SwRI produces winners in engine technology and software engineering.
The R&D 100 awards represent the 100 most significant technological advances of the year, as determined by R&D Magazine and 75 consulting experts. Winners are selected from hundreds of entries developed by individuals, companies, research organizations, and universities worldwide. This year, Southwest Research Institute garnered its 16th and 17th R&D 100 awards.
The winners are a rich-burn/lean-burn (RBLB) engine that has the same thermal efficiency as a natural gas engine, but with lower exhaust emissions levels, and Weather Environment Simulation Technology (WEST) software that creates compelling, real-time views of weather phenomena from meteorological data.
New engine designs are rare in the established field of engine technology. However, an innovative, stationary RBLB engine, designed and developed by SwRI engineers, has demonstrated significantly lower oxides of nitrogen (NOx) 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 NOx figures mean the engine can compete in highly regulated areas in the United States such as Southern California, where existing engines at stationary power plants might have to be replaced with electric motors to meet proposed emissions standards. Until now, only electric engines have met 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 it meets proposed California 1999 NOx limits for retrofit stationary engines in nonattainment areas; it uses natural gas, which is a low cost fuel; and it 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 NOx 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 of 0.6. These equivalence ratios have been selected because they lie at the thresholds of the NOx equivalence ratio envelope, where NOx production is minimal. 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 mixture 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 A. Smith, who helped bring the RBLB engine to the field test stage. "RPECS helps maintain both combustion events near their operating thresholds, where NOx 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, Diamond Bar, Calif.; the Southern California Gas Company, Los Angeles, Calif.; and the Waukesha Engine Division of Dresser Industries, Inc., Waukesha, Wis. The RBLB design will be field tested in a Waukesha VGF-F18GLD stationary gas engine used to pump water in Los Angeles County, Calif.
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 Dr. David Naegeli, and Dr. Thomas W. Ryan III, of SwRI, and Steven R. King, formerly of SwRI and currently with Mesa Environmental, Fort Worth, Texas.
Published in the Fall 1996 issue of Technology Today®, published by Southwest Research Institute. For more information, contact Joe Fohn.