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 2f signal with the 1f 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 1f-normalized WMS-2f signals ratio and a 1f-normalized WMS-2f peak values ratio model. CO2 concentration is inferred from the 1f-normalized WMS-2f 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.

Temperature measurement of SO2 based on mid‐infrared laser absorption spectroscopy

“…Similarly, the temperature expression of WMS and WMS‐2f/1f can also be deduced with the following expressions 5,10,11 $$${T}_{\mathrm{WMS}}=\frac{\frac{{hc}}{k}\left({E}_{2}^{^{\prime\prime} }-{E}_{1}^{^{\prime\prime} }\right)}{\mathrm{ln}({R}_{\mathrm{WMS}})+\mathrm{ln}\left(\frac{{S}_{2}({T}_{0})}{{S}_{1}({T}_{0})}\right)+\left(\frac{{hc}}{k}\right)\left(\frac{{E}_{2}^{^{\prime\prime} }-{E}_{1}^{^{\prime\prime} }}{{T}_{0}}\right)+\mathrm{ln}\left(\frac{I(\bar{{\nu }_{2}}){M}_{2}}{I(\bar{{\nu }_{1}}){M}_{1}}\right)},$$$ $$${T}_{\mathrm{WMS}-2{\rm{f}}/1{\rm{f}}}=\frac{\frac{{hc}}{k}\left({E}_{2}^{^{\prime\prime} }-{E}_{1}^{^{\prime\prime} }\right)}{\mathrm{ln}({R}_{\mathrm{WMS}-2{\rm{f}}/1{\rm{f}}})+\mathrm{ln}\left(\frac{{S}_{2}({T}_{0})}{{S}_{1}({T}_{0})}\right)+\left(\frac{{hc}}{k}\right)\left(\frac{{E}_{2}^{^{\prime\prime} }-{E}_{1}^{^{\prime\prime} }}{{T}_{0}}\right)+\mathrm{ln}\left(\frac{{M}_{2}}{{M}_{1}}\right)},$$$…”

“…TDLAS‐based temperature measurement has been extensively investigated and utilized in recent years. Cai et al demonstrated accurate and fast measurement of carbon dioxide concentration and temperature based on TDLAS 5 . Zhang et al presented the measurement of C 2 H 4 concentration and temperature using TDLAS in the combination of differential absorption scheme 6 …”

Simulation and experimental study of diesel engine emission temperature based on tunable diode laser absorption spectroscopy

“…According to the Beer-Lambert law [10], when a monochromatic laser passes through a gas medium, the intensity change can be expressed as:…”

A TDLAS Sensor for Simultaneous Measurement of Temperature and C2H4 Concentration Using a Differential Absorption Scheme at High Temperature

“…Sun et al demonstrated the measurement of multi-species concentrations and temperature in a slagging coal gasifier with high pressure and high temperature using TDLAS, proving the capability of TDL sensors to monitor transient changes in gas temperature and the syngas heating value [13]. Cai et al demonstrated accurate and fast measurement of carbon dioxide concentration and temperature based on TDLAS at high temperature and high pressure [14].…”

“…Through an investigation of relevant literature, it has been found that there are many studies on measurements of species concentration and temperature by direct absorption spectroscopy (DAS) or wavelength modulation spectroscopy (WMS) employing isolated absorption lines of the measured gas molecules [12][13][14][15][16][17][18][19]. However, for the molecules with dense absorption spectral features (such as ethylene and methane, which contain hydrocarbon bonds), there will be self-mixing or overlap with other molecules at an elevated temperature and pressure, making it difficult to accurately infer the complete transition properties through a single line or line pair.…”