RCCI progress paces university’s advanced-combustion and fuels activities

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RCCI progress paces university’s advanced-combustion and fuels activities

Inside an Engine Research Center test cell with the RCCI development engine are (from left) Reed Hanson, Dr. Rolf Reitz, Derek Splitter, and Sage Kokjohn.

The advanced combustion and fuels research at the University of Wisconsin-Madison’s Engine Research Center (ERC) is world-renowned, but never in the facility’s 65-year history has its work been so important, given the global powertrain industry’s need for higher fuel efficiency and reduced exhaust emissions.

Reactivity Controlled Compression Ignition (RCCI) technology is among a number of priority programs under the leadership of Dr. Rolf Reitz, Mechanical Engineering Professor and director of the ERC’s Diesel Engine Consortium. He is confidant about the long-term potential for RCCI.

“We have submitted two patent applications on this technology,” Reitz said. “My group’s dual-fuel compression-ignition engine research has demonstrated that RCCI’s thermal efficiencies are greater than 55%, while meeting EPA 2010 emission regulations in-cylinder and without the need for aftertreatment,” he explained.

The RCCI combustion process to which Reitz referred uses in-cylinder blending of two fuels of different reactivity—diesel and gasoline—to successfully reduce emissions levels. The strategy employs port injection of the low-reactivity (gasoline) fuel mixed with a measure of recirculated exhaust gases, followed by direct injection of the higher reactivity fuel prior to ignition. Multiple injection events and precise intake valve control are critical to optimize the combustion process.

“What we have done is essentially develop a recipe for mixing two fuels according to several key parameters, including operation speed,” said Reitz. “For example, if you operate at high engine speed, you’ll want the overall mix to be more reactive because there is less time for it to combust.”

When fully developed, RCCI could emerge as an alternative to the aftertreatment burden currently facing diesels, Reitz believes. (See AEI Online, Aug. 4, 2010: http://www.sae.org/mags/aei/power/8388.) The technology also could be a potential contender to the spark-ignition (SI) engine technologies that are also a focus of intense ERC research.

“We have recently shown that it is possible to operate diesel engines using gasoline fuel, or combinations of gasoline and diesel fuel, to obtain engine fuel efficiencies that are as much as 20% better than standard diesel engines,” he noted.

In addition, the ERC is engaged with research projects on the use of alternative fuels, including bio-fuels, ethanol, and natural gas, he said. Ethanol is under investigation as a low-reactivity fuel for RCCI, offering fuel efficiency gains when blended with diesel fuel in the combustion chamber.

Reitz has spent 22 years of his more than 30 years in engine research at the U of W-Madison. His resume also includes six years at the General Motors Research Lab in Warren, MI, and a stint as ERC director.

Advanced computer modeling of internal-combustion engine physics is one of the greatest assets of the ERC, which is claimed to be the largest university center for engine research in the U.S. Modeling, simulations, and use of optical diagnostics for model validation are critical for testing various gas and diesel fuel blends in the RCCI environment.

Such advanced tools and expertise will continue to allow ERC research engineers and scientists—the team is currently comprised of more than 50 graduate students and seven faculty members—”to explore new combustion regimes that offer significant advantages in terms of fuel efficiency and low pollutant emissions,” Reitz asserted.

ERC researchers also collaborate with their counterparts at U.S. government labs and other universities, as well as within industry. Public and private sector groups can work together pre-competitively to solve specific engineering challenges using ERC’s resources. They include 18 fully instrumented engine test stands, several optical engines, labs for injector/spray characterization, and combustion research vessels for laser-based experiments under simulated engine conditions.

The facility also offers “dedicated computer clusters consisting of more than 300 multicore computers, plus access to more than 4000 computers on campus,” noted Reitz.

Kami Buchholz