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Fokker Next Gen designing dual-fuel LH2 / SAF commercial aircraft

Fokker Next Gen is designing a clean sheet aircraft to contribute towards the net zero carbon emission vision of the future of flight. The design is a single aisle narrow body commercial aircraft seating 120 to 150 passengers, and has a flight range of 2,590 km (1,400 nm).

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The aircraft will have an innovative dual fuel design, enabling the aircraft to fly on liquid hydrogen combustion (LH2), sustainable aviation fuel (SAF), or—if no other fuel type is available—jet fuel.

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When pure hydrogen is combusted, the only byproducts are oxygen and water, meaning a flight purely powered by LH2 would produce zero CO2 emissions while in flight. If the liquid hydrogen has been produced through one of the various zero-emission production methods (e.g. green hydrogen) this will provide a truly zero-CO2 emitting fuel.

Entry into service is currently scheduled for 2035, although Fokker Next Gen is exploring all possibilities to accelerate this timeline.

Comments

Davemart

Interesting choices to ensure flexibility.
I was wondering if the range will differ when it is fuelled on SAF instead of hydrogen, but it seems it does not, or at least they do not mention it.

Gryf

This is an interesting concept and similar to some of my ideas.
SAF would definitely have greater range than hydrogen, so how the “dual fuel” concept is implemented would relate to aircraft range.
This design looks similar to the NASA X-66 Sustainable Experimental Airliner which would extend the range due to better aerodynamic efficiencies.
https://www.nasa.gov/image-article/new-look-at-nasa-boeing-sustainable-experimental-airliner/

Using the NASA design combined with the MTU Water Enhanced Turbines (WET) would lead to an even greater range, much more than their “ flight range of 2,590 km (1,400 nm).” The SAF and/or Jet fuel tanks could be in their typical location of the wings, so this concept might be able to switch between the fuels easily. Maybe explore the use of using partial combustion using both fuels which would also extend range.

My final idea would be to explore Liquid Organic Hydrogen Storage (LOHC), which has almost the same volumetric energy density of liquid Hydrogen (Liquid H2 ~60kg/m3 and LOHC 54 kg/m3). It would be necessary to handle the endothermic dehydrogenation of LOHC (around 300 degrees C) which would require something like the MTU Water Enhanced Turbine.
LOHC has similar handling characteristics to jet fuel, so the LOHC could be placed in regular belly tanks with the SAF/jet fuel in the wing tanks. This would mean almost no loss of range for the aircraft.

References:
http://evs36.com/wp-content/uploads/finalpapers/FinalPaper_Acher_Thomas_Will_Christian.pdf
https://about.bnef.com/blog/liebreich-the-unbearable-lightness-of-hydrogen/
https://greengroup.mit.edu/lohc-powertrains-decarbonize-long-haul-trucks

SJC

I favor sustainable aviation fuel with hybrid turbo fan use a smaller turbo fan for cruising but you have the electric for climbing

Roger Pham

The one of the two LH2 tanks in the rear could be moved to the nose of the aircraft, thereby achieving good weight balance at all phases of flight. This will also save weight, because this will shorten the tail section and hence lower the bending load on the tail end of the fuselage. The cockpit is simply placed behind the nose fuel tank, and the pilot can view outside via multiple cameras instead of a glass windscreen like in normal aircraft.

An aircraft optimized for LH2 would have much lower gross weight for the same payload capacity due to reduction in the size and weights of the wings, tail, engines, and landing gears..., though the wings still can hold regular kerosene jet fuel, but because the wings are smaller, will carry less jet fuel and thus will have lower range when using jet fuel.

@Gryf,
LOHC would be far too heavy and will never have any role in aviation. Nothing can beat LH2 as aviation fuel, due to the incredible lightness of LH2 that can nearly DOUBLE the payload-mile fuel economy per BTU of fuel energy. So, with LH2, the airlines will use 1/2 as much fuel energy per flight, and this will permit LH2 prices to cost twice as much as jet fuel per BTU of energy to come out even. If LH2 will ever cost the same as jet fuel per BTU of energy, then all airliners will be fueled with LH2. Fuel cost is the biggest operating expense for airlines.

Gryf

@Roger Pham
LOHC weighs the same as jet fuel.

I don’t know what your technical background is. Maybe you will let us know.
BTW I did work and consult many years in the aviation field.

dursun

More lame Greenwashing.

Roger Pham

@Gryf,
Let's look at energy density in kWh / liter. LH2 : 2.2 kWh per liter, LOHC: 1.8 kWh per liter and kerosene: 9.6 kWh per liter.

Per weight, LH2 has 33 kWh per kg, LOHC: 2.25 kWh per kg, and kerosene 12 kWh per kg. So, LOHC is far too heavy, it has far too little energy per kg to be a viable aviation fuel.

Gryf

@Roger Pham
Stop using Gravimetric measures, i.e kWh/kg. Using kWh/liter is the correct measure and LOHC and LH2 are very close.

So what is your background?

Roger Pham

In a car, volumetric energy density is important for the purpose of internal space.
In a plane, gravimetric energy density is far more important, because a heavy plane won't get off the ground.

For long distance flight, the payload is 1/4 of the gross take off weight, fuel weight makes another 1/4, and the rest is for the empty plane which takes 1/2 of the gross takeoff weight.
If you manage to reduce the fuel weight down to 1/6 of the previous fuel mass, then you can reduce the wing weight, the tail weight, engine weight, and landing gear weight...and the gross takeoff weight will be down to 60% of previous takeoff weight.

Now then, if you use the LH2 supercold temp to cool down the intake air into the core turbine, then you can improve the engine efficiency by 20%-25%....and all these factors combined will reduce fuel energy of LH2 to 50% of that of kerosene jet fuel. And this is a very big deal!

SJC

In aviation weight is an important factor this is why LH2 is of Interest it takes up more space but it weighs less let's not get hung up on people's backgrounds mine's bigger than yours that is childish.

Gryf

@SJC
Your comment is insulting.

Davemart

Gryf:

Your comment was a bit: ' A cat shouldn't look at a king'
Arguments of authority are not persuasive.

Now I have no technical background whatsoever, but am not too bad at adding up, and my understanding is that fuel weight is pretty critical in aviation, and LOHC looks pretty darn heavy.

Sure, you can do it, but you spend rather too much energy lugging the fuel around instead of payload, in a negative spiral.

For that reason it appears clear that the range of a aircraft running on LOHC would be less than the same aircraft fuelled by jet fuel.

Perhaps it is reasonable to assume that Fokker are not considering LOHC but SAF or hydrogen for that reason,

If that is not the case, please explain why.
Expertise is all very well, but if you put two experts together on many subjects you will get three opinions, so 'because I say so' is neither persuasive not informative,

Nocreditreports

We might as well be saying that the moon is made of green hydrogen.
Someday we'll get very expensive fuel from the conversion of C02. This fuel will be used in aircraft.
Someday we'll get a lightweight, energy dense battery. This battery will be used in aircraft.
Someday air travel will carry a stiff carbon tax, so people won't fly so much.
Someday someday ...

Davemart

Just had another dig around the influence of weight on fuel consumption in aircraft, especially for relatively short haul single isle, which is what is under discussion, ie broadly in the 737 class for a couple of hours or so flights.

https://www.pprune.org/tech-log/9473-how-much-extra-fuel-carry-fuel.html

'Orangewings' comment is the pertinent one:

' On the B737-300/700,for every tonne of fuel above flight plan fuel carried,we burn an extra 40kgs. So for 3 extra tonnes on a 2hr flight we burn an extra 240kgs.I think.'

Note that this is for a marginal increase in weight.
Obviously weight is the relevant metric, not volume, as the size of the fuel tanks are fixed, it is just how much they are filled, ie the weight of the fuel.

For LOHC or ammonia, which one commentator suggested, you are not talking about a marginal increase in weight over jet fuel, but multiplying it by several times.

That is clearly a complete non starter, which is why it is not contemplated by the very expert folk at Fokker and Airbus, who are looking to SAF or hydrogen.

SAF is identical for weight and volume with jet fuel, which is why it is the easier fix.
Hydrogen is more bulky although potentially weighing a lot less, with composite tanks, so really needs redesigned aircraft as well as low temperature hassles,

Roger Pham

Thank you, Davemart, for the insight above.
@Nocreditreports,
What will happen in the future is totally dependent on what we are doing today. We have to research, analyze, do all the calculations, then experiment, testing, build working models, then put to practice limited real-life operation to fine tune the technology and logistics...before full-scale deployment.
But the first conceptual step is the most important. All the maths have to line up before proceeding any further.

So far, LH2 is the most practical green fuel for aviation. The doubling in efficiency per kg of payload-mile over jet fuel is fantastic. H2 can be produced from solar and wind farms for relatively low costs, and transported to end users and to the airports via pipelines. Then, near the airport terminals, liquefaction plants will use grid-excess solar and wind energy to convert gaseous H2 into LH2 and stored locally.
The most modern electrolyzers consume around 43 kWh per kg of H2, then it takes around 10 kWh of energy to liquify this gaseous H2 into LH2. So, in total, 53 kWh per kg of LH2.
LH2 is already stored in space ports and used in rockets and space vehicles, so the technology is already developed. It just has to be further fine-tuned for aviation use.

LH2 is safer than jet fuel when the LH2 is stored in the rear section of the aircraft. In the event of a survivable crash or crash landing, the tail end of the aircraft is the part most likely to remain intact and safe from fire hazard. In impact-survivable crashes, most deaths come from post-crash fires due to rupture of the wings' fuel tanks, spilling the fuel and engulfing the entire airplane with passengers still trapped inside. Even with the rupture of the LH2 fuel tank, the fuel is too cold to catch fire, and it must vaporize and fly upward to mix with air before it can combust, so the flame will be well above ground level and not engulfing the plane nor the passengers.
Even if the LH2 is stored in another tank in the nose section, this fuel here can be dumped quickly before unscheduled ground landing.

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