In-situ photoacoustic measurement of soot profiles in laminar flames using a high repetition-rate pulsed fibre laser

Gordon S. Humphries, Robert Roy, John D. Black, Michael Lengden, Iain S. Burns

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We present a photoacoustic technique for in situ sensing of particulates in reacting flows. The method is demonstrated by measuring soot distribution in laminar flat-flames. The excitation source is a high repetition-rate pulsed fibre laser. The resulting acoustic signals are measured using a uni-directional microphone and lock-in amplifier. Based on an Allan-Werle plot, the detection limit is estimated to be a soot volume fraction of 3 parts-per-billion. Fluence curves are presented, showing a plateau region similar to the behaviour typically observed for laser-induced incandescence. A dependence of the photoacoustic signal on pulse repetition rate is also demonstrated.
Original languageEnglish
Article number60
Number of pages6
JournalApplied Physics B: Lasers and Optics
Issue number4
Early online date14 Mar 2019
Publication statusPublished - 30 Apr 2019
Event8th International Workshop on Laser-Induced Incandescence - Evangelische Akademie, Tutzing, Germany
Duration: 10 Jun 201813 Jun 2018


  • soot measurement
  • photoacoustic
  • fibre laser
  • combustion
  • laminar flames

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