The behaviors of supersonic combustion wave through a perforated plate in a stoichiometric mixtures of H2/CH4/O2 and H2/O2

Abstract

In this study, we reported the supersonic combustion wave behaviors as it propagated through a perforated plate in stoichiometric mixtures of H2-CH4-2.5O2, H2-CH4-4O2 and 2H2-O2. The perforated plate maintained an identical thickness of 10 mm with different hole diameters of 4 mm, 8 mm and 10 mm, respectively. Explosion pressures were recorded using pressure transducers flushed-mounted on the top wall, based on which the average velocity was calculated. Meanwhile, the cellular structures of the supersonic combustion waves were recorded by soot foils. According to the average velocity and soot foils, the propagation modes were classified into four regimes including Fast-flame to fast-flame, Fast-flame to detonation, Detonation to fast-flame, Detonation to re-initiation and Overdriven detonation to detonation. The perforated plate exerts a positive effort on fast-flame by disturbing the flow flied, therefore the fast-flame does not decelerate downstream of the perforated plate. However, the effect of the perforated plate is opposite for detonation, and it weakens the detonation and even causes detonation failure. And this effect is weakened with the hole diameter increasing, which is proven by the limit of re-initiation decreases from d/λ = 0.98(d = 4 mm) to d/λ = 0.71(d = 10 mm). However, the re-initiation mechanisms are different at various initial pressures. At higher initial pressure, the detonation front is elongated dramatically but not failed and it recovers downstream. However, the failed detonation needs the aid of the shock refection off the tube wall to re-initiate at lower initial pressure. With increasing the sensitivity of the mixture, the overdriven detonation characterized by d/λ > 1 was found to transmit the holes with no failure. By comparing with the failing cases owning small cells, d/λ > 1 is not the sole condition to ensure a detonation traveling through with no failure.