Fig. 1. Infrared absorption spectra of three gases

Fig. 2. Principle and structure design of three-ellipsoidal air chamber. (a) Schematic diagram of elliptical structured light path; (b) structure diagram of inner cavity of three ellipsoidal air chamber

Fig. 3. Simulation diagram of light transmission in three-ellipsoidal gas chamber

Fig. 4. Light scattering diagrams of three-ellipsoidal gas chambers

Fig. 5. Illumination grating and three-dimensional distribution of illumination intensity in three-ellipsoidal air chamber.(a) Illumination grating of CO₂ receiving surface; (b) illumination grating of SO₂ receiving surface; (c) illumination grating of CO receiving surface; (d) light intensity of CO₂ receiving surface; (e) light intensity of SO₂ receiving surface; (f) light intensity of CO receiving surface

Fig. 6. Flow direction diagram of sensor in air environment

Fig. 7. Cloud diagrams of CO₂ mass fraction at different times when length of gas chamber is 50 mm. (a) 0.5 s; (b) 1.0 s; (c) 1.5s; (d) 2.0s; (e) 2.5s

Fig. 8. Cloud diagrams of CO₂ mass fraction at different times when length of gas chamber is 60 mm. (a) 0.5 s; (b) 1.0 s; (c) 1.5s; (d) 2.0s; (e) 2.5s; (f) 3.0 s

Fig. 9. Structural design of direct and multi reflection air chambers. (a) 3D model drawing of direct air chamber; (b) placement design of direct type detector; (c) 3D model drawing of multi reflection air chamber

Fig. 10. Statistical distribution of optical path length of three-ellipsoidal gas chambers

Table 1. Optical path length, reflection times, and the number of light reaching receiving surface of different air chamber structures

Table 2. Statistical distribution of reflection times of three ellipsoidal gas chambers

Table 3. Luminous flux P value and signal-to-noise ratio on photosensitive surface of detector with three structures