Experimental study of the effect of CF3I addition on the ignition delay time and laminar flame speed of methane, ethylene, and propane

doi:10.1016/j.proci.2014.05.096

Proceedings of the Combustion Institute

Volume 35, Issue 3, 2015, Pages 2731-2739

https://doi.org/10.1016/j.proci.2014.05.096 Get rights and content

Abstract

Since no suitable replacement has been found for Halon 1301 (CF₃Br), the approach for the next generation of fire suppressants has been to identify diverse agents or blends of agents for specific applications. Halon 13001 (CF₃I) is a possible candidate for unoccupied areas. However, there are very few fundamental data to help in validating its detailed kinetics mechanism. In this study, ignition delay time and laminar flame speed measurements of the effects of CF₃I on CH₄, C₂H₄, and C₃H₈ have been investigated for the first time. The ignition delay times were obtained in a shock tube with mixtures of fuel/O₂/CF₃I highly diluted in 98% argon (vol.), and the flame speeds were measured using an expanding, spherical flame. Results from the new experiments show a significant decrease in the laminar flame speed for small additions of suppressant. The effects on the ignition delay time are strongly dependent on the hydrocarbon: the ignition delay time of CH₄ is significantly decreased by CF₃I addition, while a significant increase in the ignition delay time was observed for the lowest temperatures investigated with C₂H₄. Ignition delay times for C₃H₈ were mostly unchanged, except for the lowest temperatures (below 1400 K) where a small decrease in the reactivity was observed. Compared to recent results obtained with CF₃Br, CF₃I showed a smaller suppressant effect under the conditions investigated. A detailed kinetics mechanism assembled from a C1–C3 mechanism from NUI Galway and a CF₃I sub-mechanism from NIST predicts well the results obtained in the shock tube with CH₄ and C₃H₈. The C₂H₄ data with CF₃I are however poorly predicted, pointing at some deficiencies in the model for C₂H₄/CF₃I interactions.

Introduction

With its high suppression efficiency [1], along with a relatively low toxicity, Halon 1301 (CF₃Br) was the most commonly used fire suppressant prior to being phased-out by the Montreal Protocol. Although a large body of work has been performed to find a suitable replacement [2], no component that meets all the required criteria has been found [3]. To date, CF₃Br is still the subject of extensive research in order to have a detailed understanding of its combustion chemistry (to identify/design similar reaction pathways for candidate replacements) [4], [5] and to serve as a benchmark for new compounds [3], [6], [7]. However, few -- if any -- fundamental combustion data have been available for the development of the CF₃Br chemical kinetics mechanism [1], [8], [9], explaining the discrepancy between the model and recent fundamental combustion data (ignition delay time (τ_ign) and laminar flame speed (S_L⁰)) [5].

Since no single substitute for Halon 1301 has been found, a more likely approach is to identify diverse agents or blends of agents for specific applications. Amongst the possible replacement candidates, CF₃I (Halon 13001) displayed some interesting properties. Notably, when released into the lower atmosphere, the fluorinated iodoalkanes degrade by photolysis of the carbon–iodine bond and are expected to have short atmospheric lifetimes (and hence not reaching and depleting the ozone layer) [2]. Numerical studies have shown that it has the same extinction efficiencies, sometimes even superior on a molar basis, than CF₃Br for inhibiting CH₄, CH₃OH, C₂H₆, and C₂H₄ [10] and alkanes (C1–C4) burning velocities [6]. Smith and Everest [11] compared OH and soot concentration measurements in propane/air diffusion flames inhibited by CF₃Br or CF₃I. Overall, under their experimental conditions, CF₃I was slightly superior to CF₃Br in terms of (i) requiring smaller concentrations at extinction, and (ii) producing less within-flame soot. The reductions in the OH concentration were essentially the same for CF₃I and CF₃Br. The flame structure was compared between low-pressure flames doped with CF₃I or CF₃Br by Sanogo et al. [12]. Results showed that the flames are essentially similar, and species involved in the inhibition process are formed in similar amounts. CF₃I also has a boiling point that is low enough for in-flight application consideration, even if its release at high altitude can be problematic for the ozone layer [2]. One can however mention a few drawbacks with the use of CF₃I such as its cardiac sensitization at levels well below the extinguishing concentration, which restricts its utilization to unoccupied areas [2].

Despite the interesting characteristics of CF₃I, there is a noticeable lack of fundamental data to have a good understanding of its flame inhibition mechanisms and to better assess its fire suppressant potential. The aim of the present work was therefore to provide fundamental combustion data, namely ignition delay times (for kinetics model assessment) and laminar flame speeds (suppressant assessment), on the effects of CF₃I on methane (main component of natural gas), ethylene (one of the most-used hydrocarbons in the petrochemical industry), and propane (to represent saturated-chain hydrocarbons). Pressure conditions were the same as in Osorio et al. [5], but sub-atmospheric experiments were investigated as well herein using the shock-tube technique to account for possible in-flight applications.

Section snippets

Shock-tube

Ignition delay times were determined behind reflected shock waves (RSW) in a single-diaphragm, stainless-steel shock tube. The driven section is 15.24-cm i.d., 4.72-m long; and the driver section is 7.62-cm i.d., 2.46-m long. A schematic of the shock-tube setup can be found in Aul et al. [13]. Five PCB P113A piezoelectric pressure transducers, equally spaced alongside the driven section and mounted flush with the inner surface, were used to measure the incident-wave velocities. A curve fit of

Shock tube

The ignition delay time was defined as the time between the passage of the RSW and the intersection of lines drawn along the steepest rate-of-change of OH de-excitation (i.e., chemiluminescence) and a horizontal line which defines the zero-concentration level, as documented in Osorio et al. [5]. The chemiluminescence emission from the A²∑⁺ → X²Π transition of the excited-state hydroxyl radical (OH) was followed at the sidewall location using an interference filter centered at 307 ± 10 nm with a

Discussion

During this study, the effect of CF₃I addition on the ignition delay times and laminar flame speeds of methane, ethylene, and propane were investigated experimentally. The addition of CF₃I was found to decrease τ_ign for methane. A similar effect was observed with CF₃Br over similar conditions by Osorio et al. [5]. A sensitivity analysis points at the same reaction for the two suppressants: CF₃ + O₂ ⇄ CF₃O + O (r1).

For C₃H₈, no reaction involving CF₃I or its products is amongst the 25 most-sensitive

Conclusion

During this study, the effect of CF₃I addition on the ignition delay times and laminar flame speeds of methane, ethylene, and propane was studied experimentally for the first time. Overall, the effects on the ignition delay time were found to be fuel dependent: a decrease in τ_ign was observed with methane, whereas an increase in τ_ign was observed at low temperature with C₂H₄ and, to a lesser extent, with C₃H₈. Flame speed measurements allow assessing the suppressant effect of CF₃I. A

Acknowledgments

Financial support was provided by the Mary Kay O’Connor Process Safety Center at the Artie McFerrin Department of Chemical Engineering, Texas A&M University for the TAMU effort and by CNRS-France for the work performed at ICARE, CNRS-INSIS Orléans.

References (18)

T. Noto et al.
Combust. Flame
(1998)
G.T. Linteris et al.
Combust. Flame
(2012)
Y. Saso
Proc. Combust. Inst.
(2002)
C.H. Osorio et al.
Combust. Flame
(2013)
V. Babushok et al.
Combust. Flame
(2000)
V. Babushok et al.
Combust. Flame
(1996)
T. Noto et al.
Proc. Combust. Inst.
(1996)
K.C. Smyth et al.
Proc. Combust. Inst.
(1996)
C.J. Aul et al.
Combust. Flame
(2013)

There are more references available in the full text version of this article.

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Experimental study of the effect of CF3I addition on the ignition delay time and laminar flame speed of methane, ethylene, and propane

Abstract

Introduction

Section snippets

Shock-tube

Shock tube

Discussion

Conclusion

Acknowledgments

Combust. Flame

Combust. Flame

Proc. Combust. Inst.

Combust. Flame

Combust. Flame

Combust. Flame

Proc. Combust. Inst.

Proc. Combust. Inst.

Combust. Flame

Experimental study of the effect of CF₃I addition on the ignition delay time and laminar flame speed of methane, ethylene, and propane