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Published February 21, 2023 | Supplemental Material + Published
Journal Article Open

Single-pulse real-time billion-frames-per-second planar imaging of ultrafast nanoparticle-laser dynamics and temperature in flames

Abstract

Unburnt hydrocarbon flames produce soot, which is the second biggest contributor to global warming and harmful to human health. The state-of-the-art high-speed imaging techniques, developed to study non-repeatable turbulent flames, are limited to million-frames-per-second imaging rates, falling short in capturing the dynamics of critical species. Unfortunately, these techniques do not provide a complete picture of flame-laser interactions, important for understanding soot formation. Furthermore, thermal effects induced by multiple consecutive pulses modify the optical properties of soot nanoparticles, thus making single-pulse imaging essential. Here, we report single-shot laser-sheet compressed ultrafast photography (LS-CUP) for billion-frames-per-second planar imaging of flame-laser dynamics. We observed laser-induced incandescence, elastic light scattering, and fluorescence of soot precursors - polycyclic aromatic hydrocarbons (PAHs) in real-time using a single nanosecond laser pulse. The spatiotemporal maps of the PAHs emission, soot temperature, primary nanoparticle size, soot aggregate size, and the number of monomers, present strong experimental evidence in support of the theory and modeling of soot inception and growth mechanism in flames. LS-CUP represents a generic and indispensable tool that combines a portfolio of ultrafast combustion diagnostic techniques, covering the entire lifecycle of soot nanoparticles, for probing extremely short-lived (picoseconds to nanoseconds) species in the spatiotemporal domain in non-repeatable turbulent environments. Finally, LS-CUP's unparalleled capability of ultrafast wide-field temperature imaging in real-time is envisioned to unravel mysteries in modern physics such as hot plasma, sonoluminescence, and nuclear fusion.

Additional Information

© The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. The authors thank Dr. Geng Ku for experimental assistance. Y.N.M. gratefully acknowledges the Swedish Research Council for the financial support of grant # IPD2018-06783. These authors contributed equally: Yogeshwar Nath Mishra, Peng Wang. Contributions. Y.N.M. proposed the LS-CUP of soot and PAHs and designed the flame planar imaging system. Y.N.M. and P.W. integrated CUP with the flame imaging module. P.W. built and characterized the CUP system. Y.N.M. and P.W. performed the experiments. Y.N.M., P.W., and Y.Z. developed the image reconstruction algorithm. Y.N.M. and P.W. conducted the image reconstruction. F.J. B. and P.W. performed the numerical modeling. Y.N.M., P.W., and F.J. B. analyzed the experimental data and drafted the manuscript. D.H. and S.W. reviewed the technical details and advised on evaluation approaches. L.V.W. supervised the project. All authors revised the manuscript. Data availability. The data that support the findings of this study are available from the corresponding author on reasonable request. Code availability. The reconstruction algorithm is described in detail in Supplementary Information. We have opted not to make the computer code publicly available because the code is proprietary and used for other projects. Competing interests. The authors disclose the following patents for the CUP technology: WO2016085571 A3 (L.V.W.) and US10992924B2 (L.V.W. and P.W.).

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Additional details

Created:
August 22, 2023
Modified:
October 25, 2023