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from the the-Hindenberg-steam-engine-crossbreed dept.
‘They said we were eccentrics’: the UK team developing clean aviation fuel:
“Anyone passing would have wondered why these people were staring at a pipe and whooping and laughing,” says Bobby Sethi, associate professor of gas turbine combustion at Cranfield University. “But we were almost certainly the only people in the world right then burning anything without producing CO2.”
[...] “We were able to demonstrate successful ignition and safe combustion of pure hydrogen and air at high temperature and pressure – producing no carbon emissions,” he says. Even if, he adds, the passing layperson would have only seen a pipe and some steam.
[...] Sethi recalls the scepticism of even five years ago, when he was pursuing funding for the hydrogen research project, known as Enable H2: “They said we were eccentrics. Now they’re queueing up to be on our advisory board.”
There are broadly three strands of work that the aviation industry is frantically investigating for an environmentally acceptable future. One is to create greener fuels for the large aircraft currently in service. A second is electric flight, which appears feasible for smaller aircraft and short-haul hops. And a third is hydrogen.
Two projects pioneered at Cranfield are using hydrogen in the form of fuel cells to power electric motors and propel planes: ZeroAvia flew a six-seater from here last September, and hopes to scale up the technology for commercial short-haul flights in the coming decades. Another, Project Fresson, is planning to use fuel cells for a green, short-hop passenger service around the Orkney islands as soon as 2023.
But the ambitions for direct combustion of hydrogen are on a bigger scale; whether a radically different plane and propulsion system could replace the modern, paraffin-fuelled passenger jet. Which is where Sethi’s research comes in.
Nothing yet in the sheds looks anything like a plane. The rig here is a unique facility, Sethi says, assembled to show that hydrogen can be clean, safe and efficient for aviation, and produce data showing the optimum temperature and pressure to minimise other harmful emissions such as nitrogen oxides or NOx, a family of highly poisonous gases.
Not the only scientists looking for controlled ignition of hydrogen. What's described still seems a long way away from something that produces thrust, which is the ultimate need. However, technology usually advances in small steps, and that's fine as long as there's an ultimately reachable goal.
(Score: 2) by Immerman on Friday August 20 2021, @10:14PM
>Even with safety protocols, though, not sure I'd be comfortable being around a big bag of element 1 while floating up where lightning starts.
And that's the problem. Perception killed it despite the actual safety levels.
It's not like even a direct lightning strike could make a hydrogen airship explode. Hydrogen is only flammable in the presence of oxygen, which means you can only get fire when there's already a leak in the bag allowing the hydrogen to escape. And even then it will only be a relatively small fire hovering around the leak - unlike a balloon there's only a slight pressure difference caused by the weight of the ship, so you won't even get a significant jet of escaping gas forming a "hydrogen torch" - the flame can't enter the bag, and so long as the skin itself isn't flammable you'll get little more than a small "pool" of flame filling the hole. Which was one of the big problems with the Hindenburg - escaping helium would be it's own passive fire-suppression system, while escaping hydrogen instead accelerated the burning of the highly flammable skin.
> the ideal solution would seem to be generating the required hydrogen at runtime through ambient extraction
Umm...how would that work? Are you planning to deflate the ship when unused? Why bother? There's already at most only a skeleton crew on board, who can be evacuated relatively easily. It's not like an airship consumes hydrogen, aside from leakage losses. To be airborn, it has to be filled with hydrogen, and offhand I don't recall ever hearing about the supplemental/buoyancy-adjustmanttanks being a source of problems. They're already contain only a fraction of the hydrogen in the bags themselves.
Plus, do you have any idea how long it would take to extract that much hydrogen from the air? The atmosphere is only 0.00005% hydrogen gas, meaning that you'd have to process at least 2 million airship-volumes worth of air to fill one airship with hydrogen. Even if you split water vapor instead (with the huge energy requirements that implies), the atmosphere only averages about 4% water vapor, so you'd still have to process at least 25 airship-volumes worth of air.