Sadao Uchikawa

Quench simulation analysis of a superconducting coil

Abstract A quench simulation program has been developed with the intention of identifying a quench position in a superconducting coil and it has been applied to behaviour analysis of an artificially quenched superconducting coil. The superconducting coil is a solenoidal, bobbinless, and densely wound impregnated coil with many voltage terminals, thermocouples and heaters. The propagation of a normal zone was made two-dimensional by a one-turn-heater or three-dimensional by a point-heater set in the coil. The time-spatial changes in terminal voltages and temperatures agree well with those obtained from the simulation analysis within an accuracy of ± 10 ms or ± 1 mm. If accurate thermal properties of the materials constituting the superconducting coil are obtained, identification of the quench position in the coil should be possible. Normal front velocities and effective thermal conductivities of the radial, azimuthal and axial directions are also analysed from experimental results.

Generation of boundary-fitted curvilinear coordinate systems for a two-dimensional axisymmetric flow problem

One of the most efficient methods for dealing with fluid mechanical problems having irregularly shaped boundaries is to use a curvilinear coordinate system in which coordinate lines are coincident with all boundaries. Thompson et al. proposed a method for automatic numerical generation of such coordinate systems [I], where the coordinates are taken to be the solution of an elliptic equation in the physical plane. In the case of the physical x-y plane, a Laplace equation has been successfully taken as the equation for coordinate transformation, primarily because it exhibits a maximum principle which guarantees that the maximum values of the curvilinear coordinates occur on the boundary of the physical region, and secondly because the equation for the stream function has the same form as a Laplace equation in the physical x-y plane. However, this situation does not hold in the case of cylindrical geometry. The objective of this note is to apply three possible transformations to the solution of two-dimensional axisymmetric flow problems and to clarify the differences among them.

Boiling transition predictions for BWR fuel bundles by the subchannel analysis program MENUETT

Abstract A comparative study with simulated 3 × 3 rod bundle experiments verified the ability of a two-fluid subchannel analysis program, MENUETT, to predict (i) distributions of mass flow rate and equilibrium quality, and (ii) boiling transition when the modified Biasis correlation for critical quality was used. The models for void drift and turbulent mixing effectively calculated the two distributions, and a factor accounting for the difference between the heated and wetted perimeters near the bundle wall in the modified Biasis correlation improved the boiling transition predictions.