By Bjorn Fehrm
September 21, 2020, © Leeham News: Airbus held a webcast today, announcing three zero-emission airliner concepts called the ZEROe line (Figure 1). The two conventional designs, the turbofan airliner and the turboprop use hydrogen as the fuel for their gas turbine engines. The blended wing-body is a more futuristic concept where propulsion technology was not specified.
The idea is to use these concepts as work paths to explore the technologies around them and their aerodynamic characteristics. The concepts “are not products” underlined Airbus EVP development Jean-Brice Dumont. “It’s rather examples of designs around which the technologies can be explored and results compared. After concepts follow demonstrators and then products.”
Airbus CEO Guillame Faury about the announcement:
“This is a historic moment for the commercial aviation sector as a whole and we intend to play a leading role in the most important transition this industry has ever seen. The concepts we unveil today offer the world a glimpse of our ambition to drive a bold vision for the future of zero-emission flight. I strongly believe that the use of hydrogen – both in synthetic fuels and as a primary power source for commercial aircraft – has the potential to significantly reduce aviation’s climate impact.”
We could talk to Airbus CTO, Grazia Vittadini in connection with the announcement. She explained how Airbus has drawn knowledge from all it’s concept projects like E-Fan, Vahanna, City-Airbus, and E-Fan-X. This has lead to an understanding that hydrogen-based propulsion is the solution for today and that electric technologies will come into play as these mature. Vittadini further:
“Right now we can integrate electrical starter-generators into the gas turbines, where the generator run as a motor helps the engine with power shifts. The core can then be harder optimized around cruise conditions. The energy source for the motor is a hydrogen fuel cell. There have been several projects around replacing the APU with hydrogen-based fuel cells, but these are not practical when the rest of the aircraft is carbon fuel-based. Now a hydrogen-fueled aircraft opens this avenue as well.”
The three concept aircraft released today represent different technologies and challenges. They are all three codenamed ZEROe which stands for a climate-neutral commercial aircraft.
The two concepts closest to what can later emerge as demonstrators and eventually products are the 120-200 seat Turbofan aircraft (Figure 2) and the 100 seat Turboprop (Figure 3).
The architecture of the aircraft differs from today’s airliners as the hydrogen fuel tank is not in the wings, it’s placed behind the cabin in the rear of the aircraft, behind the rear pressure bulkhead. For those who want to understand why read my Corner series about the Challenges of Hydrogen.
The Turboprop has the same architecture except here the hydrogen-burning gas turbine engines are a turboprop design. The Hydrogen Corner series also goes through the propulsion alternatives available and why converting today’s Turbofans and Turboprops makes sense.
The most futuristic and perhaps most challenging concept in the Blended Wing-Body (BWB) variant, Figure 4.
Here the BWB shape enables better integration of the cryogenic (cryogenic = extreme low temperature, -253°C) tanks that liquid hydrogen storage requires.
If the fuselage allows the tanks a better fit, the central cabin now presents challenges to give the passengers a decent cabin ambiance. Here the passengers have the light come in from above in an atrium-style cabin.
Airbus Faury emphasizes that this is as much about building an eco-system as making new aircraft:
“These concepts will help us explore and mature the design and layout of the world’s first climate-neutral, zero-emission commercial aircraft, which we aim to put into service by 2035.
The transition to hydrogen, as the primary power source for these concept planes, will require decisive action from the entire aviation ecosystem. Together with the support from government and industrial partners we can rise up to this challenge to scale-up renewable energy and hydrogen for the sustainable future of the aviation industry.”
Airbus will use the slump in normal airplane development caused by the pandemic to advance its positions for tomorrow’s technologies. Its bet is on hydrogen as a future energy store and distribution system. It has 200 times the energy-specific weight of batteries and three times that of Jet fuel, making a change to a non-carbon-fueled low emission air transport realistic.
Airbus will kick off several hydrogen demonstrator programs over the coming months. These will test hydrogen fuel cell and hydrogen combustion technologies. A full-scale aircraft demonstrator is expected late in the decade.