Characterizing Drop-Wall Interactions of Engine Fuels at Engine-Relevant Conditions Using Smoothed Particle Hydrodynamics

Abstract

Abstract In an internal combustion engine, interactions of fuel droplets and heated walls can significantly affect the combustion process and engine performance. The formation and characteristics of secondary droplets from drop-wall interactions are functions of various factors such as fuel properties, impact velocity, ambient conditions, and wall temperature. Understanding the impact behavior is of great importance to optimize the distribution of the fuel-air mixture for efficient and clean combustion and to develop a comprehensive spray-wall interaction model. In this study, three-dimensional smoothed particle hydrodynamics (SPH) simulations are performed to investigate the interactions of n-heptane and F-24 droplets with a super-heated surface at atmospheric and elevated pressures over a range of Weber numbers (We). The SPH model is validated using available experimental data. Secondary atomization is characterized by using size distributions of secondary droplets for all cases. In contrast to n-heptane, F-24 results in a narrower droplet size distribution where secondary droplets are mainly clustered in the range of 0 to 7μm, resulting in a smaller mean secondary droplet size. Following these cases, this paper presents qualitative description of the impact process and proposes empirical correlations relating mean secondary droplet size to ambient pressure in the film-boiling regime. Post-impingement vaporization characteristics are also analyzed.