A modular laboratory rotating detonation engine (RDE) for combined mass flow rates below 10g/s has been designed and tested. To our knowledge, this is the first successful RDE experiment in the UK. Design and experimental setup have been developed over three successive final year group design projects in aerospace engineering.
A rotating detonation engine utilises a detonation wave which travels azimuthally within an annular chamber to expel propellant and generate thrust. The chamber is formed by two coaxial cylinders, and the radial gap between them, referred to here as the chamber width, forms the chamber. The detonation wave is maintained by constantly feeding fuel and oxidiser into the chamber, thus ensuring that there is a constant mixture of reactants in front of the detonation.
RDEs are of interest due to their potential efficiency gains in hypersonic propulsive systems. The efficiency gains of a detonation engine are due to the greater temperature and pressure increase produced by detonation over deflagration, allowing more work to be extracted from the same amount of propellant.
Constructed as a small-scale laboratory demonstration project, the objective was to utilize as small mass flow rates as possible. This naturally lead to the adoption of a RDE rocket design supplied with pure oxygen. For safety and ease of handling ethylene was selected as fuel.
The annular slit size between insert and outer shell (Fig. 1) in successful tests was 1.2mm. The detonation wave is initiated by pre-detonator tube with internal Shelkin spiral; several aerospike nozzle attachments (Fig. 2) lead to considerable thrust increases. During the experiments (Figs. 3 and 4) the engine was mounted on rails to allow measuring the thrust. Depending mass flow rates between one and three simultaneously spinning detonation heads have been observed by high speed photography and confirmed by analysis of the pressure signals measured with a high-frequency transducer in the chamber.
