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Flame Propagation to Lean Region in Stratified Mixture Formed by Transient Gas Fuel Jet
Toshiaki KITAGAWA,Hiroyuki KIDO,Kyu Sung KIM,Hirotaka KOGA 한국자동차공학회 2001 한국자동차공학회 Symposium Vol.- No.-
Combustion characteristics of the stratified mixture were examined by the experiments using a constant volume bomb and the numerical simulations of counterflow premixed flame. We investigated the characteristics of the flame propagation to the lean region and examined the minimum equivalence ratio of the lean region that the flame generated in the rich region can propagate to, as the bulk quenching was found to occur in the over lean region.<br/> In the experiments, the stratified mixture was formed in the constant volume bomb by the injection of gaseous propane into the lean propane-air mixture charge, whose equivalence ratio was less than the lower flammability limit of the premixed mixture. The flame generated in the fuel jet region propagated wide into the lean mixture charge region as the stoichiometry of the mixture charge was increased, even though the charge was too lean to ignite. This result shows the flame in the rich region propagates into the lean region by the "back-support" of the rich flame.<br/> Numerical study of counterflow premixed flame was examined next in order to investigate the interaction between the rich flame and the lean region. Rich and lean mixtures were opposed and the stoichiometry of the lean mixture was varied widely. Reaction rate of the propane in the lean mixture was large when the equivalence ratio of the lean mixture was 0.40 or more.<br/>
안성율,Hiroaki Watanabe,Toshiaki Kitagawa 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4
A numerical simulation was performed with the two competing model in the devolatilization process for a pulverized coal combustion jet flame by means of LES. The target was a simple jet burner flame in CRIEPI. To solve the LES equations, a CFD code FFR. Comb was employed with the dynamic Smagorinsky SGS turbulent model. A simple global kinetic mechanism was implemented to predict combustion of the gas and solid phase combustion. The interactions between the two phases were calculated by PSI-Cell model while the reaction rate in turbulent flow was established by SSFRRM. The simulation was validated by comparing results to the experimental data in terms of particle dispersion and velocity as well as gaseous velocity. The flame structure was discussed with temperature, mole fraction of major species. In addition, the effect of the devolatilization model was investigated simultaneously by comparing to another simulation that employed the single first order reaction model because the devolatilization was one of the major processes in coal combustion and it had an influence on the flame structure from all reactive regions. The release rate was calculated by two different parameter sets in the Arrhenius rate equation for the two competing model that were corresponding different temperature regions whereas the released rate was determined by only one fixed parameter set in the single first order reaction model. From the simulation, it was revealed that the main reactions took place at the upstream and the first fuel oxidation was stronger at the inner reaction zone comparing to the far side combustion. It was confirmed as well that the two competing model could capture the quick devolatilization faster than the single first order reaction model though the dominant part appeared later than the single first order reaction model.
Seongyool Ahn,Panlong Yu,Hiroaki Watanabe,Ryoichi Kurose,Kenji Tanno,Toshiaki Kitagawa 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.5
A three-dimensional numerical simulation was performed to investigate the physics and combustion characteristics of a two-phase reacting turbulent flow in a pilot-scale pulverized coal combustion furnace. This included an elementary reaction mechanism using an extended flamelet/progress variable (EFPV) method. The simulation was validated via comparison with an experiment in terms of the gaseous temperature and distribution of the gas mole fraction. The EFPV method predicted the flame structure and combustion characteristics of the pulverized coal. In the main reaction zone where the released gas combustion was dominant, two separate combustion regions were observed, and they were attributed to hydrocarbons and CO combustion. Gas flow characteristics such as mixing of low temperature gas and hot burnt gas were well described in the inner recirculation zone. The CO 2 conversion reaction to CO occurred slowly and decreased the gaseous temperature beyond the main reaction zone in the low and zero oxygen environments. The simulation predicted the unburned CO combustion correctly beyond the flame when staged air was injected; however, the combustion rate was overestimated due to the fundamental assumption of the EFPV method, attributable to the limitations of the steady state flamelet approach.
Genetic association of swine leukocyte antigen class II haplotypes and body weight in Microminipigs
Tatsuya Matsubara,Masaki Takasu,Noriaki Imaeda,Naohito Nishii,Satoshi Takashima,Takashi Nishimura,Toshiaki Nishimura,Takashi Shiina,Asako Ando,Hitoshi Kitagawa 아세아·태평양축산학회 2018 Animal Bioscience Vol.31 No.2
Objective: Microminipigs are a novel animal model with extensive applications in laboratory studies owing, in part, to their extremely small body sizes. In this study, the relationship between swine leukocyte antigen (SLA) class II haplotype and body weight was evaluated in the Microminipig population. Methods: A total of 1,900 haplotypes, covering SLA class II haplotypes Lr-0.7, Lr-0.23, Lr-0.17, Lr-0.37, Lr-0.16, Lr-0.11, Lr-0.13, and Lr-0.18, were analyzed in 950 piglets. Birth weights and weights on postnatal day 50 were examined in piglets with eight different SLA class II haplotypes. Results: The mean birth weight of piglets with the Lr-0.23 haplotype (0.415 kg, n = 702) was significantly lower than that of piglets with Lr-0.17 (0.445 kg, n = 328) and Lr-0.37 (0.438 kg, n = 383) haplotypes. At postnatal day 50, the mean body weight of piglets with the Lr-0.23 haplotype (3.14 kg) was significantly lower than that of piglets with the Lr-0.13 haplotype (3.46 kg, p<0.01). There were no significant differences in daily gains (DGs) among the eight haplotypes. However, piglets with the Lr-0.11 and -0.18 haplotype combination or any heterozygous haplotype combinations containing Lr-0.23 had significantly lower DGs than those of piglets with the Lr-0.18, 0.37 haplotype combination. Conclusion: Piglets with the Lr-0.23 haplotype had relatively low body weights at birth and on postnatal day 50 and slightly lower DGs than those of piglets with other haplotypes. Therefore, the Lr-0.23 SLA class II haplotype may be a suitable marker for the selective breeding of Microminipigs with small body sizes.