Ikkoh Funaki

This paper explores the innovative direction control of rotating detonation waves in rotating detonation engines (RDEs) by adjusting the ignition location and employing helical combustors with a sinusoidal cross section. In our experimental setup, we conducted 25 combustion tests using two distinct combustor geometries, each featuring different helical profile directions. The following conclusion drawn from the results: when the ignition was positioned 30.6–46.0 mm from the inlet, the detonation wave direction was invariably influenced by the helical direction. This correlation was statistically significant, with an occurrence probability (assuming a random direction probability of 0.5) being [Formula: see text], far exceeding the 0.05 significance level. Furthermore, the helical combustors generated a measurable torque due to the pressure differentials created by shock waves within the combustor. This torque, recorded between [Formula: see text] at a mass flow rate of 28.5–29.0 g/s, indicates the potential of power extraction from the combustor. Notably, the torque direction was also controllable via the helical direction. This study presents a significant advancement in propulsion technology, demonstrating a novel method to control detonation wave direction and torque generation in RDEs through helical combustor design, paving the way for more efficient and controllable propulsion systems.

A coupled cylindrical rotating detonation engine (RDE) with two cylindrical RDEs (both combustors had a combustor inner diameter of 23 mm and an axial length of 30 mm) placed next to each other was tested for rocket clustering application. The objective of the experiment was to achieve two-engine synchronized initiation with a single igniter. Experiments were conducted on the inner wall of the combustors with different connecting-hole diameters and wall heights to evaluate the ignition delay time, combustion mode, and propulsion performance. The propellants were gaseous ethylene and oxygen, and experiments were conducted under constant conditions of mass flow rate ([Formula: see text]), equivalence ratio ([Formula: see text]), and backpressure (approximately 10 kPa). When the two combustion chambers were completely separated by a wall, ignition occurred with a time delay of 260 ms in the chamber without an igniter. However, when a large hole ([Formula: see text] diameter) was placed in the wall separating the two combustion chambers, synchronous initiation was successful. Synchronous initiation was also successful when the wall height was lowered (7-mm height). Under both conditions, the same level of specific impulse was achieved as for RDEs operating at the same mass flux.