Optimization of an Air Core Dual Halbach Array Axial Flux Rim Drive for Electric Aircraft

The anticipated development of the on-demand-mobility (ODM) market has accelerated the development of electric aircraft. Most proposed electric aircraft have propulsion systems that consist of fans directly driven by electric motors. The lower complexity of these propulsion systems opens the door to more custom propulsion system designs that are tailored to a given aircraft and its mission. This paper represents initial steps in the development of an electric propulsion system design code. A proof of concept version of the code is presented. The proof of concept version of the code is for the design of an axial flux rim driven propulsion system. NASA's all electric aircraft X-57, is used as a case study for this design code. The results of this case study are used to discuss the feasibility and potential benefits of using an axial flux rim driven propulsor on X-57. The final result of the case study shows a potential 4km increase in range over the current design

Advanced Integrated Power and Attitude Control System (IPACS) study

Integrated Power and Attitude Control System (IPACS) studies performed over a decade ago established the feasibility of simultaneously satisfying the demands of energy storage and attitude control through the use of rotating flywheels. It was demonstrated that, for a wide spectrum of applications, such a system possessed many advantages over contemporary energy storage and attitude control approaches. More recent technology advances in composite material rotors, magnetic suspension systems, and power control electronics have triggered new optimism regarding the applicability and merits of this concept. This study is undertaken to define an advanced IPACS and to evaluate its merits for a space station application. System and component designs are developed to establish the performance of this concept and system trade studies conducted to examine the viability of this approach relative to conventional candidate systems. It is clearly demonstrated that an advanced IPACS concept is not only feasible, but also offers substantial savings in mass and life-cycle cost for the space station mission

Thermal and mechanical analyses of high-speed permanent-magnet electrical machines

In the thesis, methods for the thermal and mechanical analyses of high-speed PM electrical machines are presented and implemented. The first method implemented for the thermal analysis is a combined 2D-3D numerical method. The thermal and turbulent properties of the flow, such as the temperature rise in the flow and the coefficients of thermal convection, are estimated using a 2D multiphysics method that couples CFD with heat-transfer equations. The detailed distribution of the temperature rise in the whole solid domain of the machine is determined using a 3D numerical heat-transfer method. The temperature rises in the machine are also estimated with the traditional thermal-network method, which uses a totally different approach to the heat-transfer analysis. The methods used for the mechanical analysis of the machine include finite-element rotordynamics modelling of the rotor for estimation of the critical speeds and the shapes of the bending modes and also analytical estimation of the stress in the retaining sleeve. The implemented methods are used for the comparative thermal and mechanical analyses of three different high-speed PM rotor constructions. The first type of rotor construction is retained with a carbon-fibre sleeve and uses a shield for eddy currents made of aluminium. The second rotor construction is retained with a retaining sleeve made from the alloy Ti-6%Al-6%V-2%Sn and the sleeve of the third rotor construction is made from the alloy Ti-2.5%Cu. The last two rotor constructions do not have separate eddy-current shields. The comparative analysis shows that the rotor with a carbon-fibre sleeve and an aluminium eddy-current shield shows the best thermal properties. The rotor with a retaining sleeve made of the titanium alloy Ti-6%Al-6%V-2%Sn offers promising thermal properties because the critical temperatures in the rotor are not exceeded. Additionally, the same rotor construction provides the best rotordynamics properties when compared to the other rotor constructions. The rotor construction retained with a sleeve made of the alloy Ti-2.5%Cu is inferior from the thermal and mechanical points of view when compared with the previous rotor constructions. The methods used for the thermal and mechanical analyses are also used for the determination of the maximum power limits for high-speed PM electrical machines for air-compressor applications. For that purpose, five high-speed PM electrical machines for the speeds of 20,000 rpm, 40,000 rpm, 60,000 rpm, 80,000 rpm, and 100,000 rpm are designed in order to determine their maximum mechanical powers. The electromagnetic, thermal, and mechanical designs of each machine are performed simultaneously and all the critical values of the thermal and mechanical design constraints are considered. The obtained maximum power limit defines the speed-power region of safe operation of the high-speed PM electrical machines intended for compressor applications

An Assessment of Integrated Flywheel System Technology

The current state of the technology in flywheel storage systems and ancillary components, the technology in light of future requirements, and technology development needs to rectify these shortfalls were identified. Technology efforts conducted in Europe and in the United States were reviewed. Results of developments in composite material rotors, magnetic suspension systems, motor/generators and electronics, and system dynamics and control were presented. The technology issues for the various disciplines and technology enhancement scenarios are discussed. A summary of the workshop, and conclusions and recommendations are presented

High speed high power electrical machines

DEng ThesisHigh Speed High Power (HSHP) electrical machines push the limits of electromagnetics, material capabilities and construction techniques. In doing so they are able to match the power performance of high speed turbomachinery such as gas turbines, compressors and expanders. This makes them attractive options for direct coupling to such machinery as either a power source or as a generator; eliminating the need for gearboxes and achieving a smaller system size and greater reliability. The design of HSHP machines is a challenging, iterative process. Mechanical, electromagnetic and thermal constraints are all placed on the machine shape, topology, operating point and materials. The designer must balance all of these constraints to find a workable solution that is mechanically stable, can work within the available electrical supply and will not overheat. This thesis researches the fundamental origins and interaction of the mechanical, electromagnetic and thermal constraints on electrical machines. Particular attention was paid to improving the accuracy of traditional mechanical rotor design processes, and improving loss estimation in inverter fed machines. The issues of selecting an appropriate electric loading for low voltage machines and choosing effective, economic cooling strategies were explored in detail. An analytical iterative design process that combines mechanical, electromagnetic and thermal design is proposed; this process balances the need for speed versus accuracy for the initial design of a machine, with Finite Element Analysis used only for final validation of performance and losses. The design process was tested on the design and manufacture of a 1.1MW 30,000rpm PM dynamometer used in an industrial test stand. The machine operating point was chosen to meet a gap in the industrial machines market and exceed the capabilities of other commercially available machines of the same speed. The resulting machine was successfully tested and comfortably meets the performance criteria used in the design process

Suurnopeusmoottorin prototyypin tuotteistaminen sarjatuotantoon

Productization is the art of developing a customized product, service or prototype into a standardized marketable and commercialized product. In this thesis a high-speed induction motor prototype is designed for manufacturing. The motor has an output power of 86 kW, rotational speed of 21000 rpm and IEC frame size 160. The motor has a copper coated solid rotor concept, hybrid bearings and a totally enclosed air cooling system. High-speed motor systems provide advantages as improvement of over-all efficiency and reliability in comparison to conventional systems by eliminating the gear box normally used for applications requiring high-speed. In the literature study mechanical restrictions and design considerations due to high rotational speed and centrifugal forces on machine elements are reviewed. Different machine elements are presented as alternatives for high-speed motor components. To construct a profitable product from manufacturing point of view a concurrent engineering philosophy and DFMA method is adopted. The system of hybrid bearings was retained and the bearing support parts design was reconstructed by reconsidering necessity of the tolerances and altering unnecessarily tight tolerances. It was decided that the bearing end shields and the motor frame foot should be incorporated into one part and produced by casting iron in serial production. Prototype evaluation concludes that a standard stator frame can be used and several rotor concepts were evaluated. The potential for reducing the manufacturing costs of the prototype motor are substantial. However, regarding the rotor concepts more development needs to be done to ensure a functional rotor concept.Työn tavoitteena oli tuotteistaa suurnopeussähkömoottorin prototyyppi sarjatuotantoa varten. Lähtökohteena oli 86kW:n suurnopeusmoottori, jonka pyörimisnopeus on 21000 r/min ja IEC runkokoko 160. Moottorilla on kuparipinnoitettu massiiviroottori roottorikonseptina, hybridilaakereita ja ilmajäähdytys. Suurnopeusteknologia mahdollistaa paremman kokonaishyötysuhteen ja kestävämmän järjestelmän poistamalla perinteisesti käytetty vaihteisto suurta pyörimisnopeutta vaativissa sovelluksissa. Suuri pyörimisnopeus ja keskipakovoimien vaikutus suurnopeusmoottorissa aiheuttaa mekaanisia rajoituksia sekä erilliskomponenttien tarvetta. Kirjallisuustutkimuksessa esitellään eri komponenttivaihtoehtoja suurnopeusmoottorin kone-elimistöön. Tuotteistamisprojektissa käytetään rinnakkaissuunnittelun ja DFMA:n periaatteita. Laakerointiosien toleranssien tarkkuus sekä roottorikonsepti on arvioitu uudestaan ja laakerikilvet ovat yhdistetty staattorirungon jalkaan. Standardistaattorirunko sekä alunperäiset hybridilaakerit soveltuvat käytettäväksi sarjatuotantomoottorissa prototyyppimoottorin evaluoinnin mukaan. Moottorin sarjatuotannon kustannukset ovat merkittävästi pienempiä verrattuna prototyyppimoottoriin tuotantokustannuksiin, mutta tarvitaan kuitenkin lisätuotekehitystä saavuttaakseen kannattavan hintalaatusuhteen

Multiphysics 3D modelling of ironless permanent magnet generators

Analytical method is widely used for the preliminary design and optimization of electrical machines. It has short calculation time and low computational cost (cost of simulation codes and supporting hardware), but the calculate result is normally considered to be not as accurate as finite element method (FEM). On the other hand, it is time-consuming to optimize machines with FEM if the optimization is not parallelized. Parallelizing optimization requires many licenses when commercial FEM codes are used, which can be very expensive. Ironless permanent magnet generator has large diameter and small aspect ratio, therefore, multiphysics approach is expected to be used for investigating the magnetic and thermal field. To address the above challenges, this paper presents a multiphysics modelling strategy for the design and optimization of ironless permanent magnet generators. Open-source codes are used to reduce the computational cost. A design example is presented to demonstrate the detail of this design method. This approach is expected to be used in super computer in the future, so that the calculation time can be largely reduced

AN INTEGRATED ELECTROMAGNETIC MICRO-TURBO-GENERATOR SUPPORTED ON ENCAPSULATED MICROBALL BEARINGS

This dissertation presents the development of an integrated electromagnetic micro-turbo-generator supported on encapsulated microball bearings for electromechanical power conversion in MEMS (Microelectromechanical Systems) scale. The device is composed of a silicon turbine rotor with magnetic materials that is supported by microballs over a stator with planar, multi-turn, three-phase copper coils. The micro-turbo-generator design exhibits a novel integration of three key technologies and components, namely encapsulated microball bearings, incorporated thick magnetic materials, and wafer-thick stator coils. Encapsulated microball bearings provide a robust supporting mechanism that enables a simple operation and actuation scheme with high mechanical stability. The integration of thick magnetic materials allows for a high magnetic flux density within the stator. The wafer-thick coil design optimizes the flux linkage and decreases the internal impedance of the stator for a higher output power. Geometrical design and device parameters are optimized based on theoretical analysis and finite element simulations. A microfabrication process flow was designed using 15 optical masks and 110 process steps to fabricate the micro-turbo-generators, which demonstrates the complexity in device manufacturing. Two 10 pole devices with 2 and 3 turns per pole were fabricated. Single phase resistances of 46Ω and 220Ω were measured for the two stators, respectively. The device was actuated using pressurized nitrogen flowing through a silicon plumbing layer. A test setup was built to simultaneously measure the gas flow rate, pressure, rotor speed, and output voltage and power. Friction torques in the range of 5.5-33µNm were measured over a speed range of 0-16krpm (kilo rotations per minute) within the microball bearings using spin-down testing methodology. A maximum per-phase sinusoidal open circuit voltage of 0.1V was measured at 23krpm, and a maximum per-phase AC power of 10µW was delivered on a matched load at 10krpm, which are in full-agreement with the estimations based on theoretical analysis and simulations. The micro-turbo-generator presented in this work is capable of converting gas flow into electricity, and can potentially be coupled to a same-scale combustion engine to convert high-density hydrocarbon energy into electrical power to realize a high-density power source for portable electronic systems