Influence of halon replacements on laminar flame speeds and extinction limits of hydrocarbon flames

Many practical soot-emitting combustion systems such as diesel and jet engines rely on diffusion flames for efficient and reliable operation. Efforts to mitigate soot emissions from these systems are dependent on fundamental understanding of the physicochemical pathways leading from fuel to soot in laminar diffusion flames. Existing diffusion flame−based soot studies focused primarily on overventilated coflow flame where the fuel gas (or vapor) issues from a cylindrical tube into a co-flowing oxidizer, and counterflow flame, where a reacting zone is established between two opposing streams of fuel and oxidizer. As a canonical diffusion flame configuration, laminar counterflow diffusion flames have been widely used as a highly controllable environment for soot research, enabling significant progress in the understanding of soot formation for several decades. In view of the possibility of fuel/oxidizer premixing in practical systems, counterflow partially premixed flames have also been studied. In the present work we intend to provide a comprehensive review of the researches on various aspects of soot formation utilizing counterflow flames. Major processes of soot formation (formation of gas phase soot precursors, soot inception and surface reactions, as well as particle-particle interactions) are examined first, with focus on the most recent (post-2010) research progress. Experimental techniques and associated challenges for the measurement of soot-related properties (some knowledge of which is helpful for full appreciation of the experimental data to be reviewed) are then introduced. This is followed by a detailed description of soot evolution in counterflow flames, which is complemented by a discussion on the similarity and differences of the sooting structures between counterflow and coflow diffusion flames. Parametric studies of the effects of fuel molecular structure, fuel additive, partial-premixing, pressure, temperature, stoichiometric mixture fraction, and residence time on soot formation in counterflow flames will then be addressed in detail. This review concludes with a summary of the knowledge and challenges gathered and demonstrated through decades of research, and an outlook on opportunities for future counterflow flame−based soot research towards a more complete understanding of soot formation and the development of novel techniques for soot mitigation in practical combustion devices.

show abstract

“…Interest in halogenated species originated with their use as flame extinguishing agents [733][734][735],…”

Section: Other Dopants A) Addition Of Chlorinated Speciesmentioning

confidence: 99%

Soot formation in laminar counterflow flames

Wang

Chung

2019

Progress in Energy and Combustion Science

307

112

View full text Add to dashboard Cite

show abstract

“…This phenomenon might also explain overpressure increase observed in the FAA-ACT experiments [18] where the introduction of inhibition powders actually led to faster flames and higher overpressures. Many authors [38][39][40][41] have proposed an explanation for the observed overpressure increase based on thermodynamic equilibrium calculations and perfectly stirred reactor simulations. A non-uniform inhibitor distribution prior to ignition, and the subsequent flame surface increase, may also explain the increase in pressure during these experiments.…”

Section: Resultsmentioning

confidence: 99%

Theoretical analysis and simulation of methane/air flame inhibition by sodium bicarbonate particles

Dounia

Vermorel

Poinsot

2018

Combustion and Flame

View full text Add to dashboard Cite

show abstract

“…After a group of test runs, the volumetric flow rate of the carrier gas was fixed at 5.5 standard liters per minute (SLPM, at 0 °C and 1 atm). During the experiments, the burner assembly and pipelines were heated using a of the burner implemented several technical solutions considered previously in the building of nozzle burners [26,27]. In particular, it used a profiled converging nozzle to reduce the boundary layer thickness and to yield a top-hat (plug-flow) velocity profile at the exit plane.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

Combustion Inhibition of Aluminum–Methane–Air Flames by Fine NaCl Particles

Xu¹,

Jiang²

2018

Energies

Self Cite

View full text Add to dashboard Cite

The effect of NaCl as an extinguishing agent on metal dust fires require further exploration. This paper reports the results of an experimental study on the performance of micron-sized NaCl powders on hybrid aluminum–methane–air flames. NaCl particles with sub-10 μm sizes were newly fabricated via a simple solution/anti-solvent method. The combustion characteristics of aluminum combustion in a methane-air flame were investigated prior to the particle inhibition study to verify the critical aluminum concentration that enables conical aluminum-powder flame formation. To study the inhibition effectiveness, the laminar burning velocity was measured for the established aluminum–methane–air flames with the added NaCl using a modified nozzle burner over a range of dust concentrations. The results were also compared to flames with quartz sand and SiC particles. It is shown that the inhibition performance of NaCl considerably outperformed the sand and SiC particles by more rapidly decreasing the burning velocity. The improved performance can be attributed to contributions from both dilution and thermal effects. In addition, the dynamic behavior of the NaCl particles in the laminar aluminum–methane–air flame was investigated based on experimental observations. The experimental data provided quantified the capabilities of NaCl for metal fire suppression on a fundamental level.

show abstract

Influence of halon replacements on laminar flame speeds and extinction limits of hydrocarbon flames

Cited by 44 publications

References 45 publications

Soot formation in laminar counterflow flames

Soot formation in laminar counterflow flames

Theoretical analysis and simulation of methane/air flame inhibition by sodium bicarbonate particles

Combustion Inhibition of Aluminum–Methane–Air Flames by Fine NaCl Particles

Contact Info

Product

Resources

About