Researchers Tout Dual-Fuel Combustion Technology

Scientists from the University of Wisconsin-Madison’s Engine Research Center are developing a reactivity-controlled compression ignition (RCCI) system they claim is more efficient and cleaner than traditional combustion engines.

The team, which is led by Rolf Reitz, recently demonstrated the dual-fuel technology in a modified two-stroke engine. They detail their work in the latest issue of the Journal of Automobile Engineering.

Described as a variant of homogeneous charge compression ignition systems, RCCI uses in-cylinder fuel blending with at least two fuels of different reactivity and multiple injections to optimize combustion phasing, duration and magnitude. Unlike other advanced combustion systems, the researchers say, RCCI can be tailored to engine speed and load to allow stable low-temperature combustion over a broad drive cycle.

The two-stroke outboard engine was adapted to accommodate two direct fuel injectors for RCCI combustion in one cylinder. The other cylinder maintained a conventional direct-injection spark ignition combustion system, which provided a direct comparison.

Several mixtures were evaluated. The most successful was a combination of gasoline and n-heptane (a highly volatile test fuel), which the researchers say showed significant benefits at 1,200 rpm and 1,500 rpm.

Initial tests with gasoline and diesel as the two RCCI fuels resulted in unstable combustion and rapid accumulation of particulate matter in the emissions-sampling equipment. But the researchers are confident further work will enable the use of a standard diesel fuel instead of n-heptane.