Carbon black is a carbon nanoparticle, which is used as a reinforcing agent for rubber, and is produced utilizing the heat of combustion. Since the morphology of carbon black greatly affects the performance of tires, the technology to control the morphology of carbon black is industrially important. In this paper, the formation mechanism of carbon black is reviewed, followed by experimental investigations on morphology control of carbon black and other notable experimental investigations. Then, numerical models are presented to build a prediction model to achieve the morphology control of carbon black.

Core shell particles comprise a core content and a coating shell of another material. The core shell structure can realize a new functional material that cannot be realized by a particle which has only a single composition. Wet chemical synthesis is commonly used in the fabrication of core–shell particles, but recently, some reports on flame aerosol synthesis of core-shell particles have been published. Flame aerosol synthesis can offer continuous one-step production process including high-temperature treatment, and results in high-purity fine crystalline particles. Therefore, it is expected that flame aerosol synthesis method for core-shell particles will be further developed in the future. In this paper, we explain the details of flame aerosol synthesis method for core-shell particles and give an interpretation of the physical processes.

A burner with an oxidant nozzle with an inner diameter of 0.7 mm surrounded by six fuel nozzles with an outer diameter of 0.45 mm at an even distance established separated or merged microflames where flames were categorized into four types of flame structure. Solid particles doped into oxidant flow were treated by those flames and sampled for XRD and SEM analysis. Temperature distributions and histories of particles were measured to characterize the flames for flame aerosol synthesis. Torus-shape flame applied to flame aerosol synthesis is suitable for the oxidation reaction of particles and can oxidate TaN and heat up as high as to melt Ta₂O₅ particles to form a spherical shape. The merged microflames containing an inverted diffusion flame are suitable for the reduction reaction of particles. They can reduce TiO₂ and heat up to a temperature as high as to melt substoichiometric titanium oxide particles to form a spherical shape. All those features come from the unique flame structure that accomplishes high flame zone density and thus high heat release density.

The flame synthesis nanoparticle production has several advantages as the simple apparatus construction and eases to accomplish high temperature for nanoparticle generation. The authors studied TiO₂ nanoparticle production by using a flash boiling spray with flame synthesis. In this method, the precursor and low boiling point organic solvent mixed solution is used as the starting material to improve the evaporation characteristics of the precursor. The starting material is evaporated by using flash boiling spray to form a homogeneous vapor. Finally, nanoparticles are generated with the diffusion flame. The controlling factors of this method are start-material-solution, spray characteristics, and flame characteristics. In this paper, the relationship between the flame characteristics such as equivalence ratio, ambient pressure and particle trapping position, and particle characteristics are discussed.

We have developed a technology to spheroidize oxide particles using a high-temperature flame of oxygen combustion. We focused on the development of oxygen burners, which are important in the production of spherical particles. The functions required of the oxygen burner are that it has a wide high temperature region, the residence time of the particles in the flame is long, and the dispersibility of the particles in the flame is good. Taking these points into consideration, we developed two types of oxygen burners with different flame characteristics and evaluated their performance using aluminum oxide particles. In addition, we have established a technique for predicting the behavior of particles in an oxygen burner and a furnace using numerical analysis.

In-flame treatment technology uses the high temperature environment within a flame. The processing material is used fine powder, slurry or solution, and is supplied directly into the flame to be melted, spheroidized, or baked. In recent years, to create the desirable properties of functional material, the proportion of submicron-sized powder and nano-sized powder used which have size advantage over conventional large size powder is gradually increasing. In order to meet these fine powder needs, we have been researching and developing new dispersion technology and oxide synthesis technology in addition to the conventional multi-nozzle technology. Dispersion technology could produce submicron-sized powder by dispersing the agglomerated particles immediately just before supplied into the flame. Oxide synthesis technology uses the principle of the vapor phase method to produce nano-sized metal oxides from virous metal materials. Furthermore, we utilize the computational fluid dynamics technology to predict the furnace temperature distribution and fluid behavior in advance for making the optimum design conditions of each powder. On the other hand, as part of decarbonization, hydrogen fuel which does not generate carbon dioxide during combustion is received increasing attention. It's expected to play an important role in the construction of a decarbonized society in the future. Therefore, we have developed new hydrogen burner for application to in-flame treatment process. As the evaluation results, it's showed good flame combustion characteristics and powder properties.

To elucidate the detailed mechanism of multiphase combustion flames, experimental studies with optical measurements were conducted. In the experiment of spray flames, simultaneous time-series measurements of OH chemiluminescence, CH-band light emission, and Mie scattering from droplets by using a Multi-color Integrated Cassegrain Receiving Optics (MICRO), spray image illuminated by laser light sheet, the droplet diameter and velocity measured by using phase Doppler anemometer (PDA) are applied to a premixed spray flame of kerosene. In addition, in the experiment of pulverized coal combustion flame. A laboratory-scale pulverized coal combustion burner was specially fabricated for observing detailed flame structures. For measuring particle velocity and size simultaneously, PDA is widely used nowadays. However, the application is limited to spherical particles. Therefore, in this study, the velocity and shape of non-spherical coal particles were measured by shadow Doppler velocimetry (SDV) and the results on velocity was compared with those of laser Doppler velocimetry (LDV).

Laser Absorption Scattering (LAS) technique using ultraviolet and visible laser lights was proposed for the simultaneous measurement of the vapor and liquid phase concentration distributions in an axisymmetric engine spray. A pulsed Nd:YAG laser of the wavelengths 266nm and 532nm was used as a light source as well as α-methylnaphthalene (α-MN) as the LAS test fuel of a Diesel fuel surrogate. The LAS principle is the extinction of the light transmitted through the fuel spray due both to the fuel vapor (light absorption) and droplets cloud (light scattering). Since the 266nm light is absorbed by α-MN vapor though the 532nm light is out of the absorption wavelength band, the 266nm laser light extinction is due to the vapor absorption and droplet scattering, whereas the 532nm light extinction is due only to the droplet scattering. The subtraction of the extinction of 532nm light from that of the 266nm light gives the vapor extinction, then the vapor concentration can be determined. P-xylene or toluene was used as the LAS test fuel of a gasoline fuel surrogate. The LAS technique was extended to the measurement of the vapor mass distribution in a non-axisymmetric spray. For improving the similarity in the spray characteristics of the LAS test fuel to the Diesel fuel, the tracer LAS technique, that adopted the mixture of tiny amount α-MN doped in tri-decane as the LAS test fuel, was developed. The tracer LAS technique improved the measuring accuracy of the vapor and liquid phase concentration distributions as well as the spray characteristics similarity.