1D Modeling of the Outwardly Opening Direct Injection for Internal Combustion Engines Operating with Gaseous and Liquid Fuels 2021-24-0006

The in-cylinder direct injection of fuels can be a further step towards cleaner and more efficient internal combustion engines. However, the injector design and its characterization, both experimental and from numerical simulation require accurate diagnostics and efficient models.

This work aims to simulate the complex behavior of the gaseous and liquid jets through an outwardly opening injector characterized by optical diagnostics using a one-dimensional model without using three dimensional models. The behavior of the jet from an outwardly opening injector changes according to the type of fuel. In the case of the gas, the experimental investigations put in evidence three main jet regions: 1) near-field region where the jet shows a complex gas-dynamic structure; 2) transition region characterized by intense mixing; 3) far-field region characterized by a fully developed subsonic turbulent jet. In the case of the liquid fuel, the behavior of the jet is characterized by a uniform hollow cone that retains its shape from the first instants of the start of injection.

The one-dimensional model solves mass, momentum, and energy transport equations along the jet. Then, it is particularized for the case of both gaseous and liquid jets, giving appropriate initial and boundary conditions. For gas jets, the boundary condition is built using the experimental data with pressure injection ranging from 10 to 16 bars. To validate the one-dimensional model, the behavior of the gas jet for injection pressures from 18 to 22 bars has been simulated. The numerical results are in good agreement with the experimental data obtained by optical diagnostics.

From a practical point of view, this one-dimensional model allows to get a simple and rough idea of what the behavior of a jet might be when the injection parameters change. A strong reduction of computational costs and time is observed.