Dissertations

Geometric Scaling of Cylindrical Rotating Detonation Rocket Engine Combustors

PhD Student: Tyler Mundt                        Advisor: Carl Knowlen

A Rotating Detonation Rocket Engine (RDRE) is a propulsion device employing detonation waves moving circumferentially around an annular channel. Theoretically, this device provides benefits with respect to combustion pressure loss and thermodynamic efficiency compared to deflagration-based combustors, but these results have not been obtained experimentally. Dominant design characteristics have also not been identified, and the relationship between performance, wave dynamics, and geometric parameters is not thoroughly explored.

In an effort to obtain scaling laws and investigate small-scale RDRE dynamics and operability, two experimental studies were performed. The first concentrated on radius of curvature effects through changes in the cylindrical combustor’s outer diameter and required the design and fabrication of two modular engines. The second study encompassed the consequences of altering the annular gap width at the smallest diameter scale of the original study, and includes a coreless configuration as the upper limit. In total, over 400 runs showing stable operation across six different engine configurations were completed.

Analysis is already underway to correlate results and observed wave dynamics with the variations in geometry and test conditions. Intermediate results based on constant mass flux and equivalence ratio sweeps are presented, with planned comparisons to other parameters, including detonation cell size, wave dynamics, and exhaust back pressure. The culmination of engine design, experimental work, obtained results, and analysis will aid in the advancement of the technology and have immediate application to the design of future RDREs.
Tyler’s research shows that Rotating Detonation Engine operation is possible in combustors at the edge of the theoretical minimum size scale limit.  He is significantly increasing our fundamental understanding of the smallest scale of RDEs for spacecraft propulsion and attitude control thruster applications.  
Carl Knowlen