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SwRI engineers successfully complete ARES program
San Antonio, Texas -- August 12, 2002 -- A cooperative research study led by Southwest Research Institute® (SwRI®) has helped define tomorrow’s large, stationary, natural gas-powered reciprocating engine. Such engines are widely used by electrical power companies and end users to generate electrical power.
Funded jointly by the Department of Energy and industry, the Advanced Reciprocating Engine System (ARES) consortium has investigated the improvements necessary in today’s 1- to 3.5-megawatt engines to improve efficiency by 20 percent and to reduce oxides of nitrogen (NOx) emissions by more than 90 percent.
SwRI engineers expect the ARES engine of the year 2010 to have dramatically improved performance characteristics, including a power density of 24 bar, peak cylinder pressure of 220 bar, and a 15- to 18-degree crank angle combustion duration. The fully developed engine will have a 65-percent or greater turbocharger efficiency and a mechanical efficiency of better than 91 percent. The engine will require emissions aftertreatment and, in all probability, turbocompounding, from which additional energy is recovered from the engine exhaust gas.
“The overall objectives of the ARES study were to identify technologies that would increase the reciprocating engine brake thermal efficiency to 50 percent and reduce NOx emissions to 0.14 gram/kilowatt-hour (g/kW-hr),” said Tim Callahan, ARES program manager and a principal engineer in the SwRI Engine and Vehicle Research Division. “The engine manufacturers are planning a multiphase program to meet the overall goals. In the next three to four years, manufacturers, using aftertreatment technology, will achieve the final emissions goal of 0.14 g/kW-hr of NOx and an intermediate efficiency of 45 to 46 percent. Then, as the state of the art increases, additional engine improvements will achieve the final 50-percent brake thermal efficiency in the 2010 time frame,” Callahan predicted.
An engine’s brake thermal efficiency represents the percentage of fuel converted into useful work. Today’s stationary natural gas engines in the 1- to 3.5-megawatt range usually have a 38- to
42-percent brake thermal efficiency and emit approximately 1.5 g/kW-hr of NOx. Performance characteristics include a power density of 12 to 14 bar, peak cylinder pressure of 100 to 140 bar, and a 25- to 30-degree crank angle combustion duration. The engine also has a 56-percent turbocharger efficiency and a mechanical efficiency of 87 to 89 percent. As currently configured, these engines do not have emissions aftertreatment or turbocompounding as standard equipment.
During the three-year consortium effort, SwRI performed feasibility analyses to define the goals and used single-cylinder engine testing to confirm design assumptions. Efforts addressed a number of advanced technologies including alternative engine cycles, variable valve timing, engine modeling, and knock mitigation. Other technologies included exhaust gas recirculation, reformer technology for fuel gas, turbocharger enhancement, and exhaust aftertreatment.
“Although the study emphasized power generation engines, the technology will also apply directly to engines for mechanical drive of compressors and, in many cases, this technology can be retrofitted,” said Callahan. “The engine manufacturers in our program, including Caterpillar Inc.; Cummins Engine Company; and Waukesha Engine, Dresser Inc., are implementing the concepts developed in this program in their engine designs. SwRI is providing assistance to the manufacturers with engine design, development, controls, and aftertreatment emissions technology.”
Reciprocating engines are the fastest-selling, lowest-cost distributing generation technology in the world today. In a 2001 survey by Diesel and Gas Turbine Worldwide, diesel, dual-fuel, and natural gas reciprocating engine orders totaled 10,795 units, a 68-percent increase over the 6,414 units ordered the previous year. The 2- to 3.5-megawatt range natural gas reciprocating engines showed an increase of 95 percent in sales (277 engines versus 142 in 2000). Power-generation companies use these engines as peak shaving and premium power producers for use during peak load, thus enhancing power distribution quality and reliability. Reciprocating engine technology is expected to be one of the keys to the future of the distributed power generation marketplace. To meet the nation’s need for high-quality, reliable electricity, distributed energy resources offer a faster, less expensive alternative to constructing large, central power plants and high-voltage transmission lines. Continuous improvements in reciprocating engine technology through programs such as ARES will enhance the nation’s ability to meet its growing appetite for high-quality, reliable power.
Consortium members, along with SwRI, included the Department of Energy; GTI; Caterpillar Inc.; Cooper Energy Services; Cummins Engine Company; and Waukesha Engine, Dresser Inc. Other members were Southern California Gas, Altronic Inc., Federal Mogul, Champion and Woodward Governor.
For more information contact Deborah Deffenbaugh, Communications Department, (210) 522-2046, Fax (210) 522-3547.