Fig. 1. TDLAS-based Doppler velocimetry: (a) Diagram of velocity measurement system; (b) diagram of frequency shifts between absorption signals.基于多普勒效应的激光吸收光谱测速原理　(a)激光吸收光谱多普勒测速系统示意图; (b)吸收光谱信号多普勒频偏示意图

Fig. 2. Model and multiple projection system design for two-stage velocity distribution: (a) Velocity distributions assumed in the analysis; (b) illustration of optical system for TDLAS velocity distribution measurement.两段式速度分布模型与多光路测试系统示意图　(a)速度分布流场模型示意图; (b)激光吸收光谱速度分布测试系统示意图

Fig. 3. Function diagram of E_θ, A_h/A_l and . E_θ与A_h/A_l和 的函数关系图

Fig. 4. Relative error of average frequency offset under different conditions.不同工况下平均频率偏移计算误差结果

Fig. 5. Function relationship between and A_h/A_l at 60° optical path: (a) varies with A_h/A_l; (b) 1 st derivative of varies with A_h/A_l. 60°光路投影条件下 与A_h/A_l的关系　(a) 随A_h/A_l的变化; (b) 一阶导数随A_h/A_l的变化

Fig. 6. Comparison of model with calculation results.模型与计算结果对比图

Fig. 7. Relationship between A_h/A_l and at different E_θ. 不同E_θ条件下A_h/A_l和 之间函数关系

Fig. 8. Absorbance features at projection in different velocity models.不同速度模型条件下投影光路光谱信号特征

Fig. 9. Effect of noise on velocity distribution measurement.噪音对速度分布测量的影响