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Tits row of brick hangars, enclosed in overgrown country lanes in Bedfordshire, are a far cry from the conference hall’s brilliant presentations on sustainable aviation. But recently that was the backdrop, in search of 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 we were almost certainly the only ones in the world to burn anything without producing CO2. “
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 have been 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 passing layman would only have seen a pipe and steam.
Like a Harold Ramis character in Ghostbusters, Sethi had long worked on experiments in an old-fashioned, almost derided field – before the company decided she was indeed frightened, in this case by the fumes from the frying jets. the planet. Who are you going to call? Cranfield Propulsion Engineering Center.
Sethi remembers the skepticism from five more years ago when he was looking to fund the hydrogen research project known as Enable H2: “They said we were eccentrics. Now they are lining up to be part of our advisory board.
There are basically three streams of work that the aviation industry is frantically exploring for an environmentally friendly future. One is to create greener fuels for the large planes currently in service. A second is electric flight, which seems feasible for small planes and short-haul flights. And a third is hydrogen.
Two projects launched at Cranfield use 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 develop the technology for short-haul commercial flights in the decades to come. . Another, the Fresson project, plans to use fuel cells for short-haul green passenger service around the Orkney Islands as early as 2023.
But the ambitions of direct combustion of hydrogen are on a larger scale; if a drastically different aircraft and propulsion system could replace the modern paraffin-fueled passenger jet. This is where Sethi’s research comes in.
Nothing in the hangars yet looks like an airplane. The platform here is a unique facility, Sethi says, assembled to show that hydrogen can be clean, safe and efficient for aviation, and to produce data showing the optimum temperature and pressure to minimize other harmful emissions. such as nitrogen oxides or NOx, a family of highly toxic gases.
The most important component is a pebble bed heating pressure tank, which supplies very hot pressurized air into a combustion chamber, where hydrogen is mixed and ignited. Cases of lasers are stacked outside, ready to unpack, to help observe “the shape of the flame” and provide more data.
The combination of lasers and combustible hydrogen, he admits, looks like a health and safety nightmare (an adjacent control room has a giant red shutdown button to flood the system with nitrogen). But the experiments here will prove, he believes, that hydrogen is no more difficult or risky to relight at altitude than paraffin.
“Technically, there is nothing impossible about hydrogen – although there is research and development to be done. The main problem with hydrogen is the cost.
That will change, he believes, as fossil fuels become environmentally and politically unsustainable and taxes, subsidies and demand change. He believes hydrogen will be part of aviation “somewhere between 2040 and 2050, depending on subsidies and political pressure.”
“It is the pressure of green lobbyists, people like Extinction Rebellion, that has brought hydrogen back to the fore,” he adds.
The radical shift in interest in sustainable aviation has re-energized research at Cranfield. Tim Macckley, director of the university’s Aerospace Integration Research Center, says: “We’ve always been interested in efficiency, but over the past two or three years there’s been a lot of emphasis that what the manufacturers foresaw was not really enough.
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Sustainable Aviation Fuels, or Safs, could make strides in reducing carbon emissions, and last month the government announced early development funding for eight UK-based projects, which propose to build factories to convert household waste, atmospheric carbon and sewage into jet fuel on a commercial scale.
Safs can only be an interim measure, says Macckley. “They are sustainable in terms of production – but they always burn by producing CO2. “But such ‘alternative fuels’, which can be added to the mix with current technology, still have a valid role now, he argues – especially given the enormous carbon impact of replacing an entire global fleet of vehicles. planes by new types of planes.
For short range jumps, these could include something like the odd contraption that sits in the center of the stage, albeit very well behind closed doors, in Mackley’s Cranfield part. This is an experimental eVOTL – an electric vertical take-off and landing aircraft, a development project in collaboration with Rolls-Royce. While partial images of the plane sparked some excitement among enthusiasts when they leaked online last year, the full image reveals one problem: it moves while attached to a large truck.
“It was never designed to fly,” Mackley explains. Instead, what the model is designed to test is how the rotors react to the difficult moment when turning between vertical takeoff and forward thrust – and, being too big to put in a wind tunnel. , the plane is affixed to a huge German fire. truck and down the Cranfield track. “That was the only thing with the acceleration to 80 mph and the power to carry the plane.”
Cranfield is one of the many players working on eVTOLS, usually in isolation, which leads to very individual designs. Sometimes during the big reveal, Macckley admits, “Absolutely, I think what the hell is this.”
But, he says, “To get the most out of electricity, we have to be inventive about how it looks.”
Whether hydrogen or electric, planes will evolve – and the flight may well be slower than before, he says. In addition to the environment, designers will always have to keep in mind how their planes will work for passengers, he warns, “If you don’t build the concept that airlines love, then it won’t work. “
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