Oxygen concentration and temperature measurements in N2-O2 mixtures using rotational coherent anti-Stokes Raman spectroscopy

The accuracy and precision of oxygen concentration and temperature measured by dual-broadband rotational Coherent Anti-Stokes Raman Spectroscopy (CARS) were investigated in nitrogen-oxygen mixtures at atmospheric pressure and temperatures between 290 and 1410 K. The relative standard deviation of temperatures evaluated from pure oxygen rotational CARS spectra was found to be around 5%, and the mean temperature was the same as for nitrogen CARS spectra, except for temperatures above 1000 K, where the temperature was 120 K below the correct value. The in situ calibrated oxygen concentrations were within 10% of the correct value, with a standard deviation of around 1.2% for the mixtures of 12 and 20% oxygen in nitrogen. For the lowest oxygen concentrations considered in this study (2 and 4%), the systematic errors in the evaluated concentrations were very large, and the standard deviation of repeated single-shot measurements was above 2%. However, employing weighting in the spectral fitting routine reduced the errors in the concentration and the single-shot standard deviation was lowered to 0.5%. Finally, it was shown that spectral interference (from oxygen) in a rotational CARS spectrum of nitrogen generally had little impact on the temperature evaluated from fitting the spectra to theoretical nitrogen spectra.

Bengtsson, P. E.Lund University,Lunds universitet,Förbränningsfysik,Fysiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Combustion Physics,Department of Physics,Departments at LTH,Faculty of Engineering, LTH(Swepub:lu)forb-pbe (author)
Aldén, MarcusLund University,Lunds universitet,Förbränningsfysik,Fysiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Combustion Physics,Department of Physics,Departments at LTH,Faculty of Engineering, LTH(Swepub:lu)forb-mal (author)
Lund UniversityFörbränningsfysik (creator_code:org_t)

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