Advances in Laser Imaging Diagnostics for Understanding Turbulence-Flame Interactions

摘要

Recent advances in the application of laser imaging diagnostics for understanding the structure and temporal evolution of turbulent flames are presented. Tomographic particle image velocimetry provides direct measurements of the three-dimensional velocity field and enables determination of key fluid dynamic quantities, such as strain rate and vorticity. Advances in high-repetition rate imaging at multi-kilohertz rates provide insight into the temporal evolution of transient combustion events. The growth of three-dimensional and high-speed imaging measurement capabilities poses data analysis challenges while enabling unprecedented opportunities for determining conditional statistics of the three-dimensional interactions between turbulent flows and flames. Studies of vorticity-strain alignment and strain rate orientation relative to flame-front surfaces illustrate these capabilities. Comparisons of non-reacting and reacting flows elucidate effects of flame heat release on turbulence. Applications of high-speed imaging measurements to high-pressure transient flows using a 100 kHz pulse-burst laser are demonstrated for turbulent mixing of vaporized fuel from a Diesel injector and the velocity field in the central region of a multi-plume gasoline injector. An approach for using numerical simulations to aid in the quantification of uncertainties in tomographic particle image velocimetry is also discussed.