Visual experimental research on the propagation instabilities in a plane-radial rotating detonation engine

Abstract

Using visualization method, assisted by synchronous pressure and ion measurements, the characteristics of four instabilities and operating ranges are investigated in a plane-radial rotating detonation engine. At fuel-lean limits, the rotating detonation wave (RDW) propagates in an incoherent mode. The propagation is unstable with obvious interruption characterized by local flameout, decoupling, re-initiation and propagation direction change. At low mass flow rates, the quasi detonation mode with fairly low pressure peak but high velocity is obtained, in which the outer circumferential flame and central flame occur alternately. The modes switching of RDW operates at critical operating conditions. Two modes are obtained in one test and sudden change in the wave-head number exists in the combustor. An asymmetric dual-wave mode is obtained at special conditions with low mass flow rates and fuel-rich conditions, and the intensities of two asymmetric RDWs alternately increase and decrease with time. The phenomena of decoupling and re-initiation occur periodically, and an amplitude-frequency low-frequency oscillation is observed in this instability. In these instabilities, the pre-combustion phenomenon ahead of detonation wave occurs on the deflagration surface, which promotes the development of RDW. Furthermore, the pressure rising rates is greatly affected by combustion modes and wave-head number. The pressure rising rates of quasi detonation mode is an order of magnitude lower than that of stable detonation mode.