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Travas Lenard

Student’s summer research drives development of cleaner, more efficient lean-burn engines

Travas Lenard

Travas Lenard, pictured here beside a European BMW, spent his summer at Oak Ridge National Laboratory modeling the fuel economy of a lean-burn engine using a silver-based catalytic converter. His research was conducted as part of the Volkswagen Distinguished Scholars Program, a 10-week program managed by Oak Ridge Associated Universities that provides six Tennessee university students the opportunity to participate in cutting edge, automotive-related research.

Travas Lenard spent his summer donning safety goggles near the dismembered body of a European BMW, its lean-gasoline, direct-injected engine exposed to a laboratory filled with emissions-testing equipment and tools. A computer science major at Fisk University and a self-proclaimed gearhead, Lenard thought it would be a great experience to take part in the 10-week Volkswagen Distinguished Scholars Program at Oak Ridge National Laboratory, managed by Oak Ridge Associated Universities. “I always knew that my brain was technical,” he said. “I was always smart enough to solve problems.”

The program, which embraced Lenard’s inherent ability as a critical thinker, turned out to be just what he needed. As a program scholar, Lenard executed hands-on research for the first time in his academic career. The program placed him in an interactive, energetic atmosphere where he could gain perspective on the instrumentation and technologies involved in automobile research. “I come in here and it’s like my foot is on the gas pedal,” he said. “Things are happening around you at a much quicker pace [than in the classroom] and you can see it.” Through focused, applied study he gained a degree of specialization in his research area that he may not have received from textbooks alone. 

At the lab, Lenard’s project focused on modeling the fuel economy of a lean-burn engine using a silver-based catalytic converter as opposed to the more expensive, standard platinum one. Lean-burn engines—those with higher than the stoichiometric, or ideal, air-fuel ratios—can be more fuel-efficient than conventional gasoline engines, but they do not work well with three-way catalytic converters. For this reason, lean-burn engines are not as effective at reducing nitrogen oxide (NOx) emissions and must be equipped with either a NOx trap or a hydrocarbon selective catalytic reduction (HC-SCR) device. “The silver-based catalytic converter isa HC-SCR device,” said Shean Huff, Lenard’s mentor, “but it is much cheaper than a NOx trap.”

The downside to the NOx trap is that it requires the engine to run “rich” for periods of time while it cleans up the catalyst of the NOx it collected over a period of time. These rich periods increase the vehicle’s fuel consumption. “The goal is to run lean long enough to far outweigh that rich short period,” explains Huff. The HC-SCR device functions much differently from the NOx trap. It requires an injection of a hydrocarbon, like ethanol, downstream of the engine to create the chemical reaction inside the catalyst that then reduces the NOx.

Even with these reduction devices, U.S. emission standards do not allow lean-burn engines to be sold in the U.S. That’s where the silver comes in. “We know that silver with ethanol or hydrocarbons leads to NOx reduction of about 85 percent at high temperature,” said Lenard. In order to be efficient, the fuel savings must outweigh the cost of the injected hydrocarbon needed to keep the engine running lean.

The team expected a silver-based catalytic converter to require a smaller amount of hydrocarbons to be injected, thereby reducing overall cost. If silver reduced NOx and performed efficiently fuel-wise, the U.S. auto industry could consider developing the lean-burn technology for gasoline engines.

To conduct research, Lenard connected the BMW to a dynamometer, essentially a treadmill that simulated road driving forces. He attached a pipe to the exhaust and connected the pipe to gas emission analyzers to measure the diluted exhaust, which in turn, generated thousands of rows of emissions data for pollutants like carbon monoxide, hydrocarbons and nitrogen oxide. “I spent a lot of time in my cube doing data analysis,” Lenard said, “manipulating the data to get it to show me what I wanted it to show me.”

Using the emissions data to determine the amount of burned fuel, he then formulated a way to simulate the fuel economy of this lean-burn engine as if the NOx trap was removed. Removing the rich spikes required by the NOx trap modeled an engine retrofitted with a silver-based catalytic converter. This data, when combined with the data from the HC-SCR device, could be used as a baseline to better predict the fuel economy of an engine with the silver catalyst.

Research is still ongoing, but preliminary results show that engines using silver catalysts can run leaner, get slightly better gas mileage and reduce emissions at a much higher rate than with a platinum catalytic converter. In the future, Lenard’s research will look at retrofitting the import for further tests with an actual silver-based catalytic converter.

Lenard took pride in the lab and said he enjoyed his time in the VW Distinguished Scholars Program thoroughly. A large part of this enjoyment stemmed from his independence, a critical component of his personal work ethic. “My mentors helped me and gave me direction, but I was the one doing a lot of the research,” he said. “I kind of took ownership of the project, and I think that was pretty cool.”

The program provided Lenard with an opportunity to hone his skills as a researcher and problem-solver instead of playing his previous role as developer. “I think it’s interesting to not have all the answers and start from that position as opposed to saying, ‘Here’s the answer, now implement something with it.’ In research it’s, ‘here’s the question now see what the answer is.’”

Lenard also gained presentation experience in the program’s end-of-summer poster session. “A handful of people stopped by [my poster] and I got some great feedback from many different grad school recruiters that were there,” he said. After he earns his degree at Fisk, he plans to pursue a field of graduate study that complements his engineering and computer science background. “I’m always looking for the next opportunity,” he said. “You never know what’s around the corner.”

Learn more about the Volkswagen Distinguished Scholars Program and other educational programs available at ORNL.