Modeling of Advanced High-Pressure Fuel Injection Systems for Passenger Car Diesel Engines 1999-01-0910
A one-dimensional, transient and compressible flow model was used in order to simulate the flow and pressure distribution in advanced high-pressure fuel injection systems; these include electronic distributor-type pumps with either axial or radial plungers and a common-rail system. Experimental data for the line pressure, needle lift, injection rate and total fuel injection quantity obtained over a wide range of operating conditions (from idle to high speed/full load) were used to validate the model. The FIE system used for validation comprised an electronic high-pressure pump connected to two-stage injectors of different type including 6-hole vertical and 5-hole inclined conical-sac and VCO nozzles.
Following successful validation of the model, a number of important parameters that cannot be easily obtained from experiments, such as the actual injection pressure at the nozzle tip, the effective hole area at the hole exit due to the presence of hole cavitation, the fuel injection temperature, as well as the hole-to-hole variability of inclined nozzles, were predicted for three high pressure fuel injection systems connected to different nozzle types and including a distributor-type pump with both axial and radial plungers and a common-rail system. From this analysis, it has become clear that all important nozzle exit conditions for the control of the subsequent spray development are strongly dependent on the detailed geometric and operating characteristics of the injection system and can be provided by computer models which are becoming valuable tools in understanding the operation of emerging highly sophisticated fuel injection systems, allowing better matching between the spray characteristics and the in-cylinder flow and thermodynamic conditions.