| Abstract: | The coast-down behavior is specially designed to satisfy the certain flow requirements in a special kind of canned motor pump when it is used in primary reactor coolant system. However, coast-down models once used are not suitable for designing ultra-large canned motor pumps with flywheels, in which case rotor's fluid resistance of canned motor is modeled by an empirical constant. When the size of canned motor increases, the error of empirical relationship becomes remarkable. In thrall to material's density and strength, flow resistance of coast-down behavior should be dynamically modeled accurately to reduce the demands of materials. In this paper, an improved analytical model is proposed to study barbell-like canned motor's coast-down characteristic based on basic torque behavior researches in Taylor-Couette flow and hydraulic coupler, where bearing's resistance is ignored. This model takes geometric and kinematic parameters into consideration. In addition, the influence of pressure and temperature is coupled into this coast-down model by using Reolands' viscosity relationship.Based on this model, coast-down behavior is studied and parameters sensitivity analysis is conducted from design view point. Parameters sensitivity analysis indicates that the density and distribution of materials have more remarkable influence on coast-down behavior compared with working condition and geometric parameters. |
