Innovative low NO_x engine wins R&D 100 award

San Antonio, Texas -- October 11, 1996 -- New engine designs are rare in the seasoned field of engine technology. However, an innovative rich-burn lean-burn (RBLB) low NO_x engine, designed and developed by SwRI^® engineers has been named one of the 100 most significant technical accomplishments of 1996 by R&D Magazine.

The stationary natural gas engine provides significantly lower NO_x emissions (less than 30 ppm) than comparable engines of up to 500 hp, without sacrificing power or efficiency and without the need for complex aftertreatment systems.

These extremely low NO_x figures mean the engine can compete in highly regulated emissions areas in the United States such as Southern California, where existing stationary powerplants might have to be replaced by electric motors to meet proposed standards. Currently, electric motors are the only engines to meet the stringent emissions standards mandated by the California South Coast Air Quality Management District.

"Electric motors are expensive and merely relocate the point of emissions production to an electric power plant," says project manager David P. Meyers, a senior research engineer in SwRI's Engine and Vehicle Research Division. "Advantages of the RBLB," he adds, "are that the engine meets proposed California 1999 NO_x limits for retrofit stationary engines in nonattainment areas; uses natural gas, which is a low cost fuel; and can easily be adapted to a full spectrum of new engines and retrofitted into existing power plants, providing cost savings to both the consumer and utility companies.

The RBLB engine design takes advantage of the fact that low NO_x levels are produced during combustion of very rich or very lean fuel-air mixtures. One cylinder of a multi-cylinder engine is fueled with a rich mixture of natural gas and air with a fuel-air equivalence of 1.4, and the remaining cylinders operate on an extremely lean mixture with an air-fuel equivalence ratio of 0.6. The exhaust gas from the rich cylinder is routed through a water-gas shift catalyst where carbon monoxide and water vapor react to form additional carbon dioxide and hydrogen. The catalyzed rich exhaust is then used to enrich the lean air-fuel in the remaining cylinders where the excess hydrogen aids ignitability of the lean cylinder charge.

"Controlling the combustion system is the SwRI-developed rapid prototype engine control system (RPECS)," says Research Engineer Jack Smith, who has helped to bring the RBLB engine to the field test stage. "RPECS helps maintain both combustion events near their operating thresholds, where NO_x production is minimal, and at the same time keeps the engine in a stable operating mode for maximum power production."

Sponsors of RBLB design and development include the South Coast Air Quality District located in Diamond Bar, California; the Southern California Gas Company, Los Angeles, California; and the Waukesha Engine Division of Dresser Industries, Inc., Waukesha, Wisconsin. The RBLB design will be field tested in a Waukesha VGF-F18GLD stationary gas engine used to pump water in Los Angeles County, California.

Early design and development concepts incorporated in the RBLB engine were published in two U.S. patent awards: No. 5,297,515, issued March 29,1994, and No. 5,339,634, issued August 23, 1994. Both patents are titled Fuel Supply Systems for Engines and Combustion Processes Therefor. Inventors are Nigel F. Gale, Dr. David Naegeli, and Dr. Thomas W. Ryan III (all of SwRI), and Steven R. King (of Mesa Environmental, Fort Worth, Texas).

The R&D 100 awards will be presented October 14, at a national ceremony held in Philadelphia, Pennsylvania.

Related press release: Innovative vehicle suspension system wins R&D 100 award

For more information about the rich-burn lean-burn engine, contact Deborah Deffenbaugh, Communications Department, Southwest Research Institute, P.O. Drawer 28510, San Antonio, Texas 78228-0510, Phone (210) 522-2046, Fax (210) 522-3547.

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