Date of Award
Spring 4-21-2026
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
First Advisor
Casey Allen
Second Advisor
Adam Dempsey
Third Advisor
Jared Zeman
Abstract
Internal combustion engines (ICEs) are expected to remain a critical component of many energy systems due to their superior power density, low-cost established infrastructure, and rapid fueling capability. However, their continued use will require a transition to reduced-emission, sustainable alternative fuels, such as pure ethanol. This transition introduces significant engineering challenges, as these fuels are not inherently compatible with conventional ICE architectures. To address these challenges, one of the most promising developments is the integration of actively fueled prechambers (APCs) to ICEs. APCs function by expelling reacting jets into the main combustion chambers of an ICE. These high-energy jets can enhance ignition stability, extend lean operating limits, and enable entirely new combustion modes. Motivated by this potential, this work presents the development and application of a novel experimental platform with full optical access inside an APC. This configuration enables direct observation of key processes including fuel injection, spray-wall interactions, fuel film formation, ignition behavior, and flame propagation. Ethanol is selected as the primary alternative fuel of study due to its potential to significantly reduce lifecycle carbon dioxide emissions relative to conventional hydrocarbon fuels. Additionally, ethanol is selected for its low volatility properties, which present a critical challenge for mixture preparation under cold start conditions, where insufficient vaporization can lead to misfire and unstable combustion. This challenge is extremely relevant to the spark ignition process within APCs, representing a previously unexplored and important engineering barrier to broadening the adoption of ethanol APC-ICEs. A comprehensive set of experiments are presented that identify the governing variables influencing evaporation and combustion within the APC environment. The results indicate that ethanol evaporation is strongly governed by the thermal conditions during injection, with spray targeting, droplet dynamics, and shot size also playing key roles. Following, advanced APC operating strategies are presented that mitigate the cold-start limitations and improve APC combustion reliability. The strategies function by intentionally altering the combustion mode to favor stratified or diffusion-dominated behavior.