Advanced Modelling of a New Diesel Fast Solenoid Injector and Comparison with Experiments

Upcoming Euro 4 and Euro 5 emission standards are increasing efforts on injection system developments in order to improve mixture quality and combustion efficiency. The target features of advanced injection systems are related to their capability of operating multiple injection with a precise control of the amount of injected fuel, low cycle-by-cycle variability and life drift, within flexible strategies. In order to accomplish this task, injector performance must be optimised by acting on: optimisation of electronic, driving circuit, detailed investigation of different nozzle hole diameter configurations, assessment of the influence of manufacturing errors on hole diameter and inlet rounding on injector performance.

The paper will focus on the use of an integrated lump-1D/3D methodology for the design of advanced new fast solenoid Common Rail (C.R.) injector for high speed diesel engines. A lump-model built up in AMESim^® environment was used to address the injector design. Particular attention has been devoted in the simulation of the electromagnetic circuit. The functional relation between current and electromagnetic force at different air-gap values, as well as of fluid dynamics parameters was obtained by running an axial-symmetric model built into a finite-element code. Sub-models were introduced in order to account for the contribution of squish motion and actual fluid-dynamics force acting upward on needle surfaces. Multidimensional CFD simulations were extensively used in order to feed the model with the discharge coefficient of the orifices as a function of flow regimes and geometrical details.

Preliminary experimental results in terms of instantaneous flow rate and integrated injected volume for different operating conditions will be presented in order to validate the modelling methodology and to highlight new injector performance.