1. Cavity ring down absorption of oxygen in air as a temperature sensor
Carlos E. Manzanares and Parashu R. Nyaupane
Department of Chemistry and Biochemistry
Baylor University, Waco, TX 76798

3. Optical Cavity
Our current research uses the phase shift method for determining the photon lifetime within the optical cavity

4. PS-CRD The absorption spectrum is obtained by :
The PS method obtains the lifetime from the change in phase angle after passing through a CRD cavity using:
The absorption spectrum is obtained by :

5. Low Temperature Cryostat
Liquid N2
Path length range : (2- 6)Km
Lewis, E.K., Moehnke, C.J., Manzanares, C. Rev. Sci. Instrum. 2006, 77,073107

8. For our low resolution spectra the only transitions considered are the PP transitions that correspond to absorptions from the ground state rotational quantum number J”= K” = 1, 3, 5, 7…, with final states J’ = 0, 2, 4, 6…, respectively.

12. Open cavity

16. # Peaks Aver.
Slope/10-3 cm
Intercept
Calculated Temp (K)
Measured Temp (K) 6
‒ (16.4 ± 0.8)
‒ (24.32 ± 0.09)
88 ± 5 90 4
‒ (9.62 ± 0.54)
‒ (24.60 ± 0.12)
150 ± 8
150 7
‒ (4.78 ± 0.09)
‒ (25.47 ± 0.02)
301 ± 6
298
‒ (4.40 ± 0.10)
‒ (25.58 ± 0.03)
327 ± 8
321 2
‒ (4.13 ± 0.12)
‒ (25.62 ± 0.03)
348 ± 11
356 1
‒ (3.76 ± 0.15)
‒ (25.67 ± 0.04)
386 ± 15
383

17. Summary
The study has shown that the oxygen absorption is a very good choice to determine temperature in a flow system. Although it will be ideal to have a diode laser to resolve the peaks, the study has shown that a low resolution spectrum is capable of giving the correct temperature of the flowing air.
The flowing air temperature sensor will be used to measure the temperatures of cooling air at the input (cold air) and output (hot air) after cooling the blades of a laboratory gas turbine. The results could contribute to improvements in turbine blade cooling design.

18. Robert A. Welch Foundation
Acknowledgement
Robert A. Welch Foundation
Baylor University Undergraduate Research and Scholarly Achievement (URSA) Program