Rotor Design Research Articles

Impact of Rotor Design on Its Wear and Work Efficiency of the Aluminum Refining Process

Both the wear and the geometry of the rotor determine the efficiency of the process of aluminum refining. The paper presents wear tests of two different rotors: I (pump type) and II (propeller type). The operation of both rotors in industrial conditions was compared and their service life was examined. It was found that rotor I is more durable than the tested rotor II, and at the same time it provides a good level of hydrogen removal throughout the operation period, i.e., 1112 refining cycles. Rotor wear after refining was calculated by 3D scanning. The study also investigated the impact of rotor geometry on the efficiency of the refining process. The degassing efficiency was determined during refining in a foundry using the Dichte Index (DI). The alloy density and the volume of hydrogen removed were also tested for five stages of rotor wear: 0%, 25%, 50%, 75% and 100%. Both new rotors performed worse in removing hydrogen from the liquid alloy than the worn rotors due to their humidity which cannot be eliminated in the initial stage of their operation. A Dross Test was also performed to determine non-metallic impurities and compare size and number of cavities for rotor I and II. The best results of removing non-metallic inclusions by flotation were obtained for rotor I at the end of its operation.

Estimation of power performances and flow characteristics for a Savonius rotor by vortex particle method

AbstractThis study investigates the implementation of the vortex particle method (VPM) with the goal of efficiently and accurately estimating the power performances and flow characteristics for a Savonius rotor. The accuracy and efficiency of simulation methods are critical for the reliable design of Savonius rotors. Among various approaches, VPM is chosen because it can be flexibly incorporated with self‐correction techniques, and the distribution of bound vortex particles can effectively represent complex geometries. In this work, a double‐trailing‐edge‐wake‐modeling vortex particle method (DTVPM) is presented to extend the working range of VPM for dealing with large rotating amplitudes and high tip speed ratios (TSRs). DTVPM addresses asymmetrical torque predictions for a Savonius rotor without gap width. However, DTVPM performs poorly at high TSRs due to the absence of viscous effects near the surface. To capture complex wake structures, such as reverse flow structures, the viscous correction for tip vortices is suggested. The current research focuses on the implementation and validation of DTVPM for predicting torque coefficients and wake patterns, as well as comparisons to OpenFOAM results. Two‐dimensional and incompressible flow is estimated at = 0.2–1.2. For the studied cases, a maximum power coefficient is obtained at , consistent with published experimental data. In addition, the process of trailing‐edge vortices generation and detachment is captured by DTVPM. The comparison results between OpenFOAM and DTVPM show that DTVPM allows to efficiently simulate a Savonius rotor without any empirical parameters. DTVPM will help to improve existing engineering models for wind energy fields.

A solar-wind hybrid system developed by integrating wind blades into a Dish-Stirling concentrator

Dish-Stirling systems are usually installed in open fields, and therefore they are often exposed to strong winds. This research proposes to hybridize Dish-Stirling systems aiming at the wind energy recovery, increasing its availability factor, and enabling electricity generation during periods without solar radiation. The technical proposal is based on a new concept of parabolic concentrator, which integrates wind turbine blades on its structure, making possible the harvesting of solar and wind energy. The design for the hybridized concentrator was based on the geometric and thermal design methodologies for Dish-Stirling systems, blade element momentum theory combined with axial rotor design (pumps and fans) methodology, and CFD. The technical feasibility was analyzed comparing the electricity generation between the proposed hybrid system and its analogous non-hybridized Dish-Stirling system. In proposed hybrid system, the electricity generation increased by 27% compared to its non-hybridized system. The economic feasibility was analyzed comparing the LCOE between the proposed hybrid system, its analogous hybridized system (composed of wind turbine and Dish-Stirling system) and its analogous non-hybridized system. For the proposed hybrid system and its analogous systems (hybridized non-hybridized), the LCOE are respectively 0.69, 0.73 and 1.13. The results demonstrate the technical economic feasibility of the proposed hybrid system.

Electromagnetic and Mechanical Analysis and Measurements of Interior Permanent Magnet Motors Based on Equivalent Magnetic Circuit Method

This paper is about the magnetic field analysis of an interior permanent magnet motor (IPM motor) by using the equivalent magnetic circuit method (EMC method), which requires a small amount of computation time compared with the finite element method (FEM). IPM motors have a specific shape of rotor in which the permanent magnets are embedded. Therefore, in the bridge region, the magnetic saturation is generated due to the shape of the permanent magnet, which affects the magnetic flux density distribution in the air gap and the characteristics of the IPM motor. Thus, to design an IPM motor, the magnetic saturation effects should be considered along with the rotor shape. In addition, because the rotor of the IPM rotates at a high speed directly in connection with the load, the stress generated from the rotor must be stably distributed. Consequently, according to the rotor shape characteristics of the IPM, the stress is concentrated in the thin bridge region during high-speed rotation. When the stress generated in the bridge region exceeds the yield stress of the rotor iron core material, the bridge part is destroyed. Therefore, it is important to analyze the stress that occurs in the rotor during high-speed rotation in the rotor design stage of the IPM. In this study, we analyzed the magnetic field characteristics of an IPM motor using its equivalent magnetic circuit while considering the magnetic saturation in the bridge region. The stability of the rotor was determined by presenting a safety factor based on the maximum stress generated at the rotor for each speed. We derived the stator natural frequency to evaluate the resonance possibility between the electrical frequency and the stator natural frequency. Finally, the validity of the constructed equivalent magnetic circuit was verified by comparing the results with those obtained via the FEM analysis and experiments.

Response Surface Method for Optimization of Synchronous Reluctance Motor Rotor

In order to define the best design structure of the synchronous reluctance motor (SynRM) rotor, optimization must be carried out, implying the selection of the best alternative for each specific criterion. The optimization of an electrical machine is a complicated work involving meeting different criteria requirements while dealing with a range of constraints. In order to implement the optimization, it is necessary to process a huge number of options, changing the combinations of the factors affecting criteria and restrictions, which is a time-consuming process. This research presents the optimization technique that gives a mathematically proven solution of the optimal rotor design of a synchronous reluctance machine obtained by using metamodels in the form of local polynomial approximations. Analysis of the results of numerical modeling and experimental investigation has been performed in order to validate the developed technique and recommendations. SynRM rotor was manufactured, with the stator to be taken from the 1.1 kW W21 WEG induction motor, which makes possible the relevant experimental study. The performance analysis of the developed SynRM is shown in the paper.

Evaluation of direct-quadrature position and saturation of a SynRM machine with Segmented Rotor

The synchronous reluctance machine has gained popularity in traction and other smaller application thanks to its design that need very little or even no permanent magnet. Without internal permanent magnet assistance, an adequate level of torque density could be achieved by having an optimized rotor design to attain the optimum ratio of direct inductance over quadrature inductance. In order to properly control the machine, the direct and quadrature position need to be identified. In this study, a segmented rotor topology without permanent magnet was chosen. We evaluate the direct and quadrature position of the rotor topology, its saturation level and provide the flux linkage and the inductances of the machine.

Validation of a numerical model for hot-spot detection on the surface of a rotor pole using a scale model of a hydroelectric generator

To meet the ever-increasing demand for electricity, Hydro-Québec is investigating the viability of running its existing hydroelectric generators at higher power levels than their current operating limits. To assist in this investigation, numerical models capable of simulating the conjugate turbulent air flow and heat transfer phenomena in these generators were formulated and then validated, by using them to predict these phenomena within a scale model of a hydroelectric generator available at Hydro-Québec’s Research Institute and comparing the results to complementary experimental data. Reynolds-averaged governing equations were used, with turbulent stresses and heat fluxes approximated using eddy-viscosity and eddy-diffusivity approaches, in conjunction with the standard k − ɛ and a k − ω shear-stress-transport models, constant turbulent Prandtl number, and specialized treatments of the near-wall regions. Variable- and constant-fluid-property formulations (with coupled and decoupled solutions of the fluid flow and heat transfer) were assessed. The discretization of the complex geometry and the governing equations, and solutions of the discretized equations, were done using commercial codes. These numerical models gave favorable and comparable results, with predictions of global flow quantities (such as windage losses and overall mass flow rates) lying within 4%, and average and maximum temperatures of the pole surface within 5 °C and 3 °C, respectively, of the corresponding experimental data when using the constant-property, coupled, standard k − ɛ model with specialized wall functions. However, the equivalent decoupled model, which was the least computationally intensive, was also adequate for the task at hand. Numerical assessments of two alternate ventilation configurations in the scale model were also undertaken. They showed that increasing the surface area of the spider arms reduced the maximum temperature of the pole by 2.6 °C; and restricting the rotor inlet area reduced the windage losses and the maximum temperature of the pole by 4.7% and 1.5 °C, respectively. • 3D Conjugate heat transfer simulations of a hydroelectric generator scale model. • Validation of flow and temperature distributions by way of experimental measurements. • In contrast with design assumptions, flow across the rotor rim ducts is non-uniform. • Numerical predictions of hot-spots on the scale model’s rotor to within 2.7 °C. • Proposed modifications to the rotor design to reduce rotor pole hot-spot temperatures.

Control and navigation problems for model bio-inspired microswimmers

Navigation problems for a model bio-inspired micro-swimmer, consisting of a cargo head and propelled by multiple rotating flagella or propellers and swimming at low Reynolds numbers, are formulated and solved. We consider both the direct problem, namely, predicting velocity and trajectories of the swimmer as a consequence of prescribed rotation rates of the propellers, and inverse problems, namely, find the rotation rates to best approximate desired translational and rotational velocities and, ultimately, target trajectories. The equations of motion of the swimmer express the balance of the forces and torques acting on the swimmer, and relate translational and rotational velocities of the cargo head to rotation rates of the propellers. The coefficients of these equations, representing hydrodynamic resistance coefficients, are evaluated numerically through a custom-built finite-element code to simulate the (Stokes) fluid flows generated by the movement of the swimmer and of its parts. Several designs of the propulsive rotors are considered: from helical flagella with different chirality to marine propellers, and their relative performance is assessed.

Modal sensitivity of three-dimensional planetary geared rotor systems to planet gear parameters

A parameter study is presented to determine effects of planet gear design parameters on the global modal behaviour of planetary geared rotor systems. The modal sensitivity analysis is conducted using a three-dimensional dynamic model of a planetary geared rotor system for the number of planet gears, planet mistuning, mass of planet gears, gear mesh stiffness and planet gear speed. These parameters have varying impacts on both natural frequencies and mode shapes, therefore the sensitivity of the planetary geared rotor vibration modes to the planet gear parameters is determined by computing the frequency shifts and comparing the mode shapes. The results show that the mass and mesh stiffness of planet gears have a larger influence on the global dynamic response. Torsional modes and coupled torsional-axial modes are more sensitive to gear mesh stiffness whereas lateral vibration modes are more sensitive to gearbox mass. Planet mistuning results in coupling between lateral and torsional vibrations. The planetary gearbox becomes more rigid in the torsional-axial modes and more flexible in the lateral modes with an increase in the number of planet gears. Planet gears are also found to be having significant gyroscopic effects inside the planetary gearbox. The main original findings in this study can be directly used as initial guidelines for planetary geared rotor design.

Numerical Studies of Batch and Inline High Shear Melt Conditioning Technology Using Different Rotors

When casting aluminum alloy billets, high shear melt conditioning (HSMC) technology refines the resulting grain size, reduces the number of defects, and improves mechanical properties without the need to add polluting and expensive chemical grain refiners. These resultant improvements spring from the high shear rates that develop in the rotor–stator gap and the stator holes facing the leading edge of the rotor. Despite the growing literature on rotor–stator mixing, it is unclear how the different rotor–stator parameters affect the performance of high shear treatment. To upscale this technology and apply it to processes that involve large melt volumes, an understanding of the performance of the rotor–stator design is crucial. In this paper, we present the results of computational fluid dynamics (CFD) studies of high shear melt conditioning in continuous and batch modes with different rotor designs. These studies build upon our earlier work by studying the effect of rotor variation in a stator design consisting of rows of small apertures at different rotor speeds spanning from 1000 to 10,000 revolutions per minute. While no clear-cut linear pattern emerges for the rotor performance (as a function of the design parameters), the rotor geometry is found to affect the distributive mixing of microparticles, but it is insignificant with regards to their disintegration.

A WaveNet-based fully stochastic dynamic stall model

Abstract. Accurate modeling of the dynamic stall remains a challenge for the design and construction of turbine blades and helicopter rotors. At the same time, wind turbines, for instance, are becoming steadily larger, further increasing the demands on their structure and necessitating even more detailed modeling of the forces at hand. The primarily used (semi-)empirical models today have a long research history and are invariably based on phase-averaged data from oscillating blade pitch experiments. However, much potential for more accurate modeling of uncertainties and force peaks is wasted here, since averaging blurs many features of the response signals. Even computational fluid dynamics can help little in this regard, since the Reynolds-averaged Navier–Stokes equations used in practice cannot account for cycle variations, and scale-resolving models require extremely large amounts of computational resources. This paper presents an approach for a fully stochastic machine learning model that can nevertheless simulate these critical properties. Aerodynamic coefficients are compared with experimental data for different test cases. It is shown that synthetic force profiles which cannot be distinguished from the experimental data visually and are very close to them in the frequency spectrum can be generated. Additionally, attention is drawn to the difficulty of evaluating such a model, as traditional error metrics are of little use. A combination of dynamic time warping and the Earth mover's distance provides a robust solution for this problem.

Design and economic analysis of a hydrokinetic turbine for household applications

Social and political concerns on climate change have made renewable energy an essential component of government’s work plans. Grid-connected horizontal-axis hydrokinetic turbines are promising eco-friendly power sources for electrical energy supply to households near middle-to-high discharge rivers, while providing an opportunity to sell the energy surplus. In this work, a rotor design analysis of a hydrokinetic turbine with a 1 m nominal radius is performed based on blade element momentum theory. Then, an economic analysis is presented in terms of the discounted payback period and the internal rate of return. The numerical results show that three-bladed hydrokinetic turbines with a nominal tip speed ratio of 5 and state-of-the art high lift-to-drag ratio hydrofoils (∼100) lead to maximum performance with a power coefficient around 0.45. Performance can be further improved in an affordable manner using diffuser-augmented hydrokinetic turbines. The use of hydrokinetic energy in household applications can be profitable in leading economic countries with a discounted payback period of 4–6 years. In energy developing countries, this technological solution can be cost effective accompanied by economic subsides and implementation of a local industry, resulting in similar payback periods.

Experimental Examination for the Electric Power Generation of a Commercial Small-scale Wind Turbine with Modified Aerodynamic Design

Small-scale horizontal axis wind turbines (SSHAWT) have recently gained more interest due to fuel shortages and environmental issues. Generally, they are installed close to the ground in the wind boundary layer, where the velocity is relatively small. This study aims to evaluate the performance of a commercial SSHAWT and to modify rotor design based on wind velocity in the field. The experimental measurements are performed to examine a commercial 1.5 m radius rotor of 1 kW SSHAWT, which was designed at a rated velocity of about 8 m/s. The CFD calculations are performed as well to understand flow characteristics and to verify the experimental measurements. In the experimental procedure, the test of the wind turbine with a permanent magnet synchronous generator showed that at a wind velocity of 5 and 6 m/s, the highest generated power is 163.9 and 306 W corresponding to power coefficients of 0.255 and 0.28 when AC voltage of the generator is 24.4 and 37.76 V, the DC voltage after rectified 22 and 34 V, and the load current 7.45 and 9 A, respectively. Then the available wind velocity was measured in the field, and the average velocity was 4 m/s. Therefore, a more appropriate rotor is designed based on field velocity. The CFD calculations are used to test the new rotor. The results clarify that for the new rotor, the maximum blade's power coefficient is enhanced by more than 60 % compared to the commercial rotor.

Manufacture and Testing of a Magnetically Suspended 0.5-kWh Flywheel Energy Storage System

This article presents crucial issues regarding the design, manufacture, and testing of a steel rotor for a 0.5-kWh flywheel energy storage system. A prototype was built using standard industrial components. The rotor has a maximum operating speed of 24 000 min <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> and is magnetically suspended. The introduced critical issues regarding the manufacture include the thermal stress during the rotor hardening process, the fixation for the rotor components of the drive machine and the magnetic bearings, etc. The rotor strength was validated by the overspeed testing according to the standard <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IEC 60034-1</i> . A rotation of up to 28 800 min <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> (120% of the maximum speed) was realized and maintained for 2 min. The proved rotor was suspended by commercial magnetic bearings in the flywheel system. Despite simple decentralized control, the rotor was successfully driven up to the designed maximum speed. The rotor dynamic behavior is analyzed by analytical calculation, simulation, and measurements. Different eigenmodes are identified. The results prove the possibilities to build and operate a flywheel system using standard industrial components, showing potential for cost-effective designs.

Experimental investigations on flow and heat transfer characteristics in a high-speed rotor–stator disk cavity with axial throughflow

The rotor–stator disk cavity system is of great importance for turbine blade cooling and preventing gas invasion in the aircraft engine. This study presents an experimental investigation on a high-speed rotor–stator disk cavity with axial throughflow. The aims are to experimentally measure and reveal the pressure characteristics, windage heating, swirl characteristics, and relative temperatures at a high rotational speed of 0–9000 rpm with mass flow rates of 0.05–0.15 kg/s. Especially, a new measurement idea was proposed and tested that relative temperature in the rotor system can be obtained by measuring absolute parameters in the stator system. Experiment results reveal that rotational speed and inlet mass flow are the main parameters to determine flow characteristics in the rotor–stator cavity. The increase of rotational speed will enhance the effect of centrifugal boosting, windage heating, and swirl characteristics. But increasing inlet mass flow rate will lead to the opposite effect. When the airflow is in the heat balance state, relative total temperature and adiabatic temperature can be acquired by measuring absolute temperature and swirl ratio at the same radius. The maximum deviation is below 2 K. The results can be beneficial to the optimization design of rotor–stator disk cavity in the gas turbine engines.

Design of a Brushless Doubly-Fed Machine for Aviation Electric Propulsion

This article discusses a high-speed brushless doubly-fed machine (BDFM) for aviation turboelectric distributed propulsion application. After a brief overview of the machine fundamentals and propulsion architecture, the electromagnetic properties of the newly designed BDFM are analyzed. An innovative rotor mechanical design is introduced, which allows for a significant increase of speed compared to legacy rotor designs. Experiments were conducted to verify the 12 000-r/min high-speed operation. The findings in this article will give prominence to the feasibility of applying BDFMs for aviation applications.

Improved Torque and Efficiency of Induction Motors by Changing Rotor Structure of Permanent Magnet Assistance Synchronous Reluctance Motors

Many authors have recently studied line start permanent magnet assistance synchronous reluctance. This paper presents a method to improve the electromagnetic torque and efficiency of induction motors of 7.5kW-4P (which consists of 36 stator slots and 40 rotor bars) by changing the design of the permanent magnet assistance synchronous reluctance rotors. This means that permanent magnets will be inserted to the squirrel cage induction motors (induction motors). The electromagnetic torque and efficiency of an induction motor is analyzed and compared with that of the line-start synchronous reluctance motor via a finite element analysis. In addition, the influence of position and length permanent magnets on the electromagnetic torque and efficiency of the line-start synchronous reluctance motor is also considered and simulated. The model of this motor Linh is finally designed with four U layered- magnet rotor to verify the developed method. The development of the method is also validated on the practical induction motor.

Design of a V-Twin with Crank-Slider Mechanism Wind Energy Harvester Using Faraday’s Law of Electromagnetic Induction for Powering Small Scale Electronic Devices

The maintenance of wireless sensor networks involves challenges such as the periodic replacement of batteries or energy sources in remote locations that are often inaccessible. Therefore, onboard energy harvesting solutions can provide a viable alternative. Experimental energy harvesting from fluid flow, specifically from air flow, is typically restricted to a rotor and stator design or a model that strikes a piezoelectric. On the other hand, energy harvesting from mechanical vibrations routinely uses the linear motion of a magnet passing through a coil or vibrating piezoelectric elements. In this paper, we propose a novel V-twin harvester design that converts wind energy from a rotational input into the linear motion of a magnet inside a coil via a crank-slider mechanism. This design allows for high performance with a smoother voltage output when compared to a reference rotor/stator harvester design or piezoelectric method. At 0.5 Hz, a single crank-slider generated a voltage of 0.176 Vpp with an output power of 0.147 mW, whereas the reference harvester generated 0.14 mW at 1.0 Hz with a 0.432 Vpp. A single crank-slider operating at regulated frequencies of 0.5, 1, 2, and 3 Hz, with a stroke length of 50 mm and a generated continuous power of 0.147, 0.452, 2.00, and 4.48 mW, respectively. We found that under ambient wind speeds of 3.4 and 4.1 m/s the V-twin formation with the optimized configuration, in which the coils and loads were both connected in series, generated 27.0 and 42.2 mW, respectively.

A Review on Magnet Loss Analysis, Validation, Design Considerations, and Reduction Strategies in Permanent Magnet Synchronous Motors

Eddy current losses in magnets are a major consideration in the rotor design of permanent magnet synchronous motors (PMSMs). Stator design choices and the use of modern inverters with high switching frequency introduce harmonics that can contribute to significant losses in the magnets, causing the rotor to heat up. In typical PMSMs, the lack of rotor cooling can cause the magnet’s performance to degrade at high temperatures and eventually demagnetize. This review examines a large number of studies analyzing magnet eddy current losses using analytical methods and finite-element analysis. In some of these studies, magnet segmentation is carried out to reduce the losses; however, their loss-reduction effects depend highly on the type of PMSM and the mix of stator harmonics. Magnet segmentation without considering these effects can, in fact, increase the magnet losses, in addition to the extra manufacturing efforts. Multiple design analysis show the influence of rotor–stator geometric features on magnet losses. Although measuring magnet eddy current losses for these motor designs is a tedious task, authors have proposed calorimetric and loss segregation-based techniques to provide validation. This paper addresses magnet loss modeling techniques, PM material considerations, magnet segmentation effectiveness, motor and stator design effects, and experimental validation to inform motor designers about the costs and benefits of rotor designs that minimize rotor losses.

Аналіз роботи гідростатичного підшипника на перехідних режимах

The design of reliable rotor supports for modern high-speed machines is associated with the solution of many complex problems, both theoretical and experimental. Experimental studies play an important role in the system of scientific research and allow improvement and refine mathematical models and the application of numerical methods for their implementation. Experimental studies are usually selective and therefore require careful preparation. The task was set to investigate the characteristics of a hydrostatic bearing in the starting and braking modes. A program of experimental studies of the behavior of a shaft on hydrostatic bearings for the most difficult operating conditions has been developed. The advantages of hydrostatic bearings are given compared with other types of plain bearings, as well as compared with rolling bearings. The effectiveness of hydrostatic bearings is shown, compared with other types of bearings, for modern high-speed machines, in which there is an increase in vibration overloads and vibration displacements. Hydrostatic bearings have proven themselves in all operating modes, including transient ones. A description of the experimental setup for the study of transient modes of operation of the shaft on hydrostatic bearings is given. Studies of the transient modes of operation of the shaft on hydrostatic bearings were conducted at various values of the pressure of the working fluid supply, residual unbalance, as well as various values of the diameter of the hydrostatic bearing. To identify the movement of the rotor on hydrostatic bearings, the values of the amplitudes of oscillations during stationary (steady) movement of the rotor are also presented. It is shown that the comparison of the oscillation amplitudes of the rotor on hydrostatic bearings with a diameter of 0.06 m for the cases of non-stationary and stationary modes of its operation during the acceleration of the amplitude of oscillations in the entire range of rotational speeds is slightly lower (by about 15…20 %) than in the case of a stationary mode of operation of the rotor. When the rotor slows down, the amplitude of the rotor oscillations at high speeds is somewhat larger (by about 7…9 %), and at low speeds it is less by 8…10 % than in the case of a stationary rotor operation. The small influence of the non-stationary nature of the rotor movement on the dynamic characteristics can be explained by its large mass.