Simple system may curb auto emissions

By the middle of this decade, some cars and trucks may carry their own oil refinery as standard equipment. Although the miniature distillery won’t realize science fiction’s dream of converting garbage into gasoline, it may provide a way to significantly reduce the hydrocarbon emissions in exhaust from internal combustion engines.

Gasoline is a mixture of liquid hydrocarbons that have a variety of boiling points. Only the most volatile components of gasoline vaporize and burn when a cold engine first turns over, says Ronald D. Matthews, a mechanical engineer at the University of Texas in Austin and a codeveloper of the new system. The rest of the fuel forms a puddle in the engine’s intake manifold and then, as the engine warms, gradually evaporates and goes out the exhaust pipe.

Up to 80 percent of the unburned hydrocarbons emitted during a typical 30-minute drive is generated during the first 2 minutes of engine warm-up, Matthews notes. The researchers’ new system could eliminate almost half of these emissions, he estimates.

Here’s how it works: While the engine runs warm, the onboard distillery collects the most highly volatile portions of the gasoline, which vaporize at an intermediate temperature. The system condenses them and routes them into a small tank under the hood. On future cold starts, the engine pulls its fuel only from this reservoir of easy-to-evaporate components. Over the next few minutes, the fuel system shifts to pull gasoline from the main fuel tank. This technique provides the benefits of using two fuels without the hassle of filling two tanks at the gas pump, Matthews notes.

Besides the 1-gallon reservoir, which will hold enough fuel for two cold starts, the relatively unobtrusive system will require only two fuel switches and one small distillation device. “Most people looking under the hood wouldn’t recognize anything different,” says Matthews.

The system will add less than 5 pounds to the engine and be relatively inexpensive, Matthews claims. He says his team bought the four components in the prototype system for about $400 retail, but costs for a production version of the onboard refinery could drop to around $60.

Matthews and his colleagues plan next to install the emissions-trimming equipment on a 2001 Lincoln Navigator. During laboratory tests of the vehicle over an 18-month period, the researchers will refine the device’s performance and evaluate the cost-effectiveness of the system. It could be ready for vehicles rolling off the production line in 3 to 4 years, Matthews says.

By using catalytic converters and other equipment, automobile manufacturers have made great strides in reducing emissions of unburned hydrocarbons, says Donald E. Zinger, assistant director of the Environmental Protection Agency’s Office of Transportation and Air Quality in Washington, D.C. Cutting those emissions even further will help automakers meet the agency’s tougher tailpipe standards scheduled to be phased in beginning in 2004, he adds.

“Anything [automakers] can do to cut cold-start emissions is going to be helpful,” he notes.

More Stories from Science News on Tech