High-Pressure Measurements of Temperature and CO2 Concentration Using Tunable Diode Lasers at 2 μm

Abstract

A sensor for simultaneous measurements of temperature and carbon dioxide (CO2) concentration at elevated pressure is developed using tunable diode lasers at 2 µm. Based on some selection rules, a CO2 line pair at 5006.140 and 5010.725 cm−1 is selected for the TDL sensor. In order to ensure the accuracy and rapidity of the sensor, a quasi-fixed-wavelength WMS is employed. Normalization of the 2 f signal with the 1 f signal magnitude is used to remove the need for calibration and correct for transmission variation due to beam steering, mechanical misalignments, soot, and windows fouling. Temperatures are obtained from comparison of the background-subtracted 1 f-normalized WMS-2 f signals ratio and a 1 f-normalized WMS-2 f peak values ratio model. CO2 concentration is inferred from the 1 f-normalized WMS-2 f peak values of the CO2 transition at 5006.140 cm−1. Measurements of temperature and CO2 concentration are carried out in static cell experiments ( P = 1–10 atm, T = 500–1200 K) to validate the accuracy and ability of the sensor. The results show that accuracy of the sensor for temperature and CO2 concentration are 1.66% temperature and 3.1%, respectively. All the measurements show the potential utility of the sensor for combustion diagnose at elevated pressure.