High-Pressure Hydrogen Flows through Single- and Multi-Hole Nozzles: A Computational Study

<div>Efficient propulsion technologies that utilize alternative fuels are becoming increasingly critical to achieve high efficiency at the vehicle scale while fulfilling global regulations in terms of emissions and criteria pollutants. In this scenario, hydrogen (H<sub>2</sub>) represents an important and appealing part of the solution due to its molecular composition and unique physical and chemical properties. With reference to internal combustion engines, much research is needed to overcome technical challenges that make H<sub>2</sub> use not yet viable at the industrial scale. This work focuses on the computational modeling of some of the fundamental aspects of H<sub>2</sub>’s physical behavior, which can be useful to the development of high-pressure H<sub>2</sub> injection systems. Computational fluid dynamics simulations are discussed with the goal of understanding the near- and far-nozzle behavior of H<sub>2</sub> using single- and multi-hole nozzles. This study presents the validation of the computational framework against literature data, followed by its extension to a multi-hole geometry relevant to the automotive industry. The role of parameters such as ambient gas composition, minimum allowable temperature in the domain, different turbulence models, and grid strategies are all discussed in detail while keeping into consideration computational costs. The authors’ goal is to provide a series of best practices and guidelines that can be useful to researchers in the automotive industry who are interested in understanding the behavior of H<sub>2</sub> injectors by means of numerical simulations.</div>