Characterization of the thermal structure of six clustered microflames seeded with TaN particles through emission spectroscopy
Characterization of the thermal structure of six clustered microflames seeded with TaN particles through emission spectroscopy
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DOI：
10.1016/j.expthermflusci.2018.03.022
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发表时间：
2018-09
影响因子：
3.2
通讯作者：
Zhaojin Diao;M. Winter;T. Hirasawa;Kozo Saito
中科院分区：
文献类型：
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作者：
Zhaojin Diao;M. Winter;T. Hirasawa;Kozo Saito
TaN种子颗粒和电子激发CH自由基（即CH自由基）的温度从甲烷-空气微火焰燃烧器的特点是使用VIS-NIR发射光谱，而不同的燃料-空气流量。该燃烧器由六个微喷嘴组成，它们围绕中心喷嘴排列成一个圆圈，空气和尺寸在0.3 μ m和3 μm之间的TaN种子颗粒通过该中心喷嘴喷射。在不同高度以上的中央喷嘴的基础上，通过他们的可见-近红外连续发射的粒子的温度分布，显示出一个明确的恒定的温度区域，远远超出了实际的火焰前锋和燃料和氧化剂的流量变化而变化。通过高光谱分辨率的测量获得了CH_2A_2 Δ-X_2 Π发射光谱，并与Lifbase模拟的理论CH_2A_2 π发射光谱进行了比较，确定了转动和振动温度。CH 3的振动温度明显大于转动温度，其差异是由于转动温度与气体动力学温度的平衡以及通过化学反应激发振动态所致。使用扫描电子显微镜（SEM）和X射线光电子能谱与能量色散X射线分析（XPS/EDX）的分析之前和之后的TaN颗粒的表面氧化发生在火焰中。比较的光谱发射的形状与理论普朗克发射校正TaN发射率和Ta 2 O 5透射率，氧化层被发现是明显薄于100 nm的高温区域。我们的研究结果表明，通过调整燃料和氧化剂的流速，以控制种子颗粒进行高温反应的持续时间的能力。
The temperatures of TaN seed particles and electronically excited CH radicals (i.e. CH∗) emanating from a methane-air microflame burner were characterized using VIS-NIR emission spectra while varying fuel-air flow rates. The burner consisted of six micro-nozzles arranged in a circle surrounding a central nozzle through which air and TaN seed particles with sizes between 0.3 and 3 μm were injected. The temperature profiles of the particles at various heights above the base of the central nozzle, obtained by their VIS-NIR continuum emission, showed a well-defined constant temperature region that extended well beyond the actual flame front and changed as fuel and oxidizer flow rates were varied. High spectral resolution measurements were conducted to obtain CH∗A2Δ-X2Π emission spectra which were then compared with theoretical CH∗emission spectra fromLifbasesimulations to determine rotational and vibrational temperatures. The CH∗vibrational temperatures were clearly greater than the rotational temperatures, the difference of which was attributed to equilibration of the rotational temperature with the gas dynamic temperature and the excitation of vibrational states through chemical reactions. Analyses of the TaN particles before and after seeding using scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy with energy dispersive X-ray analysis (XPS/EDX) showed surface oxidation occurred in the flame. Comparing the shapes of the spectral emission with theoretical Planck emission corrected for TaN emissivity and Ta2O5transmittance, the oxide layer was found to be clearly thinner than 100 nm in the high temperature regions. Our results show an ability to control the duration to which seed particles are subjected to high temperature reactions by adjusting fuel and oxidizer flow rates.