Plasma NOx ’em out


Years ago, meeting emissions regulations was simply a matter of better engineering. Improved combustion meant that a cleaner engine was a more efficient engine. Those days are gone, it’s been lamented. With fuel-robbing exhaust gas recirculation (EGR) already here, and the specter of traps for particulate matter (PM or soot) and oxides of nitrogen (NOx) looming, there is no silver bullet.

Wait a minute…Move over, Coors Light, there’s a new bullet in town. ArvinMeritor is onto a breakthrough exhaust emissions technology that promises to help manufacturers meet upcoming emissions regs, and reclaim mpg.

The Plasma Fuel Reformer uses a strong, continuous spark to partially combust a mixture of air and onboard fuel. There is deliberately insufficient air to support combustion. So, instead of burning, the fuel dissociates to create a hydrogen-rich gas, which reacts with NOx trapped in the exhaust system to form water and free nitrogen.

Pedro Ferro, vice president and general manager, commercial vehicle exhaust & specialty products, says the device is so effective at cleaning up NOx traps that injection timing could be advanced to pre-2000 levels, making for better mpg with no emissions penalty. Moreover, he adds, there’s only one fuel on board. No additives or separate tanks, as are required with selective catalytic reduction (SCR) systems used in Europe.

The reformer also has potential when employed before combustion on gasoline engines. “Hydrogen-rich gas has real promise to achieve ultra-lean turbocharged operation,” says Ferro, “with improved fuel economy and dramatically reduced emissions.”

ArvinMeritor recognized that concepts being pioneered by the Plasma Science and Fusion Center at the Massachusetts Institute of Technology (MIT) could be applied to systems that can be mass-produced. The company now has exclusive rights to use the technology, and development of the Plasma Fuel Reformer is being led in North America with MIT at ArvinMeritor’s Commercial Vehicle Engineering Center in Columbus, Ind.

Significant progress is being made, according to Ferro. Reductions in size, cost and complexity, and improvements in performance, are ongoing. For example, during early development, the Plasma Fuel Reformer required as much as 2,000 watts of electricity to operate, and took several seconds to produce hydrogen from cold exhaust. Current prototypes use an average of less than 100 watts, and are up and running in less than a second. Also, the first prototypes produced hydrogen at just one flow rate, while current versions can manage varying flow demands.

The Plasma Fuel Reformer should be available in 2010 – just in time for the phase-in of super-stringent emissions regulations to be complete. If the fuel reformer works, there’s a good chance that compromises like EGR will no longer be needed. Engines could be set up to run efficiently, produce as much NOx as they want and leave it to the reformer to clean up after them.

Those, my friends, will be the good old days – fuel economy up and emissions down.