The Air Force Office of Scientific Research joined forces with the National Science Foundation in awarding a $1.5 million grant to Harsha Chelliah, a University of Virginia mechanical and aerospace engineering professor, to expand the validity of turbulence models that researchers use to predict high-speed reacting flows of air and fuel in hypersonic engines. The grant is the latest in a series of awards that has placed UVA’s School of Engineering and Applied Science at the forefront of an international effort to make hypersonic flight a reality.
“The ultimate goal is to find ways to stabilize combustion over a shorter distance,” Chelliah said. “By reducing the overall length of the combustor, we will be able to decrease overall engine weight and increase the payload.”
The Air Force had also awarded Chelliah a $2.2 million grant in 2012 to explore a viable catalytic cooling system that uses a scramjet’s own fuel as a coolant. A traditional liquid coolant system capable of controlling temperatures of this magnitude would be prohibitively heavy.
The airflow inside the UVA scramjet engine test facility is moving extremely fast, from between Mach 0.6 to Mach 1.5. At these velocities, it takes just 400 microseconds to burn the fuel/air mixture. Understanding the fundamental modes of turbulence-flame interactions under these conditions is critical.
The researchers at UVA, along with partners at NASA Langley and George Washington University, will focus on the experimental side of the project, trying to raise the limits of spatial resolution to 50 microns using non-intrusive laser-based diagnostic techniques. Researchers at North Carolina State University and Sandia National Laboratory will handle the computational and modeling side, attempting to create more detailed and extensive models than were previously possible.
“We are trying to get down to the most basic scale of turbulent energy dissipation and feedback,” Chelliah said. “That way we will minimize uncertainties involved in making predictions about how to control it.”
One advantage that Chelliah and his colleagues have is access to UVA’s Aerospace Research Laboratory, one of the few laboratories in the nation capable of reproducing the velocities found inside scramjet engines. They are also able to use NASA Langley’s 3-D printing facility, which will enable Chelliah’s team to test superalloy combustor geometries with different shapes.
SOURCE – University of Virginia Today