Spectral analysis and self-adjusting mechanism for oscillation phenomenon in hydrogen-oxygen continuously rotating detonation engine

Abstract The continuously rotating detonation engine （CRDE） is a new concept of engines for air- craft and spacecraft. Quasi-stable continuously rotating detonation （CRD） can be observed in an annular combustion chamber, but the sustaining, stabilizing and adjusting mechanisms are not yet clear. To learn more deeply into the CRDE, experimental studies have been carried out to inves- tigate hydrogen-oxygen CRDE. Pressure histories are obtained during each shot, which show that stable CRD waves are generated in the combustor, when feeding pressures are higher than 0.5 MPa for fuel and oxidizer, respectively. Each shot can keep running as long as fresh gas feeding main- tains. Close-up of the pressure history shows the repeatability of pressure peaks and indicates the detonation velocity in hydrogen-oxygen CRD, which proves the success of forming a stable CRD in the annular chamber. Spectrum of the pressure history matches the close-up analysis and confirms the CRD. It also shows multi-wave phenomenon and affirms the fact that in this case a single detonation wave is rotating in the annulus. Moreover, oscillation phenomenon is found in pressure peaks and a self-adjusting mechanism is proposed to explain the phenomenon.

A fluid dynamics route for producing graphene and its analogues

A novel fluid dynamics route for scalable and efficient production of graphene and its analogues is demonstrated.Atomic force microscopy and transmission electron microscopy analyses strongly suggest that the bulk layered materials(graphite,BN,MoS2,and WS2)are efficiently exfoliated into individual layers containing mono-and few-layer nanosheets.Computational fluid dynamics analysis indicates that multiple fluid dynamics events are responsible for efficient exfoliation.Cavitation and pressure release can generate normal force for exfoliation.The velocity gradient-induced viscous shear stress,the turbulence-induced Reynolds shear stress,and shear effects stemmed from turbulence and flow channel-induced collisions can generate lateral force for exfoliation,resulting in theses bulk layered materials self-exfoliation down to single or few layers through their intrinsically lateral self-lubricating ability.

Progress of continuously rotating detonation engines

Continuously rotating detonation engine （CRDE） is a focus for concern in the field of aerospace propulsion. It has several advantages, including one-initiation, high thermal efficiency and simple structure. Due to these characteristics, it is expected to bring revolutionary advance- ments to aviation and aerospace propulsion systems and now has drawn much attention throughout the world. In this paper, an overview of the development of CRDE is given from several aspects： basic concepts, applications, experimental studies, numerical simulations, and so on. Representative results and outstanding contributions are summarized and the unresolved issues for further engi- neerin~ applications of CRDE are 13rovided.