摘要：Floating solids drawdown speeds of up‐pumping pitched‐blade and hydrofoil impellers increase with increasing impeller submergence, with the pitched‐blade speed increasing more rapidly than that of the hydrofoil. For submergences greater than 40 % of the vessel diameter, performance of the pitched‐blade impeller is adversely affected by the discharge flow impinging on the vessel wall rather than the free liquid surface. Drawdown speeds of both impeller types decrease in a similar manner with increasing impeller diameter. For both impeller types, drawdown torque continually increases with increasing impeller diameter, while drawdown power exhibits a minimum at an intermediate impeller to tank diameter ratio; however, power is not a strong function of impeller diameter to tank diameter ratio over the range of this parameter typically used industrially (D/T ranging from 0.2 to 0.5 was studied in this work). Drawdown torque and power of the hydrofoil impeller are lower than those of the pitched‐blade impeller, with the differences between the impeller types increasing rapidly with submergence.
