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This paper addresses the design and detailed modeling of a novel electronically controlled, pneumatic/hydraulic valve actuator (EPVA) for both the engine intake and engine exhaust valves. The valve actuator's main function is to provide variable valve timing and variable lift in an automotive engine. The design of the combination of pneumatic and hydraulic mechanisms allows the system to operate under low pressure with an energy saving mode. A system dynamics analysis is provided and is followed by a mathematical model. This modeling approach uses the Newton's law, mass conservation and thermodynamic principles. The air compressibility and liquid compressibility in the hydraulic latch are modeled. The discontinuous nonlinearity of the compressible flow due to choking is carefully considered. Provision is made for the nonlinear motion of the mechanical components due to the physical constraints.

The focus of this research effort was to develop a technique to measure the cyclic variability of the mass injected by fuel injectors. Successful implementation of the measurement technique introduced in this paper can be used to evaluate injectors and improve their designs. More consistent and precise fuel injectors have the potential to improve fuel efficiency, engine performance, and reduce emissions. The experiments for this study were conducted at the Michigan State University Automotive Research Experiment Station. The setup consists of a fuel supply vessel pressurized by compressed nitrogen, a Dantec laser Doppler anemometry (LDA) system to measure the centerline velocity of fuel, a quartz tube for optical access, and a Cosworth IC 5460 to control the injector. The detector on the LDA system is capable of resolving Doppler bursts as short as 6μs, depending on the level of seeding, thus giving a detailed time/velocity profile.