Fuel Property Effects on Spray Atomization Process in Gasoline Direct Injection 2020-01-0329
This paper presents a computational fluid dynamics (CFD) study of the Engine Combustion Network (ECN) Spray G, focusing on the impacts of fuel properties as well as realistic geometry on the atomization process. The large-eddy-simulation method, coupled with the volume-of-fluid method, was used to model the high-speed turbulent two-phase flow. A moving-needle boundary condition was applied to capture the internal flow boundary condition accurately. The injector geometry was measured with micron-level resolution using x-ray tomographic imaging at the Advanced Photon Source at Argonne National Laboratory, providing detailed machining tolerance and defects from manufacturing and a realistic rough surface. A 2.5-µm fine mesh was used to resolve the details of liquid-gas interface and the breakup process. The fuel properties, i.e., density, dynamic viscosity and surface tension, were investigated by comparing three fuels, iso-octane, ethanol and E30 (70% iso-octane and 30% ethanol blend by volume). The consequent global Weber number and Ohnesorge number vary by as much as 47.5% and 80%, respectively. Moderate impacts were seen on the mass flow rate, injection velocity and breakup rate due to the fuel effects, while the impacts of in-nozzle geometry details were more significant. However, the Sauter mean diameter prediction was shown to be insensitive to varied fuel properties.