A Single-Phase Model for Simulation of Exploding Bridge Wire Ignition

Exploding bridge wires (EBWs) are commonly employed to ignite solid and gaseous detonations but are poorly understood and difficult to model because of the extraordinarily short timescales and rapid fluctuations in temperature, pressure, and density. This paper presents a simplified gas-phase-only model that allows the blast wave to be resolved without needing to simulate the phase change, electrodynamics, and plasma physics. CONVERGE CFD was used to study the effect of the blast wave on hydrogen detonation in stoichiometric mixtures ranging from pure oxygen to air. Different wire diameters, pulse energies, and mixture conditions were simulated in highly resolved 2D simulations to determine the potential for direct initiation of detonation. Despite extreme overpressure in the blast, direct initiation was only observed with large energies in highly oxygen-enriched mixtures. Some cases near the threshold of direct initiation showed complex critical behavior with decoupling followed by an overdriven re-detonation. The blast simulations were also calibrated against EBW experiments in pure air, showing that about 90% of the electrical energy is lost to sinks unaccounted for in the 2D gas-phase model. The results indicate that smaller wires are more effective at direct initiation for the same energy release, but that larger wires are more effective if the energy release is functionally constrained to an energy ratio determined by the mass of the wire. The results also indicate that blast wave ignition is not a reliable method of triggering detonation of hydrogen in air despite extremely high localized temperatures and pressures.