Experimental study on the flame length and burning behaviors of pool fires with different ullage heights

Jinlong Zhao, Xiang Zhang, Jianping Zhang, Wei Wang, Changkun Chen

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Floating-roof tanks are widely used in chemical parks and in case of fires, it is common to form pool fires with varying ullage height. This paper is aimed at examining experimentally and analytically the effects of ullage height on the burning and flame behaviors of heptane pool fires. A series of pool fire tests with four fuel tray sizes (D=20-35 cm) and five ullage heights (h=3 cm, 5 cm, D/2, D, 2D) was conducted. The flame characteristics (length and position) and mass burning rate were measured. Experimental results indicate that the total flame length can be divided into (i) a down-reaching flame length, (Lf,down), and (ii) an upper flame length (Lf,upper). The data shows that Lf,down increases as the ullage height increases whereas Lf,upper shows an opposite trend. For the tests with very large ullage heights (h/D=1.93), it was found that the flame fluctuated periodically and, in some cases, self-extinguishing of the flame occurred due to lack of oxygen inside the fuel tray. A theoretical model is developed to calculate the total flame length by considering the influence of ullage height on air entrainment and heat feedback and subsequently validated against the experimental data.
Original languageEnglish
Article number123397
Pages (from-to)1-10
Number of pages10
Early online date5 Feb 2022
Publication statusPublished (in print/issue) - 1 May 2022

Bibliographical note

Funding Information:
This study was sponsored by the National Natural Science Foundation of China (No. 51906253 ), the Fundamental Research Funds for the Central Universities (No. 2020QN05 and No. 2021JCCXAQ01 ), Key Laboratory of Emergency Management Department of Fire Emergency Rescue Equipment ( 2019XFZB16 ).

Publisher Copyright:
© 2022 Elsevier Ltd


  • Pool fire
  • Ullage height
  • Upper flame length
  • Theoretical model
  • Down-reaching flame length


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