Rotor Concept Research Articles

A concentric 3D-printed centrifuge rotor to study the effects of hypergravity on small organisms at three different but concurrent radial accelerations

For life to reach space, it must first escape Earth's gravity—hence exposure to hypergravity during launch, and interplanetary acceleration and deceleration. Long-term colonisation of space requires the establishment of sustainable, in situ, food production systems. Earthworms may be involved as a regolith/soil ameliorant, a source of protein, and for organic waste conversion. Earthworms, however, have hydrostatic skeletons that may be susceptible to hypergravity exposure. We investigated whether earthworms (Eisenia andrei) would survive prolonged centrifugal hypergravity using a table-top centrifuge. Our intention was to concurrently test three different hypergravity treatments (plus a 1 G control). Our concentric rotor concept, with appropriate design adaptations, allows concurrent testing of three different gravity treatments on small- and microorganisms, cell cultures, plants, microcosm, and chemical/biochemical reactions for extended periods of hours to months. Our concentric concept therefore is easily adaptable and may facilitate other terrestrial-based research on chemical, molecular, and organismal levels.•We designed a 3D-printed centrifuge rotor with three concentric rings, each ring with four separate 125 mL compartments.•This design was tested with an 8-day pilot run with four young worms per container at 1.7 G, 2.5 G, and 3.1 G, with a 1 G control.•All worms at all treatments gained body mass, the mean increases of which were almost indistinguishable between treatments, illustrating the utility of the design.

Study on the efficiency of small-scale wind turbine with rotor adapted for low wind speeds

This article aims to present the results of tunnel tests and field tests of small-scale horizontal-axis wind turbines. The article proposes a new concept of turbine rotor adapted to improve efficiency at low wind speeds. The methodology for calculating the rotor and generator is shown. The turbine construction solution is presented briefly, along with the technology for manufacturing turbine components and assembly. An analysis of the obtained results is also conducted.

Power production and large-scale wake effects of offshore wind turbines with low specific rating

With the aim to increase the energy yield of large offshore wind farm clusters, especially during low wind speeds, innovative rotor concepts with low specific ratings are being developed. We use mesoscale simulations, to compare wakes and power production of a wind farm cluster with a rated power of 1.17 GW, equipped with a turbine featuring a low specific rating turbine concept, and the IEA 15 MW offshore reference turbine. While the IEA turbine resembles typical offshore wind turbine concepts, the HL rotor features a very large rotor diameter compared to its rated power, thus resulting in a very low specific rating for an offshore turbine. We simulate two wind farms made up of either of the two turbines that have the same installed capacity and farm layout. We found an improved power production of 86 % to 100 % for the HL wind farm in partial load conditions and comparable power production at rated operation. While the HL wind farm exhibits a more pronounced cluster wake during partial load operation, the IEA wind farm induces a larger wind speed deficit in the wake during rated operation. We discuss observed differences in wake behaviour, attributing them to the larger rotor diameter and lower thrust coefficient of the HL concept.

Hybrid-Lambda: a low-specific-rating rotor concept for offshore wind turbines

Abstract. We introduce an aerodynamic rotor concept for an offshore wind turbine which is tailored for an increased power feed-in at low wind speeds by a substantial increase in the rotor diameter while maintaining the rated power. The main objective of the conceptual design is to limit the steady-inflow loads (blade flapwise root bending moment (RBM) and thrust) to the maximum values of a reference turbine. The outer part of the blade (i.e. outer 30 % span) is designed for a higher design tip speed ratio (TSR) and a lower axial induction than the inner part. By operating at the high TSR in light winds, the slender outer part fully contributes to the increased power capture. In stronger winds the TSR is reduced and the torque generation is shifted to the inner section of the rotor. Moreover, the blade design efficiently reduces the power losses when the flapwise RBM is limited through peak shaving, below rated wind speed. This is of high importance, given the wind speed distribution at offshore sites. The characteristics of the rotor are first investigated with stationary blade element momentum simulations and further analysed with aeroelastic simulations, considering the flexibility of blades and tower to show that a structural design is feasible even for a blade of this size and complexity. The economic revenue and the cost of valued energy of the turbine are estimated and compared to the IEA 15 MW offshore reference turbine, considering a fictitious wind-speed-dependent feed-in price. Our results for the turbine concept with an increase in rotor diameter by 36 % show that the revenue can be increased by 30 % and the cost of valued energy can be reduced by 16 % compared to the reference turbine.

The Financial Aspects behind Designing a Wind Turbine Generator

This article investigates the construction of a wind power generator requiring the lowest possible cost. The proposed model is an Axial Flux Permanent Magnet (AFPM) Synchronous Machine, which contains two iron rotors and a coreless stator between them, constructed from resin. The scientific contribution relates to the coupling of economic and technical parameters, which will clarify the feasibility, i.e., a wind turbine construction capable of producing approximately 3.5 KW, using a simple mill and a generator of nominal rotor speed 100 rpm. Such studies are few in international literature and mainly concern low levels of rotor speed in relation to the produced output power. For the generator dimensioning, analytical equations are used, while the type and the dimensions of the magnets are determined, before the start of dimensioning. The authors carried out research in the international market, ending up with specific cost-effective magnets, while trying to adjust the remaining dimensions and materials of the machine based on these cost-effective magnets and the aforementioned nominal values of the generator. The machine, whose dimensions are derived by analytical equations, was simulated and analyzed using the Two-Dimensional Finite Element Method (2D-FEM) and the Three-Dimensional Finite Element Method (3D-FEM), for comparison purposes. Moreover, an economic analysis of the generator and its individual parts was conducted. Finally, a novel idea for reducing the total generator cost is proposed, by replacing the rotor disks with rings. The investigation revealed that analytical equations can predict with satisfactory accuracy the generator’s parameters. In addition, as permanent magnets are the most expensive materials in the construction, their predetermination using low-cost magnets can reduce the construction cost. Finally, the proposed concept of a ring-shaped rotor instead of a disk rotor, provides a cost reduction of up to 20%.

Stabilization of isolated hybrid microgrids with electric vehicle-based energy storage systems using a fractional order proportional-integral-derivative control

ABSTRACT Electric vehicles (EVs) are considered to be the most promising technology upgrades in the coming years to reduce the carbon emission, since the EVs could replace the conventional combustion vehicles as well as mitigate power fluctuations in power grids. This paper focuses on addressing the frequency stability issues in isolated hybrid grids (IHGs) by introducing a fractional order proportional-integral-derivative (FOPID) control for grid-connected power converters. A particle swarm optimization (PSO) technique is adopted to optimize the parameters of the controllers. The advantages of the proposed control method over the conventional proportional-integral-derivative (PID) control, proportional-integral with proportional-derivative (PI-PD) control, and proportional-integral-derivative with filter (PIDF) control schemes are verified by simulation case studies. Besides, a modified virtual rotor concept (MVRC) is proposed in this paper to enhance the inertia of the system. Furthermore, the performance of using EVs to regulate the frequency of IHGs is compared to the superconducting magnetic energy storage (SMES) units, capacitive energy storage (CES) units, and redox flow batteries (RFB) under fixed and variable load conditions.

Active alleviation of fatigue stress on blades by adaptively maneuvered deformable trailing edge flaps (DTEF).

The concept of "smart rotor" is an evolving advancement in wind turbine which enables an intelligent active flow control in rotor. The deformable trailing edge flap (DTEF) is a part of smart rotor concept which implements a customized active load control. The trailing edge flap actuator effectively replaces the tedious blade pitch actuation and conserves the actuation energy required for pitching the entire blade. The DTEFs require a fast computing, anticipatory controller for optimally tuning the flap angle with minimal power compromise. This work analyzes the performance of advanced control strategies like model predictive control (MPC), adaptive MRAC control, and DQ controllers. The MRAC controller is found to reduce the fatigue stress by 40% and the MPC controller damps up to 70% more efficiently than the typical feedback controller. The control strategies are aided by the LiDAR-based preview wind data for the active manipulation of trailing edge flap angle control. The validation of proposed controller is done using power analysis curve and the component fatigue lifetime analysis using MLIFE software. The above analyses are done in NREL Onshore 5-MW FAST wind turbine model which could be interfaced with MATLAB with modified AeroDyn code for active flap deflection.

Rotor and wake aerodynamic analysis of the Hybrid-Lambda concept - an offshore low-specific-rating rotor concept

The low-specific-rating rotor concept Hybrid-Lambda introduces a blade design with nonuniform distribution of design variables (design tip speed ratio and axial induction) along the blade span to alleviate loads of the outboard section in strong winds. In this paper, we validate aerodynamic design calculations, which were carried out with the blade element momentum theory by comparing the results to free vortex wake investigations (FVW). Furthermore, we investigate the wake behaviour with FVW and large-eddy simulations. The results show good agreements between the blade element momentum theory and FVW for integrated rotor quantities (power and thrust). Small deviations are present when the gradients of axial induction along the span are large. The wake of the Hybrid-Lambda Rotor shows advantages in the near-wake region (up to 4 diameters [D] downstream), especially in the outer wake annulus and in low turbulence scenarios. For further downstream positions, the wake is comparable to that of the reference turbine.

Advanced manufacturing concept of a bio-inspired reaction wheel rotor for small- and medium-sized constellation satellites

The increasing number of constellation satellites requires re-thinking of the design and manufacturing process for reaction wheel rotors. Mass optimisation of reaction wheel rotors leads to cost reduction and performance increase. Those optimisations can be realised by taking ideas from nature. Therefore, design principles of diatoms were screened, abstracted and implemented in an algorithm-based design process. In this way, a bio-inspired rotor was created, which considers launch and in-operation loads, is capable of up to 7500 RPM and shows a compact design with a diameter of 282,text {mm}. Regarding mechanical performance, an energy density of 4661,text {J kg}^{-1} and a mass moment of inertia ratio of 0.7584, which considers the component and an idealized design, could be achieved. Compared to a commercial rotor, this is equivalent to a similar inertia ratio and +85 % energy density, but +44 % mass due to manufacturing restrictions. Based on different boundary conditions, different first natural frequency for launch and operation conditions were obtained (658,text {Hz} and 210,text {Hz}). The new design was cast from nano-reinforced aluminium alloy (AlSi10Mg + Al2O3) in 3D-printed sand moulds that were produced via binder-jetting process. Thus, a hybrid manufacturing process was used, by combining additive manufacturing and casting. Post-processing of the cast part via turning and milling was performed to compensate distortion and achieve the required surface quality. Preliminary vibration measurements were performed, showing a large need for balancing to achieve low vibration emissions.

Investigation of permanent magnet synchronous machines with buried magnets and carbon fiber sleeve for automotive application

Due to the limited space available in vehicles, traction drives with high torque densities are a key objective of machine design in the automotive sector. In order to be able to dispense with a multispeed transmission and still achieve high vehicle end speeds, there is also the design objective of a high motor speed. Therefore, permanent magnet synchronous machines with buried magnets are preferred. In the following, a rotor concept is presented as a combination of buried rotor magnets and a carbon fiber sleeve in order to eliminate the radial and tangential rotor iron ribs. The resulting reduction in magnetic flux leakage, in combination with high mechanical strength, leads to an increased magnet utilization for the air-gap field and, thus, allows for a high torque density as well as high maximum speed. A disadvantage, however, is the increased manufacturing effort required for the production and assembly of the carbon fiber sleeve.

Reduced Axial Length Pole-Specific Rotor for Bearingless Induction Machines

The induction machine has proven to be one of the most difficult motor technologies to transform into a bearingless motor due to currents that are induced in the squirrel cage rotor by the suspension field. This paper develops a new rotor for use in a bearingless induction motor to solve this problem. The rotor is described as “pole-specific” because its winding couples to the motor field but not the suspension field. This new structure uses a common end-ring to reduce the rotor’s axial length, solving rotor dynamic challenges present in previous efforts to develop a pole-specific rotor. This paper presents the new rotor concept and leverages traditional cage rotor design theory to develop equivalent circuit models and a theoretical framework that reveals which combinations of poles and slots can be used to implement the new rotor. Experimental results validate the new rotor concept and demonstrate its performance improvement over the classical squirrel cage rotor. A case study is presented of a high performance 50 kW, 30,000 r/min design for an industrial compressor with a modeled efficiency of 96.8%.

Analytical and Computational Study of Hover Performance of Novel Dissimilar Coaxial Rotor

This paper studies a novel dissimilar coaxial rotor concept with significantly reduced rotor–rotor aerodynamic interaction during hovering flight. The proposed concept’s performance is systematically compared with regular coaxial and conventional single rotor configurations using 1) analytical and 2) blade element momentum theory (BEMT)-based analysis for hover flight condition. The hover performance among different rotor configurations is compared using a baseline main rotor combined with various antitorque mechanisms. Through this study it is established that the dissimilar coaxial rotor configuration shows improved performance for torque equilibrium cases when compared to both conventional and regular coaxial configurations for moderate- to high-thrust conditions with power reduction of 16–37% when compared to a conventional single main rotor–tail rotor configuration and 14–17% of power saving when compared to a regular coaxial rotor during hovering flight with rotor thrust in the range of . The analytical method from momentum theory and BEMT results correlate well for the induced and profile torque balanced conditions. The proposed concept appears to be an efficient alternative to the conventional single main rotor with tail rotor and regular coaxial rotor for hovering flight conditions within the scope of the analysis.

Flutter behavior of highly flexible blades for two- and three-bladed wind turbines

Abstract. With the progression of novel design, material, and manufacturing technologies, the wind energy industry has successfully produced larger and larger wind turbine rotor blades while driving down the levelized cost of energy (LCOE). Though the benefits of larger turbine blades are appealing, larger blades are prone to aeroelastic instabilities due to their long, slender, highly flexible nature, and this effect is accentuated as rotors further grow in size. In addition to the trend of larger rotors, non-traditional rotor concepts are emerging including two-bladed rotors and downwind configurations. In this work, we introduce a comprehensive evaluation of flutter behavior including classical flutter, edgewise vibration, and flutter mode characteristics for two-bladed, downwind rotors. Flutter speed trends and characteristics for a series of both two- and three-bladed rotors are analyzed and compared in order to illustrate the flutter behavior of two-bladed rotors relative to more well-known flutter characteristics of three-bladed rotors. In addition, we examine the important problem of blade design to mitigate flutter and present a solution to mitigate flutter in the structural design process. A study is carried out evaluating the effect of leading edge and trailing edge reinforcement on flutter speed and hence demonstrates the ability to increase the flutter speed and satisfy structural design requirements (such as fatigue) while maintaining or even reducing blade mass.

Analysis and design of the gas generator multifunctional bulkhead considering the thermal and structural loads

The operation of gas generators brings relatively high thermo-mechanical loads on the gas generator structure. The objective of this article is to determine the operating conditions, in terms of mechanical loads at extremely high temperatures in very limited and narrow space, of a multifunctional bulkhead for application on specific kinds of gas generators with back-to-back rotor concept. The paper contains numerical analysis and experimental investigation for determining the loads and behavior of the structure. Numerical analysis indicates that there is significant influence of the Tesla turbine effect on flow parameters. Also, uneven pressure distribution and significant thermal loads are identified. With experimental investigation and subsequent exploitation tests, it was concluded that the presented methodology identifies the operating conditions, truthfully simulates the bulkhead stress state and deformations and that the presented design solution satisfied all demands. Regarding results obtained by these numerical simulations, the innovative design solution for the multifunctional bulkhead was proposed.

Innovative aerodynamic rotor concept for demand-oriented power feed-in of offshore wind turbines

We introduce an aerodynamic rotor concept for a 15 MW offshore wind turbine which is tailored for an increased power feed-in at low wind speeds. The main objective of the conceptual design is to limit the stationary loads (blade flapwise root bending moment (RBM) and thrust) to the maximum value of the IEA 15 MW offshore reference turbine, while greatly increasing the swept rotor aera. The outer part of the blade (e.g. outer 30% of the rotor) is designed for a higher design tip speed ratio (TSR) and a lower axial induction than the inner part. By operating at the high TSR in light winds, the slender outer part fully contributes to the increased power capture. In stronger winds the TSR is reduced and the torque generation is shifted to the inner section of the rotor. Moreover, the blade is designed in a way that makes the limitation of the flapwise RBM through peak shaving aerodynamically more efficient. With static blade element momentum simulations the characteristics of the rotor are investigated and the economic revenue of the turbine is estimated, considering a wind speed dependent feed-in price. Our results show that the revenue can be increased by 30% compared to the reference turbine with an increase of rotor diameter by 36%.

Influence of Geometrical Parameters on the Shape of the Cycloidal Function Curve of a Fan with a Cycloidal Rotor

Even though the cycloidal rotor concept has been around for almost a century, it is still not as popular as it should be. Most often it is used to propel unmanned aerial vehicles or sea-going ships, or it is applied as a river- or sea-energy converter. Despite the possibility of directing the flow by changing the inclination angle of blades and the possibility of working in both directions, there are no scientific studies on the use of the concept in HVAC (heat, ventilation and air conditioning). One of the most important elements characterizing the operation of the cycloidal rotor is the cycloidal function describing the change in the angles of the blades during rotation. To properly design a cycloidal rotor for a preferred application, an analysis of the rotor geometrical parameters must be performed and analyzed. This was performed on a four-blade rotor equipped with CLARK Y blades. Using Ansys CFX software, a CFD model of a fan operating with various cycloidal functions was created. The results were compared with the experimental data with the use of the LDA technique. Different velocity profiles were obtained despite the use of cycloidal functions with similar waveforms and small angular differences. This is due to the considerable sensitivity of the cycloidal regulation system to differences in the geometrical sizes that describe it.

An alternative for wind energy conversion using improved Savonius rotor turbine model

The current society development is dependent of the planet energy resources and if we take an overview on renewable energies used worldwide it can be said that they are constantly gaining ground. This trend represents an important step forward towards maintaining a clean environment by focusing on capitalizing considerable resources that are sustainable over time, such as solar energy, together with waves and wind force. Regarding the energy production solution based on the atmospheric air masses movements or wind energy, the alternative to the constructive model of horizontal axis turbines (HAWT), currently widely used in wind farms is presented the alternative of using vertical shaft turbines (VAWT) for reduced installed power wind farms. The aspects that form the advantages of these turbines are presented as well as the fact that although they offer a lower power coefficient, they can play an important role for smaller power farms, the investment being at lower values. The basic rotor construction model is based on the SAVONIUS type which has been continuously improved, the results being better in terms of energy performance. A rotor concept that can be used within wind turbines with better performance results compared to SAVONIUS classic model is presented in this paper. The novelty elements consist in the use of a larger number of blades as well as the placing method on the rotor basic circle profile. The numerical analysis results made on virtual rotor model are presented, which highlight the improved values obtained on the analysed model.

Redesign of an upwind rotor for a downwind configuration: design changes and cost evaluation

Abstract. Within this work, an existing model of a Suzlon S111 2.1 MW turbine is used to estimate potential cost savings when the conventional upwind rotor concept is changed into a downwind rotor concept. A design framework is used to get realistic design updates for the upwind configuration, as well as two design updates for the downwind configuration, including a pure material cost out of the rotor blades and a new planform design. A full design load basis according to the standard has been used to evaluate the impact of the redesigns on the loads. A detailed cost model with load scaling is used to estimate the impact of the design changes on the turbine costs and the cost of energy. It is shown that generally lower blade mass of up to 5 % less than the upwind redesign can be achieved with the downwind configurations. Compared to an upwind baseline, the upwind redesign shows an estimated cost of energy reduction of 2.3 %, and the downwind designs achieve a maximum reduction of 1.3 %.

Aerodynamic Analysis of Coning Effects on the DTU 10 MW Wind Turbine Rotor

The size of wind turbine rotors is still rapidly increasing, though many technical challenges emerge. Novel rotor designs emerge to satisfy this up-scale trend, such as downwind load-aligned concepts, which orients the loads along the blade spanwise to greatly decrease the bending moments at the root. As the studies on the aerodynamics of these rotor concepts using 3D body-fitted mesh are very limited, this paper establishes different cone configurations based on the DTU 10 MW reference rotor and conducts a series of simulations. It is found that the cone angle and the distance from the blade section to the tip vortex are two deterministic factors on conning. Upwind rotors have larger power output, less thrust, smaller wake deficit, and smaller influencing area than downwind rotors of the same size, which provides superior aerodynamic priority and benefits wind farm design. The largest upwind cone angle of 14.03°, among the cases studied, leads to the highest torque to thrust ratio which is 3.63% higher than the baseline rotor. The downwind load-aligned rotor, designed to reduce the blade root bending moments at large wind speed, performs worse at the present simulation conditions than an upwind rotor of the same size.

Servo-aero-gravo-elastic (SAGE) scaling and its application to a 13-MW downwind turbine

Reduced scale wind turbines can be extremely cost-effective to test new rotor concepts since prototype costs are heavily dependent on the rotor diameter. Ideally, the scaled model would have the same non-dimensional deflections, dynamics, and control behavior as the full-scale model. This would provide a high-fidelity demonstration of the full-scale performance, which is ideal if the full-scale turbine has significant aeroelastic interactions. To this end, servo-aero-gravo-elastic (SAGE) scaling is developed and applied to a 13-MW turbine that is scaled to a 20% scale model. The scaling preserves the tip-speed ratio, the rotor speed normalized by the flapping frequency, and the tip deflections normalized by the blade length. In addition, the controller employs the same control structure (gain-scheduled pitch control and variable speed torque control) and is scaled dynamically (e.g., matching non-dimensional time constant of the pitch angle, etc.). Furthermore, the thrust, gravity, and centrifugal moments are scaled such that the load angles are preserved as a function of a non-dimensional wind speed. However, the environmental scaling must consider differences in Reynolds number (since this parameter cannot be held constant) and subsequent changes in the axial induction factor. While the presented results showcase these differences during operational conditions, the non-dimensional tip deflections remain comparable through all wind speed ranges, indicating the viability of the SAGE scaling method in matching full-scale aeroelastic responses.