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The paper describes a completely new approach to fully variable valve actuation (FVVA), which allows almost unlimited continuously variable control of intake and exhaust valve opening and closing events, and duration without the use of a camshaft. DigitalAir replaces conventional poppet valves with horizontally actuated valves located directly above the combustion deck of the cylinder head, which open and close a number of slots connecting the cylinder with the intake and exhaust ports, Figure 1. The stroke of the valves to provide the full flow area is approximately 25% of the stroke of the equivalent poppet valve, thus allowing direct electrical actuation with very low power consumption. This design arrangement also avoids the risk of poppet valve to piston collision, or the need for cut-outs in the piston crown, since the valves do not open into the cylinder.

Continually increasing the maximum specific power output of engines used in military vehicles is vital to maintaining a battlefield advantage. An enabling technology for power optimization on existing engine architectures is advanced engine control based on real-time feedback control of the combustion. An engine equipped with intelligent controls and multi-fuel capable components has been used to demonstrate power improvements based on feedback control of the fueling by means of in-cylinder pressure measurements. In addition to optimized power output for the engine, the technology suite provides the capability to utilize both standard diesel fuel and alternatives such as jet fuel, biodiesel, or any mixture. A cylinder-balancing algorithm adjusts the fueling to achieve even power distribution between cylinders for improved performance and durability, or to operate all cylinders at the cylinder pressure limit when maximum power is required.

This paper provides an overview of the analysis and design of the DigitalAir™ camless valve train including the architecture and design of the valve and head; the details of the electric valve actuator, and the flow characteristics of the valves and resulting charge motion in a motoring engine. This valve train is a completely new approach to fully variable valve actuation (FVVA), which allows almost unlimited continuously variable control of intake and exhaust valve timing and duration without the use of a camshaft. This valve train replaces conventional poppet valves with horizontally actuated valves located above the combustion deck. As the valves move, they open and close a number of slots connecting the cylinder with the intake and exhaust ports. The valve stroke necessary to provide the full flow area is approximately 25% of the stroke of the equivalent poppet valve, thus allowing direct electrical actuation with very low power consumption.