Spool Valve With Arbitrary Area-Schedule and Application to a Camless Engine Valve Actuator

This paper presents the design of a flow control valve in which the area-schedule i.e., the relationship between the spool position and the metering orifice area, can be chosen arbitrarily. The motivation for such a flow controller comes from a novel hydraulic actuator intended for camless valve actuation in internal combustion engines. The proposed actuator has a unique internal feedback system in which the motion of the flow regulator’s spool is hydro-mechanically coupled to the motion of the actuator. Lack of direct control over the spool position necessitates the appropriate modification of the area-schedule in order to control the variation of the orifice area. The design modifications required to realize the area-schedules are first discussed. A systematic procedure which combines CFD analysis and geometry based analysis is then developed to characterize the variation of the effective orifice area for various spool designs. The proposed analysis procedure is validated with experimental data from a prototype spool valve. The fast turn around time of the proposed analysis technique is used to develop an automated procedure to design the 3D features on the spool required to realize a specified area-schedule.