One-Dimensional Fs/PS Coherent Anti-Stokes Raman Scattering for Reacting Flows 16 views

A one-dimensional femtosecond/picosecond coherent anti-Stokes Raman scattering (1D fs/ps CARS) technique has been developed for reacting and high-speed flows. Coherent anti-Stokes Raman scattering (CARS) is a laser diagnostic that measures the populations of specific energy levels of a given molecule. Information about the energy distributions informs thermodynamic quantities such as temperature, pressure, species concentration. Typically, CARS is a “point” based measurement where information is acquired at a single location. Expansion of the point to a line measurement enables the acquisition of many spatially resolved measurements within a single frame. This work develops a 1D CARS technique suitable for largescale facilities that can overcome the challenges associated with high-speed and reacting flows. A vibrational 1D fs/ps CARS technique was developed using an optical parametric amplifier. Detailed characterization of the 1D measurement has been completed, including spatial resolution measurements, beam size and quality considerations, beam energy effects, phase matching schemes, and probe volume imaging. A 1D CARS technique has been developed to be suitable in large-scale test facilities and has been validated in a laminar, premixed flat flame where a resolution of 37 µm has been achieved. A single-shot 5 mm line measurement allowed for temperature gradients of over 800 K/mm to be observed in a single measurement without the need to scan the probe volume relative to the environment. The diagnostic was then deployed in a transient environment to measure post-shock temperatures of a CO2 dominant environment. 1D CARS was further developed to perform simultaneous detection of pure-rotational and vibrational transitions of CO2 and O2. Simultaneous detection of rotational and vibrational CARS was deployed in a counterflow diffusion flame to measure the temperature profile and species of the reaction zone.

PHD (Doctor of Philosophy)

CARS; high-speed; combustion; reacting flows; optical diagnostics

English

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2026-07-29