Analysis of the step responses of laminar premixed flames to forcing by non-thermal plasma
Analysis of the step responses of laminar premixed flames to forcing by non-thermal plasma
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DOI：
10.1016/j.proci.2016.06.178
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发表时间：
2017
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影响因子：
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通讯作者：
D. Lacoste;J. Moeck;W. Roberts;S. Chung;M. Cha
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文献类型：
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作者：
D. Lacoste;J. Moeck;W. Roberts;S. Chung;M. Cha
报道了贫甲烷-空气火焰对非热等离子体强迫的阶跃响应。实验装置由轴对称燃烧器和石英管喷嘴组成。等效比为0.95，允许火焰稳定在v形或m形几何形状，在中央不锈钢棒。等离子体由持续时间为10ns，最大电压幅值为8kv，施加频率为10khz的短脉冲产生。中心杆用作阴极，而阳极是一个不锈钢环，固定在石英管的外表面。等离子体强迫是由等离子体的正或负步骤产生的。火焰的阶跃响应通过热释放率（HRR）波动进行研究，以便与火焰对声扰动的响应进行比较。利用配备光学滤光片的强化相机记录了两个连续脉冲之间CH*的化学发光，以估计HRR波动。结果表明，火焰对单个等离子体脉冲没有响应，而只受平均等离子体功率的影响，证实了强迫的阶跃性质。分析了HRR的时间演化规律，确定了火焰传递函数。提出了一种强迫机制，即靠近杆的流体的局部反应性增加，并与数值模拟进行了比较。实验结果与数值模拟结果定性一致。
The step responses of lean methane-air flames to non-thermal plasma forcing is reported. The experimental setup consists of an axisymmetric burner, with a nozzle made of a quartz tube. The equivalence ratio is 0.95, allowing stabilization of the flame in a V-shape or an M-shape geometry, over a central stainless steel rod. The plasma is produced by short pulses of 10-ns duration, 8-kV maximum voltage amplitude, applied at 10 kHz. The central rod is used as a cathode, while the anode is a stainless steel ring, fixed on the outer surface of the quartz tube. Plasma forcing is produced by positive or negative steps of plasma. The step response of the flame is investigated through heat release rate (HRR) fluctuations, to facilitate comparisons with flame response to acoustic perturbations. The chemiluminescence of CH*between two consecutive pulses was recorded using an intensified camera equipped with an optical filter to estimate the HRR fluctuations. First, the results show that the flame does not respond to each single plasma pulse, but is affected only by the average plasma power, confirming the step nature of the forcing. The temporal evolutions of HRR are analyzed and the flame transfer functions are determined. A forcing mechanism, as a local increase in the reactivity of the fluid close to the rod, is proposed and compared with numerical simulations. Experiments and numerical simulations are in good qualitative agreement.