The Preliminary Design of a Direct Actuation for CNG Pressure Regulator Low-Pressure Stage Control

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. Finally, the proportional solenoid is introduced into a standard electro-magnetic control circuit, and its driving capabilities, its dynamic performance and its limit of applications are determined for different actual operating conditions of the second stage needle.