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

Committee Member 1

Jaclyn Johnson

Committee Member 2

Thomas Wallner

Committee Member 3

William DeOjeda


In this work, the advantages of partially stratified direct injection natural gas versus premixed port-fueled injection natural gas spark ignited engines has been studied. The volumetric efficiency, ratio of specific heats and turbulent kinetic energy was found to be higher with direct injection versus port-fueled injection thus improving thermal efficiency. A background study of optical chamber experimental data was performed to develop an understanding on the effect of pressure ratio on direct injection of methane under both fully-expanded (sub-sonic) and under-expanded (super-sonic) conditions. Under-expanded jets had a noticeable advantage in terms of turbulent kinetic energy, which led to enhanced air entrainment and mixing. An experimental study using a 200bar four hole 1mm diameter injector was performed repeatedly for upstream versus downstream pressure ratios, within the range 1.3 < pressure ratio

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Available for download on Sunday, July 30, 2023