In- and near-nozzle and external flow characterization in Gasoline Direct injection (GDi) engines – A review of latest technologies and trends. Part 2: Computational background

Abstract

In an era where engine design has been influenced by the interest in emissions reduction, the use of gasoline direct injection systems has proven to be an effective means to approach this goal, enhancing the efficiency of these engines. This objective has led researchers to explore new technologies, greatly branching out research in the injection process, especially those that use fuel as one of their energy sources. Gasoline direct injection is now being combined with many other techniques with the aim of increasing efficiency. The use of fuel blends, such as the combination of gasoline with biofuels, hydrogen, compressed natural gas (CNG), and others, holds significant potential to reduce emissions in the transportation sector. These blends enable a transition to cleaner and more sustainable energy sources. However, the mechanics applied, not only to the combination of various technologies but solely to gasoline, have not yet been fully understood. This is largely due to, for example, the relative novelty of this technology compared to its diesel counterparts. The study of the gasoline direct injection processes is essential for the transition to cleaner and more efficient vehicles. Despite the importance of alternative fuels, a thorough understanding of gasoline is crucial for advancing toward more sustainable mobility. Therefore, it has been considered of interest to summarize in this article the latest research topics related to the gasoline direct injection (GDI) process, providing researchers with a valuable resource to understand the current state of research, the different technologies of gasoline direct injection and the phenomena that take place in this process. Since research applied to gasoline direct injection systems is extensive, this article proposes to make a distinction between the injection process and combustion, focusing solely on the injection. In the same way, it is suggested to study the injection process in several phases: in- and near-field of the injector and downstream of the injector. In this study, an extensive analysis is conducted on the CFD techniques employed in recent research. In the same way as Part 1 of this article, which is dedicated to experimental techniques, the goal is to promote a better understanding of the gasoline direct injection processes. In Part 2, this objective is achieved through the study of computational techniques, focusing solely on the injection and mixture formation process.