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Natural gas is a low cost, abundant and clean burning fuel. Current internal combustion engines can be readily adapted to use natural gas fuel either in conjunction with conventional liquid fuels or as dedicated systems. Use of modern electronic controls allows consideration of new engine management strategies that are not practical or even possible with mechanical systems. The preferred approach is pre-mixed lean burn with cylinder-by-cylinder fuel injection and full time control of optimized air/fuel ratio and ignition.

A new type of diesel fuel injection uses a simple, medium-pressure, common-rail system with pressure intensifier and accumulator type unit injectors with digital electronic control to achieve high performance at low cost. The desirable features of high injection pressures with quantity and timing controlled directly by microprocessor are attained with a simple unique system. Data are presented on performance, efficiency, emissions, and relative cost. It is concluded that electronically controlled high pressure injection offers a practical and economical solution for efficient combustion in a diesel engine.

The benefits of direct cylinder fuel injection to the fuel economy and exhaust emissions of small spark ignited two-stroke engines is well known. The selection of a commercially viable fuel injection solution continues to receive evaluation and scrutiny by the engine manufacturers. This paper describes the development and demonstration of an EDFI solution which is applicable to low cost and high production volume engines in several industries. The system is based on the “accumulator” fuel injection operating principle, which involves pressurizing fuel within an injection nozzle and subsequently releasing the pressurized fuel into the combustion chamber on command. This concept provides very short injection duration throughout the dynamic operating range of the engine as well as high injection frequency capability.