Temperature Measurement in Turbulent Flames Via Rayleigh Scattering

Using laser Rayleigh scattering, temperature measurements have been made, on a turbulent jet diffusion flame, with a frequency response, DC-5 kHz,unachievable by any other present day laser based technique. The flame reactants and products had nearly equal Rayleigh scattering cross section so that temperature could be inferred directly from the scattering intensity from a point on a probe laser beam. Probability densities, means, higher moments, and power spectrum are generated from the time series of temperature. The intensity of Rayleigh scattered light can be written as ( 1, 2, 3, 4 ), where the constants, K′ and K, contain experimental details such as solid angle of optics, slit opening, phototube quantum efficiency, pressure, etc. N, T, and (dσ/dΩ)eff are respectively number density, temperature, and effective Rayleigh scattering cross section, defined by: where xi and dσ i /dΩ are respectively the mole fraction and Rayleigh scattering cross section for species i. Assuming the laser intensity to be constant