| Rotating detonation engine(RDE)is a new kind of propulsion device.Due to the rapid energy release rate,high thermal cycle efficiency,simple and compact structure,high operation frequency,it has broad application prospect in propulsion field of the future and has attracted widespread attention in recent years.The study object of this thesis is a RDE using hydrogen/air as propellant.Experimental investigation and numerical simulation were conducted to study the initiation and propagation characteristics of the rotating detonation wave and the propulsion performance of the engine.RDE experiment and measurement system were built up and a modular engine was designed.Three ignition methods,including the ordinary spark plug,high-energy spark plug and pre-detonator tube were used in the tests to reveal the initiation characteristic of the RDE.The initiation process of rotating detonation wave was recorded and analyzed by a high frequency pressure measurement system and high-speed photographs.Operating range of the model engine was determined by series of experiments.Results indicated that the engine could be successfully run by all these three ignition methods,and the formation time of detonation wave reduced with a higher ignition energy.It was found that the operating characteristic of the model engine was independent of the ignition device in the same operating condition.Three operation modes of the engine model have been observed,which were deflagration,unstable detonation and continuous detonation.Different operation modes could be converted each other with the change of working condition,and the stable operating range was extended by increasing the fuel mass flow rate.Experimental study on the stability of rotating detonation wave was carried out.Two methods were proposed to capture the peak values of the detonation waves.Three unstable propagation modes of the rotating detonation wave were discovered,which are oscillation of the pressure peak,decoupling of detonation wave and propagation direction change of detonation wave.The forming conditions and changing process of the unstable propagation modes were analyzed.The results showed that the continuous propagation of the rotating detonation wave was effected by the interaction of the combustion chamber pressure and injection process.As the injection position of hydrogen moved forward,the stability of detonation wave was improved and the operating range of the engine was extended.Three-dimensional flow field structure of RDE with separate injection of fuel and oxidant was simulated.A high-re solution upwind scheme(AUSMPW+)and detailed reaction kinetics model were applied.The effect of the mixing process,inlet condition and chamber construction were analyzed.It was found that the detonaton wave could spread upstream and affect the injection presuure of the propellant plenums.The thrust had a linear growth with the increasing of mass flow rate,while the total inflow temperature and detonation wave number had little impact on the propulsion performance.However,the exhaust flow of two-wave mode was more homogeneous.As the fuel injection position moved forward,the mixing quality of propellant was better.The intensity and propagation velocity of detonation wave were improved.The leading shock wave tended to decouple with the increase of the curvature.The influence rules of converging nozzle on the RDE propulsion performance and propagation mode of detonation wave were investigated experimentally and numerically.The transition process was analyzed.With a converging nozzle,the propulsion performance was increased significantly and the height of detonation wave decreased.A reflected shock wave was formed at the converging section of nozzle.As the mass flow rate increased,single wave mode,single/dual-wave hybrid mode,and dual-wave mode were obtained in sequence.With a narrower throat,the improvement of the propulsion performance was larger and the critical mass flow rate of the propagation mode was lower. |
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