Spatially Resolved Diagnostics Using Tunable Laser Absorption Spectroscopy

温度和物质浓度的精确测量对于表征高温气体流动非常重要，特别是在燃烧区域。光学测量是理想的，因为它们是非侵入性的，非干扰的，并且探头不受恶劣环境的影响。吸收测量提供沿视线吸收物质浓度的简单定量定义；这有时是足够的信息，但更多时候需要空间分辨的测量。原则上，二维温度和浓度场应该通过使用层析重建（一种广泛用于医学成像的方法）从有限数量的视线测量中恢复。然而，由于重建算法对输入数据的误差非常敏感，很难实现温度和浓度场的精确定量重建。该计划的主要目标是利用红外二极管激光器的调谐能力，利用重建技术同时测量温度和浓度场，从而大大降低重建方法对输入数据中的随机和系统误差的灵敏度。这项研究将从重建轴对称流动中的径向温度和浓度分布（CO和CO2）开始，随后将扩展到重建三维流动的二维部分。定量激光诊断在工业场景中的应用一直受到所涉及设备的典型高成本和实现定量结果所需的用户复杂性的阻碍。这些成本更低、用户更友好的系统的成功很可能导致工业上更广泛的应用；开发的软件和硬件应该能够在各种应用中实现层析吸收诊断技术。潜在的，这项技术的进一步发展，使用廉价的激光二极管源，可能使仪器封装便宜和坚固，足以用于工厂内的过程控制系统。

Accurate measurements of temperature and species concentrations are important for characterization of high temperature gas flows, particularly in the area of combustion. Optical measurements are desirable since they are nonintrusive, nonperturbing, and the probe is not subject to a hostile environment. An absorption measurement provides a simple quantitative definition of the concentration of the absorbing specie along a line-of-sight; this is sometimes adequate information, but more often spatially resolved measurements are needed. In principle, two-dimensional temperature and concentration fields should be recoverable from a limited number of line-of-sight measurements using tomographic reconstruction, a method widely used in medical imaging. However, accurate quantitative reconstructions of temperature and concentration fields have been difficult to achieve because reconstruction algorithms are very sensitive to errors in the input data. The principal objective of this program is to measure temperature and concentration fields simultaneously using a reconstruction technique that exploits the tuning capability of infrared diode lasers to greatly reduce the sensitivity of the reconstruction methods to both random and systematic errors in the input data. The study will begin with reconstruction of radial temperature and concentration profiles (CO and CO2) in an axisymmetric flow, with subsequent extension of the procedures to reconstruction of two-dimensional sections of three-dimensional flows. The application of quantitative laser diagnostics to industrial scenarios has been hampered by the typical high cost of equipment involved and by the user sophistication required for achievement of quantitative results. Success with the these lower-cost, more user-friendly systems may well lead to wider usage in industry; the software and hardware developed should enable implementation of tomographic absorption diagnostic techniques in a wide variety of applications. Potentially, further development of this technology, with use of inexpensive laser diode sources, may allow instrumentation packages cheap and robust enough for use in in-plant process control systems.