Access Type

Open Access Dissertation

Date of Award

January 2014

Degree Type


Degree Name



Mechanical Engineering

First Advisor

Ming-Chia Lai


This research presents a critical study of injector nozzle geometry on high-pressure Gasoline Direct Injection, GDi, injector spray morphology. The study was conducted with the aid of multi-fluid Volume-of-Fluid, Large-Eddy-Simulation, VOF-LES, method. Alternative nozzle geometries, that are the subject of current interest including varying nozzle hole length to diameter ratio, counter-bore presence and nozzle-hole skew-angle geometry, are studied in detail in order to provide insight into their specific influence on spray plume targeting and jet primary breakup characteristics. A comparison of the simulation results with near-field shadowgraph and Mie scatter imaging as well as phase-contrast x-ray imaging is provided. When near-field experimental imaging validated the simulation results further investigation of the fundamental flow mechanism internal to the injector was studied using VOF-LES to gain insight to the cause of spray morphology changes within the injector valve group. The complementary analysis of Computational Fluid Dynamics method and empirical data supported definitive conclusions on nozzle design parameter effects for l/d, skew angle, counterbore for varying injection pressure as well as provided an understanding of the underlying physical mechanisms involved to engender the resulting spray plume characteristics.