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Journal Article

DigitalAir™ Camless FVVA System – Part 1, Valve Train Design, Capability and Performance

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.
Technical Paper

Design and Analysis of a Self-Refueling CNG Vehicle to Provide Home Refueling

Home refueling systems for natural gas vehicles are commercially available but suffer from long refilling times and high system costs. A novel concept of selectively repurposing one cylinder of a compressed natural gas (CNG) engine to be used as a compressor would allow a CNG vehicle to refuel itself quickly and with low capital cost. Using funding from the DOE through the ARPA-E program, such a vehicle is being designed and built by Oregon State University with the help of Czero, Inc. This paper outlines some of the early design, analysis and simulation work done to prove the concept and arrive at a first prototype design. Some of the unique challenges associated with the concept are discussed and the solutions to them are presented. An accompanying paper will present test results for the system.
Technical Paper

Design and Control of a Two-stage Electro-hydraulic Valve Actuation System

This paper discusses the design and control of a two-stage electro-hydraulic camless Variable Valve Actuation (VVA) system designed for gasoline engines that encompass a wide rpm range. The VVA portion of each engine valve assembly in the system consists of two miniature pilot valves, a proportional valve, a compound engine valve actuator and an engine valve return mechanism. The design and proper control of these devices allow for variable valve timing, lift, duration, seating velocity and flank velocity. This flexibility enables an array of combustion strategies. Many of these strategies (such as Miller cycle operation, cylinder and valve deactivation, etc.) have been tested on fired engines that have been redesigned to incorporate the VVA system. Test results for both bench and fired engines running in a dynamometer cell are presented. These results indicate the current level of controllability of the system and the power consumed by the system in a variety of test conditions.