Available at: https://digitalcommons.calpoly.edu/theses/3405
Date of Award
8-2026
Degree Name
MS in Aerospace Engineering
Department/Program
Aerospace Engineering
College
College of Engineering
Advisor
Dianne J. DeTurris
Advisor Department
Aerospace Engineering
Advisor College
College of Engineering
Abstract
Rotating detonation engines offer a route to pressure-gain combustion by sustaining one or more detonation waves in an annular chamber supplied by continuous propellant injection. This thesis evaluates whether potassium seeding can make the high-temperature product flow of a hydrogen–air rotating detonation engine conductive enough to serve as the working fluid for magnetohydrodynamic acceleration. To the author’s best knowledge, the complete configuration modeled here has not been reported previously in open literature. This configuration consists of a hydrogen–air RDE with KOH-based potassium seeding, local conductivity estimates, and imposed Lorentz-force acceleration. The thesis therefore develops an initial computational model for this proposed EM-RDE configuration rather than attempting to reproduce an existing EM-RDE design. The model includes a two-dimensional unwrapped rotating-detonation simulation, finite-rate neutral and charged chemistry, potassium seeding through injected KOH, a mixture-averaged conductivity estimate, and reduced-order Lorentz-force source terms in ANSYS Fluent.
The baseline hydrogen–air grid convergence study showed that the 1.0 mm production mesh gives cycle-averaged thrust and specific impulse within 0.3 percent of the 0.5 mm mesh while maintaining physically credible detonation speed. The conductivity model was checked against a multispecies Saha balance and detonation-tube calculations. The seeded case contains 1% potassium by mass, injected as gaseous KOH, which gives a conservative atomic-potassium Saha estimate of approximately 2.47×10^21 m−3, compared with 1.79×10^17 m−3 for the unseeded case. Full RDE calculations showed that potassium seeding raises conductivity by several orders of magnitude and shifts dominant ionization from delayed NO-controlled production to prompt potassium ionization.
A reduced-order MHD model then imposed an out-of-plane current through the computed conductivity field and an externally applied transverse magnetic field. The completed current-field matrix used gas currents from 225 A to 1225 A and RDE accelerator fields from 2.5 T to 10 T. Across the completed cases, the model produced total-flow-normalized specific-impulse gains from 0.150% to 11.54% and gross outlet-plane thrust changes from −0.608% to 10.50% while keeping the active-region temperature below 3500 K. A conservative air-breathing interpretation with ideal frozen-composition expansion and inlet ram-drag subtraction produced fuel-based specific-impulse gains up to 134.3%. These results indicate that the first computational model of this potassium-seeded EM-RDE configuration can produce a measurable numerical Lorentz-force response under the modeled assumptions. However, the present reduced-order results do not by themselves establish complete system practicality, which will require future treatment of electrode physics, current attachment, three-dimensional analyses, magnet mass, cooling, power conditioning, and integrated generator sizing.