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Past experiences showed that the retainer life varied across different types of pressure regulators - even when the retainer designs and materials remained the same. The objective of this work was to identify the root causes behind this phenomenon and to improve the retainer life. Both analytical and experimental approaches were employed. For the analytic approach, a CAE tool (the SABER code) was used to simulate the system dynamics of the pressure regulator components (as main spring, valve body, valve ball, retainer, and valve spring) under repetitive pressure surges caused by fuel injection. The predicted relative motions were used to characterize impacts between the valve ball and the retainer, and then to estimate the retainer life through a simplified fatigue model. Effects of nine parameters on pressure regulator's dynamic performance were studied.

FuelNet is a generic computer code that predicts the flow transient processes in the fuel delivery systems. FuelNet uses the bond graph modeling technique to match the input and output boundary, and the modal approximation to simulate wave dynamics in the fuel lines. It also contains modules for fuel delivery components and engine operating conditions. This work is an application of FuelNet on the injector noise, the fuel rail fuel pressure pulsation, and the injector maldistribution at various operating conditions, such as the temperature, the fuel line material, the engine speed, and the injector pulse width. The effects of pulse dampers are also studied. Models for effective bulk modulus and modal number are developed to address the effect of fuel line materials and dimensions. The predicted liquid fuel pressure is applied to the acoustic model to estimate the injector noise, i.e., the air pressure inside the passenger compartment.

FuelNet is a generic computer code to predict flow transient dynamics in the fuel delivery systems. It employs modal approximation to simulate wave dynamics in fuel lines. This modal approximation provides the accuracy comparable to the quasi-method of characteristics, which is one step more accurate than the standard method of characteristics. The bond graph approach is used to ensure the whole fuel delivery system is properly connected and the input/output causalities are matched at the junctions and interfaces. All the ordinary differential equations are integrated in the time-domain by the Runge-Kutta method to obtain the pressure and the flow rate. FuelNet takes into account the hydraulic effects of the fuel injector, the pressure regulator, the fuel pump, and the pulse damper, as well as the operating conditions such as the engine speed, the injector pulse width, the injector firing strategy and sequence, and the PID controls.