Rotational Speed Of Rotor Research Articles

A nano universal joint made from curved double-walled carbon nanotubes

A nano universal joint is constructed from curved double-wall carbon nanotubes with a short outer tube as stator and a long inner tube as a rotor. When one end of the rotor is driven (by a rotary motor) to rotate, the same rotational speed but with different rotational direction will be induced at the other end of the rotor. This mechanism makes the joint useful for designing a flexible nanodevice with an adjustable output rotational signal. The motion transmission effect of the universal joint is analyzed using a molecular dynamics simulation approach. In particular, the effects of three factors are investigated. The first factor is the curvature of the stator, which produces a different rotational direction of the rotor at the output end. The second is the bonding conditions of carbon atoms on the adjacent tube ends of the motor and the rotor, sp1 or sp2 atoms, which create different attraction between the motor and the rotor. The third is the rotational speed of the motor, which can be considered as the input signal of the universal joint. It is noted that the rotor's rotational speed is usually the same as that of the motor when the carbon atoms on the adjacent ends of the motor and the rotor are sp1 carbon atoms. When they become the new sp2 atoms, the rotor experiences a jump in rotational speed from a lower value to that of the motor. The mechanism of drops in potential of the motor is revealed. If the carbon atoms on the adjacent ends are sp2 atoms, the rotor rotates more slowly than the motor, whereas the rotational speed is stable when driven by a higher speed motor.

Urban Eco-Greenergy™ hybrid wind-solar photovoltaic energy system and its applications

This paper introduces the Eco-Greenergy™ hybrid wind-solar photovoltaic energy generation system and its applications. The system is an integration of the novel omni-direction-guide-vane (ODGV) with a vertical axis wind turbine (VAWT). The ODGV is designed to surround the VAWT for wind power augmentation by creating a venturi effect to increase the on-coming wind speed before it interacts with the turbine blades. In wind tunnel tests, the ODGV improves the power output of the VAWT by 3.48 times compared with a bare VAWT at its peak torque. Furthermore, the rotor rotational speed of the wind turbine increased by 182% at 6 m/s of wind speed. A solar PV panel can be mounted on the top surface of the ODGV for solar energy generation. Estimation on wind-solar energy output shows that the system can generate a total of 572.8 kWh of energy per year. By comparison, the ODGV increases the annual wind energy output by 438%. The green energy generated from the hybrid system can be used to power LED lights or other appliances (e.g., CCTV camera).

A new axial flux permanent magnet synchronous alternator autonomously adapted to wind speeds

In this study, a new axial flux permanent magnet synchronous generator (PMSA) design and prototyping procedures are presented. It is composed of a stack of rotor–stator blocks on the same shaft. In other words, it is made up of four alternators based on axial flux permanent magnets that can generate electrical energy within the limits of rotor rotational speed with varying wind speeds. A control system is also introduced to the generator. The control system connects or disconnects the stator blocks to the load according to the changing speeds of the wind. It produces electrical energy with stable voltage, frequency and variable power at the output. The efficiency of the generator is tested with different load and speed conditions. It is observed that the efficiency is high when the speed is low in case the load is connected only one stator. The efficiency is high when the speed is above 200rpm for the case where several stators are connected to the load. It can be seen that the incremental structure of the generator is suitable for changing speeds of the wind. It can have high efficiency for both low and high speeds with changing the number of stator blocks connected to the load.

Vibration attenuation of a rotor supported by journal bearings with nonlinear suspensions under mass eccentricity force using nonlinear energy sink

This paper studies the effect of a number of smooth nonlinear energy sinks (NESs) on the vibration mitigation of a rotor supported by journal bearings with nonlinear suspensions under mass eccentricity force. The NESs have a linear damping and an essentially nonlinear stiffness. Two NESs in the perpendicular directions are located on the bearing body. The equations of motion are derived and numerically solved. In order to optimize the parameters of the NESs, a genetic algorithm is utilized. For different values of the system parameters, periodic, two-periodic (2T) and qusai-periodic motions, occur in the system. It is shown that the NESs reduce effectively vibration of the rotor-bearing system in an operating speed range. However, the type of motion does not change in the most rotational speeds of rotor. Furthermore, for lower values of damping, the NESs demonstrate a high performance.

ヘリコプタ・ロータのワール不安定性に対するパラメータ共振解析

The mechanism of the helicopter rotor whirl instability in the forward flight is investigated by the parametric resonance analysis. By comparing the system natural frequencies with the frequency components of the aerodynamic forces that are observed in the SH-60K simulation, it is shown that the particular frequency components might cause the parametric resonance. By applying the aerodynamic forces with the particular frequencies to the right-hand side of the equations of motion, the method of the variation of constants is used to evaluate the parametric resonance. These results show that the parametric resonance between the backward whirl mode and the scissor mode makes the SH-60K whirl mode unstable. In order to suppress the whirl instability, the reduction of the rotor rotational speed or the stiffening of the rotor support structure is considered to be effective.

CFD simulation of flow and mixing in‐inline rotor‐stator mixers with complex fluids

The objective is to apply CFD methodology for the validation of the scale‐up of rotor‐stator units formed by flat blades and used as in‐line mixers under laminar flow conditions. The comparison between simulated and experimental data as a function of rotor geometry, rotation speed and flow rate has shown a good agreement in terms of power input and RTD curves both for Newtonian and power‐law fluids with a flow index between 0.2 and 1. The applicability of the virtual Couette analogy has been validated quantitatively and explained by the analysis of the local flow in the mixer. As a result, a shear coefficient independent of fluid rheology has been deduced from CFD data. This has been shown to depend only on the dimensionless gap when the length‐to‐diameter ratio is higher than 2.5. In this case, fast 2D simulations can provide a good approximation of the shear coefficient obtained from 3D calculations from which a master power curve can be deduced, but these are not able to predict flow transition, contrary to 3D computations. Finally, original correlations able to estimate the power and shear coefficients as a function of the mixer geometry have been established.

COMBINED DIELECTRIC AND MECHANICAL INVESTIGATION OF FILLER NETWORK PERCOLATION BEHAVIOR, FILLER–FILLER CONTACT, AND FILLER–POLYMER INTERACTION ON CARBON BLACK–FILLED HYDROGENATED ACRYLONITRILE–BUTADIENE RUBBER

ABSTRACTThe filler network percolation behavior, filler–filler contact, and filler–polymer interaction of carbon black (CB)–filled hydrogenated acrylonitrile–butadiene rubber were investigated with the combination of dielectric and mechanical properties, by means of changing CB concentration, CB-specific surface area, cycling deformation for vulcanizates, and rotation speed of rotors in the internal mixer during the mixing process. A dielectric relaxation spectrometer was used to determine the percolation threshold of the CB network, which was made up of filler–filler contact, combined with the percolation theory. Dynamic mechanical analysis and a universal testing machine were employed to observe the filler–filler contact and filler–polymer interaction. The filler–filler bonds were determined by analysis of the Arrhenius plot on the basis of temperature sweep. The filler–polymer interaction and filler–filler contact were determined by hysteresis loss dependence and analysis of the reinforcement factor on the basis of strain sweep and quasi-static stress–strain behavior. The model of variable network density proposed by Maier and Goritz was applied to explain the contribution of stable and unstable bonds, which constituted the filler–polymer interaction, to storage modulus. The results showed that the percolation threshold of the filler network increased with an increase in rotation speed and a decrease in CB-specific surface area, which indicated that the filler–filler contact was affected by increasing rotation speed to some degree. Cycling deformation did not obviously affect the percolation threshold. This means that the filler–filler contact was not obviously affected by cycling deformation. However, the filler–polymer interaction was weakened by this procedure, according to careful investigation for the variation of some mechanical properties. We found new interesting correlations between the macroscopic mechanical properties and CB concentration. The molecular nature of these findings was discussed, combined with the overlap model and traditional molecular slip theory.

A study on the absorption of ammonia into water in a rotor‐stator reactor

This article presents experimental and modelling studies on the absorption of NH3 into water in a rotor‐stator reactor (RSR). The influences of operating parameters such as the rotation speed of rotor, liquid flow rate, and gas flow rate on the overall volumetric mass transfer coefficient (Kya) of NH3 were investigated. It was found that Kya increased with an increasing rotation speed, liquid flow rate, and gas flow rate. A correlation to predict the Kya of NH3 in the RSR was established and found to be in agreement with the experimental data with deviations within 10 %. A comparison was made between the Kya of NH3 in the RSR and RPB, and the result showed that Kya of NH3 in the RSR was 13 % higher than that in the RPB, thus signifying that the RSR has better intensification effect for mass transfer limited processes than the RPB.

Planetary Gear for Counter-Rotating Wind Turbines

A specific problem of the wind turbines refers to the difference between the low rotation speed of the wind turbine rotor and the high rotation speed needed for the electrical generator. Usually, the adaptation between the speed of the turbine rotor and the electrical generator speed is achieved by means of a speed increaser. A recent alternative relates to the use of coaxial counter-rotating wind turbines, which can achieve higher power and improve the conversion efficiency of the wind energy into electrical energy (up to 25%) with a reduced cost of approx. 20-30% compared to similar single rotor turbines. Conceptually, the counter-rotating wind turbine systems can integrate a particular generator wherein the rotor is coupled to a row of blades and the stator with another row of blades, or a commonly generator, coupled to a differential planetary gear, that allows the summation of the blades motions.The paper describes and analyzes kinematic and dynamic aspects of a system consisting of two coaxial counter-rotating turbines and a generator, interconnected by a planetary gear with two inputs (the two turbines) and an output (the generator). The algorithm is based on the property of the differential planetary gear of adding two input motions into one output motion. The kinematic and dynamic parameters of the planetary gear are established in the paper, and a case study is further presented: a small wind turbine equipped with a transmission enabling input speed multiplication.

Modeling the effect of control on the wake of a utility-scale turbine via large-eddy simulation

A model of the University of Minnesota EOLOS research turbine (Clipper Liberty C96) is developed, integrating the C96 torque control law with a high fidelity actuator line large- eddy simulation (LES) model. Good agreement with the blade element momentum theory is obtained for the power coefficient curve under uniform inflow. Three different cases, fixed rotor rotational speed ω, fixed tip-speed ratio (TSR) and generator torque control, have been simulated for turbulent inflow. With approximately the same time-averaged ω, the time- averaged power is in good agreement with measurements for all three cases. Although the time-averaged aerodynamic torque is nearly the same for the three cases, the root-mean-square (rms) of the aerodynamic torque fluctuations is significantly larger for the case with fixed ω. No significant differences have been observed for the time-averaged flow fields behind the turbine for these three cases.

Understanding the Benefits and Limitations of Increasing Maximum Rotor Tip Speed for Utility-Scale Wind Turbines

For utility-scale wind turbines, the maximum rotor rotation speed is generally constrained by noise considerations. Innovations in acoustics and/or siting in remote locations may enable future wind turbine designs to operate with higher tip speeds. Wind turbines designed to take advantage of higher tip speeds are expected to be able to capture more energy and utilize lighter drivetrains because of their decreased maximum torque loads. However, the magnitude of the potential cost savings is unclear, and the potential trade-offs with rotor and tower sizing are not well understood. A multidisciplinary, system-level framework was developed to facilitate wind turbine and wind plant analysis and optimization. The rotors, nacelles, and towers of wind turbines are optimized for minimum cost of energy subject to a large number of structural, manufacturing, and transportation constraints. These optimization studies suggest that allowing for higher maximum tip speeds could result in a decrease in the cost of energy of up to 5% for land-based sites and 2% for offshore sites when using current technology. Almost all of the cost savings are attributed to the decrease in gearbox mass as a consequence of the reduced maximum rotor torque. Although there is some increased energy capture, it is very minimal (less than 0.5%). Extreme increases in tip speed are unnecessary; benefits for maximum tip speeds greater than 100-110 m/s are small to nonexistent.

Two-Dimensional Analytical Permanent-Magnet Eddy-Current Loss Calculations in Slotless PMSM Equipped With Surface-Inset Magnets

Two-dimensional (2-D) analytical permanent-magnet (PM) eddy-current loss calculations are presented for slotless PM synchronous machines (PMSMs) with surface-inset PMs considering the current penetration effect. In this paper, the term slotless implies that either the stator is originally slotted but the slotting effects are neglected or the stator is originally slotless. The analytical magnetic field distribution is computed in polar coordinates from the 2-D subdomain method (i.e., based on formal resolution of Maxwell's equation applied in subdomain). Based on the predicted magnetic field distribution, the eddy-currents induced in the PMs are analytically obtained and the PM eddy-current losses considering eddy-current reaction field are calculated. The analytical expressions can be used for slotless PMSMs with any number of phases and any form of current and overlapping winding distribution. The effects of stator slotting are neglected and the current density distribution is modeled by equivalent current sheets located on the slot opening. To evaluate the efficacy of the proposed technique, the 2-D PM eddy-current losses for two slotless PMSMs are analytically calculated and compared with those obtained by 2-D finite-element analysis (FEA). The effects of the rotor rotational speed and the initial rotor mechanical angular position are investigated. The analytical results are in good agreement with those obtained by the 2-D FEA.

10kW급 상반전 풍력터빈 로터의 설계와 성능 평가에 관한 연구

The counter-rotating approach on wind turbine has been recently put in interest for its certain advantages in both design and performance. This paper introduces a study on a counter-rotating wind turbine designed and modeled using NREL airfoils S822 and S823. The aims of the study is to evaluate and discover the performance of the counter-rotating system, and compares to that of single rotor turbine of same design using numerical simulation. The results show higher performance of the counter-rotating system compared with single rotor case at TSR 3 to 5 but lower performance at higher TSR. This is due to the interaction between upstream and downstream rotors. Thus, the counter-rotating turbine is more efficient at low rotor rotational speed.

Comparison of One-Dimensional and Three-Dimensional Structural Dynamics Modeling of Advanced Geometry Blades

Comparisons between one-dimensional and three-dimensional analyses are conducted systematically for advanced geometry blades, which have tip sweep, tip taper, and planform variations near the root with various materials and effects of boundary conditions in order to better understand the differences between the two approaches and the physics behind them. One-dimensional beam analysis is conducted using the rotorcraft comprehensive analysis system with variational asymptotical beam sectional analysis calculated two-dimensional cross-sectional properties. Three-dimensional finite element analysis is conducted using a commercial code MSC/Marc. Natural frequencies are calculated at various rotor rotational speeds, and the differences are quantified. There is very good agreement between the one-dimensional and three-dimensional analyses for free–free aluminum beams, even for a very short beam with beam length five times chord (). The one-dimensional analysis accurately captures the planform variation near the root for an aluminum beam. In general, the differences between the one-dimensional and three-dimensional analyses occur when there is coupling, either generated from geometry (tip sweep) or material (composite), especially for high-frequency modes. Without coupling, the one-dimensional analysis appears to capture free vibration characteristics of various advanced geometry beams and blades reasonably well for at least the six lowest frequency modes when the beam length is greater than 10 times chord.

Model-based selection of full-scale Wells turbines for ocean wave energy conversion and prediction of their aerodynamic and acoustic performances

One of the most intensively studied principles of harnessing the energy from ocean waves is the oscillating water column device. The oscillating water column converts the motion of the water waves into a bi-directional airflow, which in turn drives an air turbine. The bi-directional axial Wells turbine as a candidate for oscillating water column power take-off systems was the object of considerable research conducted in the last decades. However, there is a lack of consistent data to support practical design considerations when pre-selecting a turbine for an oscillating water column power plant. Furthermore, to minimize the overall environmental impact of this technology requires the assessment of the aero-acoustic noise associated with a Wells turbine’s operation. The effect of cascade solidity and hub-to-tip ratio on the aero-acoustic performance of Wells turbine rotors is assessed systematically by numerical simulations and model scale testing. Based on the data from the study on these generic design parameters, new Wells turbine design charts were developed. For a given plant site, main machine dimensions are identified and a time domain model is used to predict the annual energy output and the annual equivalent sound power level. Maximum values of total-static peak efficiency and low sound emission can be achieved by selecting moderate values of cascade solidity and hub-to-tip ratio. On the other hand, high hub-to-tip ratio rotors in combination with high solidity are recommended for a maximum range of operation without stall, as the pressure head is varied. The designer of an oscillating water column system usually specifies selected operating conditions on dimensional turbine characteristics. Combinations of suitable rotor diameter and rotational speeds are selected using the design chart approach. When a fully operating, full-scale Wells turbine at fixed speed is assessed, higher cascade solidity maximizes the annual energy output at minimum acoustic emission. The drawback is a slightly larger rotor diameter when, e.g. compared with a lower cascade solidity.

Mechanochemical degradation of the crosslinked and foamed EVA multicomponent and multiphase waste material for resource application

Effects of mechanochemical degradation of the crosslinked and foamed ethylene-vinyl acetate copolymer (EVA) multicomponent and multiphase waste material in a solid state are studied with a HAAKE rheometer. The ruptures of chemical bonds in its net and stereo-structures are caused by external mechanical energy input by the Roller rotors of the HAAKE rheometer. A resource application method of the degradation product is obtained. The optimum mechanochemical degradation conditions are at 120–130 °C in a Roller rotor rotation speed range of 40–60 rpm for 24 min. Smaller polymer molecules have been generated so that the interfacial morphology, phase compatibility and plastic flow properties of the degradation product are all improved. The sol extracted from the degradation product is characterized with thermogravimetric analysis, gel permeation chromatography, nuclear magnetic resonance and Fourier transform infrared spectroscopy. Free radical reaction mechanisms are demonstrated in the degradation process. The degradation product partly replaces pure EVA in preparing the crosslinked and foamed material. Results show that the degradation product could be in resource application.

Numerical Simulation on Dispersive Mixing of Solid Powders/Polymer Matrix in Two-Rotor Mixer

In this paper, employing the mixing theory of polymer and the numerical simulation of polymer processing, numerical simulation model for dispersive mixing of solid powders in polymer matrix is studied, and a multi factor accumulative size distribution function is established. Based on this, the dispersive mixing processes of black carbon/natural rubber are studied using three-dimension dynamic numerical simulation, and the influences of operating conditions on the dispersive mixing of black carbon are analyzed. The simulation results show that the final size of solid powder aggregates is depended on the rotational speed of rotors. When the maximum shear stress of polymer flow field is sufficient to overcome the cohesive force of solid powder aggregates, the size of aggregates distribution will be related with mixing time.

Numerical Investigation of Mixing Properties of Continuous Mixer with New-Type Rotors

In this paper, the 3D flow field and dynamic mixing processing in the continuous mixer with new-type rotors have been studied using finite element software package Polyflow. The influences of continuous mixer process conditions on mixing properties were analyzed by numerical simulation. The results show that the dispersion property is mainly affected by the rotational speed of rotors and the viscosity of polymer. Better dispersion property can be gained as and the viscosity increase. However, the distribution property is mainly affected by feed rate, and the distribution efficiency will reduce if feed rate is too fast.

트로코이드 펌프의 시뮬레이션 방법론

Article history: Flow rate control is the uppermost concern for a trochoid hydraulic pump. Cavitation within the flow field of the pump has the greatest effect on the flow control during high-speed pump rotation of approximately 3500~4000 RPM. In this paper, based on AMESim ® and Solid Works ® , we will present a method to simulate cavitation by analyzing the control factors of a trochoid pump, including the hydraulic pressure change at the outlet, flow rate based on the rotation speed of the inner rotor, leakage through the gap between the outer and inner rotors, and discharging angle of the outlet. The proposed methodology of the [cavitation simulation will enable field engineers to more easily design trochoid pumps, and will allow more concrete control over the flow rate of the pump by realizing an analysis model similar to the actual product model.

Tip Leakage Flow and Heat Transfer on Turbine Blade Tip and Casing, Part 1: Effect of Tip Clearance Height and Rotation Speed

Steady simulations were performed to investigate tip leakage flow and heat transfer characteristics on the rotor blade tip and casing in a single-stage gas turbine engine. A typical high-pressure gas turbine stage was modeled with a pressure ratio of 3.2. The predicted isentropic Mach number and adiabatic wall temperature on the casing showed good agreement with available experimental data under similar operating condition. The present numerical study focuses extensively on the effects of tip clearance heights and rotor rotational speeds on the blade tip and casing heat transfer characteristics. It was observed that the tip leakage flow structure is highly dependent on the height of the tip gap and the speed of the rotor. In all cases, the tip leakage flow was seen to separate and recirculate just around the corner of the pressure side of the blade tip. This region of re-circulating flow enlarges with increasing clearance heights. The separated leakage flow reattaches afterwards on the tip surface. Leakage flow reattachment was shown to enhance surface heat transfer at the tip. The interaction between tip leakage flow and secondary flows that is induced by the relative casing motion is found to significantly influence the blade tip and casing heat transfer distribution. A region of critical heat transfer exists on the casing near the blade tip leading edge and along the pressure-side edge for all the clearance heights that were investigated. At high rotation speed, the region of critical heat transfer tends to move towards the trailing edge due to the change in inflow angle.