Frequency-scanning burst-mode filtered Rayleigh scattering for kHz-rate, multi-parameter, gas-phase measurements
Amanda M. Braun, Neil S. Rodrigues, Paul M. Danehy, Alexander R. Suppiah, James Braun, Mikhail N. Slipchenko, Terrence R. Meyer
Abstract
Molecular Rayleigh scattering (RS) is sensitive to the pressure, temperature, velocity, and number density of the gaseous flow. Filtered Rayleigh scattering (FRS) utilizes a narrowband molecular filter to remove stray scattering and deconvolve the effect of flow conditions on the signal intensity. As single-frequency, intensity-based FRS techniques can typically only deconvolve a single parameter per detector angle, frequency-scanning (FS) FRS has been used to semi-spectrally resolve the signal and quantify multiple parameters using a single detector. In this work, the FS-FRS data rate was increased by a factor of 10 5 using a rapid wavelength-tunable burst-mode laser operated at 20 kHz. The technique is demonstrated for simultaneous, spatially resolved temperature, pressure, and radial velocity measurements time-averaged across 1 ms in an underexpanded jet, yielding a measurement rate of 1 kHz for potential use in high-speed flow test facilities.