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This paper describes important aspects of the development process for meeting CARB's “Ultra-Low” 3-Star emissions with engines using the new E-TEC™ direct injection system. In-house research and analysis of data from other state-of the-art engines were used to determine achievable emission levels and to set the development targets. A detailed mode-point-specific analysis of the emissions potential of the FICHT® direct injection system revealed excellent system capability in homogeneous operation and limited potential for stratified operation. Based on these results, the development work was focused on the reduction of stratified hydrocarbon emissions. Wall impingement of the fuel spray onto the piston surface was identified as a major source of hydrocarbon emissions during stratified operation. A zero-dimensional simulation of various parameters affecting wall impingement indicates that droplet size, in-cylinder temperature, and penetration velocity are the three major factors.

In recent years, it has been demonstrated that E-TEC direct injected two-stroke engines are capable of meeting the toughest emissions standards for marine outboard engines. Proper in-cylinder mixture distribution and preparation are essential for achieving low emissions, high performance, and good run-quality. The mixture distribution is driven largely by the momentum exchange between the fuel spray and the scavenging flow. It has been found that different engines can exhibit significantly different behaviors with similar fuel sprays. This difference is attributed to the difference in scavenging flow patterns and its effect on the momentum balance between the fuel spray and the air flow. In order to investigate this phenomenon, a test fixture was designed and built to evaluate fuel sprays into air-counter-flows with velocities of up to 40m/s by recording spray images and measuring spray penetration. Two different sprays were tested in the fixture and in a variety of engines.

This study investigates the performance of a rope start two-stroke outboard engine, capable of running on multi-fuel, primarily focusing on JP5/8. This engine would be predominantly used worldwide by all departments of the US Military and Special Forces. A two cylinder, direct injected, 30 HP engine was used for research with ongoing development being carried out on larger motors, ranging to 250 HP. The investigation includes the performance characteristics of JP-5/8, gasoline, diesel, kerosene, ethanol and bio-diesel as a fuel, essentially concentrating on power, torque, effects of varying compression pressures on combustion characteristics and soot deposits, detonation characteristics of different fuels, behavior in stratified and/or homogenous combustion and cold start of the engine at temperatures of 0° F.