Keywords
Laser Absorption Spectroscopy, Direct Absorption Spectroscopy, Wavelength Modulation Spectroscopy, Shock Tube, Detonation Facility
Abstract
Laser absorption spectroscopy (LAS) is a widely utilized diagnostic technique for probing gases in various combustion and detonation environments, including shock tubes, detonation tubes, and rotating detonation engines. Its advantages over other techniques, such as pyrometry or mass spectrometry, include its non-intrusiveness, noise rejection, high temporal and spatial resolution, and its ease of application across a wide range of temperatures, concentrations, and pressures. By relating the attenuation of light through a test environment to the properties of that environment, important combustion parameters such as speciation, temperature, pressure, and gas velocity can be extracted. These measurements are essential for optimizing rig performance, reducing emissions, improving safety, and validating combustion models and mechanisms. Within LAS, there exist multiple techniques, including direct absorption spectroscopy and wavelength modulation spectroscopy. Depending on the test environment, different considerations need to be made concerning the design of an LAS-based sensor. In this work, an in-depth analysis is provided regarding sensor design considerations, sensor construction and optimization, and sensor hardening. A LAS sensor composed of near-infrared and mid-infrared light sources, and capable of utilizing and rapidly switching between direct absorption and wavelength modulation techniques, is demonstrated and applied across multiple combustion and detonation environments. Emphasis is applied to constructing a modular sensor that can rapidly be interfaced with various reacting flow environments and can be utilized across a wide range of conditions. The sensor’s temperature, water and carbon oxide measurement capabilities are validated across shock tube and detonation tube facilities. Novel measurements are presented in Hydrogen-Oxygen and Methane-Oxygen detonation environments immediately following the arrival of the detonation wave and subsequent reflected waves. Additions are made to the existing literature concerning the development of modular sensors that can utilize multiple techniques with particular focus on expanding the literature on scanned-wavelength direct absorption spectroscopy at high pressure combustion environments.
Completion Date
2025
Semester
Fall
Committee Chair
Vasu Sumathi, Subith
Degree
Doctor of Philosophy (Ph.D.)
College
College of Engineering and Computer Science
Department
Mechanical and Aerospace Engineering
Format
Release Date
12-15-2026
Document Type
Dissertation
Campus Location
Orlando (Main) Campus
Subjects
Laser spectroscopy--Research; Laser spectroscopy--Industrial applications; Detonation waves--Measurement--Instruments; Combustion gases--Research; Infrared spectroscopy--Industrial applications
STARS Citation
Khanal, Nishan, "Development and Application of Near-Infrared and Mid-Infrared Laser Absorption Sensors for Reacting Propulsion and Detonation Applications" (2025). Graduate Thesis and Dissertation post-2024. 533.
https://stars.library.ucf.edu/etd2024/533
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