Airbus, in partnership with CFM International (a joint company of GE and Safran Aircraft Engines), is developing an A380 flying test rig called the ZEROe Demonstrator to examine how hydrogen combustion can be used to power turbofan jet engines.
From an environmental point of view, hydrogen is an attractive alternative to conventional jet aviation fuel for an aerospace industry that is committed to becoming carbon-free by 2050. In its gaseous form it is almost easy to Handle like natural gas, it burns easily, is relatively clean and leaves only water and 90% less nitrogen oxide emissions than kerosene.
At a cursory glance, it looks like an ideal replacement, but a closer look shows that there is still a long way to go before we see jetliners burning hydrogen. in action. For example, it would be easy to say that it eliminates fossil fuels, but most of the hydrogen produced on an industrial scale comes from oil through the vapor-methane process. So the use of hydrogen as a green fuel would mean a huge shift in production towards alternatives such as biomass or water electrolysis using non-fossil energy sources, and all the infrastructural problems that such a change would bring.
If that’s not enough, hydrogen has other problems. Although it has 2.5 times the specific energy of kerosene, it has a much lower energy density and takes up four times the volume. This means that a one-to-one exchange of hydrogen for conventional fuels would mean that a plane could only fly a quarter of the way.
To compensate for this, hydrogen would have to be turned into a cryogenic state, in which it is converted to a liquid at -250 ° C which would require transporting in specially insulated tanks that would be four times larger than current tanks. This would require aircraft that would have a bulbous appearance or be designed with a mixed body where the wing and fuselage merge into one.
This creates problems because these hydrogen planes would have a larger surface-to-volume ratio, which means more drag and reduced fuel efficiency. However, hydrogen would be lighter than conventional fuel, which would introduce a trade-off.
The alternative may simply be to live with a shorter range, but this is a problem because producing and managing cryogenic hydrogen is extremely dangerous and expensive, so it would be preferable to need as few refueling points as possible along a given route.
On the other hand, it would be possible to design a hydrogen-powered aircraft that retains most of the conventional control systems and basic jet engine configurations, so certification would not pose the main problem that an entirely new class of aircraft would pose.
Furthermore, the use of hydrogen in jet engines is not a new idea. The first German jet engine produced in 1937 used hydrogen for ground testing and a Martin B-57B Canberra bomber flew for 20 minutes with hydrogen in 1957. Since then, there have been a number of studies on the use of hydrogen. hydrogen as an alternative form of jet fuel. A number of car manufacturers are also exploring the potential of hydrogen combustion engines to power their vehicles.
Now, Airbus and CFM International are working on a hydrogen jet engine that is expected to fly in the coming years and could lead to the introduction of a zero-emission aircraft by 2035. Under the new agreement, Airbus will supply an A380 aircraft for the conversion to the ZEROe Demonstrator flying test bed with hydrogen tanks installed in the fuselage and will determine the system requirements for the test engine, which will be a GE Passport turbofan with a CFM-modified combustor to burn hydrogen.
The new engine will not power the A380, which will use conventional engines. Instead, the hydrogen engine will be mounted on the fuselage towards the stern. This will allow engineers to monitor hydrogen engine emissions in cruise mode without interference from engines mounted under the wings.
“This is the most significant step Airbus has taken to usher in a new era of hydrogen-powered flight since the unveiling of our ZEROe concepts in September 2020,” said Sabine Klauke, Airbus Chief Technical Officer. “By harnessing the expertise of American and European engine manufacturers to advance hydrogen combustion technology, this international partnership sends a clear message that our industry is committed to making zero-emission flying a reality.”
