可調諧二極管激光吸收光譜（Tunable Diode Laser Absorption Spectroscopy，簡稱TDLAS）是一種利用雷射進行光譜氣體檢測的技術。它具有非侵入式、選擇性強、靈敏度高、可瞬時量測以及抗背景光譜干擾能力強等優點，特別適用於複雜環境中的氣體量測。在惡劣環境中確定溫度和氣體濃度分佈是具有挑戰性的，因為傳統的熱電偶或氣體採樣系統等侵入式測量方法會對流場產生影響並干擾火焰。
本實驗室開發了一套基於TDLAS技術的氣體量測系統。首先，利用HITRAN數據庫對燃燒產物氣體的光譜進行詳細分析，並結合NASA CEA（Chemical Equilibrium with Applications）計算的燃燒產物組成數據，選擇出合適的雷射波段來測量燃燒尾氣的溫度及CO2濃度。為了驗證系統的準確性，將測量結果與傳統的熱電偶和氣體分析儀進行了系統性的比較和分析。
此外設計了環型反射光學氣室，該氣室利用星型反射路徑來增加雷射光的反射次數。從而有效地延長光程，顯著提高了量測靈敏度和信號強度。這一設計特別考慮了光路的偏心5度角，使得雷射光在光學氣室內部能夠進行多次反射，從而實現了更高的測量精度和穩定性。為了驗證設計的光學氣室的性能，測量了不同CO2濃度範圍內的光譜響應。實驗結果表明，該光學氣室在CO2濃度為0.5 %至5 %的範圍內，顯示出良好的線性響應，這充分說明了該系統在低濃度氣體測量中的優異表現和可靠性。
最後，將TDLAS應用於50 kW燃氣爐，測量丙烷燃燒過程中不同當量比下的溫度與CO₂濃度變化，成功在50 kW燃燒條件下精確監測溫度和CO₂濃度的動態變化，溫度量測誤差為10 %，CO2濃度與訊號呈線性關係。

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is a laser-based gas detection technique characterized by its non-invasiveness, strong selectivity, high sensitivity, instantaneous measurement capabilities, and strong resistance to background spectral interference. Determining temperature and gas concentration distribution in harsh environments is challenging because invasive measurement methods such as thermocouples or gas sampling systems can affect the flow field and interfere with flames. TDLAS is suitable for gas measurements in complex environments. Our laboratory has developed a TDLAS measurement system that utilizes the HITRAN database for analyzing the spectra of combustion by-product gases. This enables us to select appropriate laser wavelengths for measuring CO2 concentration and temperature in combustion exhaust gases. The system's performance has been compared with traditional thermocouples and gas analyzers. Additionally, we have designed a ring-shaped reflective optical cell that employs a star-shaped reflection path to enhance the number of laser beam reflections, thereby increasing the optical path length and improving measurement sensitivity. The optical cell design incorporates a 5-degree eccentric angle to facilitate multiple reflections of the laser beam inside the cell, achieving higher measurement precision. Experimental results demonstrate that the optical cell exhibits a linear response within the CO2 concentration range of 0.5% to 5%. This indicates excellent sensitivity and accuracy of our TDLAS measurement system for gas analysis in combustion processes. Finally, TDLAS was applied to a 50 kW gas burner to measure temperature and CO₂ concentration variations during propane combustion under different equivalence ratios. The system successfully monitored the dynamic changes in temperature and CO₂ concentration under 50 kW combustion conditions with high precision. The temperature measurement error was 10%, and the CO₂ concentration exhibited a linear relationship with the signal.

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