Fuel Droplet Optical Diagnostic Techniques for Lean Premixed Prevaporized Aeroengine Combustors

Recent advancements in civil supersonic transport (CST) have sparked interest in developing new technologies aimed at reducing the environmental impact of CST jet engines. Because these engines require lower pressure and bypass ratios, they tend to consume more fuel and produce higher emissions compared to their subsonic counterparts. One promising solution is the lean prevaporized premixed (LPP) combustor design, which shows potential for lowering emissions at supersonic conditions. An LPP combustor is designed to premix and prevaporize the fuel before combustion. In reality, not all the fuel vaporizes, posing a risk for increased emissions. As a result, further research is required to fully understand the performance and limitations of these combustors. Thus, a key focus is the analysis of fuel droplets in these combustors across various CST relevant operating conditions. This work employs a combination of optical diagnostics to enhance the understanding of fuel spray dynamics. Here, Mie scattering is utilized to visualize and measure the penetration depth of fuel sprays inside the combustor at reacting conditions. Both Jet-A and synthetic aviation fuel (SAF), specifically hydrotreated esters and fatty acids (HEFA) fuels are studied under various operating conditions. Two holographic imaging techniques, long standoff digital in-line holography (DIH) and digital off-axis holography (DOH), are also implemented in order to measure fuel droplet sizes at the dome face of the combustor. Due to the thermal distortions caused by the reacting flames, the distortion cancellation capabilities of these two techniques are also evaluated. Finally, narrow linewidth shadowgraphy is employed to measure liquid fuel droplet sizes in the flame at high temperature and high pressure conditions. Overall, the optical diagnostics developed and tested in this work enable more detailed studies of fuel droplet and flame interactions. The findings in this work also inform the future design of LPP combustors for CST jet engines, contributing to more efficient and environmentally friendly supersonic engines.

Level thesis:degree_level

Masters

Department dc:contributor.department

Mechanical Engineering

Grantor dc:publisher

Georgia Institute of Technology

Year dc:date.issued

2025

Author dc:creator

• Obi, Ijeoma Maryrose

Advisor dc:contributor.advisor

• Mazumdar, Ellen Y. C.

Committee members dc:contributor.committeemember

• Steinberg, Adam
• Wehe, Shawn

• Lean premixed prevaporized
• LPP
• Holography
• DIH
• DOH
• Mie scattering
• Shadowgraphy

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/1853/78645

OAI identifier oai:identifier

oai:repository.gatech.edu:1853/78645