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This paper focuses on the preliminary design of a proportional solenoid aimed at controlling the low pressure stage of a two stage pressure regulator for CNG applications. In particular, the dynamic performance of a two stage pressure regulator is firstly studied in the whole operational field of a four stroke, four cylinder spark ignition engine, equipped with a simplified low-pressure Common Rail type collector serving four PWM actuated single stage injectors. Then, with the aim of developing an electro-magnetic direct actuation, the dynamic performance of the second stage needle is adopted to drive the design of a spires type, cylindrical coil proportional solenoid. In particular, both the steady and the transients steps needed to complete the preliminary design are highlighted, and the influence of some relevant design parameters (such as the coil geometry and the air gap) on the actuation characteristics are evidenced.

The paper focuses on the mixing process of different fuels in a multi-fuel low pressure common rail injection system for a four stroke SI engine. The study is devoted to the prediction of the fuel mixture delivered by the injectors during a transient in which gasoline is being replaced by ethanol or a gasoline/ethanol blend. An integrated approach of different numerical tools is used to model the rail dynamic behavior under actual operating conditions. First, the 1D model of the injection system is constructed and the time varying conditions at the accumulator inlet and at the injectors' boundaries are assessed. The second step of the study is centered on the CFD analysis of the mixing process within the rail. The effects of the different engine operations on the fuels mixing are investigated and the injected fuel distribution among the cylinders is calculated. An open source computational fluid dynamics code is used in the simulations.

This paper studies the dependency of the total efficiency of a multiple actuation hydraulic system on the operating conditions as well as on the control strategies applicable to control valves. In particular, with respect to the parallel connection among hydraulic actuators managed by proportional control valves, a general structure of the functional relationship correlating the hydraulic power provided by the supply unit and the mechanical power exerted by actuators is proposed and used to determine the operating point and the system overall efficiency. Afterwards, the dependency of the system behavior on external load variations and on valves control is assessed, and the influence of a modification of the operating conditions on the overall efficiency is highlighted. Finally, the validity limits of some compensating corrections are determined.