Single Rotor Research Articles

Stator slotted design of axial flux permanent magnet generator for low-speed turbine

The wind power plant has an important component, namely a generator which is an electrical engine that converts mechanical energy into electrical energy. This paper discusses the design of the permanent rotor axial flux generator (Single Rotor Single Stator) using a slotted stator and using a slotted stator reference design. To find out more in detail, this work was conducted by comparing four different generator designs, the number of slots and tooth widths. Testing the width of the teeth and the number of slots varied, including 12 slots width of teeth 23 mm, 15 slots width of teeth 18 mm, and 18 slots width of teeth 15 mm. The permanent magnet used in this study is neodymium iron boron, NdFeB 48/11 with a total of 10 poles. The desired reference power is 100 Watt with a speed of 500 Rpm. The outputs of each design in the form of voltage, current, power, and efficiency are discussed. The conclusion obtained that the additional teeth to the stator and increasing the number of axial flux slots affect the specified output parameters. The result of using teeth is that the voltage, current, and power are getting bigger and the more number of slots the smaller the voltage, current, and power.

Numerical analysis on the performance of Dual Rotor wind turbine

This study investigates the aerodynamic performance of wind turbines aiming to maximize the power extracted from the wind. The study is focusing on the effect of introducing a second rotor to the main rotor of the wind turbine in what is called a dual rotor wind turbine (DRWT). The numerical study took place on the performance of small-scale model of wind turbine of 0.9 m diameter using S826 airfoil.
 Both the Co-rotating and Counter rotating configurations were investigated at different tip speed ratios (TSR) and compared with the performance of the single rotor wind turbine (SRWT). Many parameters were studied for dual rotor turbines. These include the spacing between the two rotors, the pitch angle of the rear rotor and the rotational speed of ratio rear to front rotor. Three-dimensional simulations performed and employed using CFD simulations with Multi Reference Frame (MRF) technique.
 The Co Rotating Wind Turbine (CWT) and Counter Rotating Wind Turbine (CRWT) found to have better performance compared to that of the SRWT with an increase ranging from 12 to 14% in peak power coefficient. Moreover, the effect of changing the pitch angle of the rear rotor on the overall performance found to be of a negligible effect between angles 0⁰ until 2⁰ degrees tilting toward the front rotor. On the other hand, the ratio of rotational speed of the rear rotor to the front rotor found to cause a further increase in the peak performance of the CWT and CRWT ranging from 3 to 5%.

Preparation and characterization of bakelite bonded magnet NdFeB used for electric generator

The permanent magnets based on NdFeB is well known as rare earth alloy magnets made from neodymium, iron and boron elements and has tetragonal crystalline structure Nd2Fe14B which has high coercivity, large energy product (app 50 MGOe) and curie temperature about 312 °C. In this paper will be discussed the preparation of bakelite bonded magnet NdFeB and characterization, also the purpose of this research is to make bonded magnet NdFeB using 3 % bakelite and know the extent to which can be applied in making a small electric generator. The bonded magnet NdFeB was made by mixing a magnetic powder NdFeB with a polymer as binder. The composition of the sample consisted of 97 wt. % of NdFeB powder and 3 wt.% of bakelite. The mixed raw materials were then pressed to form a disc with pressure about 40 MPa at temperature about 160 °C for 20 minutes. It was obtained a disc with size 40 x 18 x 6 mm. The disc samples were magnetized by using impulse magnetizer at 1500 Volt DC, then the samples were measured magnetic properties by using Gauss meter and Permeagraph. The measurements result show that, the bakelite bonded magnet NdFeB has Magnetic Flux = 1100 Gauss, Remanence Br = 5.20 kGauss, Coercivity Hc = 6.14 kOe and Energy product (BH) max = 4.78 MGOe. The bonded magnet NdFeB was applied to the prototype small generator with single rotor and single stator. The results of performance test of generator indicate that it is achieved output power of generator about 9.98 Watt at a maximum speed about 500 rpm.

Optimized manufacturing of the small dual wind turbine used to generate electricity in central Iraq areas

Start your Due to the importance of generating electricity from wind turbines, single rotor wind turbine and dual rotor wind turbine. There was a need to design and manufacture the turbine system operating in both types mentioned above and have advantages to increase the generation of electric power. The aim of this work was to generate electrical power at a wind speed of up to 1m/s and more to achieve this wind speed and direction of the wind were adopted from tables of the Zerbatiya Station of the Wasit Governorate (Geographically located in central Iraq). The simulation was used to generate rotational speed for front and rear blades from 1m/sec to 13m/sec. A new idea was used to induce the dual small wind turbine to generate electrical power at low speed (1m/sec). In this case, there is latent energy in the surrounding wind turbine, but it is not that helps to rotate the wind turbine. To apply this idea the starter motor is used. Passive magnetic bearing supports have been used to reduce friction of the rotors this will reduce losing of wind energy. Brakes are the mechanical devices which aimed to slow or shut down the machine. They are also designed to prevent moving after stopping. Finally, the Genetic Algorithm (GA) was used within the program for the purpose of obtaining the best amount of power generated. All the above were for the purpose of determining the best position for blades at different speeds to generate electricity by using Permanent Magnetic Synchronous Generator (400W).Results of this paper: (a)-The starter motor proved good performance when using it. (b)-Using passive magnetic bearing proved effect on increase the power generation. (c)-Mechanical brakes work to stop the system within a period of time and not immediately as this will negatively affect the performance of the system.

A fully coreless Multi-Stator Multi-Rotor (MSMR) AFPM generator with combination of conventional and Halbach magnet arrays

An axial flux permanent magnet (AFPM) generator is known to be a good candidate for both low and high-speed application. In this paper, a new design of fully coreless multi-stator multi-rotor (MSMR) AFPM generator has been presented with conventional and Halbach magnet arrangement combined with an ironless (epoxy) rotor. For MSMR topology of AFPM machine, back iron is still present in the middle rotor and to maintain the same distribution of magnetic flux, magnets are using on both side of the middle rotor. This paper suggests replacing the middle iron rotors with a single epoxy rotor which reduces the weight of the machine, hence increase power density. On the other hand, for the elimination of iron and magnets in the middle rotor, conventional magnet arrays are used to maintain a continuous flux path. In addition, Halbach array is adopted on the external epoxy rotor to reduce flux leakage on the external sides of the machine. The performance of the proposed generator is investigated in terms of voltage, current, power, power density, and torque ripple. The analytical design approach is first presented and subsequently validated using ANSYS Maxwell® electromagnetic finite element analysis (FEA) software. It is found that a fully coreless MSMR AFPM generator with conventional and Halbach magnet arrays gives higher power density and lower torque ripple with a reduced axial length which is favorable in wind power and pico-hydro applications.

Effect of tip clearance on performance of contra-rotating axial flow water-jet propulsion pump

Insufficient understanding of tip clearance on hydraulic and thrust performance is a major problem encountered in the design and application of the contra-rotating axial flow water-jet pumps. In order to investigate the effect of tip clearance on hydrodynamic and thrust characteristics of the pump, tip clearance coefficient [Formula: see text] is defined and scraping rate [Formula: see text] is introduced in this paper. Head coefficient and hydraulic efficiency are obtained with the numerical prediction and experiment as [Formula: see text], which are in good agreement with each other. With the increase of [Formula: see text], the saddle area of head coefficient slows down and the high efficiency zone narrows. Along the relative chord length of shroud of the rear rotor, the [Formula: see text] presents an opening down quadratic curve as [Formula: see text], and if [Formula: see text], it presents a “M” shape nearly. Comparing the two operating conditions of contra-rotating rotors and single rotor, the [Formula: see text] and wake effect of the rear rotor are enhanced and inhibited by the front rotor respectively for the interference between the two rotors, the thrust coefficient of the propulsion pump reaches the maximum when [Formula: see text].

A computational investigation to analyze the effects of different rotor parameters on hybrid hydrokinetic turbine performance

Cross flow hydrokinetic turbines have been considered a decent choice for riverine applications. Under the present work, performance of hybrid rotor cross flow hydrokinetic has been investigated for different rotor parameters. The proposed hybrid rotor is the combination of two conventional turbine rotors (Savonius and Darrieus). Investigations have been performed by considering flow velocity varying in the range from 0.5 m/s to 2.0 m/s. The performance of hybrid rotor was assessed in term of power coefficient (CP) and torque coefficient (CT). Further, comparison of hybrid rotor and single Darrieus rotor has been carried out on the basis of their performance. Flow behaviour across the turbine vicinity is analyzed and discussed with the pressure, velocity contours and velocity streamlines. It has been found that radius ratio and attachment angle play a crucial role in performance enhancement with reduction in torque fluctuations. For the considered range of rotor parameters, the maximum power coefficient (CPmax) and average torque coefficient (CTavg) were obtained as 0.109 and 0.1276 corresponding to radius ratio of 0.6 at an attachment angle of 90°. Further, power coefficient and torque coefficient of hybrid rotor are found to be improved by 37.97% and 35.88% respectively as compared to single Darrieus rotor.

Comparative investigations for performance and self-starting characteristics of hybrid and single Darrieus hydrokinetic turbine

Hydrokinetic turbine technology is an emerging field to produce clean energy from the riverine systems. Lot of hydrokinetic potential sites are available to provide the energy to the people living in those areas. Under the present work, two different hydrokinetic turbine rotors (hybrid and single Darrieus) are evaluated in term of performance and flow across the rotor. The flow velocity of water is considered as 1.0m/s and the model for both type of rotors are designed and modeled along with an open channel. Based on the investigations, it has been found that hybrid rotor is more efficient for hydrokinetic turbine and yields about 9.9% higher power coefficient (CP) than single Darrieus rotor. The average torque coefficient (CT) for hybrid rotor has also been found 15.9% higher than single Darrieus rotor with less fluctuations in torque. The results obtained from the numerical investigations are validated with experimentation results. Flow contours across the turbine rotor were plotted and smooth flow was observed with low-pressure range for hybrid rotor while the single Darrieus rotor experience a flow re-circulation zone with high-pressure range.

Performance of Double Blade Savonius Rotor at Low Rotational Speed

The performance of the single and double blade Savonius rotors are numerically analyzed using the K-ε/realizable turbulence model. The computations are implemented at different values of tipspeed ratio from 0.2 to 0.4 with a step of 0.05. Both rotors have the same dimensions with an external overlap between their blades equals 0.02 m. The results indicate that the double blade rotor performs better than the single blade rotor in terms of power coefficient. In addition, the torque coefficient is improved at all tested values of tip-speed ratio. Furthermore, the results of the simulation show that the maximum power coefficient was 0.163 at tip-speed ratio = 0.4 for the double blade rotor, whereas the maximum improvement of the double blade rotor occurs at tipspeed ratio = 0.2 with a percentage of 11.86% compared to the single blade rotor. Moreover, the highest value of the torque coefficient was 0.524 at tip-speed ratio = 0.2 for the double blade rotor.

New Spectral Markers for Broken Bars Diagnostics in Induction Motors

The paper discusses the spectral markers of fault rotor bars in induction motor current signature analysis (MCSA). The results of the simulation of the deterioration process for a single rotor bar, as well as the results of research for various mutual bracing of two broken bars, are reported. We proposed a simple empiric technique allowing one to obtain frequencies for spectrum markers of damaged rotor bars based on simulation analysis. The set of frequencies obtained in the experimental part of the study was compared with simulation results and the results of real-life measurements. The theoretical results were verified through the experiment with the real induction motor under load. Analysis of experimental results proved that the given algorithm for spectrum analysis is suitable for early detection of fault rotor bars in induction motors.

Controlling the Rotational Barrier of Single Porphyrin Rotors on Surfaces.

Artificial molecular machines have played an indispensable role in many chemical and biological processes in recent decades. Among all kinds of molecular machines, molecular rotor systems have attracted increasing attention. In this work, we used density functional theory (DFT) calculations to investigate the rotational behaviors of on-surface molecular rotors based on porphyrin, which is a species of molecule with wide biological and chemical compatibilities. Moreover, our comparative studies demonstrate that macrocycle metalation, supporting substrate replacement, and functional group substitutions can effectively modify the rotational barrier of porphyrin rotors. We believe that these modification methods can further guide the path to achieve highly controllable on-surface molecular rotor systems in future applications.

High-Strength Rotor Design for Ultra-High Speed Switched Reluctance Machines

High speed machines are gaining popularity in more and more applications. Besides permanent magnet (PM) machines, switched reluctance machines (SRMs) are very competitive candidates for high-speed applications in high-temperature environments due to their single material rotor without PMs. However, the conventional rotor geometries of SRMs are not suitable for the ultra-high speed applications. In this article, a novel high-strength, high-torque-density, high-efficiency rotor design for the ultra-high speed SRMs is proposed. First, a three-dimensional finite-element analysis is conducted to calculate the von-Mises stress distribution of the proposed rotor and shaft. Then, in order to improve the bonding and robustness of the design, proper high-strength adhesives are used and modeled based on the cohesive zone model. A parametric study is conducted to find the optimal length of the rotor stack. A thermal stress case study is also conducted. Finally, several prototypes are built to validate the manufacturing feasibility of the proposed design.

Effect of tip spacing, thrust coefficient and turbine spacing in multi-rotor wind turbines and farms

Abstract. Large eddy simulations (LESs) are performed to study the wakes of a multi-rotor wind turbine configuration comprising four identical rotors mounted on a single tower. The multi-rotor turbine wakes are compared to the wake of a conventional turbine comprising a single rotor per tower with the same frontal area, hub height and thrust coefficient. The multi-rotor turbine wakes are found to recover faster, while the turbulence intensity in the wake is smaller, compared to the wake of the conventional turbine. The differences with the wake of a conventional turbine increase as the spacing between the tips of the rotors in the multi-rotor configuration increases. The differences are also sensitive to the thrust coefficients used for all rotors, with more pronounced differences for larger thrust coefficients. The interaction between multiple multi-rotor turbines is contrasted with that between multiple single-rotor turbines by considering wind farms with five turbine units aligned perfectly with each other and with the wind direction. Similar to the isolated turbine results, multi-rotor wind farms show smaller wake losses and smaller turbulence intensity compared to wind farms comprised of conventional single-rotor turbines. The benefits of multi-rotor wind farms over single-rotor wind farms increase with increasing tip spacing, irrespective of the axial spacing and thrust coefficient. The mean velocity profiles and relative powers of turbines obtained from the LES results are predicted reasonably accurately by an analytical model assuming Gaussian radial profiles of the velocity deficits and a hybrid linear-quadratic model for the merging of wakes. These results show that a larger power density can be achieved without significantly increased fatigue loads by using multi-rotor turbines instead of conventional, single-rotor turbines.

Sommerfeld Effect and Unbalanced Response Analysis in Single Disk Rotor System with Eccentric Mass Considering Induction Motor Model

Sommerfeld Effect and Unbalanced Response Analysis in Single Disk Rotor System with Eccentric Mass Considering Induction Motor Model

Tuning rotation axes of single molecular rotors by a combination of single-atom manipulation and single-molecule chemistry.

Defining the axis of a molecular rotation is vital for the bottom-up design of molecular rotors. The rotation of tin-phthalocyanine molecules on the Ag(111) surface is studied by scanning tunneling microscopy and atomic/molecular manipulation at 4 K. Tin-phthalocyanine acts as a molecular rotor that binds to Ag adatoms and the substrate. Four different rotation axes are constructed at positions from the center to the periphery of the molecule. Furthermore, using the asymmetric appearance of the modified molecule, the rotation direction of the molecules is identified. This work provides a new approach for designing molecular rotors or motors with definable rotation radii and functions.

Research on Reverse Measuring Method of Screw Drill Rotor Based on Axis Section

The screw drilling tool is an important underground power tool in the oil fields. During the working process, the rotor will be damaged or unevenly worn. The repair and reuse of the damaged area of the rotor will greatly improve the utilization rate of the screw drilling tool and reduce the mining cost. To this end, based on the formation principle of the rotor surface of the five-head screw drill, the curve coordinates are described by the ray length and the rotation angle. The axis relationship equation is characterized by exploring the intrinsic relationship between the two coordinates, and the reverse model of a single screw drill rotor was constructed by point collection. At the same time, the experimental research was carried out to verify the feasibility of modeling the screw drilling tool according to the axial section. In order to provide an effective way to reverse the entire body based on the unworn area of the screw drilling tool, the inverse modeling theory of the spiral surface entity is greatly enriched.

Research on multi-mode regenerative braking energy recovery of electric vehicle with double rotor hub motor

In this study, a new type of double rotor hub motor is proposed. Then, its structure, the working principle as well as the regenerative braking energy recovery modes are described. In detail, three kinds of regenerative braking energy recovery modes, i.e., double motor regenerative braking mode, single inner motor regenerative braking mode and single outer motor regenerative braking mode, are introduced. The mathematical models of single wheel dynamics model and double rotor hub motor model are established. The three kinds of braking energy recovery modes are compared and the simulation results show that, by using the sliding mode control strategy, on the condition that the maximum braking energy recovery of the motor is satisfied, the hydraulic braking torque can make corresponding response according to the change of the regenerative braking torque of the motor. At the same time, antilock braking of the wheel is achieved.

Evaluating the Effects of Electric and Magnetic Loading on the Performance of Single and Double Rotor Axial Flux PM Machines

Axial-flux permanent-magnet machines are used particularly in applications requiring a compact structure. Their disc-shaped topology and axial airgap have led to a variety of configurations including two popular ones: the yokeless and segmented armature (YASA), and the single-stator single-rotor or single-sided machine. In this study, a comprehensive comparative analysis of these configurations is conducted at different magnetic and electric loadings. It is found that at lower loadings, typically employed for air-cooled machines, the torque/ampere characteristics of the YASA machine are almost identical to those of a single-sided machine constructed with half the magnet volume. On the other hand, the single-sided machine outperforms the YASA machine when the magnet volumes in both machines are maintained equal. However, for higher electric loadings, the torque/ampere characteristics of the YASA machine droop significantly less than those of the single-sided machine. This article includes analytical estimations, which are verified with experimentally validated finite element analysis (FEA) simulations. In addition, the impacts of the armature reaction on saturation and the magnetic flux linkage, the magnet losses, and eddy current losses in both machines are also explored.

Experimental testing of a helical rotor for compost distribution

It is well known that a manure spreader must be able to apply manure consistently, effectively and uniformly over the time. An overapplying doze will cause serios environmental problems (pollution) and a sub-applying doze will not contribute to plants growth and the applying of the fertilizer will be a loss. Corroborate with others problems such as maintaining a constant tractor speed, a constant rotational speed of the rotor, a constant and continuous flow of the material make the manure spreading machines an important subject for study and continuously improving . The propose of this study is to test a vertical helicoidal rotor for manure spreading in order to improve the machine distribution uniformity. The relation between the rotor position and rotation sense is a definitory issue for the machine performance. In order to achieve a high distribution uniformity a single helical rotor is tested and a series of possible situations of placing four rotors on the machine are analyzed. The optimal solution is given by two indicators: uniformity of spreading and distribution width. The test were made with an helical rotor having the following characteristics: high=1,1 m, maximum diameter of helical spiral=0.345 m, minimum diameter of the helical spiral= 0.114m, helical pitch=0.3m, inclination angle = 15°. After analyzing four possible situations it is observe that the combination of the maximum uniformity with minimum distribution with is the optimal solution. Experimental were carried out with compost and can be repeatable with others type of solid organic fertilizers, but a new calibration should be done. It is desirable that a trapezoidal, oval or triangle pattern with uniform sloping sides to be achieved. Because most of the spreaders actually produce an oval or triangle distribution pattern it is necessary subsequent passes that increase the time for fertilization operation.

Torque Ripple Reduction of a Salient-Pole Permanent Magnet Synchronous Machine With an Advanced Step-Skewed Rotor Design

In this paper, a salient-pole permanent magnet synchronous machine (SPPMSM) is introduced to high-speed trains, taking advantage of its high utilization of the reluctance torque from the unbalanced reactance. Torque characteristics, such as average torque and torque ripple, are rather important and should be carefully concerned during the optimal design of the SPPMSM. Both the eccentric air-gap and the advanced step-skewed rotor (ASSR) design are developed and implemented to reduce the torque ripple for comfort and safety issues. Compared to the conventional step-skewed rotor (CSSR), the ASSR takes advantage of the high utilization of permanent magnets (PMs), which are axial continuous assembled, and the easier manufacture with a single rotor lamination model, which is asymmetrically designed with pole shoes skewed by individual skewing angles. No skewing arrangement is applied to the rotor yoke and the PM chambers. The impacts of the eccentric air-gap and the ASSR on the torque characteristics are comprehensively investigated by finite element analysis. The results show that the proposed technique can significantly reduce the torque ripple with a slight expense of the average torque. Based on the optimal eccentric design, experiments of the SPPMSM with the non-skewed rotor, CSSR, and ASSR under various conditions are carried out to validate the estimated results.