Development of CFD Method for Spray Shape Estimation 2016-01-2198

Computational fluid dynamic (CFD) is widely used to develop engine combustion. Especially the in-cylinder spray calculation is important in order to resolve the issues of direct injection gasoline engines (e.g., particulate matter (PM) and oil dilution caused by fuel wetting on the cylinder walls). Conventional spray calculation methods require fitting based on measurements of spray characteristics such as penetration and droplet diameter (i.e., the Sauter mean diameter (SMD)). Particularly in the case of slit nozzle shapes that widen from the inlet to the outlet to form a fan-shaped spray, fitting the shape of spray is a complex procedure because the flow inside the nozzle is not uniform. In response, a new calculation method has been developed that eliminates the need for spray shape fitting by combining calculations of the Eulerian multiphase and the Lagrangian multiphase. The nozzle flow is calculated by the large eddy simulation (LES) turbulence model to predict non-uniform and unsteady nozzle flows. Each time-step during the injection period is saved alongside the velocity and mass flow rate of the fuel in each cell. After the nozzle flow is calculated, this data is used to calculate the velocity distribution and droplet diameter distribution that form the initial parcel values for the Lagrangian multi-phase spray calculation. These droplets behavior is calculated in the spray chamber, as a result, the simulated spray characteristics shows a good agreement with experimental results. The in-cylinder spray was calculated using this method to evaluate engine performance such as PM and oil dilution