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Study of Combustion Characteristics of Diesel Fuel/Water Emulsion Spray
( Tajul Azrizal ),( Takehiko Seo ),( Masato Mikami ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
Emulsion fuel is regarded as one of the possible alternative fuels for reducing the emissions of pollutants from combustion systems. In this study, we investigated the effect of droplet size on combustion and emission characteristics for both pure diesel and emulsion fuel. For experimental setup, a burner equipped with a twin fluid atomizer is used. A pilot burner is used to stabilize the flame with diesel fuel/water emulsion. Water percentage of 5 vol% in W/O emulsion fuel was used in this experiment. Smaller fuel droplet SMD that has larger surface to volume ratio will promote better combustion efficiency due to improvement of fuel-air mixture. However, this also will increase the combustion temperature, hence promoting the NO formation. Experiment result shows that smaller fuel droplet SMD had higher NO emission index for both pure diesel and emulsion fuel. However, emulsion fuel combustion shows improvement in NO specific emission. The vaporization of water in emulsion fuel reduced local flame temperature and thus reduced the NO formation. Emulsion fuel also had lower flame luminance as compared with diesel fuel alone. This is caused by lower soot emission of emulsion fuel. With almost same fuel droplet SMD for both sample fuels, we achieved significantly lower NO and soot emission for emulsion fuel.
( Takehiko Seo ),( Naoki Hiruta ),( Masato Mikami ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-
If jet engines of the airplane stop at high altitude, it is necessary to reignite and restart engines rapidly and surely in order to prevent the plane crash. The inside of combustion chamber will be low pressure and low temperature condition in this situation. It is difficult to reignite in this condition. The ignition performance is effected by the spray characteristics of fuel. To improve the reignition performance of jet engines and safety of airplanes, it is important to investigate the spray characteristics at low pressure. In this study, the spray characteristics at the subatmospheric pressure was investigated. The water atomization was conducted by pressure swirling atomizer that is installed in pressure chamber. The inside pressure of pressure chamber was set to 0.025 MPa simulated the pressure at high altitude condition (about 10000 m) by vacuum pump. The difference of injection pressure was 1.00 MPa. Additionally, swirler was installed around the pressure-swirl injector and provided swirling air flow on the spray by continuous running of vacuum pump. The spray characteristics were measured using PDPA. The results showed that the maximum Sauter mean diameter decreased and the droplet distribution changed from bimodal shape to monophasic shape. The reason was that swirling air flow made the entrainment weak and small droplets stayed at the main spray area.
The effect of ambient air flows on spray characteristics of a pressure atomizer
( Haruki Inoue ),( Yuichiro Otera ),( Takehiko Seo ),( Masato Mikami ),( Kimiyoshi Satoh ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
This research investigated the effect of the inner-swirl and outer-swirl flows arranged around a pressure atomizer on the spray characteristics. Water and air were used as a test liquid and an ambient gas, respectively. Spray shape was visualized by using laser tomographic method. Droplet-size and velocity were measured using a phase Doppler particle analyzer (PDPA). The air velocity was measured by PDPA using a tracer particle. The results showed that the spray shape was a hollow-cone. In the case with the inner-swirl flow, Sauter mean diameter and spray angle were small as compared with the case without inner-swirl flow. On the other hand, when the air was supplied as the outer-swirl flow, Sauter mean diameter was relatively large, while the spray angle was relatively constant and spray sheet became thinner. Recirculation zone was generated around the center of the hollow-cone spray. In the case with inner-swirl and outer-swirl flow, droplets size was relatively small. The supply of inner-swirl flow made the circulation region shift downstream.
Chick tooth induction revisited
Cai, Jinglei,Cho, Sung-Won,Ishiyama, Mikio,Mikami, Masato,Hosoya, Akihiro,Kozawa, Yukishige,Ohshima, Hayato,Jung, Han-Sung Wiley Subscription Services, Inc., A Wiley Company 2009 Journal of Experimental Zoology. Part B Vol.b312 No.5
<P>Teeth have been missing from Aves for almost 100 million years. However, it is believed that the avian oral epithelium retains the molecular signaling required to induce odontogenesis, and this has been widely examined using heterospecific recombinations with mouse dental mesenchyme. It has also been argued that teeth can form from the avian oral epithelium owing to contamination of the mouse mesenchyme with mouse dental epithelial cells. To investigate the possibility of tooth formation from chick oral epithelium and the characteristics of possible chick enamel, we applied LacZ transgenic mice during heterospecific recombination and examined the further tooth formation. Transmission electron microscopy was used to identify the two tissues during development after heterospecific recombination. No mixing was detected between chick oral epithelium and mouse dental mesenchyme after 2 days, and secretory ameloblasts with Tomes' processes were observed after 1 week. Teeth were formed after 3 weeks with a single cusp pattern, possibly determined by epithelial factors, which is similar to that of the avian tooth in the late Jurassic period. These recombinant teeth were smaller than mouse molars, whereas perfect structures of both ameloblasts and enamel showed histological characteristics similar to those of mice. Together these observations consistent with previous report that odontogenesis is initially directed by species-specific mesenchymal signals interplaying with common epithelial signals. J. Exp. Zool. (Mol. Dev. Evol.) 312B:465–472, 2009. © 2009 Wiley-Liss, Inc.</P>
( Yuichiro Otera ),( Haruki Inoue ),( Takehiko Seo ),( Masato Mikami ),( Shinji Watanabe ),( Masato Tamura ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
More viscous fuels such as residual oil tend to be burned in boilers. However, the use of high viscous fuels in conventional plants will degrade combustion characteristics, such as combustion efficiency and emission characteristics, which greatly depend on the fuel spray characteristics. The present study investigated the effects of the fluid viscosity and the atomizing air flow rate on the spray characteristics of a Y-jet atomizer. The test liquid and atomizing gas were aqueous glycerol solutions and air, respectively. Spray shape was visualized at different axial positions by using short-exposure backlight method. Droplet size and velocity were measured by a Phase Doppler Particle Analyzer (PDPA).The results show that the spray shape was similar to hollow-cone regardless of viscosity and air flow rate. Spatial distribution of total droplet volume measured by PDPA per minute had the maximum value at the opposite side of test liquid supply line. The largest Sauter mean droplet diameter (SMD) existed at the side of test liquid supply line. SMD increased with the test liquid viscosity. On the other hand, as the atomizing air flow rate was increased, SMD decreased.
Numerical Study on Flame-Spread Characteristics of Two-Dimensional Droplet Cloud
( Takehiko Seo ),( Daiki Azakami ),( Yuki Tsuchida ),( Masato Mikami ) 한국액체미립화학회 2010 한국액체미립화학회 학술강연회 논문집 Vol.2010 No.-
The mechanism of spray combustion is very complicated. The group-combustion flame forms around the fuel spray following the flame spreading. In order to improve understanding of the flame-spread mechanism, the flame spread along evenly spaced droplet arrays has been investigated experimentally, theoretically and numerically. The present study investigates the flame spread characteristics of randomly distributed two-dimensional droplet cloud using a modified percolation model based on the findings of micro gravity experiments on flame spread along droplet arrays. A modified percolation model considering the local flame-spread limit is presented to characterize the occurrence of group combustion. If the droplet number density is small enough, the flame spread terminates on its way to the sides of the lattice, leading to incomplete combustion of the droplet cloud. If the droplet number density is large enough, the flame can reach all the sides of the lattice, leading to the occurrence of group combustion of most parts of the droplet cloud. As the droplet number density is increased, probability of the group combustion occurrence rapidly increases around the threshold density. The threshold value is alternatively characterized by the critical mean droplet spacing in the droplet cloud. And, flame spread shows nonmonotonic behavior at the critical mean droplet spacing.