Influence of Initial Humidity on the Flame Propagation Rate of LPG/Air and LPG/O2/N2 Mixtures
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.
KeywordsLPG Initial humidity Flame propagation rate Chemical equilibrium analysis
Stoichiometric concentration (vol%)
Flame propagation rate (m/s)
Dry condition (relative humidity is zero)
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.
- 1.Lewis, B., & von Elbe, G. (1961). Combustion, flames and explosions of gases (2nd ed.). Cambridge: Academic Press.Google Scholar
- 2.Japan Society for Safety Engineering (JSSE). (1999). Handbook of safety engineering (p. 156). Corona Publishing (in Japanese).Google Scholar
- 3.Kuo, K. K. (2005). Principles of combustions (2nd ed., pp. 500–501). Hoboken: Wiley.Google Scholar
- 4.Egolfopous, F. N., & Law, C. K. (1990). An experimental and computational study of the burning rates of ultra-lean to moderately-rich H2/O2/N2 laminar flames with pressure variation. In 23rd Symposium on Combustion (pp. 333–340).Google Scholar
- 7.Lewis, B. (1954). Discussion: Selected combustion problems (p. 177), AGARD, Butterworths, London.Google Scholar
- 8.Umezawa, S., & Kawakami, T. (2005). Combustion characteristics near the flame propagation limit in high humidity and low oxygen concentration. In Proceedings of Annual Meeting of Japan Society of Mechanical Engineers (JSME) Kanto Branch (pp. 217–218) (in Japanese).Google Scholar
- 9.Website about GRI-Mech 3.0. (2017). http://combustion.berkeley.edu/gri-mech/ (Last accessed December 15, 2017).
- 10.Lewis, D. J. (1980). Autoignition temperature determinations and their relationship to other types of potential ignition sources and their application to practical situations. In IchemE Symposium Series No. 58 (pp. 257–273).Google Scholar
- 11.ASTM E582-07. (2013). Standard test method for minimum ignition energy and quenching distance in gaseous mixtures.Google Scholar