Validation experiments for spatially resolved one-dimensional emission spectroscopy temperature measurements by dual-pump CARS in a sooting flame

摘要

In this work, an emission spectroscopic (ES) technique for the determination of soot temperatures in an axisymmetric flame is validated against coherent anti-Stokes Raman spectroscopy (CARS) as preparation for a zero gravity measurement campaign. In order to reduce valuable measurement times during the parabolic flights, a setup for spatially resolved one-dimensional measurements along a line has been built up using an imaging spectrometer and a CCD-camera for data acquisition.In order to assess the performance of the ES technique, accurate coherent anti-Stokes Raman scattering (CARS) measurements have been performed at the same conditions. Hereby, great care has to be taken to minimize the known interferences in sooting flames. The non-resonant signal contribution was suppressed by a polarization technique and the signal wavelength was shifted to an interference free region. These modifications are discussed in detail. The temperatures obtained by both methods are in good agreement in most regions of the flame. It turned out that the described approach for ES is an appropriate and robust alternative for measuring temperatures in sooting axisymmetric flames, if more accurate techniques cannot be applied, e.g., during investigations in zero-g parabolic flight experiments.