Session: 17-05-01: Steam Turbine Generators & Auxiliaries

Paper Number: 166335

Pressure-Based Correlation of Wave Mode Transition in a Hydrogen-Fueled Rotating Detonation Engine Combustor 

Rotating Detonation Engines (RDEs) offer a promising concept for power generation and propulsion due to higher thermal efficiency and compactness. RDE combustor harnesses the continuous propagation of detonation waves to achieve enhanced thermodynamic efficiency. However, the dynamic nature of detonation waves, particularly wave mode transitions, remains a critical area of investigation for optimizing combustor performance and stability. This study employs high-fidelity Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations to investigate the internal wave dynamics of a hydrogen-fueled RDE, focusing on the correlation between pressure fluctuations and mode transition under varying flow conditions.

The primary objective of this work is to establish correlations between spatiotemporal pressure variations and the underlying wave physics governing mode transition. By systematically altering the total mass flow rate of fuel and oxidizer while maintaining an equivalence ratio of unity, we successfully captured wave mode transition in a realistic 3D RDE combustor. The pressure field was recorded at 44 numerical probes distributed along the axial direction at four azimuthal locations (0°, 90°, 180°, and 270°), ensuring a comprehensive spatial resolution of the detonation wave structure. The numerical probes, sampled at a temporal resolution of 3 × 10⁻⁸ s, provide detailed insights into wave frequency, amplitude variations, and phase relationships during mode transition. Additionally, high-resolution three-dimensional (3D) data were extracted to visualize and analyze the transient flow structures accompanying wave transition.

The analysis reveals that pressure fluctuations along the axial direction exhibit distinct signatures corresponding to different wave modes. By leveraging frequency-domain analysis and statistical correlations, we identify critical parameters influencing wave mode transition, including the axial pressure gradient, phase coherence between angular locations, shock-induced interactions within the detonation wavefront, and the deflagration mode of burning. One of the key insights gained from this analysis is the role of pressure wave interactions in determining the local mixing efficiency of the fuel and oxidizer. Since RDEs rely on rapid turbulent mixing and detonation wave interactions to sustain stable operation, the spatiotemporal pressure variations recorded at the numerical probes provide valuable indirect measures of local mixing dynamics.

The pressure probes, distributed along the axial and angular directions, capture fluctuations that reflect the mixing layer development and the degree of stratification in the fuel-oxidizer mixture. High-frequency fluctuations in pressure correspond to regions of intense shear and turbulence generation, which are indicative of enhanced mixing. Conversely, lower amplitude variations suggest weaker interactions, potentially leading to incomplete mixing and localized deflagration instead of detonation. By correlating pressure probe data with wave transition events, we establish that mixing efficiency is a crucial factor governing the stability and structure of detonation waves. In regions where pressure signals exhibit high coherence across angular locations, the mixing process is more uniform, resulting in a stable detonation front. However, when phase discrepancies arise between probes, it indicates non-uniform mixing, leading to local flame propagation via deflagration, which in turn affects the global mode transition process.

Furthermore, the transition from one wave mode to another is strongly influenced by the balance between detonation and deflagration modes of combustion. In cases where incomplete mixing causes a significant portion of the reactants to burn via deflagration, the detonation wave weakens, leading to mode bifurcation or merging. Our analysis shows that specific changes in the pressure gradient along the axial direction trigger wavefront distortions that can either enhance or suppress detonation wave propagation. When mixing is insufficient, pressure perturbations at upstream locations result in asymmetric combustion, promoting deflagration pockets that disrupt the established wave structure. As a result, the RDE undergoes mode transitions where the number of detonation waves either increases or decreases, depending on the energy redistribution within the combustor.

This research enhances the fundamental knowledge of RDE wave mode dynamics by establishing quantitative pressure-based correlations that describe wave mode evolution under changing operating conditions. The findings offer valuable insights into optimizing RDE design parameters, improving mode stability, and developing predictive tools for wave transition control.

Presenting Author: Steven Thompson University of Central Florida

Presenting Author Biography: Mr. Steven Thompson is a graduate student in the Hasti Lab at the University of Central Florida.

Authors:

Steven Thompson University of Central Florida
Veeraraghava Raju Hasti UCF
Reetesh Ranjan The University of Tennessee at Chattanooga