方案摘要
方案下载应用领域 | 能源/新能源 |
检测样本 | 其他 |
检测项目 | |
参考标准 | 暂无 |
利用LaVision公司的高速图像增强器HS-IRO和高速相机相结合,构成高速时间分辨激光诱导荧光测量系统。测量了OH-自由基和CO自由基。并着重研究了在下一代燃烧系统中解析相关化学和物理过程的超短脉冲激光技术。
Ultrashort-pulse, femtosecond (fs)-duration laser techniques are powerful tools for investigating physical and chemical processes in reacting and non-reacting flow systems, providing data with high spatial and temporal resolution. Femtosecond laser pulses are advantages over traditionally used nanosecond laser pulses because of the low average power but high peak power as well as high repetition rate provided by amplified fs lasers. The objective of this thesis research is to use fs laser pulses to investigate mixing processes and also image important intermediate chemical species in combustion systems.
The primary work on mixing process studies has been demonstrated using krypton (Kr) as an inert gas tracer. A detailed spectroscopic study was performed to investigate key fluorescence channels followed by the 5p’←←4p, two-photon excitation of Kr using 204.1-nm fs pulses. The experimentally observed spectral line locations agree well with the data in the NIST Atomic Spectra Database in the 750–840-nm emission region, although significant discrepancies in some line strengths were observed. Two-dimensional (2D), two-photon laser-induced fluorescence (TPLIF) images recorded in an unsteady jet demonstrate the potential of using the fs excitation scheme of Kr for mixing and flow diagnostic studies.
In the next part of this thesis research, fs-TPLIF was investigated for detecting carbon monoxide (CO) in flames. Interferences from photolytically produced C2 Swan-band emissions show a pronounced effect on CO fluorescence signals in fuel-rich, sooting hydrocarbon flames when using CO fs-TPLIF. Therefore, specific spectral filter is
required to reduce C2 interferences for quantitative concentration measurements in such flames. Interferences from nascent C2 originating from hot soot particles could be avoided by using a narrower detection gate width. At elevated pressures, CO fluorescence signal resulting from the fs excitation scheme, decays slower than that resulting from the ns excitation scheme. Comparison of the measured CO fluorescence signal with the calculated CO number density shows a good agreement for both premixed CH4/air and C2H4/air flames. Subsequently, fs-TPLIF imaging measurements of CO are also demonstrated in piloted liquid-methanol spray flames.
In the final part of this research, fs pulses have been used for planar laser-induced fluorescence (PLIF) measurements of the hydroxyl (OH) radicals in flames. The excitation of the (1,0) vibrational band of the A2Ʃ+←X2Π electronic manifold using single-photon transition scheme has been utilized. The measured OH-LIF signals agree well with the equilibrium calculations in a range of flame conditions. Single-laser-shot, 2D OH-PLIF images recorded at 1-kHz repetition rate in a premixed C2H4/air jet flame and a turbulent CH4/H2 diffusion flame show the potential of fs-laser pulses for OH imaging measurements in reacting flow systems.
在一个双稳湍流涡旋火焰中,对间歇性动态的时间-频率定位
Particle-laden Taylor-Couette流:高阶转变和径向局部波浪涡旋的证据
7根杆束的流体-结构相互作用:用实验数据对比数值模拟
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