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Date of Award


Document Type

Campus Access Dissertation

Degree Name

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

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeff Naber

Committee Member 1

Seong-Young Lee

Committee Member 2

Anand Gandhi

Committee Member 3

Mark Meinhart


The characteristics of gasoline sprayed directly into combustion chambers are of critical importance to engine out emissions and combustion system development. The optimization of the spray characteristics to match the in-cylinder flow field, chamber geometry, and spark location are vital tasks during the development of an engine combustion strategy. Furthermore, the presence of liquid fuel during combustion in Spark-Ignition (SI) engines causes increased hydrocarbon (HC) emissions [1]. Euro 6, LEVIII, and US Tier 3 emissions regulations reduce the allowable particulate mass significantly from the previous standards. LEVIII standards reduce the acceptable particulate emission to 1 mg/mile [2]. A good Direct Injection Spark Ignited (DISI) strategy vaporizes the correct amount of fuel at the proper point in the engine cycle with the proper in-cylinder air flow for optimal power output with minimal emissions. The opening and closing phases of DISI injectors is crucial to this task as the spray produces larger droplets during both theses phases. This work focuses on the results from a novel method to investigate fuel behavior upon closing of the fuel injector. A Design of Experiments (DOE) was used to determine the effect of pressure, temperature, and pulse-width of the fuel spray after the closing event. Experiments determined that the primary source of controlling the droplet size and the mass post injector closing for a given injector was the temperature. It was found that the end of injection behavior is a highly dynamic, complex event including, but not limited to, effects from the injector design, deposit concentration, and fuel type.