Enhanced spray-wall interaction model for port fuel injection under medium load conditions

Abstract

This study presents an Eulerian-Lagrangian framework for the numerical analysis of spray dynamics, with a focus on droplet movement, spray-wall interactions, and the effects of varying injection parameters associated with port fuel injection (PFI) system. A grid-independent criterion is introduced to optimize mesh analysis for accurate predictions of fuel penetration length. The size distribution of secondary droplets is described using a probability density function, and statistical optimization is subsequently implemented to estimate their mean size. This probabilistic approach enhances the Lagrangian wall film (LWF) model, leading to accurate predictions of the Sauter mean diameter (SMD) at a given radial width (\(R_\text{{w}}\)), with results closely matching experimental data. For \(8.0 ~\text {mm} \le R_\text{{w}} \le 24.0 ~\text {mm}\), the maximum SMD of 21.67 \(\mu\)m corresponds to \(R_\text{{w}} = 14.0, \text {mm}\), while the smallest SMD of 12.68 \(\mu\)m is computed for a radial position of \(R_\text{{w}} = 24.0 ~\text {mm}\). The numerical investigation quantifies the role of spray-wall interactions in determining the trajectory of fuel distribution, particularly in the formation of wall films and the relative spatio-temporal diesel concentration (F/A) %. The study explores aspects such as droplet size variations, heat transfer during evaporation, and film behavior under different injection pressures, providing insights into the multiphysical characteristics of spray-wall systems. Near the impingement site (\(2.0 ~\text {mm} \le R_\text{{w}} \le 4.0 ~\text {mm}\)), the plume height (\(H_\text{{w}}\)) slightly decreases with an increase in injection pressure. While the CFD methodology in this current work has been primarily developed for automotive engineering sector (PFI engines), it also has potential applications in areas such as additive manufacturing, hydropower engineering, climate science, and environmental engineering.