Origin of activated combustion in steady-state premixed burner flame with superposition of dielectric barrier discharge

Abstract

The objective of this work is to understand the mechanism of plasma-assisted combustion in a steadystate premixed burner flame. We examined the spatiotemporal variation of the density of atomic oxygen in a premixed burner flame with the superposition of dielectric barrier discharge (DBD). We also measured the spatiotemporal variations of the optical emission intensities of Ar and OH. The experimental results reveal that atomic oxygen produced in the preheating zone by electron impact plays a key role in the activation of combustion reactions. This understanding is consistent with that described in our previous paper indicating that the production of "cold OH(A 2 Σ + )" via CHO + O → OH(A 2 Σ + ) + CO has the sensitive response to the pulsed current of DBD [K. Zaima and K. Sasaki, Jpn. J. Appl. Phys. 53, 110309 (2014)].

Transient change in the shape of premixed burner flame with the superposition of pulsed dielectric barrier discharge

“…The less efficient reactions may be due to the excessive consumption of oxidizers, which is caused by the overshooting of the rates of combustion reactions by the superposition of the pulsed plasma. As reported in a previous paper, 30) we observed the oscillation of the density of atomic oxygen in the preheating zone of the bottom part of the DBD-assisted flame. However, the oscillation frequency of the atomic oxygen density in the bottom part was much higher The formation of local minimums in the axial distribution of the optical emission intensity was also observed at the top of the flame when we terminated the irradiation of the microwave power to the bottom part of the flame.…”

“…3,[26][27][28] In our recent works, we also pointed out the importance of atomic oxygen produced in the preheating zone of a premixed burner flame. 29,30) The understanding on the importance of atomic oxygen is insufficient to optimize practical systems of plasma-assisted combustion. Our recent work shows the importance of atomic oxygen in a limited part of the flame (the preheating zone), but we observe changes in combustion characteristics in a larger volume of the flame.…”

Effective species for ignition of premixed burner flame in effluent of dielectric barrier discharge

“…This conclusion was obtained by a high-resolution experiment in the transition part between the unburned gas and the reaction zone in the steady-state flame. 32) In the present work, we observed the propagation speed of the flame kernel in the effluent of DBD. The reason why we employed this experimental method in the present work is that the radial structure of the steady-state premixed burner flame from the unburned gas to the reaction zone via the preheating zone has an analogy with the temporal evolution of the flame ignition.…”

“…The premixed gas of Ar, O 2 , and CH 4 was introduced from the stainless-steel vessel toward the top of the quartz tube. We used Ar instead of N 2 in a series of our works [30][31][32][33] to avoid the optical emission of the N 2 second positive system, which contaminated the optical emission spectrum of the OH A 2 Σ + -X 2 Π transition. The flow rates of Ar, O 2 , and CH 4 were controlled using mass flow controllers and adjusted at 2.25, 0.4, and 0.2 slm, respectively.…”

“…28,29) In our previous works, we have examined the effect of the dielectric barrier discharge (DBD) on the burning velocity in a steady-state premixed burner flame. [30][31][32][33] The experimental results indicate that atomic oxygen produced in the preheating zone is the origin of the activated combustion reactions. This conclusion was obtained by a high-resolution experiment in the transition part between the unburned gas and the reaction zone in the steady-state flame.…”