eVTOL Vehicles Research Articles

Thermo-electrochemical level-set topology optimization of a heat exchanger for lithium-ion batteries for electric vertical take-off and landing vehicles

Developing electric vertical take-off and landing vehicles (eVTOL) that can meet the demanding power and energy requirements entails significant challenges, one of which is due to the weight of the battery packs. To address this challenge, optimization techniques can be employed to achieve lightweight designs while satisfying thermal criteria. This study focuses on optimizing a battery heat exchanger housing a high-energy-densitycylindrical cell using the level-set topology optimization method. To accurately account for heat generation from battery electrochemistry, we investigate both a high-fidelity, the Doyle Fuller Newman (DFN) model, and a low-fidelity electrochemical model, the Single Particle Model (SPM), which are compared to experimental results for an eVTOL flight profile. The novelty of the proposed approach resides in the integration of the electrochemical models within a three-dimensional unsteady thermo-electrochemical topology optimization framework. The battery heat exchanger is optimized considering the heat generated by the batteries at the material scale due to the system power requirements. The heat generated by the battery is incorporated as a source term in an unsteady heat conduction finite element model, forming the basis of the optimization process. Our objective is to minimize the integrated thermal compliance over time while satisfying a volume constraint, employing the level-set method. The SPM proves competent in predicting the voltage profile but underestimates the temperature increase. On the other hand, the DFN model accurately predicts both the temperature increase and the voltage profile, making it suitable for the thermal analysis of cells in eVTOL vehicles. Surprisingly, steady-state optimization turns out to be sufficient to generate optimized topologies that perform similarly to transient cases for the case investigated but at a reduced cost. By integrating electrochemical modeling, level-set topology optimization, and heat transfer analysis, our study contributes to the development of lightweight and thermally efficient battery heat exchangers for eVTOL vehicles, which can be extended to battery packs. Importantly, the presented methodology is versatile and can be applied to different battery chemistries, form factors, and power profiles.

Aerodynamic Performance and Numerical Analysis of the Coaxial Contra-Rotating Propeller Lift System in eVTOL Vehicles

Electric vertical takeoff and landing (eVTOL) vehicles possess high payload transportation capabilities and compact design features. The traditional method of increasing propeller size to cope with high payload is no longer applicable. Therefore, this study proposes the use of coaxial counter-rotating propellers as the lift system for eVTOL vehicles, consisting of two coaxially mounted, counter-rotating bi-blade propellers. However, if the lift of a single rotating propeller is linearly increased without considering the lift loss caused by the downwash airflow generated by the upper propeller and the torque effect of the lift system, it will significantly impact performance optimization and safety in the eVTOL vehicles design process. To address this issue, this study employed the Moving Reference Frame (MRF) method within Computational Fluid Dynamics (CFD) technology to simulate the lift system, conducting a detailed analysis of the impact of the upper propeller’s downwash flow on the aerodynamic performance of the lower propeller. In addition, the aerodynamic performance indicators of coaxial counter-rotating propellers were quantitatively analyzed under different speed conditions. The results indicated significant lift losses within the coaxial contra-rotating propeller system, which were particularly notable in the lift loss of the lower propeller. Moreover, the total torque decreased by more than 93.8%, and the torque was not completely offset; there was still a small torsional effect in the coaxial counter-rotating propellers. The virtual testing method of this study not only saves a significant amount of time and money but also serves as a vital reference in the design process of eVTOL vehicles.

Improving access to emergency medical services using advanced air mobility vehicles

AbstractThe latest advancements in electric vertical take-off and landing (eVTOL) vehicles indicate that soon this technology will be available in multiple fields. One potential application of this new technology is in emergency medical services. These vehicles will be able to reach emergency sites faster than ground ambulances at lower costs than traditional helicopters. So in the following years, eVTOL vehicles could be used for aeromedical transportation. One crucial decision in implementing such a technology in emergency medical services is the location of their take-off and landing areas (vertiports). In this work, we propose a methodology for locating the vertiports in a healthcare network to improve emergency medical services coverage in hard-to-reach zones. We studied the system performance locating the vertiports for emergency services in existing healthcare facilities or outside them as auxiliary bases. In addition, we evaluated the performance of different operational scenarios regarding the use of emergency eVTOL. To do so, we used data analytics techniques (i.e., clustering algorithms) in conjunction with facility location models. The approach is tested using data from the Auvergne-Rhône-Alpes region in France. Results showed that locating the vertiports in existing healthcare facilities is the best choice in terms of coverage of hard-to-reach zones. However, on average, the response times increased compared to locating the vertiports as auxiliary bases outside the healthcare facilities. Besides, the results indicated that implementing eVTOL vehicles for aeromedical transportation can provide better access to emergency medical services in hard-to-reach zones. Still, the autonomy of such vehicles plays an essential role in their applicability.

A heuristic approach for scheduling advanced air mobility aircraft at vertiports

Recent progress in electric vertical take-off and landing (eVTOL) vehicles suggests that soon these vehicles could safely and efficiently transport people and cargo in urban areas. Therefore, advanced air mobility vehicles could become an alternative means of transport to overcome traffic congestion in cities in the upcoming years. There has been enormous interest from companies and governments in recent years in developing such technologies and enabling markets for new air transportation services. Despite the interest in the topic, little research has been done to address the aircraft scheduling problem in advanced air mobility take-off and landing areas (vertiports). The vertiports serve as the airports of eVTOL vehicles and could experience congestion problems similar to those of airports. This work proposes two optimization models for scheduling departing and landing aircraft at the vertiports’ common ground taxi routes (taxiways), gates, and touchdown and lift-off (TLOF) pads. The mathematical models include advanced air mobility features such as separation rules and blocking constraints. As scheduling objectives, the first model maximizes the vertiport throughput, and the second model minimizes the deviation from the expected take-off/landing time. In addition, as a solution methodology, we developed two heuristic algorithms that use scheduling rules to assign and sequence the aircraft to the vertiport components. Computational results show that the optimization models find optimal schedules for small-sized instances of up to 10 aircraft, while the heuristic algorithms provide good results in terms of solution quality and computational time for large instances.

Advanced Air Mobility Operation and Infrastructure for Sustainable Connected eVTOL Vehicle

Advanced air mobility (AAM) is an emerging sector in aviation aiming to offer secure, efficient, and eco-friendly transportation utilizing electric vertical takeoff and landing (eVTOL) aircraft. These vehicles are designed for short-haul flights, transporting passengers and cargo between urban centers, suburbs, and remote areas. As the number of flights is expected to rise significantly in congested metropolitan areas, there is a need for a digital ecosystem to support the AAM platform. This ecosystem requires seamless integration of air traffic management systems, ground control systems, and communication networks, enabling effective communication between AAM vehicles and ground systems to ensure safe and efficient operations. Consequently, the aviation industry is seeking to develop a new aerospace framework that promotes shared aerospace practices, ensuring the safety, sustainability, and efficiency of air traffic operations. However, the lack of adequate wireless coverage in congested cities and disconnected rural communities poses challenges for large-scale AAM deployments. In the immediate recovery phase, incorporating AAM with new air-to-ground connectivity presents difficulties such as overwhelming the terrestrial network with data requests, maintaining link reliability, and managing handover occurrences. Furthermore, managing eVTOL traffic in urban areas with congested airspace necessitates high levels of connectivity to support air routing information for eVTOL vehicles. This paper introduces a novel concept addressing future flight challenges and proposes a framework for integrating operations, infrastructure, connectivity, and ecosystems in future air mobility. Specifically, it includes a performance analysis to illustrate the impact of extensive AAM vehicle mobility on ground base station network infrastructure in urban environments. This work aims to pave the way for future air mobility by introducing a new vision for backbone infrastructure that supports safe and sustainable aviation through advanced communication technology.

Automotive safety approach for future eVTOL vehicles

The eVTOL industry is a rapidly growing mass market expected to start in 2024. eVTOL compete, caused by their predicted missions, with ground-based transportation modes, including mainly passenger cars. Therefore, the automotive and classical aircraft design process is reviewed and compared to highlight advantages for eVTOL development. A special focus is on ergonomic comfort and safety. The need for further investigation of eVTOL’s crashworthiness is outlined by, first, specifying the relevance of passive safety via accident statistics and customer perception analysis; second, comparing the current state of regulation and certification; and third, discussing the advantages of integral safety and applying the automotive safety approach for eVTOL development. Integral safety links active and passive safety, while the automotive safety approach means implementing standardized mandatory full-vehicle crash tests for future eVTOL. Subsequently, possible crash impact conditions are analyzed, and three full-vehicle crash load cases are presented.

System Identification Approach for eVTOL Aircraft Demonstrated Using Simulated Flight Data

This paper describes a system identification method for electric vertical takeoff and landing (eVTOL) aircraft. The approach merges fixed-wing and rotary-wing modeling techniques with new strategies to develop a modeling method for eVTOL vehicles using flight-test data. The eVTOL aircraft system identification approach is demonstrated through application to the NASA Langley Aerodrome No. 8 tandem tilt-wing, distributed electric propulsion aircraft using a high-fidelity flight dynamics simulation. Orthogonal phase-optimized multisine inputs are applied to each control surface and propulsor at numerous flight conditions throughout the flight envelope to collect informative flight data. An aero-propulsive model is identified at each flight condition using the equation-error method in the frequency domain. The local model parameters are then blended to create a global model across the nominal flight envelope. The identified models are shown to provide a good fit to modeling data with good prediction capability. The methodology is developed with a discussion of unique eVTOL vehicle aerodynamic characteristics and practical strategies intended to inform future flight-based system identification efforts for eVTOL aircraft.

Life cycle assessment of eVTOL vehicles in island systems. Case study: Canary Islands

Life cycle assessment of eVTOL vehicles in island systems. Case study: Canary Islands

Economic and emission reduction benefits of the implementation of eVTOL aircraft with bi-directional flow as storage systems in islands and case study for Canary Islands

This research paper presents a novel approach for cost-benefit analysis for the bi-directional functionality of eVTOL (Electric Vertical Take-Off and Landing) aircraft charging. eVTOL aircrafts represents an emerging aviation market that seeks to revolutionize mobility, both intra-city and inter-city, through an air transportation system for passengers based on safety, efficiency and accessibility on demand. In this research, an optimization based on genetic algorithms has been used to find the number of eVTOL vehicles which makes vehicle-to-grid services profitable for each of the electrical systems considered. This research discusses the impact that vehicle-to-grid eVTOL aircraft would cause, changing the current demand curve peaks and the economic benefits for eVTOL end users, power plant companies and system operator. The results show that there is an increase in the penetration of renewable energy sources, causing a reduction of approximately 4.6% in global emissions. In addition, the benefits obtained by the stakeholders considered in the system is greater than zero. The methodology considered in this research offers a new perspective for electrical systems to predict the demand of eVTOL aircraft, in specific territories, such as in the presented case study in the Archipelago of Canary Islands.

Novel UAS Propeller Design Part 1: Using an Unloaded Tip to Reduce Power Requirements and Lower Generated Sound Levels for Propellers Designed for Minimum Induced Drag

Abstract Today, over 500 eVTOL vehicles are being developed for everything from Urban Air Mobility to package delivery. In addition, Unmanned Aircraft Systems (UASs) are used in a variety of applications to include intelligence, surveillance, and reconnaissance (ISR) as well as resupply for the military. Most of these vehicles utilize electric propulsion systems with propellers. Efficient propellers with reduced noise generation are necessary for these vehicles to coexist in urban environments or be used for ISR missions. Traditional propeller design uses Blade Element Momentum Theory (BEMT) to minimize induced losses. The current investigation describes a novel propeller design approach that minimizes induced drag by reducing the thrust loading near tip. This reduces the tip vortex strength lowering the Sound Pressure Level (SPL) and power required. A parametric study of 18 propellers examined performance using traditional BEMT design near the hub and progressing to zero thrust loading at the tip. A microphone on a traverse mounted behind the propeller was used to measure the peak SPL and its location in a wind tunnel. The best performing unloaded tip propeller showed 5.2% reduction in power required and 12 dB SPL reduction compared to a commercial propeller at the same test conditions. Keywords: UAS propeller, propeller design, airfoil

Computational Investigation of Blade–Vortex Interaction of Coaxial Rotors for eVTOL Vehicles

In the design of electric vertical takeoff and landing (eVTOL) vehicles, coaxial rotors have garnered significant attention due to their superior space usage and aerodynamic efficiency compared to standard rotors. However, it is challenging to study the flow field near the rotors due to the blade–vortex interface (BVI) and vortex–vortex contact between two rotors. Using sliding mesh technology and Reynolds-averaged Navier–Stokes (RANS) solvers, a numerical method was established to simulate the flow field of a coaxial rotor in hover, which was verified by experiments. Using this method, this paper analyzes the relationship between position and intensity of the tip vortex of the upper rotor, the axial velocity of induced flow and the load distribution on the blades at the azimuth when the BVI phenomenon occurs with a difference in rotational speed and rotor spacing. The results indicate that, when the BVI phenomenon appears, the blade-tip vortex of the top rotor rapidly dissipates, and the load distribution of the lower blade changes due to the induced flow of the vortex. When the rotational speed increases, the spanwise thrust coefficient of each rotor changes slightly. The vortex–vortex interaction becomes stronger, which leads to vortex pairing. When the distance between the rotors decreases, the BVI phenomenon occurs at an earlier azimuth and the location of the BVI moves towards the tip of the lower blade. The vortex–vortex interaction is also enhanced, which leads to vortex pairing and vortex merging.

Experimental Study into Optimal Configuration and Operation of Two-Four Rotor Coaxial Systems for eVTOL Vehicles

Coaxial rotors are utilized in multirotor aerial vehicles for the added thrust compared to independent rotors while keeping similar area footprints; however, performance losses should be considered. This experimental study analyzes the effects of varying motor duty cycle and propeller pitch values in motor-propeller systems with two to four coaxial rotors. The results demonstrate that in a two-rotor coaxial system, to lessen the adverse effects of a front rotor’s backwash and operate at the maximum performance, only the back motor should be operated initially up to 75% duty cycle before using the front motor up to its 75% duty cycle. Additional thrust requirements should be generated from the back rotor and then from the front rotor up to their maximum duty cycles. In two, three, and four-rotor coaxial setups, total thrust output generated is 1.6, 2.1, and 2.5 times the thrust output at system thrust performance of 86%, 76%, and 66%, respectively, of that of an isolated rotor. In a four-rotor coaxial setup, the maximum system performance is achieved when the propeller pitch values gradually increase from the first to the last rotor. The gradual increments in propeller pitch values also result in more uniform thrust sharing among rotors.

Trim Envelope Calculations for a Tiltrotor in Forward Flight, Hover and Transitions

Urban Air Mobility (UAM) is a future mode of transportation that will require revolutionary new electronic vertical takeoff and landing (eVTOL) vehicle concepts and operations. One of the challenges for these eVTOL vehicles will be the complexity of the flight control task which requires operation in hover, forward flight and the transition between the two. The trim envelope is an important piece of information for analyzing which airspeeds and either flight path angles or vertical speeds are safely achievable in each flight regime. The largest share of the vehicle concept designs for UAM are some kind of vectored thrust vehicle, highlighting the importance of analyzing these flight regime transitions. This papercalculates and compares the trim envelopes for a generic tiltrotor aircraft model for different rotor tilt angles. Preliminary results confirm a narrow transition corridor that is a well-known characteristic of tiltrotor aircraft

Up, Up and Away! [Aviation - eVTOL

Hybrid-electric vertical take-off and landing (eVTOL) vehicles could transform the air traffic ecosystem. After more than a decade, the market for electric vertical take-off and landing aircraft is on the rise, and its goal of making urban air mobility (UAM) for everyone personal, on-demand and carbon-free looks within reach. Big money is backing air taxis. In 2021, at least four leading players will go public. All will reverse-merge into existing listed investment vehicles - or SPACs - which will receive funding from current and new investors. The various companies involved in developing eVTOL vehicles are discussed.

Distributed deep reinforcement learning for autonomous aerial eVTOL mobility in drone taxi applications

The urban aerial mobility (UAM) system, such as drone taxi or air taxi, is one of future on-demand transportation networks. Among them, electric vertical takeoff and landing (eVTOL) is one of UAM systems that is for identifying the locations of passengers, flying to the positions where the passengers are located, loading the passengers, and delivering the passengers to their destinations. In this paper, we propose a distributed deep reinforcement learning where the agents are formulated as eVTOL vehicles that can compute the optimal passenger transportation routes under the consideration of passenger behaviors, collisions among eVTOL, and eVTOL battery status.

Life Cycle Engineering of future aircraft systems: the case of eVTOL vehicles

This paper introduces the first steps towards a general modelling framework for the integrated life cycle engineering (LCE) of future air transportation systems. The focus of analysis lies on the potential environmental implications of batteries powering electric vertical takeoff and landing aircrafts (eVTOLs), which have emerged as an option for urban air mobility to alleviate automobile traffic in cities. The impact of main influencing factors on the sustainability of eVTOLs is discussed, presenting the main modelling requirements for an LCE framework to accompany the transition towards a more sustainable air mobility.