Heterogeneous and homogeneous combustion of fuel-lean C3H8/O2/N2 mixtures over rhodium at pressures up to 6 bar

John Mantzaras, Ran Sui, Chung K. Law, Rolf Bombach

Research output: Contribution to journalConference articlepeer-review

1 Scopus citations

Abstract

The heterogeneous and homogeneous combustion of C3H8/O2/N2 mixtures over Rh was studied at pressures 1-6 bar, catalyst surface temperatures 680-1100 K and C3H8-to-O2 equivalence ratios 0.25-0.52. Non-intrusive laser-based measurements were applied in a channel-flow catalytic reactor and involved 1-D Raman spectroscopy of major gas-phase species across the channel boundary layer for assessing the catalytic reactivity and planar laser induced fluorescence (PLIF) of the OH radical for monitoring homogeneous combustion. Simulations were performed using a 2-D CFD code with detailed heterogeneous and homogeneous chemical reaction mechanisms. By comparing the Raman-measured and predicted transverse profiles of the limiting C3H8 reactant, the suitability of a detailed surface reaction mechanism was initially evaluated and subsequently a one-step reaction was constructed, which was applicable for the C3H8 total oxidation over Rh at 1-6 bar. The catalytic reactivity of C3H8 over Rh displayed a ∼p0.14 pressure dependence, which was substantially lower than a previously reported ∼p0.70 dependence over Pt. The weak pressure dependence of the C3H8 reactivity on Rh suggested caution when selecting catalysts for high-pressure power systems (recuperative microreactors, small-scale turbines) fueled with C3H8 or LPG. Comparisons of PLIF-measured and predicted distributions of the OH radical indicated that the employed gas-phase reaction mechanism captured the onset of homogeneous ignition at pressures ≥ 3 bar as well as the ensuing flame shapes. Predicted and measured homogeneous ignition distances agreed within 2.5% at 6 bar. With decreasing pressure, the predictions yielded gradually increasing but still modest underpredictions (up to 11.2% at 3 bar) of the homogeneous ignition distances. The key gas-phase reactions affecting homogeneous combustion at various pressures were finally identified.

Original languageEnglish (US)
Pages (from-to)6473-6482
Number of pages10
JournalProceedings of the Combustion Institute
Volume38
Issue number4
DOIs
StatePublished - 2021
Event38th International Symposium on Combustion, 2021 - Adelaide, Australia
Duration: Jan 24 2021Jan 29 2021

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Mechanical Engineering
  • Physical and Theoretical Chemistry

Keywords

  • High-pressure propane combustion on rhodium
  • In situ Raman and OH-PLIF
  • Pressure-dependent propane catalytic reactivity on rhodium
  • Propane homogeneous ignition on rhodium

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