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Power electronics design offers many options to achieve the high required power density to replace conventional aircraft components. Two promising approaches are to increase the power supply voltage and use wide-bandgap semiconductors. However, there are many concerns about the high-voltage approach, particularly regarding reliability and fault tolerance. Improving the power density with high voltages requires wide-bandgap semiconductors, which further stresses the insulation. Furthermore, the environmental stressors are partly unknown because of the need for a design basis. Existing industrial standards and other investigations address this issue only partly. This publication uses a mission profile and a design of experiment-based reliability assessment approach for creepage distances on printed circuit boards to overcome the concerns against the promising high voltage approach in aviation applications from the perspective of power electronics. The investigation delivers experimentally and mathematically described wet and dry surface flashover results. Furthermore, the influence of degradation of creepage distances caused by wide-bandgap semiconductors is experimentally investigated. The publication also gives design recommendations for gaining reliability and fault tolerance of creepage distances on printed circuit boards for operating power-dense power electronics in integrated electrified propulsion systems.

This paper focuses on a power conditioning system for an all-electric aircraft (AEA) powered by a single battery pack. The research project aims to identify a multi-port DC/DC converter topology that adequately supplies the two DC buses connected to the propulsion system and auxiliary equipment, respectively. To achieve this, a triple-active bridge (TAB) in its inherently decoupled configuration has been investigated, prototyped, and experimentally verified. The TAB voltage control system was designed, simulated, and experimentally validated. Specifically, start-up, steady-state and step-load performances were evaluated by the simulation study and then experimentally validated on a scaled prototype. The results assess the feasibility of using an inherently decoupled TAB as a power conditioning system for interconnecting the AEA battery pack with the electric propulsion and auxiliary systems. In particular, the developed TAB configuration secures the decoupled power transfer between the two output ports providing at the same time good dynamic performance in terms of voltage control during step-load variation. [ABSTRACT FROM AUTHOR]

This research addresses the increasing electrification of aircraft systems, driven by the need to improve energy efficiency and reduce CO2 emissions in global aviation. The transition to more-electric aircraft (MEA) is advocated as a promising strategy, as it is expected to improve environmental performance and economic viability. However, this shift significantly increases the demand for on-board electrical power. One alternative to traditional engine generators is novel power supply systems such as fuel cell systems. In order to design these systems effectively, it is essential to determine the electrical power requirements that the fuel cells must supply. Estimating the electrical power consumption of individual aircraft systems is critical given the proprietary nature of manufacturer data. Using existing literature methods, this study aims to identify the essential variables for estimating the magnitude of power consumption. The research focuses on different aircraft models, taking into account their system architectures and electrification trends, in particular for Airbus and Boeing models. The study includes a detailed description of the aircraft systems, calculation methods, and presentation and analysis of the estimated electrical power requirements. Despite a lack of available data for comparison, the calculated results appear to be reasonably consistent with existing literature and provide valuable insights into the electrical power requirements of aircraft systems. [ABSTRACT FROM AUTHOR]

In the aircraft industry, there is a shift towards more and all-electric power systems resulting in great research efforts on single components like batteries. At the same time there is an increasing need to investigate and evaluate the long-term behavior of the whole electric power system to ensure safe and sustainable aircraft operation. Focusing on this challenge, the objective of this article is to propose a framework for electric power system assessment in the early design stages. In particular, the focus is on identifying and handling uncertainties regarding failure behavior and degradation, both on the component and system level. The evaluation of different power system topologies is based on the integration of Model-Based Systems Engineering and robust design methods. In this context, another central aspect is the definition of system and component requirements derived from the flight mission profile. SysML diagrams are used to define use cases and possible system topologies. Sensitivity of degradation effects are evaluated using robust design methods. The application of the framework and these methods is illustrated using a short-range aircraft with an all-electric power system. The results highlight the applicability of the framework to cope with the uncertainties that occur in the early design stages and point out fields of further research. [ABSTRACT FROM AUTHOR]

The consequences of new airspace entrants, such as novel aircraft concepts with innovative propulsion systems, on air traffic management operations need to be carefully identified. This paper aims to assess the impact of future aircraft with different performance envelopes on the European air traffic network from a flow-based perspective. The underlying approach assumes that all certification-related questions concerning airworthiness have been resolved and do not take into account any economic factors related to airline operations. For example, for an innovative propulsion system, a short range all-electric aircraft is considered in this study. Aircraft trajectory calculations are based on the dataset of base of aircraft data (BADA), which are developed and maintained by EUROCONTROL. The new design concept is integrated into BADA as well, resulting in a new set of coefficients for the all-electric aircraft. In addition to the adjusted parameters which affect airborne performances, ground-related aspects are also taken into account. This includes assumptions on operational procedures, charging capacities and adaptions in infrastructure. Investigations are carried out at the trajectory level as well as at the airport and the entire network. [ABSTRACT FROM AUTHOR]

In this study, the performance of conventional aircraft using fossil-fuels and batterypowered aircraft was analyzed and compared within the framework of transitioning to all-electric aircraft. Electric aircraft are propelled by electric motors that drive the propellers using electricity as their power source. These aircraft produce zero direct emissions during flight, reduce noise pollution, and exhibit higher energy efficiency compared to combustion engines. However, before electric aircraft can be fully developed, several challenges related to battery technology must be addressed. Battery-powered aircraft currently cannot match the endurance, altitude, and range capabilities of jet fuel-powered aircraft due to the limited battery capacity imposed by today's technology. Current battery technologies have lower energy density compared to aviation fuels, resulting in shorter flight ranges and limited energy storage capacity. Presently, jet fuel exhibits a specific energy of approximately 12000 Wh/kg with an engine efficiency of 25-35%. In contrast, batteries possess an energy density of about 250-400 Wh/kg with an electric motor efficiency of 90- 96%. This indicates that jet fuel is roughly 30-50 times more energy-dense than batteries. To achieve parity in energy density, a significantly greater number of batteries would need to be added to the aircraft, resulting in a substantial increase in weight. However, due to the lower efficiency of fossil fuel engines, battery energy density does not have to reach the level of jet fuel (12000 Wh/kg) to match the flight range. Calculations indicate that, in order to fully utilize all-electric aircraft in the future, batteries should reach at least 40-50% of fuel energy density to match the performance of current turbofan aircraft. [ABSTRACT FROM AUTHOR]

In the last decades, electromechanical actuators started to be introduced in transport aircraft for primary and secondary flight control surfaces. Some innovative architectures have been proposed in the literature to use these actuators for high-lift devices (flaps and slats). The state-of-the-art architecture is built with a central mechanical shaft powered by a power distribution unit connected to ballscrew actuators that actuate the flap and slat surfaces. New innovative concepts have the potential to improve the state-of-the-art architectures. However, there is a lack of quantitative results for such innovative architectures. A new methodology is proposed to preliminarily estimate performance and reliability aspects of conventional and innovative architectures. This allows quantitative comparisons to finally be obtained. The methodology is applied to a new architecture that uses electromechanical actuators for flaps and slats, providing results in terms of performance and reliability and comparing them to the current state-of-the-art high-lift devices. Results show that the new architecture is lighter than the reference one and can be more reliable. This is achieved thanks to the removal of the mechanical links among components, which allows each control surface to be deployed independently from the others. This highly increases the operational reliability of the system. Two cases are analyzed, with and without actuator jamming. This provides more realistic results since this failure mode is currently the main reason why electromechanical actuators are not being used for more applications. The innovative architecture outperforms the conventional one in the case where the electromechanical actuators are not affected by the jamming failure mode. [ABSTRACT FROM AUTHOR]

Modern aircraft are being equipped with high-voltage and direct current (HVDC) architectures to address the increase in electrical power. Unfortunately, the rise of voltage in low pressure environments brings about a problem with unexpected ionisation phenomena such as arcing. Series arcs in HVDC cannot be detected with conventional means, and finding methods to avoid the potentially catastrophic hazards of these events becomes critical to assure further development of more electric and all electric aviation. Inductive sensors are one of the most promising detectors in terms of sensitivity, cost, weight and adaptability to the circuit wiring in aircraft electric systems. In particular, the solutions based on the detection of the high-frequency (HF) pulses created by the arc have been found to be good candidates in practical applications. This paper proposes a method for designing series arc fault inductive sensors able to capture the aforementioned HF pulses. The methodology relies on modelling the parameters of the sensor based on the physics that intervenes in the HF pulses interaction with the sensor itself. To this end, a comparative analysis with different topologies is carried out. For every approach, the key parameters influencing the HF pulses detection are studied theoretically, modelled with a finite elements method and tested in the laboratory in terms of frequency response. The final validation tests were conducted using the prototypes in real cases of detection of DC series arcs. [ABSTRACT FROM AUTHOR]

This research addresses the increasing electrification of aircraft systems, driven by the need to improve energy efficiency and reduce CO2 emissions in global aviation. The transition to more-electric aircraft (MEA) is advocated as a promising strategy, as it is expected to improve environmental performance and economic viability. However, this shift significantly increases the demand for on-board electrical power. One alternative to traditional engine generators is novel power supply systems such as fuel cell systems. In order to design these systems effectively, it is essential to determine the electrical power requirements that the fuel cells must supply. Estimating the electrical power consumption of individual aircraft systems is critical given the proprietary nature of manufacturer data. Using existing literature methods, this study aims to identify the essential variables for estimating the magnitude of power consumption. The research focuses on different aircraft models, taking into account their system architectures and electrification trends, in particular for Airbus and Boeing models. The study includes a detailed description of the aircraft systems, calculation methods, and presentation and analysis of the estimated electrical power requirements. Despite a lack of available data for comparison, the calculated results appear to be reasonably consistent with existing literature and provide valuable insights into the electrical power requirements of aircraft systems.

The consequences of new airspace entrants, such as novel aircraft concepts with innovative propulsion systems, on air traffic management operations need to be carefully identified. This paper aims to assess the impact of future aircraft with different performance envelopes on the European air traffic network from a flow-based perspective. The underlying approach assumes that all certification-related questions concerning airworthiness have been resolved and do not take into account any economic factors related to airline operations. For example, for an innovative propulsion system, a short range all-electric aircraft is considered in this study. Aircraft trajectory calculations are based on the dataset of base of aircraft data (BADA), which are developed and maintained by EUROCONTROL. The new design concept is integrated into BADA as well, resulting in a new set of coefficients for the all-electric aircraft. In addition to the adjusted parameters which affect airborne performances, ground-related aspects are also taken into account. This includes assumptions on operational procedures, charging capacities and adaptions in infrastructure. Investigations are carried out at the trajectory level as well as at the airport and the entire network.

This paper focusses on implementing force equalisation to reduce or eliminate torque disparities in a four-lane torque-summed electromechanical actuator that drives the inner board aileron control surface on the Sea Harrier aircraft. Proportional, integral, and derivative control action achieved position control of the common output shaft, following two failures. The analysis included the effect of inherent motor disparities and drift in feedback transducers. Three-phase motor models were considered to account for the influence of the inherent torque ripple effect, and the influence of inertial and aerodynamic loads over various flight envelopes were also included in the analysis. Simulation tests demonstrated that although torque disparities between mismatched lanes are influenced by drift in potentiometer readings, force equalization was proven to be effective in eliminating such deviations.

To make an all-electric aircraft possible, both high power densities and efficiencies are needed. However, particularly high demands are also placed on the thermal management system. Often, the electric motor and cooling system are considered without co-optimization. Particularly in the case of electric motors with conductors directly cooled by a liquid, there is great potential for optimization, since the temperature-dependent Joule losses determine the largest part of the losses. This publication shows the main influencing parameters for the electric motor and cooling system: coolant speed and winding temperature. In addition, the influence of the cooling system control during a flight mission is demonstrated and its potential in mass reduction is quantified. It could be shown that with a low utilized electric motor the maximum winding temperature of 130 ° C is beneficial, the cooling system should work in almost all operation points in its sized operation and the mass of the heat exchanger and pump is negligible compared to the mass of the electric motor and energy storage. [ABSTRACT FROM AUTHOR]

The main purpose of this article is to provide an instructive review of the technological challenges hindering the road toward more electric powertrains in aircraft. Hybrid, all-electric, and turboelectric powertrain architectures are discussed as possible fuel consumption and weight reduction solutions. Among these architectures, the short-term implementation of hybrid and all-electric architectures is limited, particularly for large-capacity aircraft due to the low energy/power density levels achievable by state-of-the-art electrical energy storage systems. Conversely, turboelectric architectures with advanced distributed propulsion and boundary layer ingestion are set to lead the efforts toward more electric powertrains. At the center of this transition, power converters and high-power density electric machines, i.e., electric motors and generators, and their corresponding thermal management systems are analyzed as the key devices enabling the more electric powertrain. Moreover, to further increase the fuel efficiency and power density of the aircraft, the benefits and challenges of implementing higher voltage powertrains are described. Lastly, based on the findings collected in this article, the projected roadmap toward more electric aircraft powertrains is presented. Herein, the individual targets for each technology, i.e., batteries, electric machines, and power converters, and how they translate to future aircraft prototypes are illustrated.

High-temperature superconductors (HTS) can carry high currents with almost zero loss when transmitting direct current (DC). Their compact size and lower weight make them suitable for the application of all-electric aircraft. However, the current carrying capability of a single HTS tape is limited to a few hundred amps; therefore, for high-current applications, multiple HTS tapes need to be connected in parallel. The flat geometry of HTS tape and its critical current (IC) dependence on strain complicate grouping them in parallel. Furthermore, the length of HTS tape is limited by its crystal structure, necessitating low-resistance joints for extended applications. A superconducting busbar design for high-current applications is developed and tested to address these challenges. The superconducting busbar is designed in a way that it helps to reduce the effect of the self-field on critical current and also ride through the fault events. Yttrium barium copper oxide (YBCO) tapes are used to develop the busbar prototype, tested against DC currents in a liquid nitrogen environment. Joint optimization is carried out to determine the required length for efficiently joining HTS tapes. Two busbar prototypes are developed with 180° and 90° joints to join 5 HTS tapes and tested in self-field. A joint resistance of 100 n Ω is measured at self-field for the 180° joint busbar, and 800 n Ω is measured for the 90° joint busbar. Both busbar prototypes are subjected to power cycling and thermal cycling to assess joint performance in self-field and any degradation of the joint electrical parameters during testing. [ABSTRACT FROM AUTHOR]

Forecasted growth in aviation sector emissions has motivated research into reduced-emissions aircraft designs. All-electric aircraft (AEA) are of unique interest due to negligible in-flight emissions. In contrast to fuel-based aircraft, AEA emissions vary depending on power sector emissions intensity at point of departure. The present work identifies regional pathways for future AEA to reduce greenhouse gas emissions through use of novel energy and emissions models spanning the entirety of the domestic commercial aviation sector across eight separate scenarios considering different emerging battery cells and emissions scenarios. While regions with high power sector emissions intensity are ill-suited for future electrification, clear regional potential for future AEA is demonstrated, with flight networks in the Pacific Northwest, California, and the East Coast. Airports in cities such as Atlanta and Washington, D.C. are clear potential candidates for future AEA hubs, while electrifying flights between Portland, Oregon, and Seattle, Washington offers greatest potential impact. • All-electric aircraft (AEA) offer regional potential for GHG emissions reduction. • High-impact regions include the Pacific Northwest, California, and the East Coast • Reducing power sector emissions intensity is critical for broader AEA impact • A three- to four-fold increase in specific energy is critical for viable AEA. [ABSTRACT FROM AUTHOR]

In this paper, the maximum take-off mass ( M T O M ) of a 19-seat fuel cell aircraft with similar characteristics to a conventional 19-seat aircraft is estimated using the combination of a rapid method and semi-empirical equations. The study shows that the M T O M of a 19-seat fuel cell aircraft with current technology would be 25% greater than that of a conventional aircraft. However, with the expected technological improvements, the M T O M of a 19-seat fuel cell aircraft could reach lower values than that of a conventional aircraft. The most important parameter affecting the M T O M of fuel cell aircraft is the power-to-weight ratio of the fuel cells. If this ratio of fuel cell aircraft does not improve significantly in the future, fuel cell aircraft with lower power loading will become the preferred choice; thus, certain trade-offs in flight performance, such as a longer takeoff distance, will be accepted. The study provides the basis for further economic analysis of fuel cell aircraft, which has yet to be conducted. [ABSTRACT FROM AUTHOR]

This article investigates the surface electrical properties of polyether-ether-ketone (PEEK) and cross-linked polyethylene (XLPE) before and after the fluorination modification. The samples are tested for surface conductivity, surface morphology, and surface antiaging characteristics. The samples are also tested for flashover voltage with ramping voltage under 100, 20, and 10 kPa. The results showed that the surfaces of PEEK and XLPE become slightly smoother with the increase in the fluorination time and the conductivity increased with the increase in the fluorination time. After fluorination, the surface of PEEK shows significant hydrophilicity, while the surface hydrophobicity of XLPE is slightly reduced, and there is a trend of recovery with the extension of the fluorination time. After fluorination, the surface antiaging performance is significantly improved. Compared with the untreated samples, the fluorinated PEEK has a higher flashover voltage at 100 kPa, and the flashover voltage is slightly increased at 10 and 20 kPa, while the flashover voltage of XLPE after fluorination shows a downward trend, especially under low pressures. This study provides a reference for fluorinated polymers as promising candidates for the insulation systems for all-electric aircraft. [ABSTRACT FROM AUTHOR]

Aviation has, over the years, become an inseparable element of human life. Airplanes are very commonly used for various tasks, such as transport of passengers and goods, military attack and defence, rescue, recreation and so on. In spite of the many advantages of aviation, one cannot ignore its disadvantages. The most important disadvantages of aviation are the emissions that cause atmospheric pollution and noise. Additionally, one should remember about the decreasing stocks of non-renewable fuels. These drawbacks affect human health and the natural environment. Therefore, a good alternative to conventional drive units in aircraft may turn out to be electric drive units in the near future. The aim of this article is to check the extent to which today’s knowledge and technology allow the use of electric drive units instead of conventional aircraft drive units. This article presents the concept of electric aircraft, from the electric drive unit to its power supply system. The feasibility of designing an electric jet drive unit for a passenger aircraft was analysed based on the performances of PZL 104 Wilga 35 and Boeing B787 Dreamliner.

As air traffic has been increasing in recent years, the environmental impact of aviation is more obvious, forcing governments to impose stringent regulations on emissions. In order to meet these regulations, and reduce the carbon footprint, research has been directed towards the all-electric and hybrid aircraft, where the use of cryogenic HTS machines and cables has been proposed to reduce the overall size of the aircraft. With the cryogenic system already in place, research has been exploring the use of power electronics at lower temperatures in order to obtain systems with higher power densities and lower losses. In this paper several power semiconductor devices are tested at room and cryogenic temperature in order to evaluate their performance at lower temperature. One of the tested devices, a “CoolMOS” superjunction MOSFET, is used in a single voltage source phase-leg which is experimented with at room and cryogenic temperature to evaluate its efficiency as a primary indication of its usefulness in the All-Electric Aircraft. [ABSTRACT FROM AUTHOR]

Based on the technical platform of electrically actuated nose wheel steering systems, a new type of damping shimmy reduction technology is developed to break through the limitations of traditional hydraulic damping shimmy reduction methods, and an electrically actuated nose wheel steering structure scheme is proposed. The mathematical model of the electromagnetic damper is established, the derivation of skin depth, damping torque and damping coefficient is completed, and the design of the shape and size of the electromagnetic damper is combined with the derivation results and the technical index of shimmy reduction. The electromagnetic field finite element simulation results show that the mathematical modeling method of the electromagnetic damper has good accuracy, and its application to the shimmy reduction module of the electrically actuated nose wheel steering system is also feasible and superior. Finally, the key factors influencing the performance of electromagnetic damper shimmy reduction are studied and analyzed, thus forming a complete electromagnetic damper shimmy reduction technology for the electrically actuated system, and laying the foundation for the design of novel all-electric aircraft and landing gear.

The development of electric aircraft is becoming an important technology for achieving the goals set by the European Commission for the reduction of gases emissions by 2050 in the aeronautical transportation system. However, there is a technology gap between the current values of specific power in commercial electric machines and those required for aeronautical applications. Therefore, the search for alternative materials and non-conventional designs is mandatory. One emergent solution is using superconducting machines and systems to overcome the current limits of conventional electrical machines. This work reviews the new hybrid and all-electric aircraft tendencies, complementing it with recent research on the design and development of high specific power superconducting machines. This includes the main topologies for hybrid and all-electric aircraft, with an overview of the ongoing worldwide projects of these aircraft types, systematizing the main characteristics of their propulsion systems. It also includes the research on superconducting machines to achieve high specific power and consider the impact on the redesign of aircraft systems, the electrical, cooling, and fuel source systems.

The feasibility of regional electric aviation to reduce environmental impact highly depends on technological advancements of energy storage techniques, available battery energy density, and high-power electric motor technologies. However, novel airframe technologies also strongly affect the feasibility of a regional electric aircraft. In this paper, the influence of novel technologies on the feasibility of regional electric aviation was investigated. Three game-changing technologies were applied to a novel all-electric regional aircraft: active flow control, active load alleviation, and novel materials and structure concepts. Initial conceptual design and mission analysis of the aircraft was performed using the aircraft design framework SUAVE, and the sensitivity of the most important technologies on the aircraft characteristics and performance were studied. Obtained results were compared against a reference ATR-72 aircraft. Results showed that an all-electric aircraft with airframe technologies might be designed with the maximum take-off weight increase of 50% starting from the battery pack energy density of 700 Wh/kg. The overall emission level of an all-electric aircraft with novel technologies is reduced by 81% compared to the ATR-72. On the other hand, novel technologies do not contribute to the reduction in Direct Operating Costs (DOC) starting from 700 Wh/kg if compared to an all-electric aircraft without technologies. An increase in DOC ranges from 43% to 30% depending on the battery energy density which creates a significant market obstacle for such type of airplanes. In addition, the aircraft shows high levels of energy consumption which concerns its energy efficiency. Finally, the sensitivity of DOC to novel technologies and sensitivities of aircraft characteristics to each technology were assessed.

A starter generator is a core technology of the more‐electric aircraft and all‐electric aircraft. The traditional switched reluctance machine (SRM) requires a high accuracy position sensor and high‐speed processor while generating power. Therefore, the cost of the controller is high and the maximum speed of the machine is limited. A dual‐mode doubly salient starter/generator is proposed in the study. In the process of starting and generating power, the machine operates based on the SRM principle and the doubly salient electromagnetic machine principle, respectively. In order to realise the transformation of the operating principle, the machine uses a winding switching device, and half of the windings are replaced as field winding that provide DC excitation in the generator mode. A suitable power converter is proposed based on introducing the structure and working principle of the machine. A winding switching device is designed, and the conversion process is explained in detail. A finite‐element method is simultaneously used to analyse the motor‐driven performance and the power‐generation performance of the machine. A 12/8‐pole prototype machine is developed. Additionally, the effectiveness of the starting, generating, and dual‐mode conversion is verified by experiments. [ABSTRACT FROM AUTHOR]

The transportation sector accounts for 28% of US-based and 14% of global greenhouse gas emissions. Transitioning from hydrocarbon-powered vehicles to electric vehicles such as all-electric aircraft (AEA) in parallel with use of reduced-emissions power sources is one possible method to curtail future sector emissions. However, AEA market capabilities and environmental impact are uncertain and insufficiently quantified in the literature. The present work evaluates AEA in the United States on national and state-by-state bases through 2050, considering four emerging battery architectures and two emissions scenarios. AEA using lithium-air cells with a projected specific energy of 915 Wh/kg could achieve 46.6% of total domestic commercial passenger share and 20.9% of total domestic commercial revenue passenger kilometers (RPK) by 2050, corresponding to a net CO 2 -equivalent emissions reduction of 1.02% – 19.8%. This work demonstrates clear potential for AEA, although achieving substantive aviation sector emissions reductions requires transition to reduced-emissions power generation. [ABSTRACT FROM AUTHOR]

This article describes the extent to which hybrid aircraft and all-electric aircraft can present a solution for reducing HC, CO, and NO x emissions and noise in the vicinity of airports, in the category of regional passenger aircraft. The goal of the article is to identify, basing on aircraft technical characteristics and market demands, in which sectors of air transport can all-electric or hybrid aircraft be most feasibly introduced. Firstly, a simple theoretical model based on a connection between the aircraft mass and aircraft energy consumption is used to calculate basic technical characteristics and limitations of hybrid and all-electric aircraft. Second, market demands for regional aircraft are presented and discussed, with the intention of recognising the possibilities of replacing conventional aircraft with all-electric and hybrid aircraft models in regional air transport in the near future. Third, quantity of HC, CO, and NO x, CO gas emissions of regional aircraft in Europe was calculated to recognise the possible reduction of gas emissions if hybrid and all-electric aircraft would be implemented.

The demand for alternative fueling methods to reduce the need for fossil fuels is not limited to the electrification of ground vehicles. More-electric and all-electric aircraft pose challenges, with extensive requirements in terms of power density, efficiency, safety, and environmental sustainability. This paper focuses on electrical machines and their components, especially for high-power applications like the main propulsion. The electrical machine is evaluated from different aspects, followed by a closer look at the components and materials to determine the suitability of the current standard materials and advanced technologies. Furthermore, the mechanical and thermal aspects are reviewed, including new and innovative concepts for the cooling of windings and for the use of additive manufacturing. Aircraft have special demands regarding weight and installation space. Following recent developments and looking ahead to the future, the need and the possibilities for light and efficient electrical machines are addressed. All of the approaches and developments presented lead to a better understanding of the challenges to be expected and highlight the upcoming opportunities in electrical machine design for the use of electric motors and generators in future aircraft. Several prototypes of electrical machines for smaller aircraft already exist, such as the electric drive of the Siemens powered Extra 330LE. The focus of this paper is to provide an overview of current technical possibilities and technical interrelations of high performance electric drives for aviation. A 1 MW drive is exemplified to present the possibilities for future drives for airplanes carrying a larger number of passengers. All presented techniques can also be applied to other drive power classes. [ABSTRACT FROM AUTHOR]

As part of the development of all-electrical transportation systems, superconducting technology is strongly considered in propulsion systems as it enables implementation of very compact and efficient motors. However, superconductors bring a new type of possible failure mode, as they have to operate at cryogenic temperature and be stable against quench. While a failure of the cooling system or a quench may not be a critical issue in many ground-based applications, it could be fatal in airborne applications. We designed a high temperature superconducting motor to drive a general aviation aircraft and developed an auxiliary torque generation system ensuring thirty percent of the nominal torque needed for safe landing in case of quench or failure of the cooling system. The motor uses magnetized bulk superconducting plates and field coils to generate excitation field and provides 150 kW at 2700 RPM to drive a propeller. Safety torque is generated either from the electromagnetic shield or permanent magnets located in the inductor. The armature design has also been modified in order to accommodate the current increase needed to generate the required safety torque. This paper describes the design modifications done to the HTS motor in order to generate safety torque based on the minimum power needed for the aircraft to land safely. [ABSTRACT FROM AUTHOR]

A high temperature superconducting (HTS) motor has been designed to power a general aviation aircraft. The propulsion requirements of the Cessna 172 have been chosen as baseline for the study: 200 HP at 2700 RPM. The designed motor is based on flux trapping in bulk YBCO plates and concentration of the flux generated by Bi-2223 coils and an ironless air-cooled resistive armature. The eight-pole machine would exhibit high power density comparable to that of small gas turbines around 4 HP/lb. Details of this HTS motor concept have been presented in a previous paper. However, the scaling up of such a configuration is not straightforward, as single domain YBCO elements cannot exceed a few centimeters in diameter. This paper presents the design of a motor based on the same configuration but with a much higher power rating, in the range of several MW, to power High Altitude Long Endurance (HALE) aircraft or small jets. Due to the size limitation of the YBCO plates, two solutions can be used to increase the power: the radius and the number of poles can be increased, or the motor can be lengthened to accommodate more coil-plate pairs. The motor is able to reach more than 2 T in the air gap thus leading to high power density. The design optimization is done with respect to several objectives as a trade-off between amount of superconductor, efficiency, weight and volume. The cooling system is assumed to be provided by liquid hydrogen available onboard the aircraft as fuel for the fuel cells or turbo-generators. [ABSTRACT FROM AUTHOR]

Development of all-electric aircraft would enable more efficient, quieter and environmentally friendly vehicles and would contribute to the global reduction of greenhouse gas emissions. However, conventional electric motors do not achieve a power density high enough to be considered in airborne applications. Bulk high temperature superconducting (HTS) materials, such as YBCO pellets, have the capacity of trapping magnetic flux thus behaving as permanent magnets. Experimental data show that one single domain YBCO pellets could trap up to 17 T at 29 K, which enables the design of very high power density motors that could be used in aircraft propulsion. We designed a superconducting motor based on an axial flux configuration and composed of six YBCO plates magnetized by a superconducting coil wound on the outside of the motor. The six-pole homopolar machine uses a conventional air-gap resistive armature. Axial-flux configuration allows several rotors and stators to be stacked together and therefore enables the use of one or several conventional permanent magnet rotors to generate minimum safety torque in case of loss of superconductivity. All-electric aircraft are expected to be powered by fuel cells or turbo-generators fed with pure hydrogen cryogenically stored that would provide the motor with a convenient cooling system at 20 K. This paper presents the design and simulated performance of the motor for an application in aircraft propulsion. [ABSTRACT FROM AUTHOR]

The latest advances in electric and electronic aircraft technologies from the point of view of an "all-electric" aircraft are presented herein. Specifically, we describe the concept of a "more electric aircraft" (MEA), which involves removing the need for on-engine hydraulic power generation and bleed air off-takes, and the increasing use of power electronics in the starter/generation system of the main engine. Removal of the engine hydraulic pumps requires fully-operative electrical power actuators and mastery of the flight control architecture. The paper presents a general overview of the electrical power generation system and electric drives for the MEA, with special regard to the flight controls. Some discussion regarding the interconnection of nodes and safety of buses and protocols in distributed systems is also presented [ABSTRACT FROM PUBLISHER]

Abstract: The paper presents the results of an assessment of the fuel mass penalty due to generators and fuel cell systems. Based on the simulation tool SysFuel, fuel mass penalties for different mission ranges and fuel cell architectures are calculated and compared to a conventional reference architecture. Different fuel cell architectures using ram air or cabin exhaust air and different options of energy recovery are considered. As a result of the studies, target values are presented for the mass to power ratio of fuel cell systems to achieve fuel mass reductions compared to conventional generator and auxiliary power unit systems. [Copyright &y& Elsevier]

Current high temperature superconducting (HTS) wires exhibit high current densities enabling their use in electrical rotating machinery. The possibility of designing high power density superconducting motors operating at reasonable temperatures allows for new applications in mobile systems in which size and weight represent key design parameters. Thus, all-electric aircrafts represent a promising application for HTS motors. The design of such a complex system as an aircraft consists of a multi-variable optimization that requires computer models and advanced design procedures. This paper presents a specific sizing model of superconducting propulsion motors to be used in aircraft design. The model also takes into account the cooling system. The requirements for this application are presented in terms of power and dynamics as well as a load profile corresponding to a typical mission. We discuss the design implications of using a superconducting motor on an aircraft as well as the integration of the electrical propulsion in the aircraft, and the scaling laws derived from physics-based modeling of HTS motors. [ABSTRACT FROM AUTHOR]

NASA conducts and funds research to advance the state of the art in aeronautics, including improvements in aircraft design leading to enhanced performance in areas such as noise, emissions, and safety. A particular initiative involves development of an all-electric aircraft requiring significant improvements in certain technologies. NASA has started a new project with one of the objectives being the development of enabling technologies for an all-electric aircraft. Electrical aeropropulsion requires the design of more compact and efficient electrical motors. In order to me crease the power density, the weight/size must be minimized and the air gap flux density must increase significantly the use of superconducting materials is an obvious choice. Existing HTS motors are proof-of-principle demonstrators and exhibit power densities lower than 1 HP/lb, which is too low to be considered in mobile systems. This paper deals with a preliminary electromagnetic design of a 200 HP high temperature superconducting motor optimized in terms of power density. The presented configuration is a synchronous motor with a nonconventional topology enhanced by HTS bulk material. The design targets the Cessna 172 propulsion requirements that are 200 HP at 2700 RPM. [ABSTRACT FROM AUTHOR]

Some recent or near future examples of multidisciplinary systems of systems are illustrated. They include: upgraded Shuttle avionics; Airbus fly-by-wire; integrated modular electronics; electric automobiles; all-electric aircraft; and JointSTARS system [ABSTRACT FROM PUBLISHER]

Based on the technical platform of electrically actuated nose wheel steering systems, a new type of damping shimmy reduction technology is developed to break through the limitations of traditional hydraulic damping shimmy reduction methods, and an electrically actuated nose wheel steering structure scheme is proposed. The mathematical model of the electromagnetic damper is established, the derivation of skin depth, damping torque and damping coefficient is completed, and the design of the shape and size of the electromagnetic damper is combined with the derivation results and the technical index of shimmy reduction. The electromagnetic field finite element simulation results show that the mathematical modeling method of the electromagnetic damper has good accuracy, and its application to the shimmy reduction module of the electrically actuated nose wheel steering system is also feasible and superior. Finally, the key factors influencing the performance of electromagnetic damper shimmy reduction are studied and analyzed, thus forming a complete electromagnetic damper shimmy reduction technology for the electrically actuated system, and laying the foundation for the design of novel all-electric aircraft and landing gear. [ABSTRACT FROM AUTHOR]

The development of electric aircraft is becoming an important technology for achieving the goals set by the European Commission for the reduction of gases emissions by 2050 in the aeronautical transportation system. However, there is a technology gap between the current values of specific power in commercial electric machines and those required for aeronautical applications. Therefore, the search for alternative materials and non-conventional designs is mandatory. One emergent solution is using superconducting machines and systems to overcome the current limits of conventional electrical machines. This work reviews the new hybrid and all-electric aircraft tendencies, complementing it with recent research on the design and development of high specific power superconducting machines. This includes the main topologies for hybrid and all-electric aircraft, with an overview of the ongoing worldwide projects of these aircraft types, systematizing the main characteristics of their propulsion systems. It also includes the research on superconducting machines to achieve high specific power and consider the impact on the redesign of aircraft systems, the electrical, cooling, and fuel source systems. [ABSTRACT FROM AUTHOR]

The feasibility of regional electric aviation to reduce environmental impact highly depends on technological advancements of energy storage techniques, available battery energy density, and high-power electric motor technologies. However, novel airframe technologies also strongly affect the feasibility of a regional electric aircraft. In this paper, the influence of novel technologies on the feasibility of regional electric aviation was investigated. Three game-changing technologies were applied to a novel all-electric regional aircraft: active flow control, active load alleviation, and novel materials and structure concepts. Initial conceptual design and mission analysis of the aircraft was performed using the aircraft design framework SUAVE, and the sensitivity of the most important technologies on the aircraft characteristics and performance were studied. Obtained results were compared against a reference ATR-72 aircraft. Results showed that an all-electric aircraft with airframe technologies might be designed with the maximum take-off weight increase of 50% starting from the battery pack energy density of 700 Wh/kg. The overall emission level of an all-electric aircraft with novel technologies is reduced by 81% compared to the ATR-72. On the other hand, novel technologies do not contribute to the reduction in Direct Operating Costs (DOC) starting from 700 Wh/kg if compared to an all-electric aircraft without technologies. An increase in DOC ranges from 43% to 30% depending on the battery energy density which creates a significant market obstacle for such type of airplanes. In addition, the aircraft shows high levels of energy consumption which concerns its energy efficiency. Finally, the sensitivity of DOC to novel technologies and sensitivities of aircraft characteristics to each technology were assessed. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to describe the upcoming changes that will bring the transition from piston engines to all-electric aircrafts. The article focuses on the differences in operation of small general aviation aircrafts. This topic is timely, as the first all-electric aircraft was certified by the European Union Aviation Safety Agency (EASA) in 2019. As there are no data concerning this new type of operation available, the data have been derived from other applicable sources. At first, we compared the energy consumption of the same aircraft with the piston engine, and then afterwards with the retrofitted all-electric variant. Our results focus on the difference in fuel price, which is discussed in the context of electricity price comparison with AVGAS prices. Moreover, we discuss the environmental impacts, especially concerning electricity source mix and emissions produced (we estimate both with and without life-cycle assessment). In the discussion, we compare the results and identify the benefits of an all-electric solution. Furthermore, several operational restrictions of all-electric aircrafts are discussed. [ABSTRACT FROM AUTHOR]

• Solid oxide fuel cell - gas turbines hybrid achieving parity with existing turbines. • All-electric solution for long-range commercial aviation with liquid hydrogen. • Power density in excess of 0.9 kW∙kg−1, double prior estimates for aerospace. • Net system energy density in excess of 7 kWh∙kg−1, 20x state-of-the-art batteries. All-electric aircraft have the potential to eliminate greenhouse gas emissions produced by air travel, but the energy storage density of batteries, 0.35 kWh∙kg−1, severely limit s payload and range. This study introduces a fuel cell-gas turbine hybrid arrangement that utilizes liquid hydrogen fuel and superconducting motors to achieve energy storage densities in excess of 7 kWh∙kg−1, more than 20× state-of-the-art battery technology. The analysis considers off-design performance of the pressurized hybrid system meeting the flight profiles of four commercial aircraft. The estimated power density of 0.9 kW∙kg−1 is twice that of prior studies considering fuel cells in aviation, which results in a payload capacity similar to existing commercial jet aircraft powered by gas turbines achieving 10 kW∙kg−1. Prior studies considered advanced, high efficiency distributed propulsion systems to compensate for mass added by electric power systems. This study foregoes such aerodynamic enhancements and transformational aircraft designs to consider only the side-by-side performance of fuel cells against existing turbofan engines. The results show that fuel cells can power much larger aircraft than were previously considered feasible, although novel fuel cell designs are necessary to compete with next generation gas turbine technology. [ABSTRACT FROM AUTHOR]

This article describes the extent to which hybrid aircraft and all-electric aircraft can present a solution for reducing HC, CO, and NO x emissions and noise in the vicinity of airports, in the category of regional passenger aircraft. The goal of the article is to identify, basing on aircraft technical characteristics and market demands, in which sectors of air transport can all-electric or hybrid aircraft be most feasibly introduced. Firstly, a simple theoretical model based on a connection between the aircraft mass and aircraft energy consumption is used to calculate basic technical characteristics and limitations of hybrid and all-electric aircraft. Second, market demands for regional aircraft are presented and discussed, with the intention of recognising the possibilities of replacing conventional aircraft with all-electric and hybrid aircraft models in regional air transport in the near future. Third, quantity of HC, CO, and NO x , CO gas emissions of regional aircraft in Europe was calculated to recognise the possible reduction of gas emissions if hybrid and all-electric aircraft would be implemented. [ABSTRACT FROM AUTHOR]