Numerical investigation of multi-dimensional characteristics in sodium combustion

Multi-dimensional sodium combustion behavior has been numerically investigated in the present paper. A new computer code AQUA-SF has been developed for this purpose. The code includes two sodium combustion models (so called 'spray combustion' and 'flame sheet combustion'), a mass and heat transfer model considering a six-flus gas radiation and a coagulation and sedimentation model of sodium oxide and hydroxide aerosols. The spray combustion rate is evaluated by a summation of individual sodium droplet's combustion rate with various diameters. The flame sheet combustion model is applied to situations where sodium is sprinkles out on the floor surface as a pool. The model assumes an infinitely thin flame above the pool surface and is based on a mass and energy balance at the flame. As the results of numerical analyses of a sodium spray combustion test and a large-scale sodium combustion test, good agreements have been obtained in terms of the temperature distribution and the concentration distribution of the chemical species. The numerical analyses also demonstrate that the distributions of temperature and chemical species concentration vary with sodium combustion situations. If sodium scatters and the spray combustion is dominant, the distributions vary in space. When large amount of sodium is piled up on a floor and the pool area is enlarged, the distribution is uniformized. (author)