Burning characteristics of candle flames in sub-atmospheric pressures: An experimental study and scaling analysis

Qiang Wang, Longhua Hu, Adriana Palacios, Suk Ho Chung

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Burning characteristics (mass burning rate, natural convection boundary layer thickness, flame height and dark zone height) of laminar diffusion flames produced by a candle at sub-atmospheric pressures in the range of P = 50-100 kPa were experimentally studied in a reduced-pressure chamber; such data are not reported to date. Scaling analysis was performed to interpret the pressure dependence. The new experimental findings for candle flames in the sub-atmospheric pressures were well interpreted by the proposed scaling laws: (1) the mass burning rate was higher for a candle with larger wick length, and it increased with increasing ambient pressure, a stagnant layer B-number model based on natural convection boundary (flame boundary layer thickness) was developed to scale the mass burning rate of candle flames at various pressures; (2) the flame boundary layer thickness was wider in lower pressure and can be well represented by a natural convection boundary layer solution; (3) flame height was higher for a candle with larger wick length, meanwhile the ratio of flame height to burning rate was independent of pressure; (4) the flame dark zone height representing a soot formation length scale changes little with pressure, meanwhile its ratio to the total flame height is scaled with pressure by P∞-1/2/Lw,e3/4 (L is effective wick length inside flame). This work provided new experimental data and scaling laws of candle flame behaviors in sub-atmospheric pressures, which provided information for future characterization and soot modeling for diffusion flames associated with melting and evaporation processes of solid fuels.
Original languageEnglish (US)
Pages (from-to)2065-2072
Number of pages8
JournalProceedings of the Combustion Institute
Issue number2
StatePublished - Jul 8 2018

Bibliographical note

KAUST Repository Item: Exported on 2021-09-14
Acknowledgements: This work was supported jointly by National Natural Science Foundation of China (51606057), Newton Advanced Fellowship of Royal Society, UK (NA140102), Fundamental Research Funds for the Central Universities (JZ2018HGTB0256; WK2320000035; WK2320000038), NSFC-STINT joint project (51811530015), Key Research Program of Frontier Sciences of Chinese Academy of Science (CAS) (QYZDB-SSW-JSC029) and China Postdoctoral Science Foundation funded project (2018T110625; 2016M590580). SHC was supported by KAUST.

ASJC Scopus subject areas

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


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