Diesel engines are more efficient than internal combustion engines, but they do serious damage to the environment. Researchers at Penn State are trying to reduce the harmful emission in diesel engines by using dimethyl ether (DME) instead of diesel fuel.

DME is formed by the dehydration of methanol, but it can be made from natural gas as well.

At room temperature, DME exists as a gas. It has to be pressurized in the engine to turn into its liquid form. When the engine is not in use, however, the DME transforms back into a gas. Research is being done to keep DME as a liquid inside the engine.

The difference between an internal combustion engine used in a conventional car and a diesel engine is that combustion engines ignite the fuel with a spark plug, while diesels ignite the fuel with the high temperatures in its combustion chamber.

There is a difference between the fuels as well. Jennifer Stefanik (graduate-fuel science) said, "Generally conventionally gasoline is refined more than diesel."

Penn State recently purchased a shuttle bus for its research to conduct live experiments, which should take place around November.

The engines being used for the experiments are modified diesel engines. The engine is a diesel, but it has an attachment, which allows it to process DME.

"This is to learn how to manage the challenge of DME. This is a baby step to learn (about) DME," said Andre Boehman, associate professor of fuel science.

The byproducts of diesel fuel are quite harmful, when they are released into the atmosphere.

"Soot, black smoke, particulate matter — they are high emissions of nitrogen oxides that can't be controlled with current emissions technology," Boehman said. "What we're after is reducing those emissions."

Nitrogen oxides produce acid rain when it is mixed with sulfur dioxide. That mixture can destroy forests, buildings and pollute the environment.

DME does not produce soot and smoke and emits a reduced amount of nitrogen oxides. "DME is the ultimate diesel fuel if we can manage it," Boehman said.

One problem with pure DME is its poor lubricating quality. "You would like a lubricating layer between the metals," Boehman said. "We need to find additive or package of additives to solve this problem simultaneously."

If the metals in the engine are constantly rubbing together, the life expectancy of the car will not be too long.

Elana Chapman (graduate-fuel science) said, "We're mixing DME with diesel fuel to promote lubricating qualities to the DME."

Other scientists are adding lubricants such as castor oil to DME to increase its lubricating quality, but that would require a new fuel injection system.

"We can adjust the blend to have sufficient lubrication. The question is how. We want to maximize the utility of DME," Boehman said.

Researchers also are trying to improve the viscosity of DME. It does not have enough consistency in its pure state, which can cause it to clog instruments in the engine.

Though there are difficulties, Boehman has a strong faith in diesel power. "The question is — can we produce high efficiency (fuel) with negligible environmental impact?"