| Continuous Rotating Detonation Engine(CRDE)is a conceptual propulsion devices,in which the energy is released by detonation-based combustion.Comparing with traditional engines,it possesses superiorities in compact structure,high thermal efficiency and so on.However,the CRDE requires more energy when igniting with liquid fuel.Therefore,there lays difficulties for ignition using regular ways such as ignition plug.To solve this problem,this paper investigated initiation characteristics of the detonation chamber experimentally and numerically.The influences of different operational conditions and geometric construction as well as the generation process on detonation waves in initiators were studied.The findings are as follows:(1)A initiator was designed to fuel by kerosene and oxidate with pure oxygen,including centrifugal/pre-film composite atomizing injector;ignition/transmission flame concave cavity,several structural initiator chambers.The atomization testing platform were built up,for common and low output backpressure test.(2)Experimental researches was conducted on atomization characteristics of the centrifugal/prefilm composite atomizing injector and improvement of atomization by increasing fuel pressure(for better first atomization)and gas-flow(for better second atomization).The optimum geometry of initiator’s cavity and controlling sequences for ignition were found out.To realize better initiation,we should utilize light and cavity of 8mm height in rectangular section with diameter about 18%.The favorable time series should be airfeed in advance,supplement after evaluating the mixing time and ignition in a bit advance.The lower pressure the initiators outputs,the lower average pressure of detonation waves were generated,and DDT distance was increased.(3)With the optimum cavity geometry and controlling sequences,multiple initiator structure layouts were tested and all of them could generate detonation waves with high peak pressure and dissemination speed.Under some operating conditions,there existed situation that mixtures were compressed before detonation,and exhibited higher peak pressure than theoretical figures.Different peak pressures affected by atomization effect,mixed gas distribution and geometries of initiators.When the ignition tube was tangentially positioned and three pipes branched interior,the detonation waves propagation is regular.Peak wave pressures and fluctuates of thermojet outlet pressure in semicircle tubes were higher than circular and square tubes.Thus,the circular tubes were of best regularity and favorable for experiments,while semicircle tubes were of less height and smaller frontal area,which were suitable for industrial application.(4)The propagation of detonation wave from the initiator to detonation chamber was simulated.The effects of different ignition locations and multi-point ignition on pulses were found to be little.However,the time interval from ignition to stable rotating detonation was remarkably increased under multi-point ignition.The detonation waves from ignition tubes entered into rotating detonation chamber and ignited unburned mixture.Afterwards the detonation waves collided,decoupled and reignited,eventually reached a stable state. |
