A Custom, High-Channel-Count Data Acquisition System for Chemical Species Tomography of Aero-Jet Engine Exhaust Plumes

Edward Fisher, Stylianos Tsekenis, Yunjie Yang, Andrea Chighine, Chang Liu, Nicholas Polydorides, P. Wright, Joshua Kliment, Krikor Ozanyan, Thomas Benoy, Gordon Humphries, David Wilson, Michael Lengden, Walter Johnstone, Hugh McCann

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The fiber-laser imaging of gas turbine exhaust species project aims to provide a video-rate imaging (100 frames/s) diagnostic tool for application to the exhaust plumes of the largest civil aero-jet engines. This remit, enabled by chemical species tomography (CST) currently targeting carbon dioxide (CO 2 ), requires system design that facilitates expansion of multiple parameters. Scalability is needed in order to increase imaging speeds and spatial resolutions and extends the system toward other pertinent gases such as the oxides of nitrogen and sulfur and unburnt hydrocarbons. This paper presents a fully scalable, noninvasive instrument for installation in a commercial engine testing facility, technical challenges having been tackled iteratively through bespoke optical and mechanical design, and it specifically presents the high-speed data acquisition (DAQ) system required. Measurement of gas species concentration is implemented by tunable diode laser absorption with wavelength modulation spectroscopy (TDLAS-WMS) using a custom, high-speed 10-40-MS/s/channel 14-bit DAQ. For CO 2 tomography, the system uses six angular projections of 21 beams each. However, the presented DAQ has capacity for 192 fully parallel 10-Hz-3-MHz differential inputs, achieving a best-case signal-to-noise ratio (SNR) of 56.5 dB prior to filtering. A 12 Ethernet-connected digitization nodes based on field-programmable gate array technology with software control are distributed around a 7-m-diameter mounting “ring.” Hence, the high data rates of 8.96-Gb/s per printed circuit board and 107.52 Gb/s for the whole system can be reduced by using local digital lock-in amplifiers. We believe that this DAQ system is unique in both the TDLAS and CST literatures.
Original languageEnglish
Pages (from-to)549 - 558
Number of pages16
JournalIEEE Transactions on Instrumentation and Measurement
Issue number2
Early online date20 Feb 2019
Publication statusPublished - Feb 2020

Keywords / Materials (for Non-textual outputs)

  • aero-engine emissions
  • aerospace and aviation
  • Chemical Species Tomography (CST)
  • Data acquisition (DAQ) systems
  • Tunable diode laser absorption spectroscopy (TDLAS)
  • Data acquisition
  • Engines
  • laser beams
  • measurement by laser beam
  • Adsorption


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