Diagnostics of Atmospheric-Pressure Non-thermal plasmas for Air Polluion Control using Laser-induced Fluorescence Spectroscopy

低温等离子体技术被认为是脱除烟气中NOx的有效方法。为了优化反应器，为脱除NOx的数值模拟提供信息，直接研究放电诱导的等离子体化学过程对脱除反应器中的NOx具有重要意义。激光诱导荧光(LIF)是现场观察脱除NOx过程中现象的一种有用的诊断方法。这项工作的主要目的是可视化二维NO浓度和监测电晕自由基簇射反应器内NOx的去除过程。为此，采用了平面激光诱导荧光(PLIF)。电晕自由基簇射反应器由喷嘴-板式电极系统组成，电极间隙为50 mm。产生稳定的直流流光电晕放电，并在放电过程中在电极之间发射薄片形式的激光脉冲。激光板沿90度角发射的LiF信号被成像到门控ICCD相机上，并记录了反应堆各个区域的二维LIF图像。通过对NO的宽范围成像(宽240 mm，高160 mm)，不仅可以观察到放电区的二维分布，而且可以观察到反应器下游和上游的二维分布。在低主气流量下，电流体(EHD)流占主导地位，向上游流动影响了NO从上游沿反应器的降低。这些信息对等离子体过程的建模和优化以及非热等离子体反应器的设计具有重要意义。

Non-thermal plasma process has been considered to be an effective method to remove NOx from flue gas. In order to optimize the reactor and provide the information for numerical simulation of NOx removal, it is important to study directly the discharge induced plasma chemical processes responsible for NOx removal in the reactor. Laser-induced fluorescence (LIF) is a useful diagnostic method for in-situ observation of the phenomena during the NOx removal. The main objective of the presented work is visualization of two-dimensional NO concentration and monitoring the process of NOx removal inside the corona radical shower reactor. Planar laser induced fluorescence (PLIF) was employed for this purpose. The corona radical shower reactor consists of a nozzle-to-plate electrode system, having an electrode gap of 50mm. Stable dc streamer corona discharge was generated and laser pulses in the form of the sheet were shot between the electrodes during the discharge. LIF signal emitted at 90 degree to the laser sheet was imaged onto a gated ICCD camera and the two-dimensional LIF images from the various regions of the reactor were recorded. By the wide range imaging of NO (image size: 240mm in width and 160mm in height), two-dimensional distributions of NO could be observed not only the discharge zone but also both the downstream and the upstream regions of the reactor. In the present reactor at a low main gas flow rate, electrohydrodynamic (EHD) flow became dominant, and the flow towards the upstream affected the decrease of NO along the reactor from the upstream region. It is considered that this information is important for modeling and optimizing the plasma processes and designing the non-thermal plasma reactors.