Charles D. Wood

Increased mixing rate using an energy cell in a two-stroke, spark-assisted DI diesel engine

A unique combustion system using an energy cell was designed during the course of this two-stroke, spark-assisted DI diesel engine development program. The system generated high gas turbulence and significantly increased fuel-air mixing rate during combustion. Using the spark-assisted diesel engine concept, this system allowed modification of a production, loop-scavenged, two-stroke gasoline engine to increase fuel tolerance, decrease fuel consumption to levels close to diesel engines, and produce a power-to-weight ratio comparable to a gasoline engine. The experimental engine was constructed and developed by Southwest Research Institute and the project was funded by Sanshin Industries. This paper summarizes the results of the project.

An Unthrottled Gaseous Fuel Conversion of a 2-Stroke Diesel Engine

The feasibility of converting a conventional unthrottled 2-stroke diesel engine to gaseous fuel was investigated. The development work was performed in two phases. In phase 1 the conversion concepts were built and tested on a single-cylinder engine. In phase 2 one of these was put into effect in a 6-cyl (DDA 6V-71) engine. The design concept with the most promise includes a divided combustion chamber utilizing a gas inlet valve in each chamber and a spark plug ignition source located in the prechamber. The concept has the potential of reducing the exhaust emissions well below the levels new existing in commercial diesels without exhaust smoke and odor and with equivalent fuel consumption and horsepower, as demonstrated in the single-cylinder conversion.

Research Needs for Diesel Engines

Combustion of highly non-homogeneous fuel-air mixtures and the use of hydrodynamic lubrication of piston rings are identified as barriers to long-term progress in diesel engines. The characteristics of non-homogeneous mixtures are discussed and the effects of various injection system modifications are illustrated using a turbulent fuel jet model. The problems caused by the hydrodynamic oil film at the piston rings are identified, and the potential of boundary lubrication is discussed