Following a three-month feasibility study, Aviation H2—an Australian-owned company seeking to achieve net-zero emissions in the aerospace sector through green hydrogen—has selected the use of liquid ammonia to turbofan combustion as the best route to carbon-free flight and will soon start modifying turbofan engines to test and prove the concept.

The company, which is launching a $500,000 capital raise via the online platform VCEX to fund the construction of its first modification prototype, says the results from their studies were very positive. Their research shows that converting a Falcon 50 to Liquid Ammonia Turbofan Combustion is the most efficient and commercially viable avenue to building a hydrogen-powered plane.

The company’s team of engineers say they now have a clear pathway to having Australia’s first hydrogen-fuelled aircraft in the skies by the middle of 2023.

By implementing this power path, Aviation H2 can fly aircraft with hydrogen fuel using significantly less weight than alternative power paths while generating the same amount of power.

There are multiple reasons why liquid ammonia was selected. Chiefly its advantages include high gravimetric and volumetric hydrogen density that makes it lighter and easier to transport while providing a greater energy conversion rate. In fact, the stored weight of liquid ammonia energy is substantially lighter than gaseous hydrogen and can be kept at a much lower tank pressure.—Aviation H2 Director, Dr Helmut Mayer

Dr Mayer says this is supported by anhydrous ammonia reaching liquification point quicker, which makes it a lot simpler to store when compared to liquid or gasified hydrogen. Additionally, worldwide transportation and handling of liquid ammonia has been around for many years, making ammonia as a carbon-free fuel even more appealing.

The company has selected the Dassault Falcon 50 business jet—a long-ranged international business charter jet aircraft—for the flight test.

The jet has three engines, of which only two are required for flight, allowing the third engine to be used to test a smaller engine modified to use liquid ammonia before moving on to modify the main engines.

Aviation H2 Directors Dr Helmut Mayer & Christof Mayer inspecting a Falcon 50 engine.

Falcon 50s also have a larger weight capacity, reducing the risk posed by weight challenges. The costs for the test program are no larger than when using a smaller and newer type of jet.

They are also relatively common in Australia, meaning there is a time-saving in getting the aircraft ready for testing.

The company believes making use of current technologies and infrastructure will be important to future customers because it allows them to modify the aircraft they have already invested in, rather than buy a whole new fleet.

Once the test flight is successful in the middle of 2023, Aviation H2 will have a patentable method for modifying aircraft so they operate on carbon-free fuel. They will quickly seek to certify and commercialise this product via a planned public listing on a major exchange in Q4 of 2023.

Posted on 28 April 2022 in Ammonia, Aviation & Aerospace, Engines, Hydrogen | Permalink | Comments (8)

The narrow flammability limits of NH3 had me skeptical about this, but seeing that they intend to crack it to H2 and N2 before feeding the engine gets around this problem.

They still have the issue of low energy/mass of NH3.  It has about 8000 BTU/lb, compared to Jet-A at about 20,000 BTU/lb.  I suspect the cracking process will take some energy too.  On the other hand, if they can crack the NH3 with heat obtained by cooling the first few stages of turbine nozzles, that might enable greater engine performance (no dilution of the combustion gas by nozzle cooling air, less bleed air tapped for cooling).  It'll be interesting to see just what they do.

Posted by: Engineer-Poet | 28 April 2022 at 05:39 AM

Good point, E-P, about the very low energy density of anhydrous ammonia that would make long-range flight impossible with any meaningful payload. Plus it would take a lot of energy to synthesize ammonia from H2 and N2, around 50% of energy efficiency hit. It would be better off to focus on synthetic JetA fuel in the near term, and perfecting the technology for Liquid H2 for the long term.

LH2 has obvious weight advantage in term of payload weight, and safety in term of post-crash fire. Weight-wise, LH2 weighs 1/3 that of jetA, and the weight of polyurethane foam insulation is small, and can contribute to the structure of the plane. Safety-wise, the LH2 fuel will be placed in the rear compartment where it will be most protected from a survivable crash. The thickly insulated fuel vessel plus the very light fuel plus the rearward-most placement means that the fuel tank will likely remain intact after a survivable crash to prevent post-crash fire that often claimed lives even after a survivable crash.

Efficiency-wise, LH2 fuel will be more efficient when used in optimized gas-turbines, and even though it takes roughly 1/3 of the energy of the H2 to liquefy it, it really only takes 20% more energy to make LH2. It takes roughly 50 kWh to make 1 kg of H2, and turning that into LH2 will take around 10 kWh more, thus ~60 kWh per kg of LH2. So, H2 can be piped into the airport area from the H2 pipeline system, and can use grid-excess Energy from both Renewable and Nuclear sources to make LH2, and stored right at the airport tanks. This would result in the most efficient energetic and logistic distribution system for LH2 for aviation.

Posted by: Roger Pham | 28 April 2022 at 12:01 PM

@Roger--How does the aircraft handle the shifting CG if you put all the mass of LH2 at the rear of the airplane? Keeping a stable CG is one of the reasons aircraft are designed with wing fuel tanks, since wings are generally located so lift is at CG point, more or less.

Posted by: Nick Lyons | 28 April 2022 at 01:14 PM

Liquid hydrogen, fuel cells, hybrid turbo fans

Posted by: SJC | 28 April 2022 at 02:08 PM

Nick is right.  The LH2 plane schemes I've seen either had tanks fore and aft or one running the length of the plane (which would certainly have been subdivided) for just that reason.

Posted by: Engineer-Poet | 28 April 2022 at 04:02 PM

I know they claim its green H2 but this is Australia. All H2 produced will be made from syngas derived from coal. Aus has a lot of coal and they want to use it all. Greenwashing.

Posted by: bman | 29 April 2022 at 04:18 AM

For now, it can be an electrically boosted, dual fuel LNG/LH2, maybe in a propfan.

Posted by: Nocreditreports | 29 April 2022 at 12:37 PM

@Nick Lyons, LH2 is very light. For a given payload weight, the fuel mass of LH2 is about 1/5 that of JetA fuel. Such a light-weight fuel cannot cause a tail-heavy situation even fully loaded. The Plane should be loaded primarily in the front to avoid nose light. When the LH2 fuel mass is mostly consumed, the airplane will be nose-heavy, but should still be controllable with good stability margin with sufficiently-large horizontal tail plane.

Posted by: Roger Pham | 01 May 2022 at 01:15 AM

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