UC professor's research reveals combustion capabilities
Combustion studies in high-speed aircraft and rocket engines to make travel safer, faster, and more efficient
Prashant Khare, Ph.D, an assistant professor of aerospace engineering in the University of Cincinnati College of Engineering and Applied Science (CEAS), is working to understand the complex multiphase turbulent combustion phenomena that occurs in diesel, gas-turbine and rocket engines. Even with the relative reliability of modern modes of transportation, these systems are not well understood.
“We know these existing systems work very well, but how these systems work is still not well understood. That’s what I study,” said Khare.
Khare received funds from UC’s research council last spring to study turbulent combustion processes in the presence of electromagnetic fields, which he continues this summer. Khare’s primary motivation is to shed light on the many unknowns within combustion systems.
“If you can understand them better, then maybe you can make them better. Sixty years ago (during the space race), people experimented. If something worked, it worked. It was design by trial-and-error,” Khare explained.
Now, with limited time and resources available to build the next generation propulsion systems, Khare is questioning this approach.
To do this, Khare focuses on resolving the fine details of the combustion process so that the overall result can be modified (in a beneficial way). These refinements and their goals vary. For example, they may help fuel burn more efficiently or may lead to lighter components. The overall goal is to go farther and faster by understanding the mechanisms and fundamental principles underlying these systems.
The precision of such refinements is reflected in the work of two Ph.D students in his lab.
One student studies a canonical configuration of a fuel jet interacting, mixing and burning with cross flowing air in combustion chambers. In supersonic and hypersonic aircrafts, air moves at speeds greater than the speed of sound. Air flows through the combustion chamber so fast that the fuel doesn’t have enough time to mix with the incoming air and burn to produce the necessary thrust. Through understanding the underlying mechanisms and theories, they are trying to contribute to the development such vehicles that will drastically reduce travel times; for example, it could enable a trip from New York to London in 35 minutes.
Another student is performing an analysis of the liquid fuel injected in the jet engine. This includes how the droplets behave and break up at extreme speeds and in the presence of turbulence. The team produced a video of this process which earned the Art-in-Science Award at the 42nd annual American Institute of Aeronautics and Astronautics Dayton-Cincinnati Symposium.
Khare also studies the effects of turbulence on the combustion process. Turbulence is not well understood. The hardest part of fluid dynamics is predicting flowfields when the flow is turbulent.
How is something as small as a droplet of fuel studied within a large and complicated system like a supersonic jet engine? With hundreds of millions of grid points to resolve sub-micron scales.
Khare reported that just one of these painstakingly long and expensive studies took several months to gather data, running on 48 computing cores day and night (for 4-6 months) to observe and record one droplet’s movement and breakup.
To speed up the process of observation and analysis to meet industry needs, Khare is developing a machine-learning algorithm to predict such small and detailed results within certain parameters.
Khare and his students’ research data could advance technology in crucial areas like fuel efficiency, safety improvement and performance optimization.
Why study all of these things that are both tiny and difficult to observe?
“It’s fun to explore how things work! Once you see those details and look at the bigger picture, things suddenly make sense on a larger scale,” Khare said.
In addition to research, Khare teaches undergraduate courses in thermodynamics, fluid mechanics and gas dynamics. Khare, who earned his PhD from Georgia Tech in 2014, was also selected as an invited lecturer at Oxford University as a part of Georgia Tech’s study abroad program in 2016.
For more information on Khare’s research and teaching activities, please visit his research page.
For more information on the department of aerospace engineering and engineering mechanics at UC, please visit the department page.
Featured image at top: This 3-D image shows a deisel injection in a turbulent flow field. Photo/Provided by Prashant Khare.
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