Abstract
Besides operating a centrifugal pump under normal conditions there are additional operating conditions possible; for example, a pump operated as turbine. Another example would be a pump trip where there are several abnormal operating conditions possible when the direction of flow and/or the direction of rotation are changing. The machine behavior in every possible operation condition can be represented by the complete pump characteristics, often called the 4-quadrant (4Q) behavior of a centrifugal pump. To gather the 4Q behavior, a test rig allowing the flow direction as well as the rotation direction to be reverted is necessary, with time-consuming measurements at variable positive and negative discharge in both directions of rotation the complete pump characteristics are evaluated. In the present study, an approach to investigate the complete pump characteristics by means of computational fluid dynamics (CFD) calculations is presented. With steady-state calculations and additional transient CFD investigations in the normal operating conditions, the whole pump characteristics were calculated accurately. Two different types of mixed flow diffuser pumps were investigated—one equipped with adjustable impeller blades, the second one with comparable low specific speed. Experimental verifications have shown a remarkably good agreement. Furthermore, an exemplary numerical waterhammer analysis shows the successful application of the presented approach.
Highlights
The hydraulic behavior of centrifugal pumps under normal operating conditions is well known.In normal operating mode, the pumped fluid passes the pump from the suction side to the pressure side while the pump rotates in pump direction
This paper presents an additional contribution in obtaining a reliable prediction of the complete pump characteristics by means of computational fluid dynamics (CFD) calculation
The general CFD settings are summarized from the stator outlet) an average static pressure was applied as boundary condition
Summary
The pumped fluid passes the pump from the suction side to the pressure side while the pump rotates in pump direction. This behavior is of interest when operating a pump in any system, whether in a closed or an open loop. Almost every pump manufacturer offers head and efficiency curves for their pumps to calculate a stationary duty point as the intersection of the pump head curve and the system resistance curve Another item of important information is the power consumption related to this operation point. The prediction of the hydraulic performance by means of computational fluid dynamics (CFD) has been shown in recent years to be very reliable
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