Simultaneous 2D filtered Rayleigh scattering thermometry and stereoscopic particle image velocimetry measurements in turbulent non-premixed flames

The current work presents simultaneous high-resolution temperature and three-component velocity measurements taken in a series of turbulent (Re = 10,000, 20,000, and 30,000) piloted, non-premixed jet flames using filtered Rayleigh scattering (FRS) thermometry and stereoscopic particle image velocimetry (sPIV). This manuscript details the experimental approach with a key focus on the experimental protocol and specific challenges unique to simultaneous single-shot FRS/sPIV measurements in turbulent non-premixed flames. Specific areas of discussion include the experimental particle scattering rejection for FRS measurements, elimination of signal "crosstalk" between FRS and PIV channels, tracer particle selection, data processing for noise removal, and spatial resolution for both the temperature and velocity measurements. Sample joint temperature/velocity fields are presented highlighting interactions between the flow turbulence and the temperature fields, and a detailed statistical assessment of the temperature and velocity measurements demonstrates the quantitative nature of the results. Dissipation spectra from the measured temperature and velocity fluctuations are used to assess the true spatial resolution of the measurements. Results indicate that the sPIV measurements are resolved well into the dissipative range and the highest spatial frequencies (smallest dissipative scales) are resolved for the temperature measurements under all flame cases and measurement locations. The current joint FRS/sPIV approach enables the first simultaneous single-shot temperature/velocity imaging in turbulent non-premixed flames.