Application of a re-meshing procedure for the simulation of direct injection in a natural gas piston engine

Abstract

La première étape de ce travail consistera à adapter améliorer la procédure de remaillage au cas d'un moteur avec un injecteur. Elle permettra de résoudre l'écoulement dans le domaine, en considérant le déplacement des soupapes et du piston. Une modifi cation du critère de remaillage et l'impact de l'introduction de l'injection sur la procédure seront discutés. Ensuite, les résultats de l'écoulement seront utilisés pour illustrer les capacités de la procédure. Les mouvements d'écoulement cohérents inhérents à un moteur à piston seront illustrés ainsi que la contribution du jet d'injection dans ceux-ci. Un ensemble de métriques permettra de mettre en évidence l'impact de ces mouvements sur le processus de mélange et d'en évaluer sa qualité en termes d'inflammabilité et d'uniformité. Enfi n, une conclusion résumera les principaux résultats de ce rapport.

Nowadays, the challenge of reducing ecological problems and the impact of human beings on their environment is more present than ever. The development of sustainable and emissions-reduced technologies is thus promoted as a partial solution to the global warm- ing issue. The transportation sector being a key player in terms of emissions, industries are investigating alternatives to traditional fossil fuel engines, such as electric, hydrogen or natural gas cars. The engines of this last category will be the subject of this master thesis. The optimization of these sustainable engines is investigated at GDTech Engineering, through the implementation of several numerical tools. Firstly, a re-meshing procedure allowing to simulate a complete cycle of a piston engine has been developed and works in parallel with the OpenFOAM environment. The second tool is the de finition of criteria to assess the quality of the air-fuel mixture after injection. The aim of this work will be to merge these tools, in order to simulate the direct injection of hydrogen in a four-stroke piston engine. The first step of this work will be to adapt and improve the re-meshing procedure to the case of an engine with an injector. It will allow to solve the flow within the domain, considering the displacement of the valves and the piston. A modifi cation of the re-meshing criterion and the impact of the introduction of the injection on the procedure will be discussed. A mesh validation study will ensure that the results are independent of meshing parameters. Finally, the flow results will be used to illustrate the capabilities of the procedure. The large coherent flow movements inherent to a piston engine will be shown as well as the contribution of the injection jet in them. A set of mixing metrics will allow to highlight the impact of these movements on the mixing process and to evaluate the quality of the mixture in terms of flammability and uniformity. Ultimately, a conclusion will resume the key results of this report