Structural power performance targets for future electric aircraft

The development of commercial aviation is being driven by the need to improve efficiency and thereby lower emissions. All-electric aircraft present a route to eliminating direct fuel burning emissions, but their development is stifled by the limitations of current battery energy and power densities. Multifunctional structural power composites, which combine load-bearing and energy-storing functions, offer an alternative to higher-energy-density batteries and will potentially enable lighter and safer electric aircraft. This study investigated the feasibility of integrating structural power composites into future electric aircraft and assessed the impact on emissions. Using the Airbus A320 as a platform, three different electric aircraft configurations were designed conceptually, incorporating structural power composites, slender wings and distributed propulsion. The specific energy and power required for the structural power composites were estimated by determining the aircraft mission performance requirements and weight. Compared to a conventional A320, a parallel hybrid-electric A320 with structural power composites >200 Wh/kg could potentially increase fuel efficiency by 15% for a 1500 km mission. For an all-electric A320, structural power composites >400 Wh/kg could halve the specific energy or mass of batteries needed to power a 1000 km flight

Benefit and performance impact analysis of using hydrogen fuel cell powered e-taxi system on A320 class airliner

This paper presents the work carried out to evaluate the benefits and performance impacts of introducing a hydrogen fuel cell powered electric taxiing system to a conventional short-haul aircraft. Tasks carried out in this research and reported in this paper include the initial system design, hydrogen tank initial sizing, calculation of the impact on fuel burn and emissions and the evaluation of the effects on Direct Operating Cost (DOC). The Airbus A320 has been selected as the datum aircraft for sizing the system, and the benefits analysis is particularly focused on the fleet composition and financial data of a Europe-based, low-cost, large-scale A320 family operator in 2016. The maximum power capacity of 400 kW has been sized based on the rolling friction coefficient of 0.02. Based on the operator’s 2016 financial, up to 1% fuel reduction can be achieved using the proposed system and the reduction in total maintenance cost is expected to be up to 7.3%. Additionally, up to 5.97% net profit improvement is estimated in comparison with the annual after-tax profit of the datum operator in 201

Innovative airplane ground handling system for green operations

The aim of this work is to develop a new concept of taxiing, in order to reduce the pollution in terms of noise and gas emission and to introduce a higher level of safety during ground operations. In the area close to the airport gates, the airplane ground handlings are currently performed through the airplane engines, which have the task of providing the trust necessary to move the airplane to the runway. Pollutant emissions and the noise level near the gates, however, could be drastically reduced by introducing an innovative autonomous tractor called CHAT (Clean Hydrogen Autonomous Tractor), developed from the standard pushback tractor. The ground operations could be basically modified by extending the time in which the airplane engines are idle and the airplane is towed by the tractors powered by renewable energy

Use of Ram Air Turbines for electrical taxiing in Airbus 320

Twin engine Airbus 320 taxi procedures involve not only a notable fuel consumption but an increment of engine hour operation, reducing its life cycle. The possibility of using air generators is studied in this Bachelor Thesis. These air generators will be located in the aircraft fuselage so as to charge batteries. The energy stored will be used for an efficient taxiing but also for reducing main engines operating hours. Possible locations will be studied for one or more air generators, including its rightness and efficiency. Students must consider all negative effects produced by air generators that may alter aircraft aerodynamics and operation. The extra weight added due to batteries and electrical generator needed must be taken into account so as to consider its efficiency. The energetic balance relates the energy obtained during approach with the one needed for taxiing. The target is to achieve a viable implementation of this system in terms of energy and economically suitable for the airline as well.Català: El rodatge per pista d’un avió com l’Airbus 320, el qual té dos turboreactors, suposa no només un consum de combustible important, sinó que suposa també un consum notable en hores de funcionament dels motors, reduint el seu cicle de vida. En aquest Treball de Final de Carrera s’estudia la possibilitat d’utilitzar uns aerogeneradors situats al fuselatge de l’aeronau que recarreguin unes bateries que permetin fer el rodatge de manera més eficient i que no gasti hores de funcionament dels motors principals. S’estudiaran possibles posicions per instal·lar el o els aerogeneradors, la idoneïtat d’aquestes propostes així com la seva eficiència. Els estudiants hauran de tenir en consideració els efectes negatius sobre l’avió, com afecta a l’aerodinàmica d’aquest i quant d’eficient és tenint en compte el fet de que s’haurà de portar el pes extra de les bateries, així com del motor elèctric que mogui l’avió en terra. El balanç energètic relaciona l’energia que s’obté durant l’aproximació amb la necessària pel procediment de taxi. L’objectiu és aconseguir una implementació viable del sistema en termes energètics i econòmicament desitjable per a la companyia aèria

Energy Storage System Selection for Optimal Fuel Consumption of Aircraft Hybrid Electric Taxiing Systems

IEEE Aircraft taxiing is conventionally performed using the main engines’ inefficient idle thrust. Therefore, in line with greener aviation, the electrification of taxiing is the most viable option to reduce emissions, noise, and fossil fuel consumption during ground operations. This paper studies the potential of hybridising the conventional electric taxiing system, which is currently driven by the Auxiliary Power Unit, with an electrical energy storage system, comprising commercial high-energy and high-power lithium-ion batteries, for the purpose of reducing fuel consumption. Hence, a power distribution optimisation is formulated to minimise fuel consumption over a typical worst-case taxi-out profile. Three different energy management strategies are presented for a narrow-body aeroplane. The optimisation is performed for the selection of off-the-shelf batteries so that their impact on fuel savings can be evaluated in the early design stage. The study showed that a wide range of savings is achievable according to the selected strategy, the added weight allowance, and the battery characteristics. Considering a 180 kg added weight allowance and covering the three investigated strategies, up to 72% of taxiing fuel is saved

Innovative airplane ground handling system for green operations

The aim of this work is to develop a new concept of taxiing, in order to reduce the pollution in terms of noise and gas emission and to introduce a higher level of safety during ground operations. In the area close to the airport gates, the airplane ground handlings are currently performed through the airplane engines, which have the task of providing the trust necessary to move the airplane to the runway. Pollutant emissions and the noise level near the gates, however, could be drastically reduced by introducing an innovative autonomous tractor called CHAT (Clean Hydrogen Autonomous Tractor), developed from the standard pushback tractor. The ground operations could be basically modified by extending the time in which the airplane engines are idle and the airplane is towed by the tractors powered by renewable energy

Energy harvesting frictionless brakes for short-haul aircraft: thermal and electromagnetic feasibility of an axial-flux machine for a landing gear drive system

The aviation industry is currently responding to climate change with, among other technologies, electrification of aircraft, and the corresponding onboard electrical architecture provides an opportunity for electromagnetic brakes. The present work introduces a multistage yokeless and segmented armature (YASA) electric machine that replaces friction brakes and harvests kinetic energy throughout a landing. The study establishes the optimal trade-off between weight and electromagnetic torque and translates it into the design requirements for the development of an electric machine. Electromagnetic modeling is conducted using a quasi-3D transient approach and static 3D validation. The results reach 120 Nm/kg active material torque density at approximately 50 A/mm² current density. The proposed solution enables fitting an electric machine that decelerates an aircraft at autobrake level LOW for Airbus and the "1" and "2" settings for Boeing. A thermal analysis follows, where a novel cruise altitude cooling method is proposed.European Union funding: 251798

Planning and reconfigurable control of a fleet of unmanned vehicles for taxi operations in airport environment

The optimization of airport operations has gained increasing interest by the aeronautical community, due to the substantial growth in the number of airport movements (landings and take-offs) experienced in the past decades all over the world. Forecasts have confirmed this trend also for the next decades. The result of the expansion of air traffic is an increasing congestion of airports, especially in taxiways and runways, leading to additional amount of fuel burnt by airplanes during taxi operations, causing additional pollution and costs for airlines. In order to reduce the impact of taxi operations, different solutions have been proposed in literature; the solution which this dissertation refers to uses autonomous electric vehicles to tow airplanes between parking lots and runways. Although several analyses have been proposed in literature, showing the feasibility and the effectiveness of this approach in reducing the environmental impact, at the beginning of the doctoral activity no solutions were proposed, on how to manage the fleet of unmanned vehicles inside the airport environment. Therefore, the research activity has focused on the development of algorithms able to provide pushback tractor (also referred as tugs) autopilots with conflict-free schedules. The main objective of the optimization algorithms is to minimize the tug energy consumption, while performing just-in-time runway operations: departing airplanes are delivered only when they can take-off and the taxi-in phase starts as soon as the aircraft clears the runway and connects to the tractor. Two models, one based on continuous time and one on discrete time evolution, were developed to simulate the taxi phases within the optimization scheme. A piecewise-linear model has also been proposed to evaluate the energy consumed by the tugs during the assigned missions. Furthermore, three optimization algorithms were developed: two hybrid versions of the particle swarm optimization and a tree search heuristic. The following functional requirements for the management algorithm were defined: the optimization model must be easily adapted to different airports with different layout (reconfigurability); the generated schedule must always be conflict-free; and the computational time required to process a time horizon of 1h must be less than 15min. In order to improve its performance, the particle swarm optimization was hybridized with a hill-climb meta-heuristic; a second hybridization was performed by means of the random variable search, an algorithm of the family of the variable neighborhood search. The neighborhood size for the random variable search was considered varying with inverse proportionality to the distance between the actual considered solution and the optimal one found so far. Finally, a tree search heuristic was developed to find the runway sequence, among all the possible sequences of take-offs and landings for a given flight schedule, which can be realized with a series of taxi trajectories that require minimum energy consumption. Given the taxi schedule generated by the aforementioned optimization algorithms a tug dispatch algorithm, assigns a vehicle to each mission. The three optimization schemes and the two mathematical models were tested on several test cases among three airports: the Turin-Caselle airport, the Milan-Malpensa airport, and the Amsterdam airport Schiphol. The cost required to perform the generated schedules using the autonomous tugs was compared to the cost required to perform the taxi using the aircraft engines. The proposed approach resulted always more convenient than the classical one

Assessing the airport facilities in the context of UAM operations

UAM mobility is deemed as a paradigm shift in passenger transport mode for intra- and inter-urban transport. This concept is supported by the appearance of new types of aircraft with the capability of vertical takeoff and landing (VTOL) and the use of electric propulsion and energy storage. Current VTOL vehicle prototypes vary substantially in configuration and design, resulting in different UAM missions and concepts of operations. Although still in the so-called innovation trigger phase, growing interest from large investors and existing (NASA) and emerging (Lilium) companies implies the expectation of some of these VTOL aircraft to end up being pilotless, autonomous aircraft designed for between one and five passengers on board. While most of the UAM passenger-related service will require dedicated VTOL ground infrastructure for takeoff and landing (often referred as vertiports), some of the operational concepts contemplate integrating these vehicles into existing airports. This refers particularly to the UAM mission which aims to connect the city center (or suburb) with the airport. However, this process is not straightforward, as it requires a thorough evaluation of different operational and safety aspects to allow the smooth operation of these new vehicles given their distinctive characteristics. Furthermore, to accommodate these types of vehicles and provide a satisfactory level of service to all stakeholders (i.e., airlines), airports will need to acquire adequate facilities and learn to manage these new operations alongside conventional aviation. This project aims to investigate the need for new airport facilities in the light of potential integration of VTOL vehicles. With their new autonomy features, some of the airside facilities need to be radically upgraded to allow safe integration into the current airport system. To do this, this analysis is divided into two parts. The first part is oriented to the description and analysis of the different models and configurations of VTOL aircraft that can be found nowadays together with the nature of the missions that can be carried out. The second part of the study introduces a background and an initial approach to the integration of UAM services in the airport environment to finish by analysing two hypothetical application scenarios to reality with their corresponding identification of the new and existing facilities necessary to accommodate these new operations concepts.Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::11 - Ciutats i Comunitats Sostenible

An investigation of operational management solutions and challenges for electric taxiing of aircraft

Taxiing aircraft using electric towing vehicles (ETVs) is expected to significantly contribute to the objective of climate-neutral aviation by 2050. This study reviews existing work on operational aspects of electric towing of aircraft, and discusses management solutions. We first discuss the varying electric taxi systems currently under development, and their implementation progress at airports. We outline the current specifications of ETVs and the procedures needed to perform electric taxiing movements. We next discuss the management needs for implementing ETVs at an airport, by reviewing existing mathematical models for ETV fleet management: dedicated vehicle routing models, ETV to flight assignment models, fleet sizing models and battery charging optimisation models. Last, we identify remaining research challenges. For instance, a main challenge is to increase the robustness of ETV routing and towing scheduling against disruptions due to flight delay. This paper summarizes the main research directions needed to support large-scale ETV implementation in the next few decades