Nanosecond pulsed discharge dynamics during passage of a transient laminar flame

Abstract

This work presents an experimental study of a nanosecond repetitively pulsed dielectric barrier discharge interacting with a transient laminar flame propagating in a channel of height near the quenching distance of the flame. The discharge and the flame are of comparable size, and the discharge is favoured at a location where it is coupled with the reaction zone and burned gas. The primary goal is to determine how the discharge evolves on the time scale of the flame passage, with the evolution driven by the changing gas state produced by the moving flame front. This work complements the large body of work investigating the effect of plasma to modify flame dynamics, by considering the other side of the interaction (how the discharge is modified by the flame). The hot gas produced by the combustion had a strong effect on the discharge, with the discharge preferentially forming in the region of hot combustion products. The per-pulse energy deposited by the discharge was measured and found to increase with the size of the discharge region and applied voltage. The pulse repetition frequency did not have a direct impact on the per-pulse energy, but did have an effect on the morphology and size of the discharge region. Two distinct discharge regimes were observed: uniform and filamentary (microdischarges). Higher pulse repetition frequencies and faster-cooling combustion products were more likely to transition to the filamentary regime, while lower frequencies and slower-cooling combustion products maintained a uniform regime for the entirety of the time the discharge was active. This regime transition was influenced by the ratio of the time scale of fluid motion to the pulse repetition rate (with no noticeable impact caused by the reduced electric field), with the filamentary regime preferentially observed in situations where the ratio was small.

Nanosecond repetitively pulsed plasmas with MHz bursts for CO2 dissociation

“…It is assumed that CO and O 2 are the only products, e.g. no carbon deposition is visible after hours of operation, compliant with equation (1). Note that in a rigorous treatment, the change of the gas flow rate between reactor entrance and exit due to conversion should be taken into account [59,60].…”

“…Alternatively, the current and the time derivative of the voltage can be decomposed into their Fourier components and afterwards reconstructed from the dominant frequencies. The cross-correlation of the reconstructed signals allows to determine the time lag [1]. As the determined capacitance and the cross-correlation in figure C.2 seem good, we did not further look into this alternative.…”

“…Nanosecond repetitively pulsed (NRP) discharges enjoy great popularity in applications striving for energy-efficient and selective activation of gases such as plasma-assisted combustion [1][2][3] or air plasma [4][5][6][7]. In the context of plasma-assisted combustion, they are recognised for their 4 Present affiliations: AP Integer Technologies B.V.…”

Dynamic response of nanosecond repetitively pulsed discharges to combustion dynamics: regime transitions driven by flame oscillations

“…Recent work has begun to consider how dynamic gas combustion environments may affect the behavior of the plasma in systems utilizing plasma-assisted strategies. This impact of the combustion environment on the discharge has been referred to as the 'backward-problem', as opposed to the more extensively studied 'forward-problem' of how the discharge affects the flame [20,21]. In platforms with high power and turbulent flames, the gas environment changes on the time scale of many accumulated nanosecond pulsed discharges.…”