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Katsumi, Toshiyuki; Yoshida, Yasuhito*; Nakagawa, Ryo*; Yazawa, Shinya*; Kumada, Masashi*; Sato, Daisuke*; Thwe Thwe, A.; Chaumeix, N.*; Kadowaki, Satoshi
Journal of Thermal Science and Technology (Internet), 16(2), p.21-00044_1 - 21-00044_13, 2021/00
Times Cited Count：5 Percentile：36.79(Thermodynamics)The effects of addition of CO
and water vapor on characteristics of dynamic behavior of hydrogen/air premixed flames were elucidated experimentally. By Schlieren photography, wrinkles on the flame surface were clearly observed in low equivalence ratios. The propagation velocity increased monotonically as the flame radius became larger and flame acceleration was found. Increasing the addition of inert gas, the propagation velocity decreased, especially in the case of CO addition. Moreover, the Markstein length and the wrinkling factor decreased. This indicated that the addition of Co or HO promoted the unstable motion of hydrogen flames, which could be due to the enhancement of the diffusive-thermal effect. Based on the characteristics of dynamic behavior of hydrogen flames, the parameters used in the mathematical model on propagation velocity including flame acceleration was obtained, and then the flame propagation velocity under various conditions was predicted.
Thwe Thwe, A.; Kadowaki, Satoshi; Hino, Ryutaro
Journal of Thermal Science and Technology (Internet), 13(2), p.18-00457_1 - 18-00457_12, 2018/12
Times Cited Count：0 Percentile：0.01(Thermodynamics)Two dimensional unsteady calculations of reactive flows were performed in large domain to investigate the unstable behaviors of cellular premixed flames at low Lewis numbers based on the diffusive-thermal (D-T) model and compressible Navier-Stokes (N-S) equations. The growth rates obtained by the compressible N-S equations were large and the unstable ranges were wide compared with those obtained by the D-T model equations. When the length of computational domain increased, the number of small cells separated from large cells of the cellular flame increased drastically. The stronger unstable behaviors and the larger average burning velocities were observed especially in the numerical results based on the compressible N-S equations. In addition, the fractal dimension obtained by the compressible N-S equations was larger than that by the D-T model equations. Moreover, we confirmed that the radiative heat loss promoted the instability of premixed flames at low Lewis numbers.
Ono, Ayako; Suzuki, Takayuki*; Yoshida, Hiroyuki
Proceedings of 26th International Conference on Nuclear Engineering (ICONE-26) (Internet), 6 Pages, 2018/07
The mechanism of critical heat flux (CHF) for higher system pressure remains to be clarified, even though it is important to evaluate the CHF for the light water reactor (LWR) which is operated under the high pressure condition. In this study, the process of bubble coalescence was simulated by using a computational multi-fluid dynamics (CMFD) simulation code TPFIT under various system pressure in order to investigate the behavior of bubbles as a basic study. The growth of bubbles was simulated by blowing of vapor from a tiny orifice simulating bubble bottom. One or four orifices were located on the bottom surface in this simulation study. The numerical simulations were conducted by varying the pressure and temperature.
Nakahira, Masataka; Takeda, Nobukazu; Urata, Kazuhiro*
JAERI-Tech 2004-069, 55 Pages, 2004/12
JAERI-Tech-2004-069.pdf:11.46MB
This report summarizes the study on dynamic behavior of ITER tokamak scaled model according to the parametric analysis of base plate thickness, in order to find a solution to give the sufficient rigidity without affecting the dynamic behavior. For this, modal analyses were performed changing the base plate thickness from the present design of 55mm to 100, 150 and 190 mm. It was found that the thickness of 150mm gives well fitting of 1st natural frequency about 90% of ideal rigid case. Thus, the modification study was performed to find out the adequate plate thickness. Considering the material availability, transportation and weldability, it was found that the 300mm thickness would be a limitation. The analysis result of 300mm thickness case showed 97% fitting of 1st natural frequency to the ideal rigid case. It was however found that the bolt length was too long and it gave additional twisting mode. As a result, it was concluded that the base plate thickness of 150mm or 190mm gives sufficient rigidity for the dynamic behavior of the scaled model.
Onozuka, Masanori*; Takeda, Nobukazu; Nakahira, Masataka; Shimizu, Katsusuke*; Nakamura, Tomomichi*
Fusion Engineering and Design, 69(1-4), p.757 - 762, 2003/09
Times Cited Count：2 Percentile：19(Nuclear Science & Technology)The dynamic behavior of the ITER tokamak assembly has been investigated. Three experimental models have been considered to validate the numerical analysis methods for the dynamic events, mainly seismic events. A 1/8-scaled tokamak model, which is based on the 1998 ITER design, is under construction. Non-linear vibration characteristics, such as damping, can only be identified by a full-scale model. Therefore, a full-scale gravity support structure for the coil system has been designed and will be tested. In addition, for the sub-scaled tokamak model, the VV is assumed to be a rigid structure. This assumption is to be verified using a 1/20-scaled model. The above experimental models and their testing conditions have analytically and numerically evaluated. For example, both the static and dynamic spring constants obtained by static analysis and eigen-value analysis, respectively, were evaluated to be in good agreement.
Kunugi, Tomoaki
Nihon Kikai Gakkai Rombunshu, B, 63(609), p.88 - 96, 1997/05
no abstracts in English
Kunugi, Tomoaki; *; *
Proc. of 2nd Japan-Central Europe Joint Workshop on Modelling of Materials and Combustion, 0, p.205 - 208, 1996/00
no abstracts in English
31,1991,Tokai,JAERI; Research Committee on Reactor Physics
JAERI-M 92-054, 181 Pages, 1992/03
no abstracts in English
Azumi, Masafumi; Hasegawa, Mitsuru*; *; Kurihara, Kenichi; Nakamura, Yukiharu; Nishio, Satoshi; Shimomura, Yasuo; Shinya, K.*; Sugihara, Masayoshi; *; et al.
JAERI-M 92-041, 100 Pages, 1992/03
no abstracts in English
Tanzawa, Sadamitsu; ;
JAERI-M 91-215, 40 Pages, 1992/01
no abstracts in English
; Sudo, Yukio; ; Osakabe, Masahiro; ;
JAERI-M 82-075, 36 Pages, 1982/07
no abstracts in English
