Rotational Speed Of Rotor Research Articles

Empirical criterion for the occurrence of auto-balancing and its application for axisymmetric rotor with a fixed point and isotropic elastic support

We formulated the empirical criterion for the occurrence of auto­balancing for the rotors balanced by passive auto­balancers. The criterion is applicable for rigid and elastic rotors on ductile supports and for elastic rotors on rigid supports. The criterion is intended to answer the question if it is possible in principle, and under what conditions, to automatically balance a particular rotor n by passive auto­balancers of any type in n planes of correction. In accordance with the criterion, the possibility of applying passive auto­balancers for rotor balancing (in “zero approximation”) is determined not by the type of auto­balancers, but by rotor itself. In this case, reaction of rotor to the elementary imbalances, applied in the required planes of correction, is essential. That is why the criterion makes it possible to obtain universal conditions for the occurrence of auto­balancing, applied for any types of auto­balancers. The criterion is applied in the following sequence. 1. A physical­mechanical model of rotor with elementary imbalances, located in the required planes of correction, is described. 2. Differential equations of motion of the unbalanced rotor are derived. 3. Steady motion of a rotor, which corresponds to the applied elementary imbalances, is searched for. 4. A functional of the criterion for the occurrence of auto­balancing is built. As a rule, this is a quadratic form from elementary imbalances. 5. By analysis of the functional (sign definiteness of the obtained quadratic form), conditions for the occurrence of auto­balancing are determined. The result is conditions of two types. The first ones set limitations to the mass­inertia rotor characteristics. The second ones are a range of angular speeds of rotor rotation, at which auto­balancing will occur provided the first conditions are met. The criterion is used for the axisymmetric rotor with a fixed point and isotropic elastic support. It was found that auto­balancing will occur only in the case of a long rotor, relative to the point O, independent of the number of auto­balancers (planes of correction) at the speeds, which exceed the only resonance speed of rotor rotation.

Effect of operating parameters on a centrifugal partition chromatography separation

Centrifugal partition chromatography (CPC) is the branch of countercurrent chromatography (CCC) that works with single axis hydrostatic columns with rotary seals. The hydrodynamic of the liquid stationary phase-liquid mobile phase equilibrium in the CPC chambers has been studied theoretically and with specially designed CPC columns. In this work, we selected a simple analytical separation (no loading study) of three test solutes, coccine red, coumarin and carvone, with a commonly used heptane/ethyl acetate/methanol/water 1:1:1:1v/v biphasic liquid system and two different rotors: a commercially available 30-mL CPC instrument and a 80-mL prototype rotor designed for productivity. We fully studied this separation in many possible practical operating conditions of the two rotors, aiming at a generic column characterization. The rotor rotation was varied between 1000 and 2800rpm, the aqueous mobile phase flow rate was varied between 1 and 22mL/min with the 30-mL rotor and 10 and 55mL/min with the 80-mL rotor, the upper limits being mechanical constraints and some liquid stationary phase remaining in the rotor. The variations of Sf, the volume ratio of stationary phase in the rotor, were studied versus mobile phase flow rate and rotor rotation speed. A maximum mobile phase linear velocity was found to depend on the centrifugal field for the 30-mL rotor. This maximum velocity was not observed with the 80-mL rotor. Studying the changes in coumarin and carvone peak efficiencies, it is established that the number of cells required to make one theoretical plate, i.e. one chromatographic exchange, is minimized at maximal rotation speed and, to a lesser extent, at high mobile phase flow rate (or linear velocity). Considering the throughput, there is evidence of an optimal flow rate depending on the rotor rotation that is not necessarily the highest possible.

Experimental study on noise radiation from wind turbines

Noise emitted from wind turbines is composed of aerodynamic and mechanical sound and has directional radiation characteristics. To investigate the horizontal sound directivity around a wind turbine under various wind conditions, field measurements of noise generated from two different wind turbines have been performed over long periods. Wind turbine operational data such as the nacelle direction and rotor rotational speed were collected at 1 s intervals along with corresponding acoustic data. An empirical formula for the directivity correction was derived from the A-weighted sound pressure levels measured at the several receiving points around the wind turbine. We also focused on the amplitude modulation components of wind turbine noise in emission areas and compared the estimated rotor speeds by using measured sound pressure levels with actual values. The results showed that the directivity pattern of the A-weighted sound pressure level for two different wind turbines is almost the same, whereas the frequency dependence of the sound directivity is different for the individual wind turbines. Additionally, the radiation characteristics of wind turbine noise depend strongly on the rotor rotational speed, which can be estimated from the blade-passing-frequency detected by using the amplitude modulation components of wind turbine noise.

Dynamic vibrations in wind energy systems: Application to vertical axis wind turbine

Dynamic analysis of Darrieus turbine bevel spur gear subjected to transient aerodynamic loads is carried out in the present study. The aerodynamic torque is obtained by solving the two dimensional unsteady incompressible Navies Stocks equation with the k–ω shear stress transport turbulence model. The results are presented for several values of tip speed ratio. The two-dimensional Computational Fluid Dynamics model is validated with experimental results. The optimum tip speed ratio is achieved, giving the best overall performance.In this study, we developed a lamped mass dynamic model with 14 degrees of freedom. This model is excited by external and internal issues sources. The main factors of these excitations are the periodic fluctuations of the gear meshes' stiffness and the unsteady aerodynamic torque oscillations. The vibration responses are obtained in time and frequency domains. The originality of our work is the correlation between the complexity of the aerodynamic phenomenon and the non-stationary dynamics vibration of the mechanical gearing system.The effect of the rotational speed on the dynamic behavior of the Darrieus turbine is also discussed. The present study shows that the variation of rotor rotational speed directly affects the torque production. However, there is a small change in the dynamic vibration of the studied gearing system.

Novel plant development for a high performance 3 kW integrated wind and solar system

This research describes a novel system of four Savonius wind rotors, aligned in parallel. A solar panel system, generating power by solar energy, was positioned in front of the parallel system to guide the airflow impinging on the rotors. This array was installed in rural areas to generate electric power. The effect of the solar panel deflector arrangements, used to guide the air stream, was investigated. This type of plant development has not previously been examined. We employed a computational fluid dynamics software, Fluent, to analyze the flow fields and system performance prior to experimentation, then compared these simulations to our experimental data. The parameters studied include wind velocity, wind direction (with/without solar panel deflector), and the rotational speed of the rotors to identify the relationship between the tip-speed ratio (TSR) and power coefficient (Cp). For the numerical simulation results at TSR 0.8, the maximum Cp value of the parallel system without a solar panel deflector was 0.289, whereas at the optimal spacing between the parallel systems with a deflector (50 cm), the Cp was 0.389. This represents a difference factor of 1.35 between the two Cp values. The velocity vector distribution showed that the deflector could guide the airflow to impinge on the rotors from below, gaining extra wind power. The experimental results show that the wind velocity and rotational speed of the wind rotors exhibit large fluctuations in open fields. To combat this, experiments were repeated in both day and night conditions, in different seasons, to gather a range of Cp and TSR values. The average measured wind speed was 6.99 ± 1.52 m/s. Four Savonius wind rotors in a parallel system can generate 8.25 kW h of energy per day, with an optimal power generation efficiency of 20.7%. Our 3-kW hybrid wind and solar system, which used optimal simulation conditions to determine its experimental design, can generate 14.55 kW h of power per day, with a corresponding optimal power generation efficiency of 21.7%. Our measured Cp curve shows that a deflector can improve the system performance by up to 10.1%.

Role of structural noise in aircraft pressure cockpit from vibration action of new-generation engines

The evolution of new-generation aircraft engines is transitioning from a bypass ratio of 4–6 to an increased ratio of 8–12. This is leading to substantial broadening of the vibration spectrum of engines with a shift to the low-frequency range due to decreased rotation speed of the fan rotor, in turn requiring new solutions to decrease structural noise from engine vibrations to ensure comfort in the cockpits and cabins of aircraft.

Fabrication of Wood-Rubber Composites Using Rubber Compound as a Bonding Agent Instead of Adhesives

Differing from the hot-pressing method in the manufacturing of traditional wood-rubber composites (WRCs), this study was aimed at fabricating WRCs using rubber processing to improve water resistance and mechanical properties. Three steps were used to make WRCs, namely, fiber-rubber mixing, tabletting, and the vulcanization molding process. Ninety-six WRC panels were made with wood fiber contents of 0%–50% at rotor rotational speeds of 15–45 rpm and filled coefficients of 0.55–0.75. Four regression equations, i.e., the tensile strength (Ts), elongation at break (Eb), hardness (Ha) and rebound resilience (Rr) as functions of fiber contents, rotational speed and filled coefficient, were derived and a nonlinear programming model were developed to obtain the optimum composite properties. Although the Ts, Eb and Rr of the panels were reduced, Ha was considerably increased by 17%–58% because of the wood fiber addition. Scanning electron microscope images indicated that fibers were well embedded in rubber matrix. The 24 h water absorption was only 1%–3%, which was much lower than commercial wood-based composites.

Numerical research on hydrodynamic characteristics of end cover of pressure exchanger

To investigate hydrodynamic performance of the end cover under different inclined angles, a series of 3-Dimensional geometric models of the end cover with different inclined angles were built by Creo. The maximum inclined angle is 32 degrees and the minimum is 6 degrees. Numerical simulations by solving the Navier-Stokes equation, coupled with the “k-ɛ” turbulence model, were carried out. At last, regressive analysis method is used to deal with the result data. The data obtained by simulation were mainly analysed from three aspects. They are cause of the driving torque, drive efficiency and inclined angle of flow channel. The results show that the driving torque is formed mainly by the positive pressure of the water, and the influence of the viscous force on the driving torque of the rotor is negligible. What‘s more, both driving torque and pressure difference decrease with the increase of inclined angle in the form of power function. The driving efficiency increases in form of logarithmic function with the increase of inclined angle. This research has a great significance in the control of rotational speed of rotor and revealed the relationship between the driving torque of the rotor and the flow channel of the end cover.

Mineral Wool Primary Layer Formation in Collecting Chamber

The process of the mineral wool primary layer formation was investigated experimentally on a model spinning machine with sucrose as a working medium. The fibers were pneumatically transported from the spinner rotor to the accumulation grid with the aid of the blow-away and the suction airflow. The fiber primary layer formed on the accumulation grid was visualized by a camera for several different operating regimes. Acquired images were post-processed to determine the light absorption in the primary layer, which was then used to calculate the bulk density and the surface density of the layer. Based on the measured process quantities, we were able to form multiple regression models with a relatively good correlation to the experimental data. The models as well as the qualitative image analysis show a significant effect of spinner rotor rotational speed, pneumatic transport velocity and fiber deposit mass on primary layer bulk density and spatial distribution of fibers.

Computational analysis of erosion in a radial inflow steam turbine

Abstract In the present work, the erosion of the blades of a radial inflow turbine due to the ingested steam flow containing solid particles was investigated in detail. The study has been conducted by designing and modeling the 3D geometry of the turbine using the CFturbo tool and by carrying out a series of CFD simulations using the software package ANSYS CFX 15.0. As compressibility effects may affect the output results, a study was conducted to ensure the validity of the incompressible flow assumption. Furthermore, the erosion simulation results indicated that there are three main surface areas where significant erosion occurs. The first and by far the most affected part of the studied radial steam turbine is the trailing edge of the stator blade, where a relatively huge number of particles with sharp angles strike the surface. This surface area is found to be affected by a concentration effect, where a high number of particles impinge on a small surface area continuously. The second but less affected part is the leading edge of the suction side of the rotor blade, where the particles strike the blade surface many times. The particles are trapped in a vortex area between the trailing edge of the stator blades and the leading edge of the rotor blades. The third surface area which is eroded significantly is the central region of the pressure side of the rotor blade. However, the blade erosion in this area is less than the other two areas. Additionally, the effects of several factors such as the rotor rotational speed, input mass flow and particle size on the erosion have been studied in detail. The relations between these factors and the erosion rate density have been determined.

Fundamental study on aerodynamic force of floating offshore wind turbine with cyclic pitch mechanism

Wind turbines mounted on floating platforms are subjected to completely different and soft foundation properties, rather than onshore wind turbines. Due to the flexibility of their mooring systems, floating offshore wind turbines are susceptible to large oscillations such as aerodynamic force of the wind and hydrodynamic force of the wave, which may compromise their performance and structural stability. This paper focuses on the evaluation of aerodynamic forces depending on suppressing undesired turbine's motion by a rotor thrust control which is controlled by pitch changes with wind tunnel experiments. In this research, the aerodynamic forces of wind turbine are tested at two kinds of pitch control system: steady pitch control and cyclic pitch control. The rotational speed of rotor is controlled by a variable speed generator, which can be measured by the power coefficient. Moment and force acts on model wind turbine are examined by a six-component balance. From cyclic pitch testing, the direction and magnitude of moment can be arbitrarily controlled by cyclic pitch control. Moreover, the fluctuations of thrust coefficient can be controlled by collective pitch control. The results of this analysis will help resolve the fundamental design of suppressing undesired turbine's motion by cyclic pitch control.

Design, fabrication and characterization of LTCC-based electromagnetic microgenerators

Design, manufacturing process and properties of electromagnetic microgenerators fabricated in LTCC (Low Temperature Co-fired Ceramics) technology are presented in this paper. Electromagnetic microgenerators consist of planar coils spatially arranged on several layers of LTCC and of a multipole permanent magnet. Two different patterns of coils with 2-, 8-,10- and 12-layers and outer diameter of 50 mm were designed and fabricated. Silver-based pastes ESL 903-A or DuPont 6145 were used. In order to estimate the inductance of a single spatial coil the Greenhouse (self-inductance) and Hoer (mutual inductance) calculation methods were used. To verify the calculation results a single-layer coil was fabricated for each pattern and its inductance was measured using the precision RLC Meter. Fabricated LTCC microgenerators with embedded coils allow to generate voltage higher than ten volts and the electrical output power of approximately 600 mW at the rotor rotation speed of 12 thousands rpm. The self-made system was used for characterization of LTCC-based electromagnetic microgenerators.

ナセル搭載・地上設置型ドップラーライダーを用いた風車の流入風計測

Long-term operation of a nacelle-mounted lidar is important for a lidar-assisted wind turbine control system. In this study, the measurement characteristics of the nacelle-mounted lidar has been investigated. The prototype of the nine-beam nacelle-mounted lidar system of Mitsubishi Electric was used for the study. Measurement data obtained from the nacelle-mounted lidar was compared with that of a ground-based lidar. This nacelle-mounted lidar can measure wind-inflow wind using 9 beams. The minimum range of the nacelle-mounted lidar was x=75m and the maximum range was x=1000m. A Komaihaltec 300-kW wind turbine (KWT300) situated in the test field was used for this study. The ground-based lidar was used for wind condition observation at the wind turbine rotor hub height. In the measurement range close to the wind turbine, the availability of nacelle-mounted lidar was dependent on the rotation speed of the turbine rotor. The 10-min-averaged wind speed measured by two lidars had high correlation.

Numerical optimization of the asymmetric blades mounted on a vertical axis cross-flow wind turbine

In this paper, response surface methodology (RSM) based on central composite design (CCD) is applied to obtain an optimization design for the asymmetric blades geometry of a vertical axis wind turbine (VAWT). Turbine's airfoils are simulated by using computational fluid dynamics (CFD). The SST K-ω model is used to simulate turbulent flow around the asymmetric blade. The free-stream velocity is constant and the rotation speed of turbine rotor is considered 350 to 600rpm. Results show that the maximum torque coefficient is obtained at rotation of 450rpm.

Experimental investigation of melt fiberization from a perforated rotor spinning machine

Fiber formation from molten fructose sugar was investigated experimentally on a spinning machine with a hollow perforated rotor. The fiberization process was visualized by a high-speed camera in different operating points obtained by variation of melt temperature and rotor rotational speed. Contours of the forming fibers were found to significantly depend on the rotor rotational speed and melt temperature, approaching involute shape with little statistical variability at sufficiently high Weber and Rossby numbers. After exiting fiberization orifices, melt jets contracted significantly and over a relatively short distance. Surprisingly, final fiber diameter rose with the Weber number due to an increase in Rossby number reducing the degree of fiber longitudinal stretching. Fiber contours were found to be initially smooth, but developing large amplitude transversal instabilities farther downstream up to a point when fiber structure is completely disrupted, creating random and highly complex new flow structures. A structure optimal for fibrous end products may be attained by controlling initial melt superheat and assuring that fibers are cooled below the glass transition temperature.

Mathematical Modelling and Analysis for the Efficiency of Wind Power Gearbox Based on the Toroidal Drive

This paper proposed a kind of gearbox based on the toroidal drive to step up the speed of rotor rotation to a value suitable for standard induction generators for wind power field. In the inversion mechanism of the proposed gearbox, the system transmission ratio formula is obtained. Then the force analysis of the meshing components including a sun worm, a planet worm gear and an internal toroidal gear has been done respectively and the efficiency calculation formula of the gearbox system is deduced. Besides, the influences of the pressure angle and the helix angle of the sun worm and the internal toroidal gear for the gearbox have been further discussed. Finally, the verification of the efficiency analysis results of the gearbox is accomplished based on computer modelling and simulation.

Methodology to Correct the Magnetic Field Effect on Thin Film Measurements

Machined ferrous metal components may carry a magnetic field, which in rotation disturb the output of electrical sensors. To minimize the effect on the electrical instrumentation, the rotating components are usually demagnetized. However, even after the demagnetization process, a residual magnetism unavoidably remains. This paper presents a methodology to predict the effects of a rotating magnetic field induced on thin film measurements. In addition to the prediction of the magnetic effects, a procedure to correct the spurious variation in the readings of thin film gauges has been developed to enhance the fidelity of the measurements. An analytical model was developed to reproduce the bias on the electrical signal from sensors exposed to rotor airfoils with magnets. The model is based on the Biot–Savart law to generate the magnetic field, and the Faraday's law to calculate the electromotive force induced along the measurement circuit. The model was assessed by means of controlled experiments varying the rotor tip clearance and rotational speed. The presented methodologies allowed the correction of the magnetic field effects. The raw signal of the thin film sensors, in the absence of any correction, is prone to deliver errors in the heat flux amounting to about 8% of the mean overall value. Thanks to the developed corrective approach, the residual magnetic effect contribution to the heat flux error would be 2% at most.

Керування стрілочним електроприводом із застосуванням нейромережевого перетворювача керованого сигналу.

The practicability of utilization of neural network converter of controlled signal while operating a contactless switch electric drive of a closed loop control system has been shown. A simulation model of operating a contactless switch electric drive of a closed loop control system has been developed. The investigations concerning time dependencies of electromagnetic moment, rotation speed and current of a switch electric drive stator with absence and presence of negative feedback have been conducted. It has been shown that independently of perturbation action condition, negative feedback in control system provides continuous change of current, torque and speed of an engine rotor rotation according to the specified law. It has been determined that load change does not influence engine behavior significantly at that. A neural network regulator of a control system of a switch electric drive contactless engine has been developed. Unlike the existing one, built on the base of logical elements, it allows damping self-induced vibrations in the whole given range of an electric drive work and thereby provides its stable work.

Research on power coefficient of wind turbines based on SCADA data

Power coefficient Cp is an important parameter for wind turbine design and operational control. Wind speed is the basic calculation parameter of the power coefficient. Since the anemometer is fixed on the nacelle, the measured wind speed is different from the wind speed in front of the wind rotor. Calculation error will produced if the directly measured wind speed is used to calculate the power coefficient. In this paper, a calculation model of the wind speed in front of the wind rotor is presented based on the SCADA data and the aerodynamic theory. Two power coefficient calculation methods are proposed. One is based on the statistical data and the other is based on the real-time data. An actual calculation result for a 2 MW wind turbine shows that the power coefficient is near or greater than 0.593 (the theoretical maximum value) if the directly measured wind speed is used during the maximum power point tracking (MPPT). After wind speed correction, the power coefficient is reduced to 0.397 that is more realistic. When using the real time data, the power coefficient is time-varying even in the region of MPPT, since wind speed is time-varying and the wind rotor rotational speed regulation is delayed due to the wind rotor moment of inertia.

Development of a novel homogenizer using the vane pump-grinder technology for the production of meat batter

On the basis of the continuous operating vane pump-grinder technology, a novel high-shear homogenizer consisting of a saw-tooth rotor-stator system was combined with a vane pump to produce meat batters. The rotational rotor speed varied between 1000 and 3000 rpm and the volume flow rate varied between 10 and 60 L/min at either constant volume flow rate or constant rotational rotor speed. The meat batters were filled into casings and heated up to a core temperature of 72 °C in order to induce gelation. Characteristics of samples were assessed by structure, L*a*b* color values, texture, and water-binding analysis. The rotational rotor speed and the volume flow rate define the volumetric energy input that induces the degree of dispersion. Thus, the mean diameter of visible lean meat particles was between 0.361 ± 0.011 mm and 0.468 ± 0.017 mm, whereas the volume-surface diameter attained sizes between 0.626 ± 0.018 mm and 0.929 ± 0.066 mm.