Keywords

Shock Tube, Absorption Spectroscopy, Laser, Combustion

Abstract

Theoretical application and physical implementation of various laser absorption spectroscopy (LAS) diagnostics are examined within a high-pressure shock tube facility. Research focuses on the rationale behind the specific optical alignment layouts used across three distinct experimental campaigns, detailing the methodology required to maintain signal integrity in varied reacting flow environments. The first research campaign addresses the pyrolysis of hydroxyl terminated polybutadiene (HTPB) solid propellant binders for solid fuel ramjet (SFRJ) applications by measuring the species time histories of alkenes and aromatics. Alignment configurations prioritized beam stability and signal strength for the decoupling of overlapping absorption features to ensure measurements accurately reflected chemical time-histories during high-pressure experiments. The second campaign examines species time-histories for natural gas and ammonia fuel blends at elevated pressures up to 25 bar. Capturing the generation and decay kinetics of six target species over a 10 ms residence time required a six-laser multiplexed architecture. This section details the alignment necessary to transmit all six lasers through the limited optical access of the shock tube while maintaining the signal integrity needed for overlapping absorption feature decoupling. The third campaign investigates the flow field characterization of impinged shock waves using a 4.9 µm quantum cascade laser (QCL) for CO thermometry. A spatial segmentation methodology was implemented to resolve local temperature gradients from the path-averaged, line-of-sight measurements. Diagnostic alignment was held constant across three physical test configurations: an empty tube test, a mid-way test, and a full path test. Analysis of the absorption data across these varied configurations isolated the temperature of the interacting flow field from the freestream. By documenting these advanced optical techniques and experimental protocols, a comprehensive technical baseline is established for the facility's current diagnostic capabilities.

Completion Date

2026

Semester

Spring

Committee Chair

Vasu, Subtih

Degree

Master of Science in Aerospace Engineering (M.S.A.E.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Document Type

Dissertation/Thesis

Identifier

DP0053297

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