Observation of combustion characteristics of droplet clusters in a premixed-spray flame by simultaneous monitoring of planar spray images and local chemiluminescence

Tsushima, Shoji; Saitoh, Hiroyasu; Akamatsu, Fumiteru; Katsuki, Masashi

doi:10.1016/s0082-0784(98)80041-6

Cited by 24 publications

(8 citation statements)

References 9 publications

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“…Depending on the boundary conditions, both premixed-like and diffusionlike flames can exist in the combustion of fuel droplets [826]. Drop group combustion (i.e., the combustion of droplet clusters) was observed to behave like diffusion flames [827][828][829].…”

Section: Soot Formation In Counterflow Flames Of Fuel Spraysmentioning

confidence: 99%

Soot formation in laminar counterflow flames

Wang

Chung

2019

Progress in Energy and Combustion Science

336

116

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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.

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Section: Soot Formation In Counterflow Flames Of Fuel Spraysmentioning

confidence: 99%

Soot formation in laminar counterflow flames

Wang

Chung

2019

Progress in Energy and Combustion Science

336

116

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“…These images are acquired under the conditions of F16 with an exposure time of 100 ms. The detection of chemiluminescence has often been used in previous research to describe various aspects of the combustion process qualitatively. − The chemiluminescence intensities are roughly proportional to the reaction intensity. The OH chemiluminescence is free from background luminosity because it relaxes to the ground state in the UV range, with the most intense bands being the (0,0) at 306.4 nm and the (1,0) at 281.l nm. , Therefore, the OH chemiluminescence can be properly used as a marker for deciding the flame-tip behavior.…”

Section: Methodsmentioning

confidence: 99%

“…These techniques include direct still or video camera photography, luminous flame length obtained by an intensified charge-coupled device (ICCD) camera, and average flame length obtained from accumulated chemiluminescence images using an adequately filtered ICCD camera. Among those methods, the detection of chemiluminescence has been widely used by previous researchers to describe various aspects of the combustion process qualitatively. − Chemiluminescence intensities are roughly proportional to the reaction intensity. OH chemiluminescence is free from background luminosity, because it is located in the ultraviolet (UV) range. , Therefore, the OH chemiluminescence can be properly used as a marker for deciding the flame length behavior.…”

Section: Introductionmentioning

confidence: 99%

Generation of Silica Nanoparticles in Turbulent Non-premixed Flames with Oxygen Enrichment

Bae¹,

Shin²

2009

Energy Fuels

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Silica nanoparticles were made via the gas-to-particle conversion of tetraethylorthosilicate (TEOS) in co-flowing turbulent methane-oxygen-enriched non-premixed flames. The effects of fuel velocity, oxygen concentration, flame residence time, and temperature distribution on the characteristics of the silica nanoparticles were investigated. The flame length was measured by OH chemiluminescence, using an intensified charge-coupled device (ICCD) camera. The primary particle diameter of the silica nanoparticles was quantitatively measured by transmission electron microscopy (TEM). Particle number concentration, as well as the geometric mean diameter and standard deviation, were measured by a scanning mobility particle sizer (SMPS) spectrometer. Adiabatic temperatures according to oxygen concentration and mixture fraction were calculated from thermodynamic equilibrium calculations, considering chemical species using CHEMKIN EQUIL code. Flame temperature, velocity, and turbulent intensity distributions were calculated using Fluent software adapted to the presumed probability density function (PDF) model, considering chemical species in the turbulent non-premixed methane-oxygen-enriched flame burner without including the particles. For each oxygen concentration condition, the flame residence time, average primary particle diameter, and geometric mean diameter decreased as the fuel velocity increased. Typically, agglomerates of silica nanoparticles were made on averaged primary particle diameters of 9-15 nm and geometric mean diameters of 60-100 nm, according to the oxygen concentration, which varied from 50% to 100% for first jet velocities of 40 and 70 m/s.

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“…To verify the presence of the droplet group combustion in the actual flames, some numerical and experimental study has been conducted [3], [4], [5]. Nakamura et al [5] conducted two-dimensional direct numerical simulation (DNS) about spray combustion in counterflow.…”

Section: Introductionmentioning

confidence: 99%