Investigation of different valve geometries and valve timing strategies and their effect on regenerative efficiency for a pneumatic hybrid with variable valve actuation. In SAE Technical Paper Series Society of Automotive Engineers.
Urban traffic involves frequent acceleration and deceleration. During deceleration, the energy previously used to accelerate the vehicle is mainly wasted on heat generated by the friction brakes. If this energy that is wasted in traditional IC engines could be saved, the fuel economy would improve. One solution to this is a pneumatic hybrid using variable valve timing to compress air during deceleration and expand air during acceleration. The compressed air can also be utilized to supercharge the engine in order to get higher load in the first few cycles when accelerating.
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ABSTRACTA control system for pneumatic variable valve actuation has been designed, implemented and tested in a single cylinder test engine with valve actuators provided by Cargine Engineering AB. The design goal for the valve control system was to achieve valve lifts between 2 and 12 mm over an engine speed interval of 300 to 2500 rpm. The control system was developed using LabView and implemented on the PCI 7831. The design goals were fulfilled with some limitations. Due to physical limitations in the actuators, stable operation with valve lifts below 2.6 mm were not possible. During the engine testing the valve lift was limited to 7 mm to guarantee piston clearance. Different valve strategies for residual gas HCCI combustion were generated on a singlecylinder test engine.
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