Sandia explores aggressive high-efficiency sparkplug-free gasoline auto engines

by Michael Padilla

Researchers at Sandia’s Combustion Research Facility are playing a key role in developing sparkplug-free engines that will help meet ambitious automotive fuel economy targets of 54.5 miles per gallon by 2025.

They are working on low-temperature gasoline combustion (LTGC) operating strategies for affordable, high-efficiency engines that will meet stringent air-quality standards.

Sandia researchers Isaac Ekoto and  Benjamin Wolk (both 8632) say the goal of the LTGC project is an engine in which chemically controlled ignition initiates the combustion of dilute charge mixtures.

“The use of dilute mixtures avoids high flame temperatures that can lead to nitrogen oxide formation,” Isaac says. “LTGC operation increases engine efficiency relative to conventional spark-ignited gasoline engines through reduced heat transfer and pumping losses, along with increased conversion of fuel chemical energy into usable work via higher compression ratios and mixture-specific heat ratios.”

The research challenge has been to achieve effective auto-ignition control when an engine is idling or at other low-load operating conditions, where slow burn rates can cause frequent misfires.

The research was published in the September 2015 issue of the SAE International Journal of Fuels and Lubricants in a paper titled “Detailed Characterization of Negative Valve Overlap Chemistry by Photoionization Mass Spectroscopy.” The work was recognized by the Society of Automotive Engineers of Japan (JSAE) as the best paper of 2015.

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