The flow rate of a centrifugal pump can be infinitely adjusted through various methods. Generally, the pump works most reasonably at the rated point, but sometimes due to certain reasons, the pump may operate at a low flow rate, which can cause the following negative effects.
(1) Efficiency decreases and power consumption increases. Centrifugal pumps are generally designed with the highest efficiency point near the rated operating point I. If a centrifugal pump operates at a low flow rate, its efficiency will decrease rapidly. Generally, the lower the flow rate of the same pump, the lower the efficiency. Therefore, operating at a low flow rate is not economical. In general, it is necessary to re equip a suitable high-efficiency small pump at this time.
(2) The increase in vibration noise causes environmental pollution, damages pump components, and affects the service life of the pump. At the design operating point, due to the alignment of the liquid flow direction with the blade direction, the shedding loss, impact loss, and vortex loss are relatively small and close to zero. However, when the pump operates in the low flow area, it deviates from the design point, causing further increase in flow loss, impact loss, and vortex loss of the pump's flow components. These losses are accompanied by a large amount of hydraulic noise and mechanical vibration.
(3) The internal reflux of the pump increases significantly, leading to an increase in cohesive heat and causing the liquid temperature inside the pump to rise, resulting in heating of the pump body and affecting the mechanical performance of pump components. At the same time, it also deteriorates the cavitation performance of the pump, further affecting the suction conditions of the pump.
(4) The radial force of the centrifugal pump increases, deteriorating the stress situation of the pump rotor. Due to the deviation of the pump from the design operating point in the low flow area, the liquid flow velocity in the vortex chamber decreases. However, according to the velocity triangle analysis, the liquid outflow velocity in the impeller increases instead, causing the liquid to not converge and form an impact, continuously increasing pressure and generating radial force.
