Single camera 20  kHz two-color formaldehyde PLIF thermometry using a dual-wavelength-switching burst mode laser.

We propose and demonstrate a two-color formaldehyde planar laser induced fluorescence spectroscopy thermometry scheme using the third-harmonic of injection-seeded Nd:YAG lasers. The 28183.5cm-1 and 28184.5cm-1 peaks of formaldehyde are identified to measure the low-temperature combustion zone. Using a fast dual-wavelength-switching burst mode amplifier and a high-speed camera, high-repetition-rate (20 kHz) temperature field measurement is validated on a laminar coflow diffusion flame and demonstrated on a turbulent reacting jet in hot crossflow. Directly using the 355 nm output has the advantage of large energy and high signal-to-noise ratio. Combined with the fast dual-wavelength-switching method, the proposed scheme can greatly reduce experimental complexity and improve the understanding of practical combustors.