Conversion of a Homogeneous Charge Air-Cooled Engine for Operation on Heavy Fuels

As part of its single-fuel initiative, the US Armed Forces has a desire to operate all of their equipment on JP-8 fuel. Larger applications using diesel engines have been easy to convert, but small gasoline engine conversions have proven more difficult. This paper chronicles problems encountered, successful solutions, and lessons learned during the conversion of a carbureted 2kW Honda generator for use with JP-8 fuel. Cold-start, fuel delivery, load control, and auxiliary systems required significant adaptation. A catalytic plasma torch was used as the ignition source and similar technology was developed to support cold-starting at temperatures down to -40°C. Combustion chamber design and low octane number fuel made it necessary for multiple ignition sources. Load control and auxiliary systems were handled by a custom micro-controller that used RPM, generator output current, head temperature, and a knock sensor as inputs. A fleet of a five engines was assembled as a proof of concept to show repeatability of the conversion concept. One of these engines successfully passed 300 hours of MIL-STD endurance testing, demonstrating robustness of the conversion. Many of the challenges associated with this conversion are analogous to issues that confound engine conversion to a broad spectrum of alternative fuels. Therefore, fundamental and applied research needs for homogeneous charge, catalytically assisted compression ignition are derived from this case study.