M.S. Thesis Presentation by Cody Watson
Friday, June 18, 1999

(Dr. Wayne J. Book, advisor)

"Modeling of Pressure Transients for Fuel Injection Lines"


In an automobile fuel injection system, the pressure fluctuations generated by the rapid opening and closing of an injector valve propagate throughout the system.  Variations in the supply pressure to an injector results in inconsistent fuel flow.  Small variations in fuel flow can produce significant reduction in engine performance, fuel efficiency, and emission purity.  Currently, the pressure transient effect is reduced by increasing the flow in the fuel rail to exceed the  amount required by the engine.  Pumping excess fuel requires larger capacity fuel system and necessitates recirculation of the excess fuel back into the reservoir, thus warming the reservoir.

There has been significant research involving the modeling of liquid filled lines.  This project uses modal approximation of the dissipative or “exact” friction model.  The software used is a high level, general purpose math program.  Using a high level language simplifies the coding and improves the portability of code.  The integrated simulation environment provides a simple, graphical, customizable user interface.  The use of a popular math package also has the advantage that extensive analysis tools are readily available.

 The purpose of this thesis is to develop a modeling technique for fuel injection systems.  The thesis will explore alternatives for combining component elements in frequency and time domain.  The ease of reconfiguration of the computer model and the ability to measure pressure and flow at many locations in the system would be useful for the design and evaluation of an active control scheme.  An improved control scheme would allow the minimization of the pressure transients' effects, and thereby improve engine performance.