In the present study, we sysnthesize two types of MR fluids with different particle shapes and sizes. The magnetic functions are evaluated circulatingly by the analysis of cluster formation, rheological properties in the applied magnetic field and damping characteristics in the MR damper, comparing with those of commercial MR fluids. Final objective is to provide the fundamental data for the development of newly advanced MR fluids. The main topics consist of geographycal cluster formation depending on particle shapes and sizes, relating to the apparent viscosity and yield stress with magnetic flux density and further equivalent damping coefficient of two newly sysnthesised MR fluids comparing with those of LORD MR fluid.

A transient response of SF 6 thermofluid field inside the exhaust tube in a Gas Circuit Breaker under high temperature, high pressure and high velocity conditions is analyzed by taking compressible effect and some realistic processes into account related to the available experimental data of GCB test facility. Furthermore, computational simulation is conducted to clarify the effective cooling process of SF 6 hot gas flow inside the exhaust tube for transient time to avoid the SF 6 hot gas breakdown near exhaust tube exit after the arc current interruption. It is found that the SF 6 hot gas flow can be effectively cooled down for the rough inside wall of exhaust tube due to the separation of SF 6 hot gas flow from the inside wall and also active mixing with upstream cold gas. The effect of roughness pattern on the real time thermofluid field of SF 6 hot gas flow and possible breakdown region are also clarified. Finally, the computed temperature in GCB shows the good agreement with the available experimental data for smooth surface of exhaust tube.

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