according to η rot. For mass models, we classify galaxies by considering the reduced chi-square of the best-fit parameter of each model. To determine whether there is a significant association between η rot and the mass models, we utilize the chi-square test of independence. The study suggests with a 95% confidence level that there is no relation between the mass models and η rot.

A Simplified Inchworm Rotary Piezoelectric Actuator Inspired by Finger Twist: Design, Modeling, and Experimental Evaluation

Inchworm rotary piezoelectric actuators (PAs) have been widely utilized in the ultraprecision rotary positioning mechanisms because of their high precision and theoretical no backward motions. Existing inchworm rotary PAs are still bothered with the complicated structures driven by at least three piezoelectric stacks (PSAs) and relatively low speed. In this study, inspired by the finger structure, we present a simplified inchworm rotary PA driven by only two PSAs. The human finger twist motion is firstly imitated and utilized to increase the rotation from one to four times in one cycle, which improves the output speed and no backward motion can be observed in the rotation curves. Under a voltage of 150 V and a frequency of 20 Hz, the actuator achieved a maximum rotation speed of 0.16 rad/s, a carrying load of 0.5 kg and an output torque of 0.05 N·m. Furthermore, this actuator achieved a high step repeatability in the large scale of 360°, whose maximum deviation is less than 0.8 mrad.

Experimental Studies of Engine Crankcase Gas Consumption D-243 With Varying Degrees of Wear of the Cylinder-piston Group

The methodology and results of the experimental studies of crankcase gas consumption in diesel engines with varying degrees of wear of the cylinder-piston group (CPG) are presented. It is shown that the rotation speed has a significant influence on the crankcase gas consumption and the load has an insignificant influence on it. It is recommended to use the idle mode at the nominal or maximum rotation speed as a diagnostic test mode to assess the technical condition of the CPG.

Noncontact rotation of a small object using an asymmetric ultrasonic field

Noncontact manipulation techniques using airborne high-intensity ultrasound can be applied in various industrial fields such as pharmaceutical industry and future space industry. This paper discusses a method to rotate a small object in the air without physical contact using ultrasound. The experimental system consists of a vibrating disc with four bolt-clamped Langevin-type ultrasound transducers and two semicircular reflectors. The flexural vibration of the disc generates an acoustic standing wave between them, and a small object can be levitated at the nodal position. By inclining one of the two reflectors, an asymmetric acoustic field and an acoustic traveling wave in the circumferential direction are generated where the object can be rotated in the clockwise or counterclockwise direction. Vector flows of the acoustic intensity in the air between the vibrator and reflectors were calculated. When the tilt angle of the reflector was 0.32°, the object was rotated without contact, and the rotation direction corresponded with the direction of the vector flows of the acoustic intensity. A greater input current gave a greater rotation speed; the maximum rotation speed of the object was 6.84 rps in the case of 1.14 A.

Dosimetric Study of Total Marrow and Lymphoid Irradiation on a Ring Gantry-Based Medical Linac with a Two-Layer Multi-Leaf Collimator

In this study, we aimed to evaluate dosimetric quality of total marrow and lymphoid irradiation (TMLI) plans for a ring gantry-based medical Linac with a two-layer multi-leaf collimator. We retrospectively retrieved treatment planning CT images, structure sets, and plan dose for four adult patients, two male and two female, who previously received TMLI treatments on helical tomotherapy (HT) at our institution. TMLI plans were optimized for a ring gantry-based medical Linac with a two-layer multi-leaf collimator (Halcyon, Varian Medical Systems, Inc., Palo Alto, CA). A prescription dose of 12 Gy in 8 fractions was prescribed to the skeletal bones from the skull to mid-thigh, spleen, spinal canal, and lymphoid volume. Five or six isocenters were placed with equal spacing along the patient's longitudinal direction in each TMLI plan with two 6-MV flattening filter-free volumetric modulated arc therapy (VMAT) fields at each isocenter. Isocenter separation ranged from 15 cm to 16.5 cm. Each VMAT field has a field size of 28 cm to 28 cm with the collimator at 90° and a full gantry rotation. The nominal dose rate was 800 MU/minute, and the maximum gantry rotation speed was 24°/sec. Institutional dosimetric constraints were used for optimization including a mean lung dose limit of less than 8 Gy. All the plans were normalized so that 85% the primary planning target volume received the prescription dose. The average mean doses to the target volumes ranged from 12.2 to 12.6 Gy in the Halcyon TMLI plans, while they ranged from 12.1 to 12.5 Gy in the HT TMLI plans. Relative to the prescription dose, the average mean dose for normal organs ranged from 21.3% to 56.6% in the Halcyon TMLI plans, while it ranged from 10.1% to 68.4% in the clinical HT plans. The difference in the average mean dose to normal organs was less than 0.5 Gy except two organs between the Halcyon and HT TMLI plans. The average median dose for normal organs ranged from 18.2% to 48.8% relative to the prescription dose in the Halcyon TMLI plans. The mean lung dose (MLD) in the Halcyon TMLI plans met the institutional limit with an average dose of 6.75±0.42 Gy (range: 6.44 - 7.36 Gy), while the average MLD was 6.54±0.77 Gy (range: 6.24 - 7.22 Gy) in the HT plans (p-value = 0.71 in the paired t-test). The average total monitor unit in the Halcyon TMLI plans was 4,425±906 MU (range: 3,470 - 5,575 MU) with an average beam-on time of 5.1±1.3 minutes (range: 4.1 - 7.0 minutes), which excludes isocenter setup time, while the average beam-on time was 22.2±3.2 minutes (range: 19.6 - 26.1 minutes) with the HT plans. Halcyon TMLI plans met our institutional dosimetric constraints with adequate normal organ sparing and target dose coverage. The beam-on time with the Halcyon plans was significantly shorter than that with the HT plans, which could lead to shorter treatment time and increased patient comfort. This study showed the feasibility of TMLI treatments on the Halcyon machine. The same method could be used for total body irradiation on Halcyon.

Optimization and decision making of guide vane closing law for pumped storage hydropower system to improve adaptability under complex conditions

The pumped storage hydropower system (PSHS) is considered a high-quality peaking and frequency regulation energy source due to its operational flexibility and fast response. However, its frequent regulation leads to complex operating conditions with potential harm to the stability of the system. This paper focuses on analyzing and improving the adaptability of guide vane closing law under complex conditions. This is obtained by proposing a refined numerical model of PSHS considering non-linear factors and analyzing the effects of the guide vane closing law and initial operating conditions on the load rejection. The results revealed that a suitable two-stage guide vane closing law effectively reduces the risk of load rejection. In addition, when the initial load of two units is different, it is beneficial to improve the load rejection characteristics when the unit with the smaller load rejects the load first. Finally, three groups of parameters for the optimal guide vane closing law (the Pareto solution sets) are obtained by multi-objective sparrow search algorithm (MOSSA) under the rated, maximum water head, and maximum rotational speed conditions. The obtained Pareto solution and the Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) are used for scoring the solutions and obtain an optimal suitable for complex operating conditions. The water head and rotational speed are reduced by an average of 7.76 % and 3.74 % for the different operating conditions compared to the model validation results, respectively. These results provide a theoretical basis for the selection of the optimal guide vane closing laws and improve the safety during load rejection under complex practical operating conditions.

Identifying the influence of blade number and angle of attack on a breastshot type waterwheel micro hydroelectric power generator using ANOVA

This study focuses on optimizing the performance of micro-hydro power generation, specifically the breastshot type waterwheel. The limited availability of non-renewable energy sources and the high cost of developing renewable energy sources in the energy sector pose challenges, making it essential to find new energy sources and improve energy efficiency. The 2004–2022 national electricity plan aims to increase electricity access in rural areas, including remote regions like Bogor Regency, where access to electricity is limited. Many residents have constructed their own micro hydroelectric power generators, but their vulnerability to natural disasters is a concern. The study investigates the potential of breastshot waterwheel technology for micro hydroelectric power generation. The study involved testing a micro hydro power plant with 6, 8, and 10 blades and blade angles of 0°, 30°, and 45°. The current research focuses on performance optimization, including the use of ANOVA analysis to know the significant impact of blade number and angle on the waterwheel’s rotation. The maximum rotational speed was achieved with 10 blades and an angle of attack of 0°, 30°, and 45°, with respective speeds of 153.59 RPM, 155.84 RPM, and 164.95 RPM. The study indicates that the higher the number and angle of attack of blades, the greater the rotation of the breastshot type waterwheel. ANOVA tests showed that the number of blades had a significant impact on the waterwheel’s rotation, with an F-test value of 6.32 and a p-value of 0.012. On the other hand, the angle of attack of the blade had no significant impact, with an F-test value of 3.20 and a p-value of 0.067

Influence and multi-objective optimization on three-stage guide vane closure scheme of a pumped storage power plant

Selection of the guide vane closure scheme was a critical issue for the load rejection transients of a pumped-storage power plant. To fully and accurately assess the influences of the guide vane closure scheme on the transient performance and pressure fluctuation, the load rejection transients adopting the original two-stage and optimized three-stage guide vane closure schemes were simulated adopting the one- and three-dimensional coupled approach. Results suggested that the guide vane closure schemes significantly influenced the transient performances and pressure fluctuations during load rejection transients. Compared with adopting the original two-stage guide vane closure scheme, adopting the optimized three-stage guide vane closure scheme could improve the maximum rotation speed, maximum and minimum fluctuating pressures in the pumped-storage power plant, and suppress the local backflow vortexes close to the high-pressure inlet of runner and their induced low-frequency and high-amplitude pressure fluctuation close to the no-load conditions. The study results provided theoretical reference for selecting the optimized guide vane closure scheme.

An electrostatic micromotor based on electrets

AbstractThe authors report a novel electret‐based miniature electrostatic motor with an electret film as the stator and a metal electrode as the rotor. A particular commutator is used to transform the polarity of the metal electrode. When the size of the electret‐based electrostatic motor (EEM) is 42 × 44 × 15 mm3, the maximum power consumption is only 5.4 mW. The rotation speed of the EEM increases with the increase of the supply voltage, and the maximum rotation speed can reach up to 2864 rpm. Powered by two nickel‐hydride batteries with a rated capacity of 1700 mAh, the EEM can drive a fan with a diameter of 40 mm to rotate continuously for 18 h. The EEM has the characteristics of low power consumption and convenient fabrication. Experimental results show that the EEM demonstrates high reliability and has potential applications in micro‐electromechanical systems.

A multi-scale framework for life reduction assessment of turbine blade caused by microstructural degradation

The prolonged thermal exposure with centrifugal load results in microstructural degradation, which ultimately leads to a reduction in the fatigue and creep resistance of the turbine blades. The present work proposes a multi-scale framework to estimate the life reduction of turbine blades, which combines a microstructural degradation model, a two-phase constitutive model, and a microstructure-dependent fatigue and creep life reduction model. The framework with multi-scale models is validated by a Single Crystal (SC) Ni-based superalloy at the microstructural length-scale and is then applied to calculate the microstructural degradation and the fatigue and creep life reduction of turbine blades under two specific service conditions. The simulation results and quantitative analysis show that the microstructural degradation and fatigue and creep life reduction of the turbine blade are heavily influenced by the variations in the proportion of the intermediate state, namely, the maximum rotor speed status, in the two specific service conditions. The intermediate state accelerates the microstructural degradation and leads to a reduction of the life, especially the effective fatigue life reserve due to the higher temperature and rotational speed than that of the 93% maximum rotor speed status marked as the reference state. The proposed multi-scale framework provides a capable approach to analyze the reduction of the fatigue and creep life for turbine blade induced by microstructural degradation, which can assist to determine a reasonable Time Between Overhaul (TBO) of the engine.

A novel spherical ultrasonic motor with wire stators and measuring torque and preload via a new method.

The present study introduces a multi-degree-of-freedom (MDOF) ultrasonic motor, which is capable of driving a spherical rotor using spiral wire stators and a piezoelectric stack actuator. Wire stators and piezoelectric stack actuators enable the proposed motor to be smaller and simpler, lower in power consumption, and have different modes at different frequencies. In this motor, two wire stators are used to drive the spherical rotor and rotate it in different directions. The eigenfrequency and frequency domain analyses were carried out using the finite element method (FEM) to evaluate the MDOF capability of the motor in different vibration modes. It has been demonstrated that the piezoelectric stack actuator can provide MDOF motions through its vibration modes. The resonant frequency obtained by the frequency domain approach agreed with the impedance analyzer test. Rotational speed, torque, and preload force were experimentally investigated. Using shear stress caused by viscous fluid in contact with the spherical rotor, a new torque calculation method was developed. Based on the buoyancy force exerted on the immersed rotor, the preload force was measured. The experimental results indicated that the maximum rotational speed of the spherical rotor was 306rpm, and the maximum torque was 4.7 μNm.

Hydrodynamic study of the operating window of a stator-rotor vortex chamber reactor

The gas-solid vortex reactor is promising for process intensification while the huge gas consumption and relatively low solids loading can be a hurdle for some industrial applications. Therefore, an improved design, the stator-rotor vortex chamber (STARVOC) has been proposed. To construct the operating window, five materials with sizes of 300–1000 μm and densities of 700–2330 kg/m3 are tested at varying rotational speeds from 300 to 600 RPM and superficial gas flow rates from 0 to 2.3 m/s. A quantitative assessment of the bed's axial uniformity is conducted and a minimum rotational speed is determined. A semi-empirical correlation is developed for the terminal velocity of particles, enabling obtaining maximum solids loading and identifying maximum rotational speed. It is found that the operating window can be divided into six zones and the appropriate zone for uniform fluidization is identified. This framework provides operational guidelines for STARVOC implementation in drying and reactive applications.

Guest Editorial: Polymer electrets and ferroelectrets

Guest Editorial: Polymer electrets and ferroelectrets

Identification of Aerodynamic Tonal Noise Sources of a Centrifugal Compressor of a Turbocharger for Large Stationary Engines

The aerodynamics of centrifugal compressors is a topical issue, as the vibrations and noise reduce the comfort of people who are in proximity to the compressor. The current trend in rotating machinery research is therefore not only concerned with performance parameters but also increasingly with the effect on humans. An analysis of aerodynamic noise based on external acoustic field measurements may be a way to assess the nature of aerodynamic excitation. In this research, the experimental measurements at 20 operating points covered the entire characteristic operating range of the selected centrifugal compressor. The dominant noise arising at blade-passing frequency (BPF) was identified at all the operational points, and the dominant effect of the buzz-saw noise was identified at the maximum rotor speed. The determination of the total sound pressure level LPA showed a trend towards an increasingly higher rotor speed and compressor surge line. In the amplitude-frequency characteristics, the sound pressure was found to be dependent on the rotor speed for BPF. On the other hand, non-monotonicity was detected between the operational points at given speed lines, confirming the complexity of the aerodynamics of rotating machines. The metric chosen to identify prominent tones determined by the tonality of individual tones in the frequency spectrum showed a clear effect of integer multiples of the rotational frequency on the overall noise. Thus, the results presented here confirm the dominant influence of BPF in terms of the psychoacoustic impact on humans.

Ability of Black-Box Optimisation to Efficiently Perform Simulation Studies in Power Engineering

Abstract In this study, the potential of the so-called black-box optimisation (BBO) to increase the efficiency of simulation studies in power engineering is evaluated. Three algorithms (“Multilevel Coordinate Search” (MCS) and “Stable Noisy Optimization by Branch and Fit” (SNOBFIT) by Huyer and Neumaier and “blackbox: A Procedure for Parallel Optimization of Expensive Black-box Functions” (blackbox) by Knysh and Korkolis) are implemented in MATLAB and compared for solving two use cases: the analysis of the maximum rotational speed of a gas turbine after a load rejection and the identification of transfer function parameters by measurements. The first use case has a high computational cost, whereas the second use case is computationally cheap. For each run of the algorithms, the accuracy of the found solution and the number of simulations or function evaluations needed to determine the optimum and the overall runtime are used to identify the potential of the algorithms in comparison to currently used methods. All methods provide solutions for potential optima that are at least 99.8% accurate compared to the reference methods. The number of evaluations of the objective functions differs significantly but cannot be directly compared as only the SNOBFIT algorithm does stop when the found solution does not improve further, whereas the other algorithms use a predefined number of function evaluations. Therefore, SNOBFIT has the shortest runtime for both examples. For computationally expensive simulations, it is shown that parallelisation of the function evaluations (SNOBFIT and blackbox) and quantisation of the input variables (SNOBFIT) are essential for the algorithmic performance. For the gas turbine overspeed analysis, only SNOBFIT can compete with the reference procedure concerning the runtime. Further studies will have to investigate whether the quantisation of input variables can be applied to other algorithms and whether the BBO algorithms can outperform the reference methods for problems with a higher dimensionality.

Peak shaving control in OWC wave energy converters: From concept to implementation in the Mutriku wave power plant

Control algorithms for wave energy conversion technologies with air turbines require contingency tools to prevent the rated power and maximum rotational speed from being exceeded. Survival problems limit energy conversion when the available power is too large compared to the turbo-generator-rated power. Short-term predictions require information from local wave-measuring buoys, which raises reliability concerns. Wave groups in the ocean result in extremely high wave power peaks that cannot be smoothed by low-inertia power-take-off (PTO) systems, leading to survival problems. The most common strategy to cope with this situation is to set the rated power of the PTO several times more than the annual average produced electrical power. The PTO is shut-down when the available power is excessive. These two engineering decisions have a detrimental impact on the capacity factor and the energy cost. The paper shows a new control algorithm for wave energy oscillating-water-column (OWC) devices that can control the shutter position of a fast-acting valve to dissipate the pneumatic energy excess. Hence, the PTO can operate even when the available power is significantly larger than the generator’s rated power. The algorithm was validated with the 30 kW biradial turbine prototype from the OPERA H2020 European project under real sea conditions at Mutriku’s wave power plant. Results show the algorithm’s effectiveness in real situations and during a generator failure simulated during the experimental campaign. This new concept may reduce the energy cost from wave energy and open a new field of design possibilities for OWC wave energy converters.

Influence of Rotational Speed on Isothermal Piston Compression System

An isothermal piston is a device that can achieve near-isothermal compression by enhancing the heat transfer area with a porous media. However, flow resistance between the porous media and the liquid is introduced, which cannot be neglected at a high operational speed. Thus, the influence of rotational speed on the isothermal piston compression system is analyzed in this study. A flow resistance mathematical model is established based on the face-centered cubic structure hypothesis. The energy conservation rate and efficiency of the isothermal piston are defined. The effect of rotational speed on resistance is discussed, and a comprehensive energy conservation performance assessment of the isothermal piston is analyzed. The results show that the increasing rate of the resistance work increases significantly proportional to the rotational speed, and the proportion of resistance work in the total work increases gradually and sharply. The total work including compression and resistance cannot be larger than the compression work under adiabatic conditions. The maximum rotational speed is 650 rpm.

Artifact reduction in lenslet array near-eye displays

Lenslet array near-eye displays are a revolutionary technology that generates a virtual image in the field of view of the observer. Although this technology is advantageous in creating compact near-eye displays, undesirable artifacts occur when the user pupil moves outside of the pupil practical movable region (PPMR). Even with dynamic image updating based on eye-tracking techniques, artifacts can still be perceived when human eyes turn rapidly. To enlarge PPMR, we proposed a new rendering method in previous work. To improve the rendering speed in the eye tracking system, look-up tables are used. The disadvantage of the onboard system is the large memory consumption. In this study, we analyzed the system parameters of the incident pupil and pupil margin light columns, the feasibility of the optimized system, and evaluated the optimized system that can adapt to the maximum velocity of the saccadic pupil movement. We optimized the rendering method to reduce memory consumption in the process of generating microdisplay images. In addition, we provide GPU rendering method to improve system speed and reduce system latency to meet the maximum human eye rotation speed. We conducted user studies to evaluate the effect of the method using the optimized rendering method combined with eye tracking to reduce artifacts for fast eye rotation on different images and videos. Results showed that our method effectively reduced artifacts via the optimized rendering method with eye tracking, which adapted to faster human eye movements.

Single neuron PID based method for deformation suppression during CNC machining of parts

AbstractCNC machining realizes the automatic control of machine tools with digital information, which is an advanced technology widely used in today's machinery manufacturing industry. In the process of NC lathe machining of parts, thin‐walled workpieces are prone to deformation due to poor rigidity and thinner wall thickness. Therefore, it is necessary to study the deformation suppression of NC parts. By combining fuzzy control with single neuron PID and introducing fast non dominated sorting genetic algorithm, the parameters of thin‐walled workpiece milling are optimized. The results show that the neuron PID algorithm of fuzzy control has no overshoot in the environment with or without interference, and has fast response speed and strong anti‐interference ability. In the case verification, the cutting force controlled by fuzzy neuron PID can quickly reach the reference 240 N and remain stable. The removal rate fluctuates less in the range of 8000–12,000. It can improve the metal removal rate while maintaining a constant cutting force, so as to restrain the machining deformation of parts. At the same time, the introduced fast non dominated sorting genetic algorithm can increase the maximum rotational speed to 10,486.5, the maximum feed rate per tooth from 0.075 to 0.112, and the rotational speed is nearly doubled, effectively improving the processing quality, providing a technical reference for the stable control of the NC machining system, and providing a new idea and method for part deformation suppression.