Laser Rayleigh thermometry in turbulent flames

Nonintrusive, spatially and temporally resolved temperature measurements in turbulent flames, premixed and non-premixed, using laser Rayleigh scattering are reported. Through judicious design of experiments, laser Rayleigh scattering can be used to measure temperature (or concentration) at a data rate, and hence frequency response, DC-15 kHz, that is undemonstrated by any other present day laser based technique. Two demonstrations of laser Rayleigh thermometry are described: a turbulent premixed flame, and a turbulent jet diffusion flame. The turbulent jet diffusion flame uses a novel mixture of hydrogen and methane as fuel. This fuel mixture permitted the first laser Rayleigh thermometry in turbulent non-premixed flames. In these demonstrations, the Rayleigh scattered light intensity from a CW laser is used to produce a time series of temperature. From that time series, the temperature probability distribution function is generated as well as the power spectrum and autocorrelation. From the probability distribution function, the mean, variance and higher moments are easily generated.