Tomographic absorption spectroscopy (TAS) is a promising temperature and concentration monitoring technology because it has fewer optical access requirements and species selectivity. However, the inhomogeneous distribution of temperature and species concentration in a practical reaction flow can cause laser deflection, which may affect the imaging quality. Thus, this study aimed to develop a novel tomographic absorption deflection spectroscopy (TADS) technology for in-situ, quantitative, and simultaneous measurements of temperature and HO concentration. The proposed system is based on the gas mixing equation and ray tracing, considering the inhomogeneous gradient refractive index and laser bending. Moreover, multi-prior information, including smooth regularization, non-negative constraints, and topological shape constraints, is coupled to mitigate the ill-posedness of inverse problems, thereby improving the accuracy and robustness of multiparameter tomography. Numerical verification and a comparison of algorithms for multimodal flames indicate that the proposed TADS technology exhibits excellent anti-noise performance and can significantly improve reconstruction quality. Additionally, a proof-of-concept based on experimental data of a steady methane diffusion flame is performed to demonstrate the feasibility of TADS as a practical combustion diagnostic. The reconstruction results of instantaneous temperature and HO concentration on six different cross-sections show that the topological structure, dynamics, and parameter distribution can be quantitatively demonstrated. This technology is expected to enhance the practicability of laser absorption spectroscopy in the in-situ measurement of complex combustion reaction flows with high temperature, high pressure, and strong distortion.

中文翻译：

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基于拓扑演化和先验平滑的非均匀火焰温度和浓度的非线性偏转断层扫描

断层吸收光谱（TAS）是一种有前途的温度和浓度监测技术，因为它具有较少的光学接入要求和物种选择性。然而，实际反应流中温度和物质浓度的不均匀分布会导致激光偏转，从而影响成像质量。因此，本研究旨在开发一种新型断层吸收偏转光谱（TADS）技术，用于原位、定量和同时测量温度和 H2O 浓度。所提出的系统基于气体混合方程和射线追踪，考虑了不均匀梯度折射率和激光弯曲。此外，耦合多个先验信息，包括平滑正则化、非负约束和拓扑形状约束，以减轻逆问题的不适定性，从而提高多参数层析成像的准确性和鲁棒性。数值验证和多模态火焰算法的比较表明，所提出的TADS技术具有优异的抗噪声性能，并且可以显着提高重建质量。此外，还进行了基于稳定甲烷扩散火焰实验数据的概念验证，以证明 TADS 作为实际燃烧诊断的可行性。六个不同截面上的瞬时温度和 H2O 浓度的重建结果表明，可以定量地展示拓扑结构、动力学和参数分布。该技术有望增强激光吸收光谱在高温、高压、强畸变的复杂燃烧反应流现场测量中的实用性。