With its European base and global presence, it would only make sense that Airbus would take a leading role in the EU’s CleanSky 2 (CS2), a joint technology initiative (JTI) that is the follow-up to the CleanSky aerospace research program.
Both of the programs were designed to address now the tripling of air traffic that is predicted to occur by 2050, kindly not waiting until 2050 instead. Currently air traffic contributes about 3% to global greenhouse emissions (heating and electricity is said to produce about 32%), which may not seem like much except that, first, not too long ago it was 2%, and, second, those emissions happen at altitude, and much less is known about the effects of chemical interactions between emissions and the higher, thinner air than how emissions interact with the denser air closer to Earth.
To mitigate the environmental impact of the future of flight, the JTI public-private partnership brings together a variety of entities, including companies, universities, public laboratories, and the European Commission "to develop and demonstrate break-through technologies" for the civil aircraft market to cut aircraft emissions and noise.
Specifically, targets are to increase aircraft fuel efficiency enough to reduce CO2 emissions by 20-30% and reduce aircraft NOx and noise emissions by 20-30% compared to newly designed aircraft entering into service in 2014—or essentially halve 2005 CO2 emissions levels by 2050. The JTI currently has close to 600 participants, with official estimates being that about 40% of those are small-to-medium enterprises.
Within the frame of the CS2 collaborative research platform, Airbus will focus on the future of large passenger aircraft, for which it has three main platforms.
“Advanced Engine and Aircraft Configurations” will enable engineers to explore and validate the integration of the most fuel-efficient propulsion concept for next-generation short- and medium-range aircraft. Large scale demonstration will include flight testing with a full size counter-rotating-open-rotor engine mounted to an Airbus A340 test aircraft, and a full-size aft-fuselage structural propulsion integration demonstrator.
“Innovative Physical Integration Cabin–System–Structure” will target advanced fuselage structural and aircraft systems concepts for possible next-generation cabin architectures. To be able to account for the variety of the test program requirements, three individual major demonstrators will be deployed. Several smaller test rigs and component demonstrators will also be part of the program in the preparatory phase.
“Next Generation Electrical Aircraft System, Cockpit, and Avionics” will culminate in a cockpit ground demonstrator that will demonstrate features to significantly reduce pilot workload, enhance navigation with mission-management systems, and improve communications with the ground. In addition, flight tests will validate some of the features of the new cockpit concept. The cockpit demonstrator will also explore ways to monitor aircraft status.
In another initiative driven by the search for alternative solutions to fossil-fuel based propulsion and energy sources, Airbus recently entered into an agreement with South Africa’s National Aerospace Centre to jointly fund research by Hydrogen South Africa (HySA) into the application of fuel cells on airliners.
With this in mind, Airbus has identified hydrogen fuel cells as a future, emissions-free substitute to small auxiliary power units (APUs) used for generating onboard electrical power and heat while the aircraft is on the ground. Almost every airliner designed and built since the introduction of jet travel in the 1950s has been equipped with an APU, which is located in the tapered tail cone section of the rear fuselage. Replacing the fossil-fuel powered APUs with hydrogen fuel cells would help achieve, if not exceed, the ultimate goals of CS2.
Some of the focus of the three-year initiative will be on gaining an understanding of how hydrogen fuel cells could perform over an aircraft’s service life while subjected to the harsh and rapidly changing climatic and environmental regimes that commercial jetliners operate in.
Besides emissions-free and low-noise aircraft operation, fuel cells would reduce the overall weight of aircraft, leading to lower fuel burn and operating costs together with further reduced carbon emissions during flight. Hydrogen fuel cells could have the added advantage of enabling aircraft to generate their own water supplies. They also offer a safety benefit through their ability to generate inerting gas used to reduce flammability levels in aircraft fuel tanks and for suppressing any cargo hold fires, says Airbus.
Fuel cells, because they do not have any moving parts, are less maintenance intensive than conventional APUs. They could also potentially replace heavy batteries and conventional fuel tank inerting systems. In doing so they would reduce the weight and fuel consumption of fuel-cell-equipped aircraft.
Airbus has already performed test flights involving fuel cells to power individual emergency power systems, though there is much still to learn to permit the complete replacement of the electrical power systems with a multi-functional fuel cell (MFFC). The project with HySA is hoped to help close that gap. It is being undertaken at postgraduate level and will identify the factors influencing fuel cell performance, ageing and monitoring and will then consider how these could be adopted for use in aircraft.
At the 2012 Berlin Air Show, Airbus had on its display a MFFC system concept that it had developed in partnership with the DLR German Aerospace Centre and Parker Aerospace that would replace gas turbine-based APUs.
In the MFFC system concept, the fuel cell would act as an independent power source capable of supplying electrical power throughout the aircraft, including the cabin. Positioning of the fuel cell is planned in the cargo hold, while the system’s liquid hydrogen tank, heat exchangers, and fans are to be located in the tail cone section.
Providing approximately 100 kW of power, the MFFC system offers the potential for significantly higher output than a fuel cell emergency power system flight tested on an A320 during a 2008 campaign involving Airbus, the DLR, and Michelin. This earlier fuel cell was installed on a cargo pallet and produced about 25 kW.
Flight testing of an MFFC on an A320 is expected to occur within the next couple of years.
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