Experimental study of the effect of ullage height on flame characteristics of pool fires

Chunxiang Liu, Long Ding, Mehdi Jangi, Jie Ji*, Longxing Yu, Huaxian Wan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)
307 Downloads (Pure)


A series of experiments were carried out to investigate the effect of ullage height, i.e. the distance between fuel surface and the pool upper rim, on flame characteristics of heptane and ethanol pool fires. The pool diameters included 10 cm, 15 cm, and 20 cm. For each pool, ullage height was increased from zero to the value that the flame self-extinguished. During each test, the ullage height was kept constant by a fuel level maintaining device. Results show that ullage height has a significant effect on flame characteristics. When the ullage height equals zero, there is a stable conical structure near the pool upper rim, above which the unstable plume develops. Under lower ullage height conditions, plume puffing happens. The unstable plume begins to initiate around the pool upper rim, then rolling and expanding upward. At the same time, its beneath flame is stretched thinner and thinner and eventually breaks from the bulk. When the ullage height further increases, plume puffing becomes less evident. While for the mass loss rate, it generally decreases with the increase of h/D. It was proved in literature that the previous flame height model is inapplicable to pool fires with large ullage height. In this paper, to consider the effect of ullage height on plume flow structures, an equivalent hydraulic diameter, Deq., is proposed to establish one new flame height correlation. By comparing previous model predictions with the current experimental data, it is found that conventional flame oscillation models are unsuitable to pool fires with large ullage height. Based on Deq., two new dimensional and dimensionless flame oscillation models were proposed according to the current experimental data. The correlated flame height model and proposed flame oscillation models were validated and agreed well with reference data.

Original languageEnglish
Pages (from-to)245-255
Number of pages11
JournalCombustion and Flame
Early online date2 Apr 2020
Publication statusPublished - Jun 2020


  • Equivalent hydraulic diameter
  • Flame characteristics
  • Flame height
  • Flame oscillation frequency
  • Mass loss rate
  • Ullage height

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy


Dive into the research topics of 'Experimental study of the effect of ullage height on flame characteristics of pool fires'. Together they form a unique fingerprint.

Cite this