By Staff

(AXcess News) New York - Researchers from Cummings and Purdue University claim to have found a way to improve fuel efficiency in diesel engines that run on biodiesel fuel while cutting emission levels.  The process involves an advanced "closed-loop control" approach for preventing diesel engines from emitting greater amounts of smog-causing nitrogen oxides when running on biodiesel fuels.

News of the development was published in late January by the Purdue University News Service which states that the technique developed allows for modification of existing diesel engines.

Blends of ordinary diesel and biodiesel fuel are proven to reduce the emission of particulate matter, but the level of nitrogen oxides can be as high as 40 percent, depending on the blend, with fuel efficiency reduced by as much as 20 percent.  That makes blended diesel and biodiesel fuels less economical.  The challenge to Cummins, Inc., was in finding a way to improve both fuel efficiency and reduced levels soot.

Gregory Shaver, an assistant professor of mechanical engineering and a member of Purdue's Energy Center in Discovery Park, explained in the Purdue News Service story that higher oxygen levels found in burning biodiesel fuel was the major contributor to higher levels of nitrogin oxides.

Researchers at Purdue's Ray W. Herrick Laboratories used a Cummins 6.7-liter, six-cylinder diesel engine for their study, which is the same power plant used in the popular Dodge Ram truck.

Sensors where used to self-adjust engine settings based on feedback, using software algorithms to determine the fuel blend being combusted. If the fuel is changed, the system identifies the new fuel and makes critical adjustments to fuel-injection timing, the air-to-fuel ratio and how much exhaust is rerouted into the cylinders.

In a plain-speak, Shaver and his research team were able to make the Dodge engine smarter, knowing when to adjust itself according to the blend of biodiesel fuel being fed into the engine.

The outcome, explained Shaver, was remarkable, though the research team still faces fuel efficiency issues over biodiesel's inherent lack of "energy density".

"We were able to improve the fuel economy with a biodiesel blend while reducing nitrogen oxides to where they were with conventional diesel," Shaver said. "At the same time, we were able to maintain the customary biodiesel reductions in particulate matter emissions compared to ordinary diesel fuel while not increasing noise emissions.

"We improved the combustion efficiency and were able to get better mileage than before," explained Shaver.   "But still not as good as conventional diesel fuel."