Ignition enhancement using magnetic gliding arc

The non-thermal ignition enhancement by a non-equilibrium magnetic gliding arc (MGA) integrated with a counterflow diffusion flame burner plasma was experimentally and computationally investigated. The system provided a well-defined platform to study nonthermal ignition enhancement by a non-equilibrium plasma discharge. Up to a 240 K decrease in the ignition temperatures for 20% CH⁴ in 80% N² versus air counterflow diffusion flames was observed by activating the heated air stream with the MGA when compared to only heated air at the same strain rate. Modeling of the plasma production of radicals was performed and was based upon experimentally measured voltage-current characteristic curves and rotational and vibrational temperatures of the MGA. Computational simulations of the counterflow diffusion flame ignition were subsequently performed with initial conditions of the concentration of O and NO from the plasma modeling. The simulation results showed a significant decrease in the temperatures at ignition when mimicking the MGA, exhibiting qualitatively similar behavior to the experimental results. The modeling suggested that with O and NO addition, the ignition at low temperatures was purely kinetic with NO being the major contributor. However, with increasing strain rate, the kinetic ignition disappeared, being replaced by thermal ignition. The kinetic enhancement by NO became weaker with increasing temperature, eventually converging with the second ignition limit (high temperature ignition limit). This demonstrated that plasma enhancement will depend upon the species produced, their concentrations, the gas temperature and lastly the characteristic flow residence times in the system.