Common rail diesel engine, fuel pressure control scheme and the use of speed - density control

Abstract

Diesel engines in both the automotive and industrial sectors are nowadays electronically controlled. Electronic control provides accurate real time processing of the relevant sensory data on which fuelling is determined. Fuel economy as well as emissions are very dependent on the diesel fuel quantity, timing and injection pressure, which in turn determines the shape of the injection rate diagram, the spray distribution and the fuel droplet size. NOx is also known to be very dependent on flame temperature which can be controlled by the quantity of Exhaust Gas Recirculation (EGR). Research on the real time control of a common rail diesel engine was undertaken at the University of Malta. A Peugeot 2.0HDi common rail engine was controlled with a custom made electronic Engine Control Unit (ECU). A control strategy for the diesel rail pressure was developed that is based on simple 2D look up tables rather than more complex 3D maps. This allowed the ECU Graphical User Interface (GUI) and ECU firmware to be very similar to the gasoline (petrol) version of the ECU. The successfully developed fuel rail pressure scheme based on RPM, Mass Air Flow and Torque Requirement is given in this paper. Furthermore the values found experimentally for the speed-density control of the engines are also given. Top Dead Center (TDC) determination based on incylinder pressure measurements was conducted to better calculate the Start of Injection (SOI) and Indicated Mean effective Pressure (IMEP).