摘要: Hybrid fs/ps coherent anti-Stokes Raman scattering (CARS) is employed to investigate the vibrational temperature evolution of N_2 in lean methane flames exposed to pulsed microwave irradiation. Vibrational temperature during and p... 展开 Hybrid fs/ps coherent anti-Stokes Raman scattering (CARS) is employed to investigate the vibrational temperature evolution of N_2 in lean methane flames exposed to pulsed microwave irradiation. Vibrational temperature during and post microwave illumination by a 2 μs, 30 kW peak power, 3.05 GHz pulse is monitored in flames diluted with N_2, N_2 and CO_2, and N_2 and Ar. Electric field strengths inside the microwave cavity are monitored directly using electric field probes. Temperature increases up to 140 K were observed in flames with additional Ar and CO_2 dilution, whereas temperature increases by 80 K were observed in mixtures diluted with only N_2. The microwave energy deposition to excited states begins to thermalize over scales of 100 μs, however, equilibrium is not reached before excited combustion products convect out of the probe volume on the order of several 1 ms. Understanding the impact of varying bath gases on microwave interaction, magnitude of temperature rise and thermalization timescales is critical for the development and validation of new kinetic models for applications exhibiting significant degrees of thermal non-equilibrium, such as high-speed reentry flows and plasma-assisted combustion. 收起