Improvement of Take-Off Performance for an Electric Commuter Aircraft Due to Distributed Electric Propulsion

The need for environmentally responsible solutions in aircraft technology is now considered the priority for global challenges related to the limited supply of traditional fuel sources and the potential global hazards associated with emissions produced by traditional aircraft propulsion systems. Several projects, including research into highly advanced subsonic aircraft concepts to drastically reduce energy or fuel usage, community noise, and emissions associated with aviation, are currently ongoing. One of the proposed propulsion concepts that address European environmental goals is distributed electric propulsion. This paper deals with the detailed aerodynamic analyses of a full-electric commuter aircraft with fuel cells, which expects two primary electric motors at the wing tip and eight other electric motors distributed along the wingspan as secondary power sources. The main objective was the numerical estimation of propulsive effects in terms of lift capabilities at take-off conditions to quantify the possible reduction of take-off field length. However, the aircraft was designed from scratch, and therefore a great effort was spent to design both propellers (for the tip and distributed electric motors) and the wing flap. In this respect, several numerical tests were performed to obtain one of the best possible flap positions. This research work estimated a reduction of about 14% of the take-off field length due to only the propulsive effects. A greater reduction of up to 27%, if compared to a reference conventional commuter aircraft, could be achieved thanks to a combined effect of distributed propulsion and a refined design of the Fowler flap. On the contrary, a significant increment of pitching moment was found due to distributed propulsion that may have a non-negligible impact on the aircraft stability, control, and trim drag

The Enabling Technologies for a Quasi-Zero Emissions Commuter Aircraft

The desire for greener aircraft pushes both academic and industrial research into developing technologies, manufacturing, and operational strategies providing emissions abatement. At time of writing, there are no certified electric aircraft for passengers’ transport. This is due to the requirements of lightness, reliability, safety, comfort, and operational capability of the fast air transport, which are not completely met by the state-of-the-art technology. Recent studies have shown that new aero-propulsive technologies do not provide significant fuel burn reduction, unless the operational ranges are limited to short regional routes or the electric storage capability is unrealistically high, and that this little advantage comes at increased gross weight and operational costs. Therefore, a significant impact into aviation emissions reduction can only be obtained with a revolutionary design, which integrates disruptive technologies starting from the preliminary design phase. This paper reviews the recent advances in propulsions, aerodynamics, and structures to present the enabling technologies for a low emissions aircraft, with a focus on the commuter category. In fact, it is the opinion of the European Community, which has financed several projects, that advances on the small air transport will be a fundamental step to assess the results and pave the way for large greener airplanes

A survey of free software for the design, analysis, modelling, and simulation of an unmanned aerial vehicle

The objective of this paper is to analyze free software for the design, analysis, modelling, and simulation of an unmanned aerial vehicle (UAV). Free software is the best choice when the reduction of production costs is necessary; nevertheless, the quality of free software may vary. This paper probably does not include all of the free software, but tries to describe or mention at least the most interesting programs. The first part of this paper summarizes the essential knowledge about UAVs, including the fundamentals of flight mechanics and aerodynamics, and the structure of a UAV system. The second section generally explains the modelling and simulation of a UAV. In the main section, more than 50 free programs for the design, analysis, modelling, and simulation of a UAV are described. Although the selection of the free software has been focused on small subsonic UAVs, the software can also be used for other categories of aircraft in some cases; e.g. for MAVs and large gliders. The applications with an historical importance are also included. Finally, the results of the analysis are evaluated and discussed—a block diagram of the free software is presented, possible connections between the programs are outlined, and future improvements of the free software are suggested. © 2015, CIMNE, Barcelona, Spain.Internal Grant Agency of Tomas Bata University in Zlin [IGA/FAI/2015/001, IGA/FAI/2014/006

Electric Power Systems and Components for Electric Aircraft

Electric aircraft have gained increasing attention in recent years due to their potential for environmental and economic benefits over conventional airplanes. In order to offer competitive flight times and payload capabilities, electric aircraft power systems (EAPS) must exhibit extremely high efficiencies and power densities. While advancements in enabling technologies have progressed the development of high performance EAPS, further research is required. One challenge in the design of EAPS is determining the best topology to be employed. This work proposes a new graph theory based method for the optimal design of EAPS. This method takes into account data surveyed from a large set of references on commonly seen components including electric machines, power electronics and jet engines. Thousands of design candidates are analyzed based on performance metrics such as end-to-end system efficiency, overall mass, and survivability. It is also shown that sensitivity analysis may be used to systematically evaluate the impact of components and their parameters on various aspects of the architecture design. Once an EAPS architecture has been selected, further, detailed, validation of the power system is required. In these EAPS, many subsystems exist with timescales varying from minutes to hours when considering the aerodynamics, to nanosecond dynamics in the power electronics. This dissertation presents a multiphysics co-simulation framework for the evaluation of EAPS with a unique decoupling method to reduce simulation time without sacrificing detail. The framework has been exemplified on a case study of a 500kW all-electric aircraft, including models for aerodynamics, energy storage, electric motors and power electronics. Electric machines for aviation propulsion must meet several performance requirements, including a constant power speed range (CPSR) of approximately thirty percent above rated speed. This operation is traditionally achieved through the flux weakening technique with an injection of negative d-axis current. However, the degree of CPSR achievable through flux weakening is a strong function of the back emf and d-axis inductance. This dissertation reviews alternative methods for CPSR operation in machines with low inductance. A new method of current weakening has been proposed to address this challenge, involving reducing the machine\u27s current inversely proportional to the operating speed, maintaining constant power through the extended speed range. One benefit of the proposed method is that all current is maintained in the q-axis, maintaining maximum torque per ampere operation. Coreless axial flux permanent magnet (AFPM) machines have recently gained significant attention due to their specific form factor, potentially higher power density and lower losses. Coreless machine designs promise high efficiency particularly at higher speeds, due to the absence of a ferromagnetic core. In this dissertation, coreless AFPM machines with PCB stators are investigated as candidates for propulsion in electric aircraft applications. Two PCB stator design variations are presented with both simulation and experimental results

Overview of NASA Electrified Aircraft Propulsion Research for Large Subsonic Transports

NASA is investing in Electrified Aircraft Propulsion (EAP) research as part of the portfolio to improve the fuel efficiency, emissions, and noise levels in commercial transport aircraft. Turboelectric, partially turboelectric, and hybrid electric propulsion systems are the primary EAP configurations being evaluated for regional jet and larger aircraft. The goal is to show that one or more viable EAP concepts exist for narrow body aircraft and mature tall-pole technologies related to those concepts. A summary of the aircraft system studies, technology development, and facility development is provided. The leading concept for mid-term (2035) introduction of EAP for a single aisle aircraft is a tube and wing, partially turbo electric configuration (STARC-ABL), however other viable configurations exist. Investments are being made to raise the TRL level of light weight, high efficiency motors, generators, and electrical power distribution systems as well as to define the optimal turbine and boundary layer ingestion systems for a mid-term tube and wing configuration. An electric aircraft power system test facility (NEAT) is under construction at NASA Glenn and an electric aircraft control system test facility (HEIST) is under construction at NASA Armstrong. The correct building blocks are in place to have a viable, large plane EAP configuration tested by 2025 leading to entry into service in 2035 if the community chooses to pursue that goal

Architectural Trade-offs for a Hybrid-Electric Regional Aircraft

Research entities and the aviation industry are collaborating to reduce the greenhouse gas emissions of the global aircraft fleet. To move away from fossil fuels as energy carrier while reducing the aircrafts primary energy demand are the ideal but challenging means to achieve this target. The research activities within the German government funded project TELEM have shown on a conceptual level that both measures could be realized for regional aircraft with an optimized hybrid-electric propulsion (HEP) ar- chitecture. Short, but very frequently flown distances of 200 nm and more could be served fully electri- cally by advanced propeller-driven aircraft with an assumed entry-into-service (EIS) in 2035. This paper gives an overview of integration concepts pursued in the project and reflects on various design aspects of a plug-in hybrid-electric aircraft, featuring a fully electric flight capability and a kerosene-fueled tur- boshaft range-extender. The aircrafts HEP architecture is optimized with regard to the number of pro- pellers, as well as range extenders and their integration concept as to yield the best efficiency and to enable commonality with smaller aircraft leading to potential cost reductions among aircraft classes. Furthermore, a thermal management system, which is essential for the hybrid-electric propulsion archi- tecture and its requirements are discussed and a favorable option selected. The final configuration fea- tures ten propellers and one range extender. The results also confirmed the exceptional efficiency of a plug-in HEP architecture for regional aircraft, showing a 34.6 % reduction in fleet energy and 64.4 % reduction in fuel consumption compared to a conventional turboprop architecture with an EIS in 2035

A Biomimetic, Energy-Harvesting, Obstacle-Avoiding, Path-Planning Algorithm for UAVs

This dissertation presents two new approaches to energy harvesting for Unmanned Aerial Vehicles (UAV). One method is based on the Potential Flow Method (PFM); the other method seeds a wind-field map based on updraft peak analysis and then applies a variant of the Bellman-Ford algorithm to find the minimum-cost path. Both methods are enhanced by taking into account the performance characteristics of the aircraft using advanced performance theory. The combined approach yields five possible trajectories from which the one with the minimum energy cost is selected. The dissertation concludes by using the developed theory and modeling tools to simulate the flight paths of two small Unmanned Aerial Vehicles (sUAV) in the 500 kg and 250 kg class. The results show that, in mountainous regions, substantial energy can be recovered, depending on topography and wind characteristics. For the examples presented, as much as 50% of the energy was recovered for a complex, multi-heading, multi-altitude, 170 km mission in an average wind speed of 9 m/s. The algorithms constitute a Generic Intelligent Control Algorithm (GICA) for autonomous unmanned aerial vehicles that enables an extraction of atmospheric energy while completing a mission trajectory. At the same time, the algorithm automatically adjusts the flight path in order to avoid obstacles, in a fashion not unlike what one would expect from living organisms, such as birds and insects. This multi-disciplinary approach renders the approach biomimetic, i.e. it constitutes a synthetic system that “mimics the formation and function of biological mechanisms and processes.

Aeronautical Engineering: A continuing bibliography with indexes, supplement 113, September 1979

This bibliography lists 436 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1979

AIAA Design, Build, Fly: Aerodynamics

As part of the Santa Clara University Senior Design Project, the AIAA Design, Build, Fly: Aerodynamics team was responsible for designing and testing the wings, tail, and control surfaces of an aircraft designed to participate in future AIAA Design, Build, Fly competitions. Named Evergreen in honor of professor John J. Montgomery, the unmanned aerial vehicle was designed and constructed in collaboration with the AIAA Design, Build, Fly: Structures and Controls senior design team. Aiming to construct a competitive aircraft for the competition, the team decided that a target weight of approximately 3.5 kg and a cruise speed of 25 m/s would be the starting points of the design. For the general wing configuration, three options were considered: monoplane (low-wing), cantilever (high-wing), and biplane. The cantilever configuration presented the desired wing characteristics for this aircraft, such as higher lift, stability, and ease of manufacturing. To minimize wing loading and take-off speeds, a wingspan of 1.50 m was selected considering that the maximum dimension length permitted by the competition is 1.57 m (62 in). After conducting a selection study between several high-lift airfoils, the NACA 4416 airfoil would be the most suitable, with an optimal chord length of 0.3028 m due to the previously decided weight and velocity. For the wing control surfaces, a flaperon configuration was chosen instead of separate flap and aileron structures. Through the use of flaperons, the weight and complexity of the wing is reduced while maintaining the necessary functionality from the surfaces. To avoid unpredictable behavior due to vortices created at the inward tips of the flaperons, a maximum size of 42 cm was determined, which proved sufficient at providing relatively low take-off speeds (\u3c 15 m/s). In collaboration with the Structures and Controls team, the fuselage size was used to determine the optimal dimensions of the tail, minimizing drag and guaranteeing aircraft stability in all flight modes. For the stability study, XFLR5TM was utilized as it is a powerful tool that can accurately determine the stability of the aircraft in all eight relevant flight modes given the dimension of the wing, tail assembly, and the position of the center of gravity. For complete two and three-dimensional CFD analysis, SOLIDWORKSTM Flow Simulation and ANSYSTM Fluent were exploited in parallel between the many design iterations of the Evergreen, ensuring that the theoretical design produced the desired characteristics under simulated flight conditions. Through Flow Simulation, the sizing of the aerodynamic shape of the aircraft — wing and tail — proved sufficient to sustain the anticipated weight of the aircraft, and a flap deflection study provided security on the effectiveness of the flaps for lower takeoff speeds. Additionally, the CFD analysis was useful to estimate the forces and torques experiences by the control surfaces, which was in turn used by the Structures and Controls team to select the appropriate servo motors for each control surface. Once the design was deemed aerodynamically capable, the Evergreen was constructed as a joint effort of both teams. Containing minute differences in comparison to the CAD model of the aircraft, the Evergreen performed successfully in eight separate flights, satisfying the take-off distance, control, range, and payload capacity required by the competition. With the data provided in this project, the AIAA Design, Build, Fly: Aerodynamics team is confident that future generations of students can improve and adapt the Evergreen to compete for Santa Clara University

Aeronautical Engineering: A special bibliography with indexes, supplement 54

This bibliography lists 316 reports, articles, and other documents introduced into the NASA scientific and technical information system in January 1975