ID 332

A Numerical Study on Spray Characteristics at Start of Injection for Gasoline Direct Injection

 

Abstract:

This paper presents a CFD study of Engine Combustion Network (ECN) Spray G, focusing on the transient characteristics of spray at start of injection. The Volume of Fluid (VOF) method is used to model the two-phase flow. A moving needle boundary condition is applied for an injection event lasting for 100 µs after start of injection. The injector geometry was scanned with micron resolution using full spectrum x-ray tomographic imaging at Advanced Photon Source at Argonne National Laboratory, providing detailed machining error from manufacturer. For comparison, a nominal geometry is also used for the simulation. Spray characteristics such as Sauter Mean Diameter (SMD), droplet count, droplet volume and surface area are extracted by post-processing the CFD results. It is seen that, compared to the nominal geometry, the use of the high resolution real geometry predicts about 11% smaller SMD, and about 10% higher rate of injection, and also accelerates the droplet detachment in the upstream of spray, starting inside of the counter-bore during the start-of-injection. This result shows that the machining error of injector, which is usually ignored in the spray simulation work, has considerable impact on the spray process.