Abstract
In this Letter, we demonstrate a 5 kHz 1D Raman instrument for temporally and spatially resolved quantitative measurements of temperature and all the major species (N-2, O-2, H-2, and H2O) concentration in H-2-air flames. The major constituents of the system are a pulse-burst laser operated at 5 kHz and four back-illuminated CCD cameras operated in subframe burst-gating mode. The use of CCD cameras allows achieving a high sampling rate with no compromise on instrument precision, but it requires one camera for each species of interest. A cascade of dichroic mirrors and bandpass filters spectrally separates the Raman signal associated with each of the four species and directs it to a separate camera. Measurements in a well-characterized H-2-air premixed flat flame show that the system has precision comparable with the low-speed Raman system. The measuring uncertainty of the species mole fraction ranges between 1% (N-2) and 3 similar to 4% (O-2 in lean flames). Measurements in laminar and turbulent H-2/N-2 jet flames show good agreement with the theoretical prediction. By measuring all species simultaneously, important combustion quantities such as the mixture fraction are also derived. (C) 2020 Optical Society of America