@article{PhysRevE.97.013103,
title = {Electrohydrodynamic instability of premixed flames under manipulations of dc electric fields},
author = {Ren, Yihua and Cui, Wei and Li, Shuiqing},
journal = {Phys. Rev. E},
volume = {97},
issue = {1},
pages = {013103},
numpages = {8},
year = {2018},
month = {Jan},
publisher = {American Physical Society},
doi = {https://doi.org/10.1103/PhysRevE.97.013103},
url = {https://journals.aps.org/pre/abstract/10.1103/PhysRevE.97.013103}
abstruct={We report an electrohydrodynamic instability in a premixed stagnation flame under manipulations of a dc electric field. This instability occurs when the electric field strength is at a certain value below the breakdown threshold, which is 0.75 kV/cm in the experimental setup. Above this value the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field. At the transition moment, the flame spontaneously propagates upstream to the nozzle while the flow velocity at the upstream of the flame front decreases to zero, as revealed by high-speed photographs and PIV measurements. These phenomena indicate a transient balance between the fluid inertia and the electric body force around the instability threshold. A quantitative model suggests that the flame instability can be explained by a positive feedback loop, where the electric field applies a nonuniform electric body force, pulling the flame front upstream, and the pulled flame front in turn enhances the local electric body force. The electrohydrodynamic instability occurs when the electric pulling is strong enough and both the growth rates and the magnitudes of the electric body force on flame exceed those of the fluid dynamic pressure.}
}
the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field.(火炎は,燃焼場からの電流の急上昇を伴い,潤安定な平面に近い形状からノズルに定在した円錐状の形へと急激に遷移する)
the flow velocity at the upstream of the flame front decreases to zero(火炎上流の流速はゼロに減少する)
transient balance between the fluid inertia and the electric body force around the instability threshold(流体の慣性と静電気力のバランスが不安定性の閾値を決定する)
A specially designedhoneycomb, placed at the outlet of the nozzle, allowed gasto flow through and generated a nonuniform axial velocitydistribution at the inlet of the flame field
In this regime, the net charge density is approximately proportional to the applied field strength, i.e.,nc∝E, and the current density then scales as j∝encEμ∝E2(whereμisthe mobility).(この領域(平面形状)では古典的な理論に従い,電界Eの二乗に電流が比例する)
The current responses of the flame almost lie in another I−U curve completely different from the previous one. In this curve, the flame current plateaus with further increasing voltages, indicating the approaching of a saturation regime [20].(コニカルな領域では異なり,飽和領域に陥り,電圧の増加で電流はプラトーに達する)
Besides, as shown inFig.3(d), simulation of the charge transport behaviors based on the measured flame front reveals that the current density follows the conductive flame front and generates a large electric body force about 19.3N/m3localized at the upstream of the flame wrinkle.(計測された火炎面をもとにした計算結果によると,連続した火炎面に沿った電流密度が19.3 N/m3 の電気的体積力を火炎上流側に発生させている)
the maximum electric body force in this mode reaches as high as 770 N/m3, almost 40 times higher than that at the flat mode, which is large enough to reduce the upstream flow velocity to the flame speed. (最大の電気的体積力は770 N/m3 であり上流の流速を減少させるのに十分な大きさである)
Therefore, the effects of electric fields on flames strongly depend on the original flame structures, which can well explain the bifurcated flame stabilization modes for increasing and decreasing voltages.(そのためオリジナルの火炎形状が電界の与える効果に大きな影響を及ぼし,このことが電圧の上昇時と下降時の分岐した安定火炎モードと整合する)
@article{PhysRevE.97.013103, title = {Electrohydrodynamic instability of premixed flames under manipulations of dc electric fields}, author = {Ren, Yihua and Cui, Wei and Li, Shuiqing}, journal = {Phys. Rev. E}, volume = {97}, issue = {1}, pages = {013103}, numpages = {8}, year = {2018}, month = {Jan}, publisher = {American Physical Society}, doi = {https://doi.org/10.1103/PhysRevE.97.013103}, url = {https://journals.aps.org/pre/abstract/10.1103/PhysRevE.97.013103} abstruct={We report an electrohydrodynamic instability in a premixed stagnation flame under manipulations of a dc electric field. This instability occurs when the electric field strength is at a certain value below the breakdown threshold, which is 0.75 kV/cm in the experimental setup. Above this value the flame front suddenly transits from a substrate-stabilized near-flat shape to a nozzle-stabilized conical surface, accompanied by a jump in the electric current through the flame field. At the transition moment, the flame spontaneously propagates upstream to the nozzle while the flow velocity at the upstream of the flame front decreases to zero, as revealed by high-speed photographs and PIV measurements. These phenomena indicate a transient balance between the fluid inertia and the electric body force around the instability threshold. A quantitative model suggests that the flame instability can be explained by a positive feedback loop, where the electric field applies a nonuniform electric body force, pulling the flame front upstream, and the pulled flame front in turn enhances the local electric body force. The electrohydrodynamic instability occurs when the electric pulling is strong enough and both the growth rates and the magnitudes of the electric body force on flame exceed those of the fluid dynamic pressure.} }