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Rotating Detonation Engine (RDE)
Rotating Detonation Engine (RDE)
RDEs are recognized as promising future propulsion and power-generation systems due to their potential for enhanced thermodynamic efficiency over traditional deflagration-based combustors and their mechanically simple and compact designs with fewer moving parts.
Engineers at NASA's Marshall Space Flight Center in Huntsville, AL conducted the prototype rotating detonation rocket engine (RDRE) in 2022. The engine was fired over a dozen times, totaling nearly 10 minutes in duration. (see the video)
Numerical Simulations of a Full-Scale RDE
Numerical Simulations of a Full-Scale RDE
Computational Model Configuration
Computational Model Configuration
The computational domain was constructed to closely replicate the AFRL (Air Force Research Laboratory) RDE configuration (see left figure). High-speed and gaseous methane and oxygen flumes are delivered separately into the annular combustor.
A commercially available CFD package, CONVERGE (v4.1), was employed to perform large-eddy simulation (LES) of this full-scale RDE configuration. To initiate the detonation within the annular combustor, a predetonation tube was attached to the side of the chamber. The end of this tube was initially filled with a high-temperature, high-pressure fuel-air mixture to promote deflagration-to-detonation (DDT) along its length.
Macroscopic Flame Dynamics
Macroscopic Flame Dynamics
The simulation reveals key wave dynamics within the chamber (left snapshots captured from the mid-plane of the annuls chamber domain). This includes a pair of a co-rotating detonation fronts (black arrows) and an another pair of counter-rotating (CR) secondary shock wave (red arrows). Near the injector exit base, a distinct low-temperature zone forms where intense fuel-oxidizer jet interaction drives turbulence mixing. Hence, this nature leads to a mix of sub-sonic combustion and supersonic combustion regimes.
The pressure signal (shown on the left bottom image) was measured at the monitoring point positioned 8.9 mm downstream of the base in order to determine the continuous tube attenuated pressure (CTAP) values.
Injector Exit Flow Dynamics upon Wave-To-Wave Interaction
Injector Exit Flow Dynamics upon Wave-To-Wave Interaction
Figures shown below are the temporal evolution of a co-rotating detonation wave and an interacting (colliding) CR shock wave and near-injector exit flow contours of temperature and heat release rate (HRR). Two sets of monitoring locations, designated as injector pairs #1 and #2, are positioned at separate azimuthal positions to capture local flow behavior as the respective waves pass these regions.
The intensity of the CR shock wave, pressure spike, is observed to be augmented by a factor of two after the collision. This is attributed to the post-detonation gas expansion. The analysis also reveals that this expansion process contributes to sustaining the CR shock structures within the RDE chamber. In addition, the wave sweeps across the injector exit induce a significant reduction in the axial discharge velocities of both fuel and oxidizer streams, potentially choking the exit flow.
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