Sunday, December 5

‘They said we were eccentric’: UK team develops clean aviation fuel | Air emissions


Tits row of brick sheds, encased in overgrown country lanes in Bedfordshire, feels a far cry from the brilliant boardroom presentations on sustainable aviation. But recently it was the backdrop, in search of a greener flight, of a strange and remarkable scene.

“Anyone passing by would have wondered why these people were looking at a pipe and screaming and laughing,” says Bobby Sethi, associate professor of gas turbine combustion at Cranfield University. “But it is almost certain that we were the only people in the world at that time burning something without producing CO.2. “

In the painstaking groundwork of testing whether hydrogen could replace paraffin as a fuel for global aviation, Sethi and his team were celebrating a breakthrough.

“We were able to demonstrate successful ignition and safe combustion of pure hydrogen and air at high temperature and pressure, without producing carbon emissions,” he says. Even if, he adds, the layman passing by had only seen a pipe and some steam.

As a Harold Ramis character in Ghostbusters, Sethi had long been working on experiments in an old-fashioned and almost ridiculed field, before society decided that he was really scared, in this case by the fumes from frying planes. the planet. Who are you going to call? Cranfield Propulsion Engineering Center.

An old fuselage piece from an Easyjet plane at Cranfield University.
An old fuselage piece from an easyJet aircraft at Cranfield University. Photograph: David Levene / The Guardian

Sethi recalls the skepticism of five years ago, when he was seeking funding for the hydrogen research project, known as Enable H2: “They said we were eccentric. Now they are lining up to be on our advisory council. “

In general, there are three lines 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. One second is electric flight, which seems feasible for smaller planes and short-haul flights. And a third is hydrogen.

Two projects started at Cranfield use hydrogen in the form of fuel cells to power electric motors and power airplanes: ZeroAvia flew a six-seater from here last September, and hopes to expand the technology for short-haul commercial flights in the coming decades. Other, Fresson Project, plans to use fuel cells for an eco-friendly short-haul passenger service around the Orkney Islands from 2023.

But the ambitions of direct hydrogen combustion are on a larger scale; if a radically different airplane and propulsion system could replace the modern paraffin-powered airliner. That’s where Sethi’s research comes in.

There is still nothing in the sheds that looks like an airplane. The platform here is a one-of-a-kind facility, Sethi says, assembled to demonstrate that hydrogen can be clean, safe and efficient for aviation, and produce data that shows the optimal temperature and pressure to minimize other harmful emissions like nitrogen oxides or NOx. , a family of highly poisonous gases.

Specially designed Cranfield Airport Terminal, complete with gate and lounge
Specially designed Cranfield airport terminal with departure gate and waiting area. Photograph: David Levene / The Guardian

The largest component is a pebble bed heater pressure vessel, which delivers superheated air under pressure to a combustion chamber, where hydrogen mixes and ignites. Stacked outside are boxes of lasers, ready to be unpacked, to help observe “the shape of the flame” and provide more data.

The combination of lasers and fuel hydrogen, he admits, sounds like a health and safety nightmare (an adjacent control room has a giant red stop button to flood the system with nitrogen). But the experiments here will show, he believes, that hydrogen is no more difficult or risky to reignite at altitude than paraffin.

“Technically, there is nothing unviable in hydrogen, although there is research and development to be done. The main problem with hydrogen is cost. “

That will change, he believes, as fossil fuels become environmentally and politically unsustainable and taxes, subsidies and demand shift. He believes hydrogen will become part of aviation “sometime between 2040 and 2050, depending on subsidies and political pressure.”

“It’s pressure from green lobbyists, people like Extinction Rebellion, that has brought hydrogen back to the forefront,” he adds.

The sea change in interest in sustainable aviation has revitalized research at Cranfield. Tim Mackley, director of the university’s Aerospace Integration Research Center, says: “We were always interested in efficiency, but in the last two or three years there has been a huge push to say that what the manufacturers were planning was not it was really enough. “

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Sustainable aviation fuels, or Safs, could make some progress in reducing carbon emissions, and last month the government announced early development funding for eight UK-based projects, which propose to build plants to convert household waste, atmospheric carbon, and sewage into commercial-scale jet fuel.

Safs can only be an intermediate measure, Mackley says. “They are sustainable in terms of their production, but they still burn producing CO2. “But these ‘direct fuels’, which can be added to the mix with current technology, still have a valid role now, he argues, especially given the huge carbon footprint of replacing an entire global fleet of aircraft with new types of aircraft. .

For short-haul hops, those might include something like the strange craft found center stage, albeit very behind closed doors, in the Mackley part of Cranfield. This is an experimental eVOTL: an electric vertical take-off and landing aircraft, a joint development project with Rolls-Royce. Although the partial images of the plane caused some excitement among enthusiasts when it was leaked online last year, the full image reveals a problem: it moves when tethered to a large truck.

Looking at an eVTOL (Electric Vertical Takeoff and Landing) aircraft with Dr. Tim Mackley at Cranfield University.
Watching an eVTOL plane with Tim Mackley at Cranfield University. Photograph: David Levene / The Guardian

“This was never intended to fly,” Mackley says. Instead, what the model is designed to test is how the rotors react in the difficult moment when turning between vertical takeoff and forward thrust, and being too large to fit in a wind tunnel, the aircraft is clamped. to a huge former German fire. truck and driven down the Cranfield track. “It was the only thing with the acceleration to get to 80 mph and the power to transport the plane.”

Cranfield is one of many players working on eVTOLS, usually in isolation, leading to some very individual designs. Sometimes in the big reveal, Mackley admits, “Absolutely, I think what the heck is that.”

But, he says, “To get the most out of electricity, we have to be resourceful about what it looks like.”

Whether hydrogen or electric, planes will evolve, and flight may be slower than before, he says. In addition to the environment, designers will always have to consider how their planes will work for passengers, he warns: “If you don’t build the concept that airlines like, then you won’t be successful.”


www.theguardian.com

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