Date of Award


Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeffrey D. Naber

Advisor 2

Seong-Young Lee

Committee Member 1

David R. Shonnard

Committee Member 2

Jaclyn E. Johnson


Gasoline compression ignition (GCI) technology has demonstrated great potentials in improving fuel economy and reducing engine-out NOx and particulate matter emissions. Development and application of the GCI technology on multi-cylinder engines require both fundamental understandings of the gasoline spray combustion characteristics and accurate numerical tools. Due to the large differences in the thermo-physical and the chemical properties between gasoline and diesel range fuels, differences in the spray combustion characteristics between gasoline and diesel is expected. Reports on the gasoline spray combustion characteristics under conditions relevant to medium to heavy-duty engines are scarce and this dissertation aims to fill in this knowledge gap.

Experimental work were performed in a constant volume combustion vessel. Non-reacting sprays under low and high ambient charge gas temperatures and reacting sprays were performed using a high reactivity gasoline (research octane number 60) and ultra-low sulfur diesel. The experimental work were designed to isolate the effect of several important fuel properties on spray and combustion. The experimentally investigated spray combustion characteristics include spray dispersion, vapor penetration, liquid penetration, ignition, flame lift-off, and natural luminosity. These experiments provided evidence behind the lower particulate matter emissions benefit of gasoline.

A transient spray cone angle correlation was developed based on the experimental measurements. The correlation was developed to improve the description of fuel-air mixing in computational fluid dynamic (CFD) simulations. The correlation was integrated with CFD simulations and the benefits of using a transient spray cone angle profile were demonstrated.

Reacting spray CFD simulations were performed and validated extensively against the experimental spray characteristics on ignition, flame lift-off, soot natural luminosity, and external published local soot concentration measurements. The CFD simulations provided additional understanding of the soot emission processes to complement experimental measurements.