Seeing is believing: WSU tool for visualizing hydrogen fuels Airbus advances

PULLMAN, Wash. - For the first time, scientists can watch as super-cold liquid hydrogen rapidly boils off into gas inside a pipe - and they're dazzled by what they're seeing.

The hydrogen beads and fogs and sparkles in ways that were not anticipated by the Washington State University researchers, who developed the visualization tool. But the breakthrough is not merely uncanny; it's an important step in advancing WSU's work with aviation giant Airbus to accelerate the development of a hydrogen-fueled commercial airplane - work done through WSU's Hydrogen Properties for Energy Research, or HYPER lab, the only cryogenic hydrogen research hub at a U.S. university.

"As humans, we understand things best when we can see them with our own eyes," said Thierry Sibilli, the Thermo-Fluid Overall Hydrogen System Lead at Airbus who recently visited WSU labs in Pullman and the Tri-Cities. "This is the only place in the world where we can do this - not one of two or three places, the only place in the world - and that's why we're working with Washington State University."

The HYPER lab's breakthrough in visualizing hydrogen is the most recent development in a nearly four-yearpartnership with Airbus to develop hydrogen as an alternative fuel for aviation. While liquid hydrogen has been visualized in tanks, it had not been seen before boiling inside a pipe.

WSU has a "master framework agreement" with Airbus Americas, which allows the company to fund specific research projects on topics within the contract.

The partnership has led to several projects and journal publications, as Airbus pursues its plans for a hydrogen-powered aircraft as part of its decarbonization roadmap toward a full-electric, fuel-cell powered hydrogen aircraft whose operation will rely upon understanding the physics of hydrogen phase changes.

"Airbus is the first aviation company to look at the challenges of cryogenic liquid hydrogen and not get scared and run away," said Jacob Leachman, a professor of mechanical and materials engineering and founder of the HYPER lab. "It has been the best industrial partnership I have had as a faculty member at WSU. They really know how to work with the students, and it has just been fantastic working with this global team."

Sibilli said that there are many hurdles ahead for meeting Airbus' goal of hydrogen-fueled commercial aviation; even if such an aircraft is developed, widespread use would require the creation of an entire infrastructure, from airports to fuel storage and transportation, to support it. But the urgency around the changing climate and the need to reduce carbon emissions makes such an effort imperative.

When someone says that hydrogen aircraft are not feasible, they're wrong. It isn't only feasible, it's inevitable.

"When someone says that hydrogen aircraft are not feasible, they're wrong," he said. "It isn't only feasible, it's inevitable."

Among the challenges is managing the fuel on the plane. Hydrogen must be carried in liquid form and then changed into gaseous form for use in the fuel cells. Being able to precisely understand and measure the change in phases and the way that hydrogen behaves when it's in both forms within a pipeline is crucial to making such an aircraft fueling system practical.

But you cannot just look at cryogenic liquid hydrogen to get accurate information about it - it is so cold that any light from the visible spectrum will change its temperature - and hydrogen gas is invisible. So Leachman, professor Konstantin Matveev, and students in the HYPER lab designed a system using a vacuum chamber and a laser to show them what was happening as hydrogen changed phases, and allowed them to measure properties such as temperature, velocity, and pressure drops.

The visualization flow cell is fitted into a vacuum chamber that can be fitted around a pipe with liquid hydrogen; the cell is fitted with various sensors and a solid-state continuous laser is directed at the pipe, producing a visualization that can be seen through a small viewing window.

"Trying to keep the visualization chamber sealed so the smallest molecule in the universe doesn't seep out and destroy your vacuum - that's the thing that no one has really ever shared publicly for a continuous fluid pipe," Leachman said. "That's what's going to allow us to give Airbus the data they need in order to say with confidence, this is what the heat transfer will act like in these tubes."

One key element of the partnership with Airbus is the opportunity that it provides for WSU students, Leachman and Matveev said. Graduate students and undergrads have the opportunity to participate in research projects funded by Airbus, to gain internships with the company and others in the industry, and go on to jobs within the field.

Sibilli, who is based in Germany, was joined on the recent visit to Pullman and the Tri-Citieswith two other Airbus colleagues: Aaron Rubel, Airbus Americas' research and technology senior manager for university partnerships who is based in Alabama, and Surya Suryaprakash Thiagarajan, a systems engineer based in India.

In addition to the HYPER lab, they also met with the Computational Intelligence for Materials and Process Innovation lab, Multiscale Mechanical & Materials lab, visited with the Office of Research, toured the Bioproducts, Sciences and Engineering laboratory at WSU Tri-Cities, as well as taking in some of the natural and cultural highlights of the region.

"I can't wait to come back," Sibilli said.