Available at: https://digitalcommons.calpoly.edu/theses/3159
Date of Award
9-2025
Degree Name
MS in Mechanical Engineering
Department/Program
Mechanical Engineering
College
College of Engineering
Advisor
Patrick Lemieux
Advisor Department
Mechanical Engineering
Advisor College
College of Engineering
Abstract
Ignition systems for chemical rocket engines typically rely on hypergolic propellants or auxiliary electrical hardware to supply the energy required to initiate combustion. The resonance igniter is a simple and robust alternative to these conventional methods, capable of inducing autoignition of non-hypergolic propellants without an external ignition source. At the core of this concept is the Hartmann-Sprenger Tube (HST), a device in which a high-velocity jet of gas impinges on a resonance cavity. This interaction establishes self-sustaining gas oscillations within the cavity that heat the propellants to their autoignition temperature. To facilitate the development of a functional resonance igniter at Cal Poly, this thesis investigates three parameters identified as primary drivers of heating performance and oscillation behavior in an HST: nozzle pressure ratio (NPR), nozzle-cavity spacing (S/d), and cavity length (L/d). A modular HST apparatus was designed and constructed to enable a broad parametric survey of these variables and their effects on the oscillations within conical resonance cavities. Three interchangeable cavities were designed based on prior research, with geometry optimized to maximize heating and produce sufficient temperatures for igniting high-performance rocket propellants. Heating trends within the resonators were found to depend strongly on HST operating mode, either Jet Regurgitant Mode or Jet Screech Mode, and varied significantly between geometries and test conditions. Lumped-capacity solutions were applied to extrapolate short-duration test data, providing estimates of the average steady-state gas temperatures within the resonance cavities. Ultimately, the highest measured cavity-wall temperatures reached 606°C with external insulation and 454°C without, corresponding to estimated average steady-state gas temperatures of 619°C and 469°C, respectively.