Working with the Air Force to Develop Supersonic Engines

Tonghun Lee, Ph.D.

The United States Air Force has a "need for speed." Dr. Tonghun Lee, associate professor in MSU's College of Engineering, is working with researchers at the Wright Patterson Air Force Base (WPAFB) in Dayton, Ohio, to develop innovative combustion systems that will allow engines to operate at incredibly high speeds.

Lee has spent three summers at Wright Patterson's Propulsion Directorate within the Aerospace Propulsion Division (Air Force Research Laboratory), funded by their Summer Faculty Fellowship Program. "I use lasers to look at the combustion process in propulsion systems," Lee explains. "I image things like temperature and chemical species in laboratory set-ups which are designed to simulate conditions that show how an engine is running." Because much of his research is on location at WPAFB, Lee travels there frequently to set up lasers and make measurements.

Even as an undergraduate student, Lee was interested in energy conversion, which, put simply, is "going from one energy system to another." He made his initial connection with Wright Patterson while doing his graduate work at Stanford University. "I knew the work they had done, and a lot of my own research during my graduate work was with WP," says Lee. Then, when Lee became a faculty member at Michigan State University (MSU), he continued the research connection: "After I came to MSU, I visited Wright Patterson Air Force Base as I wanted to conduct research in their propulsion program. I ran into great scientists who shared my vision and who ultimately became great mentors for me over the years."

One of Lee's primary mentors is Dr. Campbell Carter, chief scientist in the WPAFB Aerospace Division. Regarding the highly technical nature of the research he and Lee are working on, Dr. Carter explains, "We have worked together to advance understanding of plasma-assisted combustion, employing a novel microwave-plasma/jet-flame configuration. We have also worked to advance the state of the art in combustion diagnostics by demonstrating a kHz-rate planar laser-induced fluorescence measurement of nitric oxide." Lee and Carter are hoping that the outcome of their research will result in optimizing the design of next-generation propulsion systems using chemical and thermodynamic technologies.

Working with WPAFB has given Lee access to cutting-edge technology and exposure to top-of-the-line diagnostic equipment. " At Wright Patterson, we had these diagnostic tools at our disposal and I wanted to look at what's going on inside these next-generation combustion systems...I enjoy the challenge of making measurements in very tough combustion environments, and being able to determine what exactly is going on in conditions where temperatures exceed 2000 degrees Kelvin."

Most combustion systems are gas-fueled, which only allows them to go up to a certain speed. When you get to speeds beyond that, energy flows using gas systems can't be stabilized. Lee compares traditional gas-fueled combustion systems with a candle: "When you light a candle and then blow on it, the candle goes out. Much the same thing happens when you use a gas-powered combustion system. When you reach speeds that are very high, it simply goes out." Lee is helping to measure and research hypersonic propulsion systems using alternative energy forms such as plasma that allow combustion-driven engines to go much faster.

When Lee came to MSU, he established the Laser Diagnostics Laboratory for Advanced Energy and Propulsion Research, where he oversees the research of several graduate students. At the lab, he and his students apply advanced laser diagnostics to investigate the combustion characteristics of new and advanced propulsion systems, energetically enhanced combustion, and thermal oxidation of alternative and renewable fuels. They also investigate innovative combustion concepts that allow for higher efficiency and cleaner chemistry based on alternative and sustainable energy sources.

Dr. Lee, along with 93 other emerging scientists, was recently honored by President Barack Obama with the Presidential Early Career Award for Scientists and Engineers (PECASE). This presidential award is the highest honor bestowed by the United States government on outstanding science and engineering professionals in the early stages of their independent careers. The award honors individuals for their pursuit of innovative research at the frontiers of science and technology and their commitment to community service as demonstrated through scientific leadership, public education or community outreach.