A little voltage can jolt existing cars into getting better gas mileage, new research shows.

Applying a strong electric field to fuel a moment before it’s injected into the engine’s cylinders boosted fuel efficiency of a Mercedes-Benz 300D from 32 to 38 miles per gallon during six months of road tests — an increase of more than 18 percent, scientists report in the Nov. 19 Energy & Fuels.

Other researchers say that the increase in fuel efficiency would probably be smaller in real-world scenarios, but they agree that the technology could raise a car’s gas mileage by 5 to 10 percent. If applied to all the cars and trucks in the United States, that fuel savings would add up to more than 300 million barrels of gasoline and about 150 million barrels of diesel per year.

The new technique works by making the fuel about 10 percent thinner — more like water and less like molasses — so that the liquid breaks up into smaller droplets when it’s sprayed into the combustion chamber.

“Making the droplets smaller has been a goal for a while,” says Rongjia Tao, a physicist at Temple University in Philadelphia who led the research. “Of course they didn’t consider using an electric field, they talked about using very high pressure.”

The small field-generating device, which currently costs about $50 per cylinder and could be retrofitted to existing car engines, applies 1,000 volts per millimeter across the fuel line as it enters the fuel injector. Despite this high voltage, the device draws less than 1 watt of power because its electrical current is tiny. This strong electric field polarizes molecules in the fuel: Each molecule develops a slightly positive electric charge at one end, while the other end becomes slightly negative. These electric charges cause the molecules to clump together, reducing the molecules’ overall surface area. Less surface area means less friction, which is what gives a fluid its thickness, or viscosity. By lessening friction, the device makes the fuel thinner.

Thinner liquids break into smaller droplets when passing into the engine's cylinders than those in thicker fluids — just think of spraying water instead of molasses through a nozzle — and smaller droplets have more surface area. Droplets of fuel burn at their surfaces, where the fuel meets oxygen in the air, so having more surface area means the fuel will burn cleaner and more efficiently.

“I think the potential of this idea is outstanding,” comments Matthew Thomas, a combustion engineer at CFD Research Corporation, a commercial research company in Huntsville, Ala. “I think in the next five to 10 years you’re going to see the option for charged fuel injection in automobiles.”

Temple University holds a patent on the device, and Tao says he has been contacted by major automobile manufacturers seeking to license the technology.

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Found in: Matter & Energy