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Kadowaki, Satoshi; Nogami, Masato*; Thwe Thwe, A.; Katsumi, Toshiyuki*; Yamazaki, Wataru*; Kobayashi, Hideaki*
Nihon Kikai Gakkai Rombunshu (Internet), 85(879), p.19-00274_1 - 19-00274_13, 2019/11
We dealt with three-dimensional cellular premixed flames generated by hydrodynamic and diffusive-thermal instabilities to elucidate the effects of unburned-gas temperature and heat loss by adopting the three-dimensional compressible Navier-Stokes equation. As the unburned-gas temperature became lower and the heat loss became larger, the growth rate decreased and the unstable range narrowed. With a decrease of unburned-gas temperature, the normalized growth rate increased and the normalized unstable range widened, which was because the temperature ratio of burned and unburned gases became larger. The obtained hexagonal cellular fronts were qualitatively consistent with the experimental results. As the heat loss became larger, the burning velocity of a cellular flame normalized by that of a planar flame increased. This was because diffusive-thermal effects became stronger owing to the increase of apparent Zeldovich number caused by the decrease of flame temperature.
-air premixed flame inside of a vessel; Numerical simulations by using XiFoamThwe Thwe, A.; Terada, Atsuhiko; Hino, Ryutaro; Kadowaki, Satoshi
no journal, ,
For the risk reduction on hydrogen combustion and explosion due to hydrogen generated by radiolysis of water inside of high-level radioactive waste vessels, understanding the phenomena and characteristics of hydrogen combustion is necessary, and CFD approaches are of important role. In this numerical simulation, XiFoam solver was modified by adding a new laminar flame speed model deduced from experiment by Katsumi et al. (Nagaoka University of Technology). It reproduced the propagation of H-air premixed flame and we clarified the effects of mesh size (2 mm to 0.625 mm) on wrinkle behavior. The results showed that the mesh size should be equal to or less than 1.0mm to observe the wrinkle behavior of flame in which the flame temperature and radius for each mesh size were almost same at 0.003s to 0.006s, and then the former increased and the later became large due to intrinsic instabilities. The wrinkle flame shape from the simulation was similar to that from the experiment when the mesh size became small.
