旋转爆震发动机中爆震波不稳定传播特性实验研究

Experimental Research on Unsteady Propagation Properties of Detonation Waves in Rotating Detonation Engines

在内径为60mm,外径为70mm的旋转爆震发动机实验件上,进行了以氢气/空气为推进剂的旋转爆震实验,以研究爆震波传播过程中的不稳定现象。实验中采用预爆管切向入射的方式起爆旋转爆震波,用高频动态压力传感器记录爆震波压力,用高速摄像机拍摄爆震波在环形燃烧室内的传播现象。在稳定工况下,爆震波传播速度达到1680.6m/s(为理论值的83.9%),工作频率达到7642Hz;在小流量工况下,爆震波的传播速度表现出很强的不稳定性,能从790.1m/s(理论值的39.4%)变化至1533.9m/s(理论值的76.6%)。实验发现了旋转爆震发动机的点火起爆过程中存在如下不稳定现象:爆震波自发改变传播方向,爆震波自发由一个变成两个,两个爆震波相互撞击。在实验中,还发现:不带喉部时,旋转爆震发动机中爆震波的传播方向具有随机性;带喉部时,爆震波的传播方向呈现出规律性。出现上述"不稳性"现象的可能原因是:点火起爆阶段,初始流场混乱,湍流度较大,爆震波的形成过程容易受到流场扰动的随机性干扰。

Experimental research on unstable propagation phenomenon of rotating detonation wave was carried out on a model rotating detonation engine with 60 mm inner diameter and 70 mm outer diameter using hydrogen and air as propellants. Detonation was initiated by a tangentially mounted pre-detonator,which emitted a detonation wave into the rotating detonation engine. Pressures and propagation processes of detonation waves were measured by dynamic pressure sensors and high speed camera,respectively. Under stable case,the detonation velocity is 1680.6 m/s（83.9% of the theoretical value）and operating frequency is 7642 Hz. However,the detonation velocity exhibited strong instability with low mass flow rate,which can vary from 790.1 m/s（39.4% of the theoretical value）to 1533.9 m/s（76.6% of the theoretical value）. In experiments it was found that during the detonation initiation process there is unstable phenomenon,including rotating direction changing,wave number changing from one to two,and two waves impinging. In this research it was also found that the direction of rotating detonation waves is random without a nozzle throat. However,in contrast when there is a nozzle throat,the direction trends to be regular. The possible reason for the unstable phenomenon mentioned above is that during the detonation initiation process,the initial flow field inside the rotating detonation engine is chaotic and very turbulent,so detonation initiation process can be easily disturbed by this random flow.