A new paper from the IMPRESS 2 Project has been published in Applied Spectroscopy. The thermal boundary layer effects on line-of-sight TDLAS gas concentration measurements by Zhechao Qu, Olav Werhahn and Volker Ebert of project partner PTB (Physikalisch-Technische Bundesanstalt) is now available from Applied Spectroscopy and also over on our Documents and publications page.



The effects of thermal boundary layers on TDLAS measurement results must be quantified when using the line-of-sight (LOS) tunable diode laser absorption spectroscopy (TDLAS) under heterogeneous conditions. In this paper, a new methodology based on spectral simulation is presented quantifying the LOS TDLAS measurement deviation under heterogenous conditions with thermal boundary layers. The effects of different temperature gradients and thermal boundary layer thickness on spectral collisional widths and gas concentration measurements are quantified. A CO2 TDLAS spectrometer, which has two gas cells to generate the temperature heterogeneity, was employed to validate the simulation results. The measured deviations and collisional widths are in very good agreement with the simulated results for different temperature heterogenous conditions. We demonstrate quantification of thermal boundary layers’ thickness with proposed method by extracting the collisional width from the path-integrated spectrum.