Keywords

Shock Tube, Solid Fuel, Ramjets, HTPB, Combustion, Absorption

Abstract

Solid Fuel Ramjets (SFRJs) are often used in tactical applications due to their simplicity, robustness, and reliability. No moving parts, atmospheric oxidizer usage, and scalable fuel grain designs make them a great solution for compact, high-speed air-breathing propulsion systems. SFRJs operate by compressing incoming air through a fixed geometry inlet and directing it over a regressing solid fuel surface, where pyrolysis gases are released and transported downstream to the combustion chamber where thrust is generated. Hydroxyl-terminated polybutadiene (HTPB) is a commonly used fuel binder in SFRJ systems due to its high energy density, stable combustion behavior, and ease of processing. Upon thermal decomposition, HTPB produces a range of intermediate hydrocarbon species that participate in downstream combustion reactions. Experimental measurements of these intermediates are important for improving chemical kinetic models used in propulsion simulations.

Shock tube experiments were conducted to measure species time histories of key hydrocarbon intermediates representative of HTPB pyrolysis products. Laser absorption spectroscopy provided time histories of ethylene (C₂H₄), 1,3-butadiene (C₄H₆), and carbon monoxide (CO) under high-temperature conditions. These measurements were compared with predictions from detailed chemical kinetic models to evaluate current modeling capabilities for fuel-rich hydrocarbon combustion relevant to solid fuel propulsion systems.

Additionally, preliminary gas chromatography mass spectrometer (GCMS) analysis was conducted to identify species generated during HTPB pyrolysis. These measurements will guide future shock tube studies targeting real pyrolysis products and enable evaluation of surrogate fuel assumptions used in current modeling approaches.

Completion Date

2026

Semester

Spring

Committee Chair

Vasu, Subith

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

DP0053298

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