Planar spontaneous raman-scattering spectroscopy for reacting jet-flow diagnostics using Lyot–Ehman tunable filter

The spatial-density distribution in burning a premixed methane–air swirling turbulent jet has been studied by measuring the intensity of the Stokes branch of spontaneous Raman scattering for vibrational–rotational transitions in nitrogen. An optical system comprising a Nd:YAG laser and the liquid-crystalline Lyot–Ehman tunable filter has been created and tested by measuring the temperature and density fields in a cone-shaped laminar flame. It has been established that the difference of data obtained using the Stokes component of Raman scattering in nitrogen and its ratio to the anti-Stokes component does not exceed 5% in a temperature range from 300 to 1800 K.