Demonstration of high-speed 1D Raman scattering line imaging

Abstract

In this manuscript, we demonstrate high-speed (10-kHz acquisition rate) 1D Raman scattering line imaging under turbulent flow conditions. Because of the inherently weak scattering process, Raman scattering measurements typically require high laser pulse energies that are not available from commercial high-repetition-rate laser systems. Using a custom pulse-burst laser system at OSU, we demonstrate the ability to generate a series of high-energy laser pulses with 100 μs pulse separations, which can be used for high-speed Raman scattering imaging. The ultimate goal is a capability of quantitatively measuring all major combustion species and deducing time-varying mixture fraction profiles in turbulent combustion environments. Toward this goal, we report initial results depicting the Raman scattering imaging of O2, N2, CH4, and H2 in a turbulent non-reacting CH4/H2 jet issuing into air. To the authors’ knowledge, this represents the first reported temporally-sequential 1D image sequences of major species measured via high-speed Raman scattering.