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Thin Filament Pyrometry Field Measurements in a Medium-Scale Pool Fire

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Abstract

This paper presents the development of a thin filament pyrometry method to characterize the time-varying temperature field in a medium-scale pool fire burning in a quiescent environment. A digital camera with optical filters and zoom lens was used to record the high temperature emission intensity of 14 µm diameter, silicon-carbide filaments oriented horizontally at various heights above the center of a steadily burning 0.30 m diameter methyl alcohol (methanol; CH3OH) pool fire. Experiments collected 30 Hz video of the planar filament array. In a separate experiment, a 50 µm diameter thermocouple was used to acquire independent temperature measurements in the high temperature zone of the fire. A correlation was developed between the probability density functions of the radiation-corrected thermocouple measurements and the camera grayscale pixel intensity of the filaments. This arrangement enables measurement of the time-varying temperature field over a temperature range from about 1150 K to 1900 K with a spatial resolution of 160 µm, a temporal resolution of 0.033 s, and an expanded uncertainty of about 150 K (at a mean temperature of 1300 K). Measurements of the grayscale pixel intensities of the filaments were obtained. False color maps of the temperature field were produced to characterize the high temperature field as a function of time. Using statistical analysis, the local time-averaged temperatures and their variance for each location on the filaments were determined. Time-averaged temperatures were compared favorably to previously reported measurements. The dominant frequency of the puffing fire was determined. The temperature field time series was transformed to consider its character during consecutive phases of the fire’s puffing cycle. The analysis emphasizes the cyclic nature of a pool fire, providing insight on its complex dynamic structure.

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Notes

  1. 1.

    Unless otherwise noted, the uncertainty in this paper is expressed as the combined uncertainty with a coverage factor of two, representing a 95% confidence interval.

  2. 2.

    Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose.

  3. 3.

    The word phase is applied as commonly used, referring to an instance in time on a cyclic waveform.

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Acknowledgements

Many thanks are due to Michael Gollner and Peter Sunderland of the University of Maryland at College Park and Howard Baum of NIST for helpful discussions. The authors are grateful to Nippon Carbon Co and Hugh Spilker of COI Ceramics for providing the SiC filament samples.

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Correspondence to Anthony Hamins.

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Wang, Z., Tam, W.C., Chen, J. et al. Thin Filament Pyrometry Field Measurements in a Medium-Scale Pool Fire. Fire Technol 56, 837–861 (2020). https://doi.org/10.1007/s10694-019-00906-9

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Keywords

  • Methanol
  • Pool fires, pyrometry
  • Temperature field measurements