10 kHz 2D thermometry in turbulent reacting flows using two-color OH planar laser-induced fluorescence

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.

Laser applications to chemical, security, and environmental analysis: introduction to the feature issue

This Applied Optics feature issue on laser applications to chemical, security, and environmental analysis (LACSEA) highlights papers presented at the LACSEA 2020 Seventeenth Topical Meeting sponsored by The Optical Society (OSA).

10 kHz two-color OH PLIF thermometry using a single burst-mode OPO

10-kHz hydroxyl radical (OH) two-color planar laser-induced fluorescence (TC-PLIF) thermometry was demonstrated with a single burst-mode optical parametric oscillator (OPO) and a single camera. A fast, dual-wavelength switched seed laser enabled a high-energy, high-repetition-rate burst-mode laser to generate two 10-kHz pulse trains at wavelengths of ${\sim}{354.8}\;{\rm nm}$. The two pulse trains are colinear with 3 µs time interval between the pulse pairs. The injection-seeded OPO efficiently converts the burst-mode laser output to 285.62 and 285.67 nm to excite the ${Q}_2({12})$ and ${P}_1({8})$ OH transitions. PLIF images were collected from each of the two excitation transitions, and intensity ratios from the images were used to determine local temperatures. The development of fast, dual-wavelength switching, burst-mode OPO technology significantly reduces the experimental complexity of the high-speed TC-PLIF thermometry and simplifies its implementation in harsh combustion and flow test facilities.