Enhancement of the transition to detonation of a turbulent hydrogen–air flame by nanosecond repetitively pulsed plasma discharges

Abstract

This work provides proof of concept for the use of nanosecond repetitively pulsed (NRP) plasma discharges to accelerate a propagating turbulent flame, resulting in enhanced deflagration-to-detonation transition and significant reduction in run-up length. The investigations are conducted on a stoichiometric hydrogen-air mixture at near ambient conditions. The effect of plasma actuation on the flame velocity is investigated using time-of-flight measurements of the propagating flame and detonation wave. The flame velocity shortly after the application of the NRP plasma discharges is more than double that obtained in cases in which no plasma is applied. High-speed imaging of OH * chemiluminescence in the electrode area confirms this result and provides insight about the mechanisms of plasma action. While the volumetric energy deposited during plasma actuation is sufficiently low as to not ignite the combustible mixture prior the arrival of the flame, the chemical and thermal enhancement of the gas is efficient enough to significantly

Effects of Nanosecond Repetitively Pulsed Plasma Discharges on a Propagating Hydrogen--Air Flame

“…This could be due to a local explosion ahead of the flame that does not transition to a detonation, but still registers as a reaction front at the ionization probe. Nevertheless, these measurements validate the previous proof of concept reported in [10] that NRP plasma discharges can successfully accelerate the transition to detonation for flames propagating at the velocities exhibited in this configuration. Table 1 Average arrival times of the propagating flames in each configuration and the corresponding delay applied between ignition and application of the first NRP plasma pulse.…”

“…The investigations with one orifice plate serve to confirm the results reported in [10]. The flame propagation velocities with and without plasma actuation are presented in Fig.…”

“…However, the energy deposition of these discharges is very large (on the order of 100 J). The authors have proposed a new concept of replacing physical obstacles with nanosecond repetitively pulsed (NRP) plasma discharges [10]. Indeed, NRP discharges have shown much promise in enhancing the chemical kinetics in plasma-assisted combustion applications in order to improve ignition, control combustion instabilities, and extend lean blow-off limits [11,12].…”

“…In a recent study by the authors, proof of concept has been demonstrated using NRP plasma discharges on a propagating flame to significantly increase flame acceleration and decrease the run-up length to DDT [10]. This strategy has proven to be very robust and reproducible.…”

Effect of non-equilibrium plasma on decreasing the detonation cell size

“…Efficient pre-dissociation in combustible mixtures [1], decrease of the ignition delay [2], extending the flammability limits and increasing the combustion stability of lean mixtures [3,4] by plasma were demonstrated both experimentally and numerically. Enhancement of the DDT transition under the action of nanosecond (ns) plasma were obtained in C 3 H 8 , C 4 H 10 , C 6 H 14 based mixtures [5] and in H 2 :air mixture [6]. The action of plasma on already formed detonation has not been investigated before.…”