Spontaneous Raman scattering is mainly used to determine the concentrations of the main species and temperature in flames. Because it involves an inelastic scattering process, this technique is molecule-specific. By using lasers with a high pulse energy in combination with high-sensitivity detection systems, it is possible to achieve experimental arrangements that permit the recording of correlated information in respect of species distribution and temperature in both point measurements (0D) and along a line (1D) using single-pulse technology. In special applications involving high densities of the medium being studied, the technique can also be applied to 2D areas.
At the Institute, a long-pulse laser (flashlamp-pumped dye laser) with pulse energies of approximately 3J is used for measurements on enclosed jet and swirling flames. A mobile 1D laser-Raman measuring system based on Nd:YAG lasers is used for experiments on high-pressure test rigs. With this system it is possible to perform very precise measurements in industrial gas turbine combustion chambers under real operating conditions. In addition to determining species and temperature distributions, Raman scattering also permits the mixture and the turbulence-chemistry interaction to be characterised.