Turboelectric Distributed Propulsion in a Hybrid Wing Body Aircraft
12 Sep 2011-
TL;DR: The N3-X, a 300 passenger hybrid wing body (HWB) aircraft with turboelectric distributed propulsion (TeDP), has been analyzed to see if it can meet the 70% fuel burn reduction goal of the NASA Subsonic Fixed Wing project for N+3 generation aircraft as discussed by the authors.
Abstract: The performance of the N3-X, a 300 passenger hybrid wing body (HWB) aircraft with turboelectric distributed propulsion (TeDP), has been analyzed to see if it can meet the 70% fuel burn reduction goal of the NASA Subsonic Fixed Wing project for N+3 generation aircraft. The TeDP system utilizes superconducting electric generators, motors and transmission lines to allow the power producing and thrust producing portions of the system to be widely separated. It also allows a small number of large turboshaft engines to drive any number of propulsors. On the N3-X these new degrees of freedom were used to (1) place two large turboshaft engines driving generators in freestream conditions to maximize thermal efficiency and (2) to embed a broad continuous array of 15 motor driven propulsors on the upper surface of the aircraft near the trailing edge. That location maximizes the amount of the boundary layer ingested and thus maximizes propulsive efficiency. The Boeing B777-200LR flying 7500 nm (13890 km) with a cruise speed of Mach 0.84 and an 118100 lb payload was selected as the reference aircraft and mission for this study. In order to distinguish between improvements due to technology and aircraft configuration changes from those due to the propulsion configuration changes, an intermediate configuration was included in this study. In this configuration a pylon mounted, ultra high bypass (UHB) geared turbofan engine with identical propulsion technology was integrated into the same hybrid wing body airframe. That aircraft achieved a 52% reduction in mission fuel burn relative to the reference aircraft. The N3-X was able to achieve a reduction of 70% and 72% (depending on the cooling system) relative to the reference aircraft. The additional 18% - 20% reduction in the mission fuel burn can therefore be attributed to the additional degrees of freedom in the propulsion system configuration afforded by the TeDP system that eliminates nacelle and pylon drag, maximizes boundary layer ingestion (BLI) to reduce inlet drag on the propulsion system, and reduces the wake drag of the vehicle.
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04 May 2015
TL;DR: In this paper, the authors provide an in-depth look into how the systems have or will be changed in the future of electric aircraft, including electric taxi and gas-electric propulsion for aircraft.
Abstract: Similar to the efforts to move toward electric vehicles, much research has focused on the idea of a more electric aircraft (MEA). The motivations for this research are similar to that for vehicles and include goals to reduce emissions and decrease fuel consumption. In traditional aircraft, multiple systems may use one type or a combination of types of energy, including electrical, hydraulic, mechanical, and pneumatic energy. However, all energy types have different drawbacks, including the sacrifice of total engine efficiency in the process of harvesting a particular energy, as with hydraulic and pneumatic systems. The goal for future aircraft is to replace most of the major systems currently utilizing nonelectric power, such as environmental controls and engine start, with new electrical systems to improve a variety of aircraft characteristics, such as efficiency, emissions, reliability, and maintenance costs. This paper provides an in-depth look into how the systems have—or will be—changed. Future aircraft capabilities such as electric taxi and gas–electric propulsion for aircraft are also included for discussion. Most recent commercial transport aircrafts are described as the current state-of-the-art electric aircraft system. Future goals, including those of NASA, are presented for future advances in MEA.
818 citations
Additional excerpts
...4 MVA each) to produce electricity [55]....
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TL;DR: In this article, the authors present a survey of electric aircraft propulsion, including all-electric, hybrid electric, and turboelectric architectures, and present an overview of electrical components and electric propulsion architectures.
317 citations
Cites background or methods from "Turboelectric Distributed Propulsio..."
...Aerodynamics FLOPS/drag polar; BLI benefit based on flatplate momentum thickness Design using vortex lattice/boundary layer codes; some CFD for analysis [51, 85, 158] CFD results from similar configuration, with increment for BLI [56] Drag polar L/D correction methods from Torenbeek [16]...
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...The N3-X relies on very advanced technology and claims -70% fuel burn reduction versus the 777-200 benchmark; the portion attributable to electric propulsion is closer to -20%, with much of the remainder a result of airframe and other technologies [56]....
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...Conceptual trade studies so far have favored superconducting architectures for very high-power applications (such as the 300-passenger NASA N3-X) and conventional conductors for megawattclass requirements and below (such as the 150-passenger NASA STARC-ABL) [56, 27]....
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...Subsequently, the concept has been the focus of more detailed analysis and design revision by NASA [56, 29, 58, 59], with refined weights [90] and noise and emissions [91]....
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...[56, 57, 58, 59, 60, 61, 27] Boeing SUGAR Volt 2035 PHE 154 68040 1....
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University of Illinois at Urbana–Champaign1, Princeton University2, Siemens3, Westinghouse Electric4, Victoria University of Wellington5, Air Force Research Laboratory6, Tokyo University of Marine Science and Technology7, Rolls-Royce Motor Cars8, General Electric9, Texas Center for Superconductivity10
TL;DR: In this article, the authors present a technology roadmap for superconducting machines with a goal to reach a Technology Readiness Level of 6+ with systems demonstrated in a relevant environment.
Abstract: Superconducting technology applications in electric machines have long been pursued due to their significant advantages of higher efficiency and power density over conventional technology. However, in spite of many successful technology demonstrations, commercial adoption has been slow, presumably because the threshold for value versus cost and technology risk has not yet been crossed. One likely path for disruptive superconducting technology in commercial products could be in applications where its advantages become key enablers for systems which are not practical with conventional technology. To help systems engineers assess the viability of such future solutions, we present a technology roadmap for superconducting machines. The timeline considered was ten years to attain a Technology Readiness Level of 6+, with systems demonstrated in a relevant environment. Future projections, by definition, are based on the judgment of specialists, and can be subjective. Attempts have been made to obtain input from a broad set of organizations for an inclusive opinion. This document was generated Superconductor Science and Technology Supercond. Sci. Technol. 30 (2017) 123002 (41pp) https://doi.org/10.1088/1361-6668/aa833e Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. 0953-2048/17/123002+41$33.00 © 2017 IOP Publishing Ltd Printed in the UK 1 through a series of teleconferences and in-person meetings, including meetings at the 2015 IEEE PES General meeting in Denver, CO, the 2015 ECCE in Montreal, Canada, and a final workshop in April 2016 at the University of Illinois, Urbana-Champaign that brought together a broad group of technical experts spanning the industry, government and academia.
307 citations
10 Jul 2017
TL;DR: In this paper, the authors present a summary of the aircraft system studies, technology development, and facility development for a single-aisle aircraft with a tube and wing, partially turbo electric configuration (STARC-ABL).
Abstract: 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.
199 citations
TL;DR: Athanassopoulou et al. as discussed by the authors have expressed their thanks to the participants at the workshop and acknowledged financial support for the road-mapping exercise on which this work is based from the University of Cambridge EPSRC Impact Acceleration Account (EP/K503757/1).
Abstract: The authors wish to express their sincere thanks to Dr Nicky Athanassopoulou, Ms Andi Jones and Dr Rob Phaal of Institute for Manufacturing Education and Consultancy Service Ltd for their excellent work in organising and facilitating the Road-Mapping exercise upon which this current work is based. The authors would also like to express their appreciation of the contribution made by the other participants at the workshop: Hari Babu Nadendla (Brunel University), Pavol Diko (Slovak Academy of Sciences), Tomas Hlasek (CAN Superconductors), John Hull (The Boeing Company), Lars Kuhn (evico), Mathias Noe (KIT), Jan Plechacek (CAN Superconductors), Yunhua Shi (University of Cambridge) and Frank Werfel (ATZ). The authors acknowledge financial support for the Road-Mapping exercise on which this work is based from the University of Cambridge EPSRC Impact Acceleration Account (EP/K503757/1).
140 citations
References
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TL;DR: The Boeing Blended-Wing Body (BWB) airplane concept represents a potential breakthrough in subsonic transport efficiency as discussed by the authors, and work began on this concept via a study to demonstrate feasibility and begin development of this new class of airplane.
Abstract: The Boeing Blended-Wing-Body (BWB) airplane concept represents a potential breakthrough in subsonic transport efficiency. Work began on this concept via a study to demonstrate feasibility and begin development of this new class of airplane. In this initial study, 800-passenger BWB and conventional configuration airplanes were sized and compared for a 7000-n mile design range. Both airplanes were based on engine and structural (composite) technology for a 2010 entry into service
641 citations
01 Jan 2006
491 citations
04 Jan 2011
TL;DR: In this article, the benefits of using a lower fan pressure ratio and of boundary layer ingestion, offset by the electric system weight and inefficiency penalties from the added components, gives a net fuel burn reduction of about 9%, before iterating and resizing.
Abstract: The benefits that turboelectric propulsion may offer transport aircraft due to the flexibility of electrical distribution of power have been discussed by various authors and are briefly summarized. Estimates of the weights and efficiencies of the electric components, based on approximate sizing models for fully superconducting motors and generators and on aggressive estimates for cryocoolers and inverters, were presented at ASM2009 in a baseline turboelectric system study. An SBIR study has since predicted that the apparently aggressive cryocooler weight and performance estimates (5 lb/input-hp at 30% of Carnot efficiency) can be met. Another SBIR study has predicted that a cryogenically cooled inverter can exceed the 10 hp/lb specific power (including cooler) and the 98.8% efficiency (including cooler) that were assumed in the baseline study. The inverter with its cooler constituted half of the baseline electrical system weight. On the other hand, new estimates for the superconducting motors and generators, based upon inclusion of additional components in the sizing models and more complete ac loss models, predict somewhat heavier and slightly less efficient motors and generators. The lighter, more efficient inverter roughly offsets the adverse motor and generator changes for machines wound with a hypothetical future high temperature superconductor with low ac losses. For such a material, the weight of the entire electric system changes very little, and the already high efficiency improves slightly, from the ASM2009 estimates. For machines wound with the intermediate temperature superconductor MgB2, the system weight increases about 25%, because MgB2 must operate much colder. The modeling and performance estimates of each component are discussed and compared to the baseline estimates and to the current state-ofthe-art. The dependence of motor and generator weights and efficiencies upon some important design parameters are presented in an appendix. These results quantify the benefits of technology development of lighter cryocoolers and of superconductors with lower ac loss. A zero-th order estimate of the benefits of lower fan pressure ratio and of boundary layer ingestion, offset by the electric system weight and inefficiency penalties from the added components, gives a net fuel burn reduction of about 9%, before iterating and resizing.
138 citations
01 Sep 2012
TL;DR: The best configuration for reduction of jet noise used state-of-the-art technology chevrons with a pylon above the engine in the crown position, which resulted in jet source noise reduction, favorable azimuthal directivity, and noise source relocation upstream.
Abstract: A system noise assessment of a hybrid wing body configuration was performed using NASA's best available aircraft models, engine model, and system noise assessment method. A propulsion airframe aeroacoustic effects experimental database for key noise sources and interaction effects was used to provide data directly in the noise assessment where prediction methods are inadequate. NASA engine and aircraft system models were created to define the hybrid wing body aircraft concept as a twin engine aircraft with a 7500 nautical mile mission. The engines were modeled as existing technology, in production, bypass ratio seven turbofans. The baseline hybrid wing body aircraft was assessed at 26.4 dB cumulative below the FAA Stage 4 certification level. To determine the potential for noise reduction with relatively near term technologies, seven other configurations were assessed beginning with moving the engines two fan nozzle diameters upstream of the trailing edge and then adding technologies for reduction of the ...
103 citations
04 Jan 2011
TL;DR: In this article, the effect of the boundary layer on the design of a turboelectric distributed propulsion (TeDP) system with a range of design pressure ratios was examined, and the impact of ingesting the boundary layers on off-design performance was examined.
Abstract: A Turboelectric Distributed Propulsion (TeDP) system differs from other propulsion systems by the use of electrical power to transmit power from the turbine to the fan. Electrical power can be efficiently transmitted over longer distances and with complex topologies. Also the use of power inverters allows the generator and motors speeds to be independent of one another. This decoupling allows the aircraft designer to place the core engines and the fans in locations most advantageous for each. The result can be very different installation environments for the different devices. Thus the installation effects on this system can be quite different than conventional turbofans where the fan and core both see the same installed environments. This paper examines a propulsion system consisting of two superconducting generators, each driven by a turboshaft engine located so that their inlets ingest freestream air, superconducting electrical transmission lines, and an array of superconducting motor driven fan positioned across the upper/rear fuselage area of a hybrid wing body aircraft in a continuous nacelle that ingests all of the upper fuselage boundary layer. The effect of ingesting the boundary layer on the design of the system with a range of design pressure ratios is examined. Also the impact of ingesting the boundary layer on off-design performance is examined. The results show that when examining different design fan pressure ratios it is important to recalculate of the boundary layer mass-average Pt and MN up the height for each inlet height during convergence of the design point for each fan design pressure ratio examined. Correct estimation of off-design performance is dependent on the height of the column of air measured from the aircraft surface immediately prior to any external diffusion that will flow through the fan propulsors. The mass-averaged Pt and MN calculated for this column of air determine the Pt and MN seen by the propulsor inlet. Since the height of this column will change as the amount of air passing through the fans change as the propulsion system is throttled, and since the mass-average Pt and MN varies by height, this capture height must be recalculated as the airflow through the propulsor is varied as the off-design performance point is converged.
97 citations