Ducted fuel injection promises cleaner combustion

By Michael Langley

Click the image to watch a video with additional information about ducted fuel injection.

An engine innovation first conceived and tested by Sandia scientists has attracted the attention of big business because it synergizes with renewable fuels and takes almost all the soot out of a diesel engine’s exhaust without sacrificing performance or increasing cost.

Ducted fuel injection, developed by Chuck Mueller at Sandia’s Combustion Research Facility, is able to fine-tune the amount of diesel used in an engine to the point of eliminating between 50 and 100% of the soot.

DFI was first conceived by Chuck from — of all things — a Bunsen burner like those found in almost every high school science classroom in the nation.

“If you unscrew the tube on a Bunsen burner and you light the gas jet, you get a tall sooty orange flame,” Chuck said. “Turn off the gas, screw the tube on and re-light the burner. Now you get a nice, short blue flame right at the end of the tube. The flame is blue because there isn’t any soot.”

Chuck thought that concept might be adaptable to combustion engines, so he and his team, Christopher Nilsen, Drummond Biles and Nathan Harry, began experiments that have now resulted in an assembly of four to six small tubes, or ducts, directing fuel mixture from the injector right to the points of ignition.

Chuck said that injectors in a traditional diesel engine create local mixtures containing 3-10 times more fuel than is needed for complete combustion.

“When you have that much excess fuel at high temperature, you tend to produce a lot of soot,” he said. “Installing the ducts enables us to closely approach what we call ‘leaner lifted-flame combustion’ — diesel combustion that doesn’t form soot — because the local mixtures contain less excess fuel.”

Read the complete story about this innovation that keeps the vast majority of the soot produced by traditional diesel engines from even forming.