Investigation on the flame and explosion suppression of hydrogen/air mixtures by porous copper foams in the pipe with large aspect ratio

In this work, the flame and explosion suppression performance of copper foams with five apertures of 10 PPI, 20 PPI, 30 PPI, 40 PPI and 60 PPI were investigated. The combustion characteristics of hydrogen/air premixed gas with stoichiometric ratio were investigated under three experimental schemes. The experiments were carried out in a circular cross-sectional pipe with aspect ratio of 108. Under the influence of copper foam, there are four phases of flame propagation, namely, laminar rapid expansion, backflow, rapid turbulence and pulsation deceleration. The results show that continuous copper foam sheets with aperture of 60 PPI can effectively prevent flame from spreading to the downstream of the pipe and make flame quenching. At the same time, the phenomenon of “negative pressure suction” was observed. The upstream overpressure was reduced to 0.06 MPa and the flame velocity was 25 m/s. As the aperture of copper foam decreased, shock wave and flame velocity decreased. The process of deflagration to detonation transition was effectively inhibited. Widely spaced copper foams can effectively prevent the impact of reflected shock wave and hindrance the flame from downstream. The results can provide a significant reference for designing hydrogen flame arrestors to improve the safety of hydrogen pipeline transportations and engineering applications. Propagation of shock waves under different experimental schemes. • Explosion of premixed hydrogen/air in a large aspect ratio pipe were investigated. • Copper foams have excellent performances of absorbing wave and preventing flame. • Phenomenon of “negative pressure suction” was observed in the upstream of pipe. • DDT was effectively inhibited by continuous copper foams with aperture 60 PPI. • Four phases and secondary peaks of flame propagation were proposed.