50-kHz-rate Rayleigh and filtered Rayleigh scattering thermometry using a pulse-burst laser

Abstract

A one-dimensional Rayleigh/filtered Rayleigh scattering system is developed using a pulse burst laser and it is used to demonstrate temperature measurements at 50 kHz repetition rate. The system utilizes a CCD camera operated in the subframe burst gating mode for improved signal to noise ratio. This improvement in precision is verified by conducting temperature measurements in a laminar flame and comparing the results with that obtained using a highspeed CMOS camera. Two experiments are conducted to demonstrate the capability of the system. Firstly, 1D Rayleigh thermometry is conducted in a turbulent jet flame with Reynolds number 15200. Time-resolved temperature profiles and spatially resolved integral time scales are presented. After this, we demonstrate a 50-kHz-rate filtered Rayleigh scattering thermometry experiment using the pulse burst laser. In this experiment, the 1D temperature profiles of a turbulent flame propagating through a narrow rectangular channel with a variable height of approximately 2mm is studied. The test facility is designed to study the flame quenching process in narrow channels and has unique measurement challenges due to the limited optical access and short flow duration. Measurements at three heights, ranging from quenching to no quenching conditions, are presented and the evolution of temperature profile is discussed. i = lineshape function of Rayleigh-Brillouin spectrum of species i P = pressure

100 kHz Narrow-Linewidth Burst-Mode MOPA Laser System With Uniform Envelope

“…The parameter measurements (e.g., temperature, velocities, and mixture fraction) for high-speed flows have greatly boosted the advancements of aerospace and scramjet by use of optical imaging techniques [1][2][3][4][5][6]. Especially, the solid-state laser system, with a high rate and high energy [7][8][9][10][11], has great potential for optical diagnostic applications, such as planar laser-induced fluorescence (PLIF) [12][13][14], particle imaging velocimetry (PIV) [15,16], and filtered Rayleigh scattering (FRS) [17,18]. Among those measuring techniques, FRS serves as a promising approach in imaging high-speed reacting flames and non-reacting jets for its strong suppression in background noise, with the same wavelength as an input laser, from the Mie scattering and windows and highlights weaker broadened Rayleigh-Brillouin scattering (RBS) signal intensity.…”