Rotating detonation combustors and their similarities to rocket instabilities

Origin and chaotic propagation of multiple rotating detonation waves in hydrogen/air mixtures

The continuous detonation engine (CDE) is based on detonation waves and is a new jet engine concept that is expected to bring a technical revolution to current aviation and aerospace propulsion sys...

Recent Progress, Development Trends, and Consideration of Continuous Detonation Engines

A non-premixed rotating detonation engine using ethylene and air

Effects of injection nozzle exit width on rotating detonation engine

A two-dimensional investigation is conducted to clarify the velocity decrease mechanism of a detonation wave propagating within a rotating detonation engine (RDE) chamber, focusing on the effect of injection conditions of the fuel and oxidizer. Two numerical studies are conducted; the first imitates the RDE chamber with injection ports in a rectangular computational domain, and the second simplifies the flow field in the RDE chamber based on observations of the first simulation. The injection is parameterized by the geometrical jet and the gas conditions (i.e., premixed or non-premixed). In the first simulation of the RDE chamber, the total length of the injection nozzles constitutes 20% of the length of the chamber's lower end. The number of nozzles, N, ranges from 10 to 500 under premixed and 25 and 125 under the non-premixed condition. As the nozzle interval increases, more burned gas exists in front of the detonation wave. Under the non-premixed condition for N = 25, the propagation velocity decreases to 84% of the CJ velocity, and 82.4% of the injected C2H4 is burned by the detonation. The CJ velocity is theoretically calculated, based on the amount of burned C2H4, to be 2283 m/s, which is not close to the propagation velocity of the simulation, 1999 m/s. In the simplified model in the second study, C2H4, O2, and burned gas are quiescently placed rather than injected, and the role of the upper wall is also examined. Significant velocity decrease, down to 86% of the CJ velocity, is observed when C2H4 and O2 are placed separately with a large width of burned gas between them. The amount of incompletely combusted C2H4 is inversely proportional to the propagation velocity except in the case with an upper wall. Therefore, burned gas has a larger effect on propagation velocity in the non-premixed condition.

Numerical investigation on detonation velocity in rotating detonation engine chamber

The rotating detonation engine is a propulsion system that obtains thrust using continuously existing detonation waves. A rotating detonation combustor usually has an annular shape that allows detonation waves to propagate in the circumferential direction. In this study, we used a disk-shaped rotating detonation combustor with a combustion chamber with flat-plane glass walls to observe the structure of the phenomena. Self-luminescence, shadowgraphs, and schlieren visualization experiments were performed and compared. Results revealed that detonation waves were propagating in a mixture layer of three gases, fuel, oxidizer, and burned gas at 1600 to 900  m/s; Chapman-Jouguet velocity was 2376  m/s. Waves maintained a three-dimensional complicated wave shape in the disk-shaped combustion chamber with parallel-jet injectors.

Experimental Visualization of the Structure of Rotating Detonation Waves in a Disk-Shaped Combustor

Numerical study for rotating detonation propagation in a two-parallel-plane combustor

Numerical simulation towards investigating the factor for velocity decrease of detonation wave in rotating detonation engine chamber

A quasi-one-dimensional analytic model is proposed for the internal fluid of rotating detonation combustors (RDCs). This model uses the shock-tube model that constrains the flow to have only a longitudinal component, while admitting the propagation of the detonation wave in the azimuthal direction. The proposed model is able to compute the thruster performance and two-dimensional distributions of gas properties. The calculation process of the model excludes iterative calculation or space discretization. The case calculations of the hydrogen-air RDC and the ethylene-oxygen RDC are conducted, and the results calculated by the analytic model are compared with those simulated by computational fluid dynamics (CFD). Good agreement has been observed between the results obtained with the proposed model and CFD, in terms of both of the qualitative and quantitative comparisons. The proposed model is simple and fast, and also maintains the fundamental characteristics of RDCs.

Jumpei Fujii

Papers

Numerical investigation on detonation velocity in rotating detonation engine chamber

Experimental Visualization of the Structure of Rotating Detonation Waves in a Disk-Shaped Combustor

Numerical study for rotating detonation propagation in a two-parallel-plane combustor

Numerical simulation towards investigating the factor for velocity decrease of detonation wave in rotating detonation engine chamber

A quasi-one-dimensional analytic model of rotating detonation combustors