Investigation of the effect of hydrogen addition on soot and PAH formation in ethylene inverse diffusion flames by combined LII and PAH LIF

Chinonso Ezenwajiaku, Robert Gray Roy, Midhat Talibi, Ramanarayanan Balachandran, Iain Burns

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Abstract

It is shown that signals from both laser-induced incandescence (LII) of soot and laser-induced fluorescence (LIF) of polycyclic aromatic hydrocarbons (PAHs) decrease with hydrogen addition (in volume fractions of 3%, 6% and 9% with respect to the fuel mixture) to ethylene–air inverse diffusion flames (IDFs). The structure of the IDF suppresses soot oxidation and the effect of hydrogen addition under these conditions has been studied. Experiments were performed using a frequency-doubled, pulsed dye laser to perform planar LIF of PAH, and a pulsed fibre laser to perform LII. In relative terms, the LII signal decreases more sharply than the PAH LIF signal. This would be consistent with the dependence of soot inception on PAH concentration as well as the suppression of soot growth via the reduced concentration of PAH and perhaps other precursors such as acetylene. Similar trends in relative signal decrease are observed at a range of heights above the burner, despite the measurement locations encompassing a wide range of absolute signal levels. As a comparison, the influence of adding methane to the IDF in the same volume fractions was also studied and found to suppress PAH LIF and LII signals but to a far lesser extent than in the case of hydrogen.
Original languageEnglish
Article number130613
JournalFuel
Volume361
Early online date21 Dec 2023
DOIs
Publication statusPublished - 1 Apr 2024

Funding

MT, RB and CE would like to acknowledge UKRI Future Leaders Fellowship (MR/T019735/1), UK Engineering and Physical Sciences Research Council (EPSRC) (EP/P003036/1) and the Nigerian Petroleum Technology Development Fund (PTDF) (PTDF/ED/PHD/ECE/97/16) for their financial support towards this work. IB and RR acknowledge financial support from EPSRC Platform Grant (EP/P001661/1) and from the European Union’s Horizon 2020 Research and Innovation Framework Programme under grant agreement No 785539.

Keywords

  • Inverse diffusion flame
  • Hydrogen
  • Laser-induced incandescence (LII)
  • Soot
  • Polycyclic aromatic hydrocarbons (PAH)
  • Planar laser-induced fluorescence (PLIF)

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