A comparison of carbon monoxide yields and particle formation at various global equivalence ratios in vitiated and under-ventilated conditions

Robert Bray, Joakim Åström, Dan Madsen, Svetlana Tretsiakova-McNally, Jianping Zhang, Vilhelm Malmborg, Patrick van Hees

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Abstract

There have been previous studies comparing experimental methods for the purpose of capturing gaseous yields at a range of global equivalence ratios. However, no work has investigated the capability of the open controlled atmosphere cone calorimeter for collecting such data where its two modes of operation are directly compared. The aim of this study is to compare carbon monoxide yields collected using vitiated and under-ventilated modes of atmospheric control in order to identify the preferable method of replicating carbon monoxide yields reported from larger scale enclosure fire experiments. Cone irradiances of 30, 50 and 65 kW/m2 were applied to PMMA and plywood samples. Vitiated tests were conducted using a mixed air/diluent gas, with an inflow rate of either 100, 150 or 180 L/min, resulting in a reduced oxygen concentration of 17.5 vol. %. Under-ventilated tests were conducted using flow rates of 5, 10 and 20 L/min in an air atmosphere. Particle formations and emissions were also measured using a particle analyser and have been reported herein. Results indicate that the under-ventilated mode of equivalence ratio control offers a more promising method of capturing species yields with favourable comparisons to other bench scale methods
Original languageEnglish
Article number103915
Pages (from-to)1-18
Number of pages18
JournalFire Safety Journal
Volume141
Early online date16 Aug 2023
DOIs
Publication statusPublished (in print/issue) - 31 Dec 2023

Bibliographical note

Funding Information:
The authors would like to thank Hydrock Consultants Ltd. For funding much of the work included within this study. Thanks also goes to Angela Brownlie at QUB for conducting the elemental analysis. The authors would also like to thank Catherine Bray for the enhancement of video footage. Robert John Bray would like to thank the Department for the Economy (Northern Ireland) Postgraduate Studentship for their financial support.

Funding Information:
This section has illustrated the different combustion conditions present in vitiated and under-ventilated tests. The two methodologies for calculating average GER/COY values highlight some of the challenges in collecting GER/COY averages. The section concludes by comparing correlations of GER/COY between test conditions to identify the operating mode best suited for collecting such data using the OCACC. The under-ventilated operating mode has resulted in the most promising CO yields where the GER is above 1. When post-chimney flaming is not observed, the gas temperatures are low enough to prevent CO oxidation within the smoke plume. The temperatures necessary to “freezeout” CO conversion to CO2 are considered to be ∼800–900 K [24]. For air flows rates 5–20 L/min it is hypothesised that the limited HRR of ventilation restricted fuels alongside heat losses within the chimney during the increased effluent transport time reduce temperatures sufficiently to prevent post chimney flaming. This is supported by COYs that are comparable to other methods (FPA/SSTF).The authors would like to thank Hydrock Consultants Ltd. For funding much of the work included within this study. Thanks also goes to Angela Brownlie at QUB for conducting the elemental analysis. The authors would also like to thank Catherine Bray for the enhancement of video footage. Robert John Bray would like to thank the Department for the Economy (Northern Ireland) Postgraduate Studentship for their financial support.

Publisher Copyright:
© 2023 The Authors

Keywords

  • Vitiated
  • Under-ventilated
  • CACC
  • Cone Calorimetry
  • Controlled Atmosphere
  • Equivalence ratio
  • Carbon Monoxide
  • Toxicity
  • Hazard Evaluation
  • Compartment fires
  • Cone calorimetry
  • Controlled atmosphere
  • Hazard evaluation
  • Carbon monoxide

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