Abstract
Balancing holes in single-suction centrifugal pumps are generally applied to attenuate the axial thrust caused by a pressure difference between the front side of a shroud and the rear side of a hub of an impeller. The magnetic drive pump, the subject of this study, has a leak-free airtight structure and an integrated structure of the impeller and inner magnet. To prevent the performance degradation of the magnetic drive caused by heat during operation, complex cooling flow paths connected to balancing holes have been designed so that a sufficient amount of coolant would flow around the magnetic drive. Due to this spatial characteristic, when balancing holes are applied to a magnetic drive pump, the balancing hole flow path becomes very long compared to that of balancing holes applied to conventional pumps. When the balancing hole flow path is long, the flow path loss increases, which in turn increases the adverse effect of balancing holes on the pump performance. Therefore, the design of highly efficient balancing holes to which a sufficient amount of coolant can be supplied is critical in a magnetic drive pump. To this end, two types of balancing holes were investigated in this study. First, balancing holes are drilled in the impeller that rotates during operation. Second, balancing holes are drilled in the inner shaft installed to maintain the centre of rotation of the impeller during pump operation. The results confirmed the flow characteristics of the two types of balancing holes and verified the effect of each balancing hole on the pump performance. Finally, this study found that drilling balancing holes in the shaft were appropriate for the magnetic drive pump, and this type can maintain relatively high efficiency and supply a sufficient amount of coolant to maintain the efficiency of the magnetic drive.
Highlights
The advancement of industries has led to the development of the uses of pumps
The results showed that the wear ring and balancing holes influenced the axial thrust, but the back gap of the impeller did not have a significant influence on the axial thrust
The impeller was set at a rotating domain of 3450 rpm, volute conditions, the inlet was set as the condition of inhaling water at a constant temperature of and front flow path, rear flow path, and balancing hole flow path were set as fixed domains.25The and atmospheric pressure, whereastothe was set asbetween the condition of discharging waterarea
Summary
The advancement of industries has led to the development of the uses of pumps. the working fluids of pumps used in petrochemical, semiconductor, food, and wastewater treatment industries are highly corrosive or toxic and can cause dangerous situations if leaked during operation due to incomplete sealing. The present study conducted computational fluid dynamics (CFD) analysis on two different types of balancing holes that can be commercialized to investigate the phenomena of the flow of working fluid in flow paths inside a pump, including the cooling flow path in the design of balancing holes These factors need to be considered in the development process of a magnetic drive pump. In this process, the effects of different structures and diameters of balancing holes on the flow rate through the complex cooling flow path and on the pump performance and axial thrust were examined through a CFD analysis using the commercial program Ansys CFX.
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