This presentation was made at the NAFEMS Americas "Creating the Next Generation Vehicle" held on the 14th of November in Troy.

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process.

The automotive engineering community is now confronting the largest technology transformation since its inception. This includes the electrification of powertrains for more efficient consumption and cleaner emissions, the reinvention of the battery with fast wireless charging capabilities and finally the advent of a fully autonomous vehicle. Compounding to these technology changes, the automotive companies design verification process is moving away from a major reliance on physical testing to almost a full virtual simulation product verification process.

Resource Abstract

As part of validation testing of GDI fuel systems, several specific system tests are conducted. It is desirable to conduct these tests virtually with 1D system models prior to actually producing prototypes in order to speed up product development cycle times. This process is called Analysis Led Design. One of the most harsh system tests is the "Dead Head" test, where the maximum fuel pump delivery is modelled attached to a static volume called the fuel rail. This test is used to test the dynamic response of the pressure relief valve (PRV) of the fuel system.



Previous simulation results of the PRV did not correlate well with test data, and showed a significantly higher system pressure. In this paper, a new pressure relief valve 1D model is described. The new PRV model takes into account various forces acting on the PRV, namely flow forces due to the valve motion. During operation, the PRV valve will open, and jet forces acting on the valve tend to increase valve lift. If the jet forces are not accounted for, accurate prediction of lift is not possible. In addition to dynamic flow forces, the thermo-physical properties of the fuel must be accounted for accurately during the test. During the pumping event of the dead head test, the fuel that is pumped to the fuel rail stays in the rail, and spills back to the pumping chamber as soon as the PRV is activated. As a result, this volume of fluid heats up, and impregnates by significant volume of fuel in the vapour phase, and the fuel compressibility (bulk modulus) changes. As the dead head process is initiated, the first two or three pumping events increase rail pressure, and then, during the charging event, the PRV starts to spill extra fuel back to the plunger chamber. The subsequent pumping events push through the discharge valve and spill through the PRV with the same fuel quantity. As a result, the fuel temperature increases greatly, and the fuel becomes saturated with vapour, which does not have enough time to dissolve. The fuel maximum bulk modulus is reduced, which leads to the reduction of the pumping fuel. As a result, the balance between pumping volume and spilling volume could be reached at a lower pressure.



In this paper, the test system and protocol under consideration will be described. The original 1D model of the test system will be described. Initial comparison between test results and simulation will be presented. A new system model, with new PRV model will be described and presented. Results from auxiliary CFD models will be presented to account for dynamic flow forces on the PRV. Simulation results of the new PRV 1D model will be presented and compared to test results.