Date of Completion
Rotating Detonation Engine Thermodynamics
Baki M. Cetegen
Thomas J. Barber
Michael W. Renfro
Field of Study
Doctor of Philosophy
A practical thermodynamic cycle model of a rotating detonation engine (RDE) is developed for the purpose of predicting performance and understanding flow field behavior. The cycle model is based on a heuristic analysis of a RDE numerical simulation. The model is compared to the simulation and to laboratory experiment with good results.
The RDE constrains a detonation wave to rotate inside a cylindrical annulus, has no moving parts and requires a single ignition sequence. Thrust is produced continuously and at high frequency. The simplicity of the RDE offers the possibility of a practical detonation engine with efficiencies that exceed conventional Brayton cycles.
A RDE numerical simulation (courtesy of the Naval Research Laboratory) is post-processed to yield the underlying thermodynamics. The time-accurate numerical simulation is averaged over many cycles. A Galilean transformation is applied to the time-averaged solution to produce a solution field in the rotating frame of reference. Streamlines are created in the transformed solution field. Velocity, pressure and temperature are extracted along the streamlines. Pressure-volume and enthalpy-entropy diagrams are plotted to expose the simulation thermodynamics.
The results are found to be consistent with the conservation of rothalpy as the fundamental statement of the conservation of energy in a rotating frame of reference. The signature of rothalpy in the RDE is shown to be a small amount of azimuthal flow or swirl. The change in flow field swirl is shown to be proportional to the change in stagnation enthalpy and consistent with the Euler turbomachinery equation.
The simulation analysis supports the construction of an analytical model based on a modified ZND (Zel’dovich-von Neumann-Döring) detonation theory. This theory is combined with the concept of rothalpy. The result is a realistic thermodynamic cycle model with a theoretical basis for performance prediction and an explanation of the flow field structure. The RDE cycle model is analytical, thermodynamically one-dimensional, steady-state, and independent of geometry and heat release rate.
The performance of the modified ZND cycle model is within 3% of the numerical simulation and in good quantitative agreement with experimental test results at the Air Force Research Laboratory Detonation Engine Research Facility.
Nordeen, Craig A., "Thermodynamics of a Rotating Detonation Engine" (2013). Doctoral Dissertations. 277.