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A Greener, Cleaner Two-Stroke Engine

Idaho lab reduces emissions

Published online: Oct 10, 2003 Feature
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Few people have ever characterized a two-stroke engine as a clean burning engine.

That may change if an idea developed by three researchers at the U.S. Department of Energy's Idaho National Engineering and Environmental Laboratory makes it from conception to market.

The invention is a small separator that will remove unburned oil and gas from the two-cycle engine exhaust without compromising engine performance.

The two-stroke engine is notoriously dirty. An unavoidable feature of the engine is that it requires oil mixed with gas for internal lubrication. During operation, the intake and exhaust ports are momentarily open at the same time, thereby pulling some of the intake stream containing fuel and oil to leak out into the exhaust port. This results in inefficiency and smoky exhaust emissions.

Typically 25-35 percent of the fuel that enters the two-stroke engine leaves unburned. The solution to both problems, according to INEEL researcher and lead engineer Terry Turner, is a technology that can be implemented in new vehicles and retrofitted to existing ones.

The separator will take the exhaust gas and spin it at a high rate, thereby centrifugally separating the heavy oil, fuel and particulates from the lighter gaseous combustion products. The heavy constituents will be burned in an afterburner or captured and removed for recycling or disposal in an environmentally friendly manner. Turner feels confident that a significant hydrocarbon emission reduction for standard engines, and per unit retail cost under $400, are realistic.

The uniqueness of the INEEL technology is the separator and its location. The separator is predicated on an innovative design. The separator will be located in the exhaust system, the muffler exhaust area, or a combination of both.

The separator also may reduce noise. Installing the separator inside the existing muffler or exhaust system would be equivalent to adding additional baffling.

"It's possible to build an engine with less exhaust, but it will be more expensive and, therefore, less marketable than current designs," Turner said. "Current manufacturers of two-cycle engines have begun aggressive research in cleaner engines in order to meet new EPA guidelines; however, in most cases, the simplicity of the engines is being lost, and in some applications, being replaced by lower performance, heavier four-cycle engines."

The best solution, Turner said, is a separator that can be put to use in new engines and retrofitted to existing ones.

For more information contact Jerry Wright (208) 526-9557.