Stephen Tse, professor and director of outreach in the School of Engineering’s Department of Mechanical and Aerospace Engineering, has waited patiently for years to run a series of experiments involving spherically-symmetrical flames known as “s-Flame” on the International Space Station.
“It was a decades-long process to get these experiments to finally run,” he says. “The project was approved around 2002, but many things occurred which cancelled and delayed it. Now, in fall 2019, we finally get to see the experiments begin.”
In September, Tse began running the first of up to three rounds of tests for his s-Flame project, which posits that gaining a fuller, more fundamental understanding of combustion can lead to improved energy efficiency, pollutant mitigation, and fire safety on Earth and in space.
Since space station experiments are subject to micro levels of gravity, flames are not subject to the buoyancy that they have on Earth, with some becoming spherical, rather than tear-shaped, depending on conditions. “A spherical flame can be considered one-dimensional because it is defined only by its radius, allowing the chemistry and transport processes controlling it to be more easily analyzed,” Tse explains.
According to Tse, this initial round of tests will take place on eight experimental days, with 12-hour windows, scattered throughout the semester. Each of the roughly 10 to 20 NASA-approved experiments conducted each testing day can last up to a few minutes.
Rutgers and Tse are equal partners with Princeton University and Princeton professor C.K. Law on the project, with all s-Flame experiments being guided in real time from Tse’s Rutgers office. Astronauts, Tse notes, are not involved during the tests, since every experiment is fully automated.
“On test days, we teleconference with NASA John H. Glenn Research Center at Lewis Field in Ohio as we run each experiment,” Tse explains. “We’re able to change parameters on the fly, and we have a secure direct video link to the experiments being run so that we can assess each one before running the next case. All the rest of the diagnostic measurements have to be downloaded later, as there are a lot of data.”
So far, Tse reports that the results of the experiments have differed from initial expectations based on detailed modeling by computational simulation. “In fact, deficiencies in the model or experimental transport parameters are what we’re looking for. Removing the effect of buoyancy – which is what we have here on Earth because of gravity – allows us to investigate basic chemical and transport aspects.”
The space station’s microgravity also allows Tse and his team to refine parameters and develop better models, which in turn will help optimize combustion systems, as well as make it possible to more accurately predict pollutant emissions and fire hazards. “Only by understanding such fundamentals can we truly propel combustion technology forward,” Tse insists.
Tse’s work on the project is supported with help from graduate student Jonathan Shi and undergraduate students, who will be analyzing data and running computational simulations. “We also have a special micro-buoyancy (not micro-gravity) low-pressure chamber in the lab that can do complementary experiments,” he adds.
Ultimately, Tse hopes his findings will aid the development of more fuel-efficient combustion systems. “With national fuel expenditures totaling on the order of a trillion dollars per year, advances in combustion efficiency and technology can considerably diminish both fuel usage and pollution,” he says.