Influence of Initial Humidity on the Flame Propagation Rate of LPG/Air and LPG/O2/N2 Mixtures

  • Tomohiko ImamuraEmail author
  • Masaya Ohtsuki
  • Shota Kumata
  • Yuki Furuya
  • Reito Ohno
  • Akira Tanaka
  • Akira Kawaguchi
Conference paper


We examined the influence of the initial humidity to the flame propagation rate of LPG/air and LPG/O2/N2 mixtures to contribute to the risk assessment of the alternative energies. The ignition chamber was 1.36 L of volume, made by SUS316 steel. The moisture was added to the chamber by introducing air or inert gas which was passed through the bubbler. The ignition was initiated by the electric spark which was generated at the gap of needle electrode. First, we found that the ignition probability of LPG decreased with adding the moisture. On the other hand, we also found that the following three effects simultaneously appeared in the LPG combustion under the presence of moisture; (1) combustion-promoting effect that the unreacted LPG reacts to the O and/or OH radicals which were decomposed from the moisture, (2) combustion-suppressing effect by cooling due to the latent heat and the sensible heat of moisture, and (3) combustion-suppressing effect due to the oxygen insufficient which was caused by adding the moisture. The present experimental results could be explained by the above three effects. Furthermore, we confirmed that the results of chemical equilibrium analysis using CHEMKIN-PRO support the above hypothesis.


LPG Initial humidity Flame propagation rate Chemical equilibrium analysis 



Stoichiometric concentration (vol%)


Pressure (Pa)


Temperature (K)


Time (s)


Flame propagation rate (m/s)



Dry condition (relative humidity is zero)


Wet condition



This work was supported by JSPS KAKENHI (Grants-in-Aid for Scientific Research), Grant No. 15K01235. The authors would like to sincerely thank Dr. Yuichiro Izato of Yokohama National University for his precious help and suggestion for conducting the chemical equilibrium analysis.


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Copyright information

© Springer Nature Singapore Pte Ltd. 2020

Authors and Affiliations

  • Tomohiko Imamura
    • 1
    Email author
  • Masaya Ohtsuki
    • 1
  • Shota Kumata
    • 1
  • Yuki Furuya
    • 1
  • Reito Ohno
    • 1
  • Akira Tanaka
    • 1
  • Akira Kawaguchi
    • 1
  1. 1.Faculty of EngineeringSuwa University of ScienceChino, NaganoJapan

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