February 22, 2022, © Leeham News: Airbus and the CFM partners, GE Aviation and SAFRAN, presented a ZEROe Sustainability demonstrator today that builds on a heavily modified A380 prototype.
On the rear roof of the A380, a pylon is integrated where a hydrogen combustion GE Passport engine is mounted, feed with hydrogen from a sealed enclosure on the main deck that contains four liquid hydrogen tanks.
The choice of the A380 for the demonstrator allows a lot of test equipment and test engineers to be housed in the test aircraft, monitoring the functioning of the propulsion system.
The demonstrator will start the flight tests end of 2026 to prepare decisions around the 2035 Hydrogen passenger aircraft configuration for 2027.
The choice of the test engine for hydrogen combustion, the GE Passport Biz-jet engine used in the Bombardier Global 7500 long-range business jet, is because it’s light enough to mount in the dorsal position at the rear of the A380. It also has the modern core engine architecture that is important for the trials with H2 combustion and study of the H20 and NOx gas residues that form from this combustion.
The placement high up and separate from the A380’s main engines is important. An essential part of the flight trials is to measure how the water vapor from the burn of H2 with the air’s Oxygen forms into water vapor contrails.
This formation and how it affects the environment is the critical issue with H2 combustion versus letting it react with Oxygen in a fuel cell, producing electricity. The fuel cell process also generates H2O, but now in a liquid form that does not create contrails.
By putting the engine high up and inside the main engines, the converted Passport engine’s exhaust stream can be measured well separated from the A380 main engine exhausts by a trailing measurement aircraft.
The placement of the different parts of the hydrogen propulsion in the first A380 test aircraft, MSN01, is shown in Figure 2.
The four tanks are placed in a special sealed container, suspended off the main floor at the rear of the cabin, Figure 3.
The MSN01 A380 is ideal as a test aircraft as these tests are all about collecting as much data as possible around the behavior of the Cryogenic (-253°C) tanks, their piping, and valving for filling, feeding, and venting of the hydrogen and how the engine runs.
The substantial MSN01 test racks will be updated with test computers and gear for these tests. The whole installation will be tested on the ground before test flights start end of 2026. Before the installation in MSN01, each component has endured endless tests in ground test environments.
The different tanks, some CFRP (Composite) and some Metallic, start their testing this year in Bremen, Nantes, and Madrid (Airbus cryogenic tank design centers).
The A380 is ideal as a ZEROe test aircraft as it has the volume, power, and facilities for the extensive testing of the tanks and engine, Figure 3.
The data from the test will be processed in real-time, both at the aircraft by test engineers and by ground crews, through data link feeds, Figure 4.
Does the announcement today mean the airliner that will come to market by 2035 will be a hydrogen combustion solution?
The flight testing of the combustion engine is to find out if the contrail problem is real and how serious it is. Is it a problem at all, and if so, can technical solutions or operational procedures alleviate the problem?
As I have written in my Corner series, a gas turbine with hydrogen combustion is a solution that is technically more straightforward than the route over a fuel cell and electric motors driving the fans or propellers. GE has eight million hours of H2 Gas Turbine combustion experience from ground gas turbine installations, so converting a gas turbine to hydrogen is a known technology.
The advantage of the fuel cell is the absence of a contrail problem and no NOx emissions (these will remain but be reduced five times with H2 gas turbines versus today’s carbon-burning engines). So the fuel cell is a true ZERO emission solution, but there are substantial installation challenges to master as fuel cell systems are heavy and produce more heat than electrical power when running.
Airbus works both these technical solutions with its partners, and the decision which way to go will be made in 2027 after these trials are done.
We can expect to hear more about Airbus Fuel Cell activities as these technologies are brought to maturity in different ground rigs.