DigitalAir™ Camless FVVA System - Application to Gasoline Engines

Paper #:
  • 2018-01-0889

  • 2018-04-03
DigitalAir™ Camless FVVA System - Application to Gasoline Engines 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 events, closing events and duration without the use of a camshaft, and without the use of hydraulics and pneumatics. This approach 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. 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 and 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. The DigitalAir FVVA concept simplifies valve actuation compared with current cam phasing and VVT solutions, which allows engine height and length to be reduced. Analytical and experimental results will be presented showing that DigitalAir can meet the performance requirements of modern gasoline engines with respect to breathing characteristics across the speed range, unthrottled operation at and above idle, opening and closing event optimization, cylinder deactivation, control of residual gas fraction / scavenging and exhaust thermal management. CFD analysis was used to better understand the opportunities for in-cylinder charge motion – tumble, swirl and turbulence and to study flame propagation, knock tolerance, quenching and hydrocarbon emissions. DigitalAir engines have been in development for several years and have successfully completed performance and durability tests, the results of which will be included in this paper.
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