EFFECTS OF VISCOSITY ON TRANSIENT BEHAVIOR OF A LOW SPECIFIC SPEED CENTRIFUGAL PUMP IN STARTING AND STOPPING PERIODS

摘要

Low specific speed centrifugal pumps have been extensively applied in petroleum, petro-chemical, and other industrial sectors to transport liquids in a variety of viscosity. Their transient performance during starting and stopping processes can be important for their operational reliability; however, this performance has not been tackled under pumping highly viscous oils conditions so far. In the article, the transient turbulent flows in a low specific speed centrifugal pump are simulated with CTD code in starting and stopping periods for three liquids. The effects of viscosity on instant performance parameters, head-flow rate curves, instant internal flow variables, and flow structures in the impeller and volute are demonstrated. The parameter synchronization characteristic, hysteresis phenomenon in head-flow rate curves, and pump affinity law modification are addressed. It is turn out that a highly viscous liquid can respond to the pump speed change more quick than water, but is subject to a more significant overshoot in the shaft-power curve; thus, a liquid with higher viscosity than water potentially can reduce the operational reliability of a low specific speed centrifugal pump during the starting period.