Low frequency instability in a H2/air plane-radial rotating detonation engine

Abstract

To investigate low frequency instability in a H2/air plane-radial rotating detonation engine, simultaneous visualization, pressure, and ion measurements are performed. Changing reactants mass flow rate and equivalence ratio, two low frequency instabilities, amplitude low frequency instability (ALFI) and amplitude-frequency low frequency instability (AFLFI) are discovered, characterized by periodic sinusoidal oscillations of detonation-wave parameters. The operating conditions of low frequency instabilities are also summarized. The ALFI with periodic fluctuations of detonation-wave pressure peak mostly occurs in single-wave modes and symmetric dual-wave modes, operating near the critical conditions of modes switching. Almost all asymmetric dual-wave modes and some triple-wave modes exhibit some degree of AFLFI characterized by periodic waxing and waning of detonation-wave pressure peak and velocity. Each low-frequency cycle contains several to dozens of rotating detonation laps. Obvious high-frequency and low-frequency oscillations are observed in air plenum, with exactly the same frequency as that in the combustor but lower amplitudes and some phase difference. The interaction between plenum and combustor affects detonation stability.