Self-sustaining And Propagation Mechanism Of Airbreathing Continuous Rotating Detonation Wave

In this thesis,the feasibility of the airbreathing continuous rotating detonation(CRD)was firstly experimentally validated.Thereafter,its self-sustaining and propagation mechanism was studied via experimental investigation,numerical simulation and theoretical analysis,from the aspect of propagation patterns of the continuous rotating detonation wave(CRDW),the interaction of the CRDW with the airflow and its propagation stability.Finally,the propulsive performance of an airbreathing CRD engine was experimentally and theoretically studied.Direct-connected facility was firstly designed and built up to simulate the high temperature airflow in the airbreathing mode,based on which validating experiments on CRD were carried out.It was found that the CRDW was sustained for a long duration of three seconds,under supersonic and high temperature airflow.The results certificated that an airbreathing propulsion system based on supersonic inlet and CRD combustor was available in principle.The propagation modes of the airbreathing CRDW are studied,namely,the one-wave homo-rotating mode,two-wave homo-rotating mode,one-couple hetero-rotating mode and two-couple hetero-rotating mode.Furthermore,detonation wave propagating along the axial direction was found.It is like pulse detonation engine(PDE),but propagates upstream and do not need repeated ignition.Thereafter,the interaction of the CRDW with the airflow was studied and classified into three modes.In the supersonic inflow mode,the airflow in the isolator remains supersonic and is not affected by the CRDW.In the subsonic inflow mode,the airflow is supersonic at the entrance of the isolator,and subsonic at the exit due to the oblique shock trains.In the inlet-affected mode,the airflow at the entrance of the isolator is affected by the CRDW,and speed down till subsonic,accompanied with high frequency pressure oscillation.The influence of the equivalent ratio,detonation combustor size and the total temperature of the airflow are investigated,and results showed that the interaction of the CRDW with the airflow transformed from the supersonic inflow mode to the subsonic inflow mode and inlet-affected mode,when the intensity of the CRDW is increased.The interaction of the CRDW with the airflow can be analogized as the flow in a nozzle under different back pressure.Results showed that the effect boundary of the CRDW obtained from the theoretical model agrees well with the computational result.Next,the CRDW propagation instability is studied.From the aspects of micro propagation instability,the relative standard deviation of the CRDW propagation velocity is computed and proposed as a quantitative evaluation.The results showed that the propagation process of the CRDW with a higher intensity is more stable when it is not coupled with the propellant feeding process.Low frequency oscillation accompanied with zigzag variation of the adjacent peak pressure of the CRDW was firstly observed.The low frequency oscillation is due to the coupling of the propagation process with the propellant feeding process,while the zigzag variation is attributed to the local blow-up on the effect boundary of the CRDW.With an increased equivalent ratio,the low frequency oscillation of the CRDW gradually faded,and the propagation process is more stable due to the increased intensity.From the aspects of macro propagation instability,the relationship between the one-wave homo-rotating mode and the two-wave hetero-rotating mode is investigated,in the terms of velocity deficit of the CRDW.Results showed that the activity of the mixture is of vital importance.Besides,the hetero-rotating mode might the extreme propagation mode of the CRDW.Unstable propagation of the two mentioned modes was studied,and it was shown that frequent mode transition is induced due to the activity of the mixture.Axial-propagating DW was observed during the reigniting process after the failing of the CRDW in the hybrid circumferential mode.Furthermore,axial-propagating DW was also an important process inducing mode transition.Finally,thrust measurement of the airbreathing CRD was performed,and the effect of the nozzle on the thrust performance was studied.It was shown that the thrust engagement and specific impulse is increased by a ratio of 20% and 50%,using an area-expansion nozzle and Laval nozzle,respectively.The influence of the nozzle on the propagation mode,propagation stability and the interaction of the CRDW with the airflow are also investigated.Finally,an analytical model of an airbreathing CRD engine was established,and its thrust performance is obtained under different flight condition,fuel types,equivalence ratio and detonation combustor size.