Tomographic imaging of carbon dioxide in the exhaust plume of large commercial aero-engines

Abhishek Upadhyay, Michael Lengden, Godwin Enemali, George Stewart, Walter Johnstone, David Wilson, Gordon Humphries, Thomas Benoy, John Black, Andrea Chighine , Edward Fisher, Rui Zhang, Chang Liu, Nick Polydorides , Alex Tsekenis, Paul Wright, Joshua Kliment, Johan Nilsson, Yutong Feng, Victor ArchillaJavier Rodriguez-Carmona, Jesus Sanchez-Valdepenas, Marta Beltran, Valentin Polo, Ian Armstrong, Iain Mauchline, Douglas Walsh, Mark Johnson, Joanna Bauldreay, Hugh McCann

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We report here the first implementation of chemically specific imaging in the exhaust plume of a gas turbine typical of those used for propulsion in commercial aircraft. The method used is chemical species tomography (CST) and the target species is CO2, absorbing in the near-infrared at 1999.4 nm. A total of 126 beams propagate transverse to the plume axis, along 7 m paths in a coplanar geometry, to probe a central region of diameter ≈1.5m. The CO2 absorption spectrum is measured using tunable diode laser spectroscopy with wavelength modulation, using the second harmonic to first harmonic (2f/1f) ratio method. The engine is operated over the full range of thrust, while data are recorded in a quasi-simultaneous mode at frame rates of 1.25 and 0.3125 Hz. Various data inversion methodologies are considered and presented for image reconstruction. At all thrust levels a persistent ring structure of high CO2 concentration is observed in the central region of the measurement plane, with a raised region in the middle of the plume assumed to be due to the engine’s boat tail. With its potential to target various exhaust species, the CST method outlined here offers a new approach to turbine combustion research, turbine engine development, and aviation fuel research and development.
Original languageEnglish
Pages (from-to)8540-8552
Number of pages13
JournalApplied Optics
Issue number28
Publication statusPublished - 29 Sept 2022


  • exhaust plumes
  • aircraft engines
  • gas turbines
  • aviation
  • global emissions
  • sustainable aviation fuels (SAFs)
  • carbon dioxide (CO2)
  • electrically driven propulsion


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  • Applied Optics Best Paper Prize 2022 - Imaging Systems

    Upadhyay, Abhishek (Recipient), Lengden, Michael (Recipient), Enemali, Godwin (Recipient), Stewart, George (Recipient), Johnstone, Walter (Recipient), Wilson, David (Recipient), Humphries, Gordon (Recipient), Benoy, Thomas (Recipient), Black, John (Recipient), Chighine , Andrea (Recipient), Fisher, Edward (Recipient), Zhang, Rui (Recipient), Liu, Chang (Recipient), Polydorides , Nick (Recipient), Tsekenis, Alex (Recipient), Wright, Paul (Recipient), Kliment, Joshua (Recipient), Nilsson, Johan (Recipient), Feng, Yutong (Recipient), Archilla Prat, Victor (Recipient), Rodriguez-Carmona, Javier (Recipient), Valdepenas, Jesus-Sanchez (Recipient), Beltran, Marta (Recipient), Polo, Valentin (Recipient), Armstrong, Ian (Recipient), Mauchline, Iain S. (Recipient), Walsh, Douglas (Recipient), Johnson, Mark (Recipient), Bauldreay, Joanna (Recipient) & McCann, Hugh (Recipient), 2023

    Prize: Prize (including medals and awards)

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