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 high-speed 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.