A new fuel injection technology for diesel engines, developed by Sandia National Laboratories, lowers harmful emissions while increasing efficiency. If it can be deployed successfully to improve just a fraction of the more than one billion engines on Earth while facilitating a transition to sustainable fuels, the whole world will benefit.  

Diesel engines have many desirable attributes, including high efficiency, fuel flexibility, and long range, for relatively low cost, but their emissions have been problematic. This is particularly true for soot and nitrogen oxides (NOx) emissions—when one is reduced, the other goes up. This is called the soot-NOx tradeoff. It’s a technical challenge that has been at the heart of diesel-engine development efforts since the first diesel emissions regulations came into force in the mid-1980s. 

Minimizing the amount of soot and NOx produced by diesel engines is critical because both emissions are toxic, soot is second in importance only to carbon dioxide as a climate-forcing substance, and the prevailing approaches to clean up these pollutants are costly and cumbersome.   

To meet emissions regulations worldwide, modern diesel engines use aftertreatment systems (analogous to catalytic converters on spark-ignition engines, but significantly more expensive). These contain platinum-group metals, require an additional fluid (diesel exhaust fluid), are large, heavy, demand management and maintenance, and/or penalize engine efficiency.  

Ducted Fuel Injection (DFI) is a patented technology invented at Sandia National Laboratories’ Combustion Research Facility that enhances engine combustion, enabling simultaneously lower soot and NOx emissions while potentially increasing efficiency. The innovation enables soot emissions to be dramatically lowered so that cost-effective exhaust-gas recirculation (EGR, i.e., feeding some of the exhaust gases back into the engine air inlet) can be applied to curtail NOx emissions. In this way, DFI can eliminate 50% to 100% of the soot and NOx produced by a diesel engine. 

It’s a simple mechanical solution that involves installing some tubes inside of a diesel engine’s combustion chamber. Passing each fuel spray through a tube enhances mixing to create combustion that produces less soot than when fuel is sprayed unconfined into a chamber.  

Any diesel engine—whether in a car, truck, ship, train, machine, or generator—can benefit from DFI. It can also be used to retrofit large-bore and expensive engines like those in ships and trains that are not replaced often. This is a cost-effective way to lower emissions on these large engines used in transportation industries where emissions are increasingly regulated.  

Because DFI is compatible with existing fuels, it can be retrofitted onto existing engines, enabling immediate environmental benefits. In addition, because of its synergies with renewable, oxygenated fuels produced in the U.S., DFI can help overcome the daunting future challenges of energy security and global climate change. Lowering petroleum consumption benefits the economy and the environment as net carbon dioxide emissions are lowered.  

While DFI is currently being evaluated as a technology for heavy- and medium-duty diesel engines, in the future this technology also could be applied to gasoline, natural gas, and jet engines. 

The Sandia DFI team is currently seeking commercial partners with whom to further develop the technology.