Design of a Disk-RDRE and High-Speed Imaging of the RDRE Chamber

To function as the upper-stage engine of a small sounding rocket, a disk-shaped RDRE chamber geometry was devised, and an initial prototype was fabricated for experimental investigation. The disk-RDRE was designed using a simplified approach suitable for rapid conceptual design in the early development phase. The empirical correlations proposed by Bykovskii et al. and the detonation wave number relation suggested by Wolanski were reviewed and incorporated into the design. Furthermore, to prevent unintended flow choking within the chamber and to optimize performance, the converging and nozzle sections were carefully designed to match the disk configuration. Experiments were conducted using gaseous ethylene and oxygen, and the internal chamber behavior was recorded with a high-speed camera. Examination of the temporal development of the rotating detonation revealed five distinct stages. Based on the high-speed camera images, frequency and modal analysis were also performed. The Short-time Fourier Transform (STFT) results confirmed that the disk-RDRE ultimately stabilized in a 2-wave mode with an operating frequency of approximately 12 kHz, demonstrating that this mode is the most stable operational mode for the designed chamber when operated with gaseous propellants. Both the Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) analyses similarly indicated that the 2-wave mode and its harmonic modes are the dominant and stable modes, whereas the remaining modes showed clear decaying behavior.