Deflagration-to-detonation transition via the distributed photo ignition of carbon nanotubes suspended in fuel/oxidizer mixtures

Here the promotion of flame acceleration and deflagration-to-detonation transition (DDT) using the distributed photo ignition of photo-sensitive nanomaterials suspended in fuel/oxidizer mixtures is demonstrated for the first time. Distributed photo ignition was carried out by suspending single-walled carbon nanotubes (SWCNTs) with Fe impurity in quiescent C2H4/O2/N2 mixtures and flashing them with an ordinary Xe camera flash. Following the flash, the distributed SWCNTs photo ignite and subsequently provide a quasi-distributed ignition of the C2H4/O2/N2 mixture. In a closed detonation tube the quasi-distributed photo ignition at one end of the tube leads to the promotion of flame acceleration and DDT and, for sensitive C2H4/O2 mixtures, appears to lead to direct detonation initiation or multiple combustion fronts. The DDT run-up distance, the distance required for the transition to detonation, was measured using ionization sensors and was found to be approximately a factor of 1.5× to 2× shorter for the distributed photo ignition process than for traditional single-point spark ignition. It is hypothesized that the increased volumetric energy release rate resulting from distributed photo-ignition enhances DDT due to the decreased ignition delay and greater early-time flame area and turbulence levels, which in turn result in accelerated formation and amplification of the leading shock and accelerated DDT.