e-thrust_en
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green aviationTRANSCRIPT
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Airbus Group InnovationsThe E-Thrust concept study is part of Airbus Group's on-going
hybrid and electrical propulsion system research, which has
seen the hybrid concept study for a full-scale helicopter, the
successful development of a Cri-Cri ultralight modified as
the worlds first four-engine all-electric aerobatic aircraft, the
demonstration flights of a hybrid electric motor glider for
which Airbus Group Innovations developed the battery system,
the flight testing of a short-range mini-unmanned aerial vehicle
with an advanced fuel cell and the integration of a piston diesel
engine into the TANAN UAV as well as the concept study of a
hybrid-electric propulsion system for this rotorcraft.
Airbus Group Innovations is the corporate network of research
centres of Airbus Group. A highly skilled workforce of more
than 800 is operating the laboratories that guarantee Airbus
Group technical innovation potential with a focus on the long-
term. The structure of the network and the teams within Airbus
Group Innovations are organised in global and transnational
Technical Capabilities Centres:
Composites technologies
Metallic technologies and surface engineering
Vehicle integration industrial and support processes
Electronics, communications and intelligent systems
Systems engineering, information technology and applied
mathematics
Energy and propulsion
Design and Projects
Rolls-Royce Research and TechnologyIn 2012, Rolls-Royce invested 919 million on research and
development, two thirds of which had the objective of further
improving the environmental performance of its products, in
particular reducing emissions. To ensure that there is a pipeline
of technology, and a balanced portfolio of research with
target applications in both the near and long term Rolls-Royce
has adopted 5, 10 and 20 year visions for the technology it
develops. Vision 5 constitutes the low risk technology ready
for application within 5 years. Vision 10 describes the next
generation of technology or capability. Vision 20 describes
emerging or as yet unproven technologies aimed at Rolls-
Royces future generations of products, much of which will
be applied right across the product range in all sectors. A
number of Vision 20 studies are currently exploring future
generations of aircraft architectures that may provide significant
improvements, particularly in areas of fuel burn, noise and
emissions, this includes electric technologies and distributed
propulsion. Rolls-Royce has also created an extensive range
of partnerships and collaborations around the globe through
our network of 28 University Technology Centres (UTCs). UTCs
are a source of both technology and highly skilled people. The
Group has also applied a similar model in creating a network
of Advanced Manufacturing Research Centres to develop
manufacturing capability. There are currently 6 operational
facilities, the latest having opened in Crosspointe, Virginia in
late 2012. These foster collaboration between companies at
all stages of the supply chain, from the Original Equipment
Manufacturers (OEMs) to material suppliers, measurement
systems providers and tool manufacturers.
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Rolls-Royce plc65 Buckingham GateLondon SW1E 6AT United Kingdom
Airbus GroupAirbus Group Innovations UKFilton, Bristol BS99 7ARUnited Kingdom
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E-ThRusTElectrical distributed propulsion system concept for lower fuel consumption, fewer emissions and less noise
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The Vision and PersPecTiVe of an elecTrical disTribuTed ProPulsion sysTem
Airbus Group Innovations and Rolls-Royce, with
Cranfield university as a partner, are jointly engaged in
the Distributed Electrical Aerospace Propulsion (DEAP)
project, which is co-funded by the Technology strategy
Board (TsB) in the united Kingdom. The DEAP project
researches key innovative technologies that will enable
improved fuel economy and reduced exhaust gas and
noise emissions for future aircraft designs by incorporating
a Distributed Propulsion (DP) system architecture.
Innovative propulsion system concepts for future air
vehicle applications are being developed by Airbus Group
Innovations, the corporate research and technology network
of Airbus Group, and by Rolls-Royce, a global provider of
integrated power systems and services to the civil aerospace,
defence aerospace, marine and energy markets. Results of
their research activities support Airbus Group divisions in
leveraging innovation solutions to further improve the efficiency
and environmental performance of commercial aviation.
These efforts are part of the aerospace industrys research
to support its ambitious environmental protection goals as
spelled out in the European Commissions roadmap report
called Flightpath 2050 Europes Vision for Aviation.
This report sets the targets of reducing aircraft CO2 emissions
by 75%, along with reductions of nitrous oxides (NOx) by
90% and noise levels by 65%, compared to standards in the
year 2000.
eConcept a future vision Airbus and Airbus Group Innovations, along with other
industry players like Rolls-Royce and Siemens, are
exploring different avenues to find innovative solutions
to the challenges the aviation industry is facing in
the future. They are investigating one such avenue
for a 2050 timeframe a hybrid/electrical distributed
propulsion system as an intermediate but necessary
step towards fully electric propulsion for airliners. Airbus,
in its role as integrator, has taken its concept plane a
vision of aviation in the future and used it to create
the eConcept, a visualisation of the architecture and
configuration of what an aircraft of the future could look
like powered by hybrid/electrical distributed propulsion.
The DEAP project (represented by the initial E-Thrust
configuration) is bringing the technologies, while Airbus
is giving its expertise as an integrator providing regular
inputs and feedback on the technology developments.
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The configuration with three fans on either side of the fuselage represents an initial
starting point for future optimisations, with the optimum number of fans to be
determined in trade-off studies in the DEAP project.
03E-Thrust
Achieving these goals requires significant performance
improvements in engine technology, systems architecture
and engine/airframe integration to enable radically more
efficient propulsion systems. Finding viable solutions requires
the pioneering of unconventional aircraft and propulsion system
concepts. In this perspective, propulsion technologies are
continuously being improved through developments in the fields
of energy storage and conversion, in electrical motors, novel
combustion cycles, ultra-high bypass ratio configurations, along
with hybrid electric/thermodynamic and fully electric systems.
The disTribuTed elecTrical aerosPace ProPulsion (deaP) ProjecTWith its experience in gas turbine and gas power unit design,
as well as in electric propulsion systems, Rolls-Royce has
for some time been a research partner of Airbus Group in
the fields of energy management and simulation, electrical
machines and superconductivity, and propulsion system
integration. Since 2012, Airbus Group Innovations and Rolls-
Royce, with Cranfield University as a partner (and some testing
subcontracted to Cambridge University), are jointly engaged
in the DEAP project, which researches key innovative
technologies for distributed propulsion systems. Compared
to engines on existing commercial airliners, such a system
will require a much higher level of integration with the airframe
design than that of todays aircraft.
The DEAP project aims to deliver a preferred electrical DP
system for future aircraft that may provide a breakthrough and
a significant contribution to mitigating the environmental impact
of the projected increase of air traffic. Rolls-Royce will develop
an optimum electrical system propulsion plant, taking into
consideration speed range, max speed, number of fan motors,
efficiency, etc.; while Airbus Group Innovations (the DEAP
project leader) will design the electrical system and work with
Airbus to optimise the integration of the propulsion system in
the airframe.
The benefiTs of a disTribuTed ProPulsion sysTem archiTecTureFor the E-Thrust concept, distributed propulsion means
that several electrically-powered fans are distributed in
clusters along the wing span, with one advanced gas power
unit providing the electrical power for six fans and for the
re-charging of the energy storage. The E-Thrust concept
can be described as a serial hybrid propulsion system.
This configuration represents an initial starting point for
future optimisations, with the optimum number of fans to be
determined in trade-off studies in the DEAP project. Initial study
results by Airbus indicate that a single large gas power unit has
advantages over two or more smaller gas power units. This will
give a noise reduction and allows the filtering of particles in the
long exhaust duct at the back of the engine.
The hybrid DP architecture offers the possibility of improving
overall efficiency by allowing the separate optimisation of the
thermal efficiency of the gas power unit (producing electrical
power) and the propulsive efficiency of the fans (producing
thrust). The hybrid concept makes it possible to down-size
the gas power unit and to optimize it for cruise. The additional
power required for take-off will be provided by the electric
energy storage.
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A fundamental aspect of optimising the propulsive efficiency is
to increase the bypass ratio beyond values of 12 achieved
by todays most efficient podded turbofans. For the DP
concept, the bypass ratio must be termed effective bypass
ratio, because the fan airstreams and the core airstream
are physically separated. With DP, values of over 20 in
effective bypass ratios appear achievable, which would lead
to significant reductions in fuel consumption and emissions.
Having a number of small, low-power fans integrated in the
airframe instead of a few large wing-mounted turbofans is also
expected to reduce the total propulsion system noise.
In addition to improving the propulsive efficiency, DP offers a
greater flexibility for the overall aircraft design that could
result in reduced structural weight and aerodynamic drag, for
example, by relaxed engine-out design constraints leading to
a smaller vertical tail plane, by being able to better distribute
the weight of the propulsion system components and by re-
energising the momentum losses in the boundary layers that
grow over the wing and fuselage causing a wake (Boundary
Layer Ingestion, BLI).
An additional efficiency gain appears possible if this boundary
layer is ingested and accelerated by the fans, because
it can reduce the aircrafts wake and hence its drag.
However, the implementation of a boundary-layer ingesting
system means that the airflow into the fans is not uniform;
to realize the potential benefits, the turbo-machinery and
in particular, the fan blades must be able to withstand the
associated unsteady conditions due to the distorted intake
flow. The design of the Rolls-Royce fans is currently being
developed in collaboration with its University Technology
Centre in Cambridge, and is specifically optimised to deliver
the best performance in the distorted flow conditions
that are experienced in a BLI configuration; its design is
supported by computer analysis as well as reduced-scale
testing and measurements.
For the power levels in the megaWatt range that are
required in an electrical distributed propulsion network,
a new high-voltage superconducting electrical
system has to be designed and validated to
stringent requirements in terms of efficiency. Such
a system must aim to reduce heat being generated due
to alternating current losses in the superconducting
wires, which are enclosed in cables and surrounded
by cryogenic fluid, so that they are kept at a constant
cryogenic temperature for their best performance.
Minimizing such losses is crucial, as extracting 1 Watt
of heat using a cryocooler at 20K (-252 C) to ambient
temperature requires 60 Watts of electrical power.
flighT Profile energy managemenT
Take-off and & ClimbPower comes from the gas power unit and from the energy storage system to provide the peak power needed during the take-off and climb phase. The energy storage system will be sized to ensure a safe take-off and landing should the gas power unit fail during this phase.
CruiseIn the cruise phase, the gas power unit will provide the cruise power and the power to recharge the energy storage system. In the unlikely event of a failure of the gas power unit, power from the energy storage is available to continue the flight to a safe landing.
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05E-Thrust
enabling Technologies
superconductivity: A key enabling technology for the DP (hybrid/distributed
propulsion) concept is using superconductivity in the cables,
generators and motors for the transfer of electrical power
from the gas power unit and energy storage to the fans.
Superconductivity is a quantum mechanical phenomenon
of exactly zero electrical resistance, which occurs in certain
materials when they are cooled below a critical temperature.
It allows the electrical system components to be much
smaller, lighter and more efficient compared to conventional
copper- and aluminium-based technology. The necessary
cooling can be achieved either by supplying cryogenic
fluids (for example: liquid hydrogen, liquid helium or liquid
nitrogen) from a reservoir, or by producing the necessary cold
temperatures using a cryocooler a technology used today
in space applications (for example a turbo-Brayton cryocooler
made by Air Liquide for ESA) or in MRI systems. A side-
by-side comparison of copper and superconducting wires
demonstrates the vast size and weight differences possible
with this technology. Magnesium DiBoride (MgB2)
superconducting wires are made by Columbus Superconductors
and used today, for example, in MRI scanners).
Energy storage: Scientists expect new generations of energy storage systems
to exceed energy densities of 1,000 Wh/kg (Watt hours per
kilogram) within the next two decades, more than doubling
todays best performance. Lithium-air batteries are the most
promising solution for the E-Thrust concepts energy storage
requirements. They have a higher energy density than lithium-
ion batteries because of the lighter cathode, along with
the fact that oxygen is freely available in the environment.
Lithium-air batteries are currently under development and are
not yet commercially available. The E-Thrust concept is based
on the assumption that the required level of energy density
can be achieved within the 25-year timeframe envisioned for
the DP concept to mature.
Descent/GlidingIn the initial descent phase, no power is provided to the fans, and the gas power unit will be switched off. The aircraft will be a glider and the energy storage system will provide the power for the aircrafts on-board systems.
Descent/WindmillingDuring the second phase of the descent, the fans will be windmilling and produce electrical power to top-up the charge in the energy storage system.
LandingFor the landing phase, the gas power unit is re-started and provides power at a low level for the propulsion system. This is a safety feature to cover a hypothetical loss of power from the energy storage system during this phase.
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E-Thrust06
The distributed fan propulsion system provides thrust for the
aircraft, replacing conventional turbofan engines. The large
fan diameter and weight of conventional turbofans limits
where they can be located on an airframe usually under the
wing. Their location does not enable advanced aerodynamic
efficiency techniques to be used, whereas having a number
of electrically-driven fans that are integrated into the
airframe allows for a more aerodynamic overall design.
During descent, the energy-efficient distributed fans are
turned by the airstream and, like wind turbines, they generate
electrical energy which can be stored.
To achieve an integrated distributed fan propulsion system
design that matches the overall airframe requirements, three
key innovative components are required:
A wake re-energising fan
Structural stator vanes that pass electrical power and cryogenic coolant
A hub-mounted totally superconducting electrical machine
Wake re-energising fan
As the aircraft flies through the air, it leaves a wake behind
it resulting in drag. The embedded wake re-energising fan is
designed to capture the wake energy by re-accelerating the
complex wake. By re-energising the wake, the overall aircraft
drag is reduced. The concept uses advanced lightweight
composite fan blades that are designed to maximise overall
propulsive efficiency whilst minimising the weight of the
propulsion system.
disTribuTed fan ProPulsion sysTem
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07E-Thrust
sTrucTural sTaTor Vanes By having an embedded propulsion system, the conventional
turbofan mounting structure is no longer required thereby
saving weight and drag. The stator section is carefully
designed to provide a row of aerodynamic and structural
stator vanes behind the fan recovering thrust from the
swirling air. The length of the distributed fan, propulsion
system has been designed to be much shorter than that of a
conventional turbofan so that the centre of gravity is located
about the structural stator vanes. In addition, some of the
stator vanes are designed to accommodate the internal
routing of the superconducting cables to the hub-mounted
superconducting electrical machine.
hub-mounTed ToTally suPerconducTing machine
The innovative hub-mounted totally superconducting electrical
machine drives the wake re-energising fan. Rolls-Royce and
Airbus Group Innovations, with Magnifye Ltd and Cambridge
University as partners, are engaged in a Programmable
Alternating current superconducting Machine (PsAM)
project.The PSAM project researches an innovative
programmable superconducting rotor and innovative AC
superconducting stator.This work is supported in part by the
UK Technology Strategy Board.
The superconducting stator generates a powerful electro-
magnetic field that rotates around the circumference at a
speed directly related to the frequency of the electrical supply.
The superconducting machine replaces the copper and iron
stator structure of a conventional machine. It is a much more
powerful, lighter and low-loss design incorporating round-
wire high temperature superconducting coils embedded within
a lightweight epoxy structure.
Electromagnetic torque is created by effectively aligning
the rotors magnetic field with the field generated electro-
magnetically within the stator.
The superconducting rotor magnetic field is generated through
the use of bulk superconducting magnets in a puck form. A
superconducting magnetic puck of this size can, when
fully magnetised, generate extremely high magnetic fields
with laboratory testing demonstrating 17 Tesla a magnetic
field capable of easily levitating a family car. The magnetic
pucks are innovatively magnetised in-situ by the stator to
create a permanent magnet field that can be programmed to
deliver different field strengths thereby improving controllability.
The superconducting machine design is
bi-directional in that it is equally efficient at driving the wake
re-energising fan to provide aircraft thrust or being driven by
the fan rotating in the airstream to generate electrical power,
which can then be stored within the airframe.
Exploded view showing the hub-mounted totally superconducting machine