Modeling and Analysis of the Low Pressure Fuel System for a Direct Injection Diesel Engine 2005-01-3854

The low-pressure side of the fuel system of a car plays an important role to ensure the performances of the engine, both for pressure drops and thermal phenomena. This is particularly true for modern common-rail diesel engines. An one-dimensional model of the low pressure section of the system has been built up accounting for the feed and return lines (including pipes, bends and pipe-fitting), diesel filter and by-pass valve. The high-pressure side has been modeled in a very essential way considering only high-pressure pump volume and leakage, and engine fuel consumption, because its only purpose is to close the circuit and allow thermal evaluations.

The model has been tested in both steady and unsteady conditions. In the first case the main results are the pressure drops of the main fuel segments; in the second case, also transient fuel temperature rise is simulated, due to the compression in the common-rail pump. A significant part of the work is the modeling of the Jet-Pump, that is part of the low pressure fuel pump inside the tank, whose behavior, in terms of pressure loss and flow suction from the tank, is difficult to model in a 1D approach. It has been modeled using a 3D CFD code; then the results have been used to build and calibrate an equivalent 1D model that could simulate both the pressure drops and the fuel mixing, that has been finally added to the complete model.

Early experimental validation has been positive.