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Is Gas the Answer for Diesel Emissions?

Tighten the fuel economy standards, and diesels begin to appear in future product plans.

Tighten the fuel economy standards, and diesels begin to appear in future product plans. Tighten the emissions standards for those same engines, and alterations are made that compromise their performance and fuel economy or add complex add-on emissions systems. What if you could create on-board the vehicle a combination of hydrogen and carbon monoxide—also known as “syngas”—that could be used to restore the fuel economy and performance, simplify the aftertreatment systems, and do things like provide the fuel to run a solid-oxide fuel cell APU, stabilize Homogenous Charge Compression Ignition (HCCI) combustion, and regenerate diesel particulate filters more precisely? Though it sounds too good to be true, NxtGen (Burnaby BC, Canada; www.nxtgen.com) says each of these claims is possible to reach with a simple, scalable unit that is mounted on the vehicle near the aftertreatment systems.

“We create the syngas from a combination of diesel fuel and exhaust gas in a non-catalytic generator that is both robust and has an adequate response time for an automotive application,” says Jeremy Holt, president and CEO of NxtGen. Currently, diesel particulate filters are regenerated by injecting raw diesel fuel into the filter to increase the temperatures in the filter and initiate regeneration. However, regeneration at light loads and low temperatures is a problem as the duty cycle under these conditions cannot create the heat necessary to clean the filter. “By using syngas,” says Holt, “we have much more precise control over the regeneration event, and can use it to desulfate the lean NOx trap, as well.” Doing the regeneration such that it cleans a quarter of the particulate filter at a time, he adds, would allow the syngas generator to be smaller, keep the regeneration event cooler, and allow the engine control unit to run with narrower parameters due to the more consistent backpressure.

In addition, the syngas generator can be used with selective catalyst reduction to avoid the use of urea and the weight associated with its holding tank and supply piping. “We envision decoupling the engine operation further from the aftertreatment system so you don’t have to change how the engine is running in order to look after the aftertreatment system’s needs,” he says. As a result, the potential exists to reduce the price of a diesel program while increasing its emissions performance and economy, “to make diesel engines a global powertrain option for an OEM that might otherwise use diesels in Europe and hybrids in North America,” says Holt. The company plans to open an administration and manufacturing facility in Wixom, MI, within the next two years.—CAS