Investigations On The Initiating Process Of Detonation Wave In Rotating Detonation Engine

In the recent years, the rotating detonation engine(RDE) has been noticed widely at home and abroad. Compared with the traditional propulsion device, RDE has some significant advantages on some aspects like propulsive performance and structure. But due to the lack of the study about the initial conditions and the formation mechanism of detonation, the structure of the ignition device on RDE is complicated, and the ignitability is relatively low. This paper based on it,and the main content is as follows:(1)A low-energy spark device was used to ignite RDE successfully. Through systematic research, the operating process was revealed, and the working conditions of RDE were definitely reported. The propagation characteristics of the working process was analyzed in detail. The conclusions were as follows:There are four working states which include continuous detonation, interrupted detonation, sporadic detonation and no detonation on RDE. When continuous detonation occur, the pressure of detonation is stable, the fluctuation of the propagation velocity is tiny, and there is no direction change. The propagation velocity of detonation wave is 1286m/s-1644.8m/s and the basic frequency fluctuate from 5090Hz to 6450.7Hz. When interrupted detonation occurs, the pressure of detonation fluctuates evidently and the propagation direction of detonation may changed. The strong detonation and weak detonation appeared alternately.(2)Three different ignition methods of low-energy spark device, high-energy spark device and pre-detonator were used to initiated the RDE. The building process of the rotating detonation wave with the three ignition method were contrastively studied through the pressure measurement and optical observation. In the same condition, the repetitive experiments with the three ignition methods were carried out, and the influence of the ignition method on the establishing time interval of detonation was statistically studied. The conclusions were as follows:The built of detonation must experience a developing process of flame like deflagration-to-detonation(DDT). Because of the flame instability, the establishing time of rotating detonation exhibited an obvious randomness. In total, the establishment of detonation with pre-detonator was faster than the other two ignition method. The ignitability of the three ignition methods were 100%, and the working frequency of RDE fluctuates around 5800Hz and keep stable. The ignition methods have no influence on the propagation characteristics of the stable working state.(3)The influences on the detonation establishment of the equivalent ratio of reactants, ignition location and the state of jet flame were comparatively studied. The exploratory research about the one-direction initiation of detonation also was carried out at last. The conclusions were as follows:In the stable working condition of RDE, the establishing time interval of rotating detonation decreased with the increase of the total mass flow rate of reactant. The establishment of rotating detonation ignited by detonation wave was faster than the establishment ignited by hot-jet. Besides, the ignition location and exhaust time of pre-detonator have no influence on the establishing time interval of rotating detonation.