A University of Wisconsin–Madison engineer is collaborating with a Wisconsin entrepreneur to produce a diesel engine that could be a quieter, more efficient power source for a variety of household and industrial applications, including lawn equipment and electric generators.

The pair has just received a $850,000 grant to fabricate and test a prototype engine, bringing it that much closer to commercialization.

The engine, a modified external combustion design by Brookfield, Wis., entrepreneur Gerald Kashmerick of Kashmerick Engines LLC, uses external combustion, burning fuel in a high-pressure chamber outside of the piston cylinder. As an external combustion engine, it can be powered by a wide range of liquid and gaseous fuels, and customers could change which fuel they use with a simple turn of a valve. The engine, called the “K6,” also uses six strokes instead of four to reduce the pressure of exhaust gases, which allows it to harvest more energy rather than expelling it with the gas.

“If you expand all of the combustion products from the air in the compression stroke at once, as in a typical engine, you end up with a pretty high pressure at the end of the stroke. So when you open the exhaust valve to dump expanded gas out to the environment, you lose all of that energy stored in the high-pressure exhaust gases and you create a lot of noise,” says Timothy Shedd, a UW–Madison associate professor of mechanical engineering.

But slowly decompressing the gases would waste less of that energy and make for a much quieter engine. “Just a shush-shush-shush instead of a bang-bang-bang,” Shedd says. “No muffler should be needed.”