Effect of medium parameters on the performance of centrifugal pumps
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1. Relationship between flow rate and power: Power consumption increases as the flow rate rises; when the flow rate is 0, the power is at its lowest level. Therefore, centrifugal pumps are usually started in a closed system. Second, the density of the liquid: When the density of the liquid changes, among the performance parameters of the pump, the head, flow rate, and efficiency remain unchanged; only the shaft power of the pump varies with the density of the medium. Third, the viscosity of the liquid: When the viscosity of the medium transported by a centrifugal pump is higher than that of water, the performance parameters change as follows compared to transporting water: 1. The flow rate decreases. Due to the increased viscosity, the inhibitory effect of the tangential viscous force gradually spreads to the fluid flow between the blades, reducing the fluid velocity inside the impeller and thereby decreasing the pump’s flow rate. 2. The pump’s head is reduced. Due to the increased viscosity, more energy is required to overcome the viscous frictional forces, which in turn reduces the head generated by the pump. 3. The shaft power of the pump increases. In addition to the increased power loss caused by the friction between the impeller back cover and the liquid, there is also an increased hydraulic loss due to the friction between the liquid and the front cover, which leads to an increase in shaft power. 4. The efficiency of the pump decreases. As the viscosity of the liquid increases, leakage decreases; however, the increase in hydraulic losses and cover plate losses leads to a reduction in the pump’s efficiency and mechanical efficiency, resulting in a lower overall efficiency. 5. The allowable net positive suction head required for the pump increases. The dynamic pressure drop from the pump inlet to the impeller inlet increases as the fluid viscosity increases.
What happens if the density increases, causing the shaft power to rise and exceed the motor’s power capacity? Will the motor’s speed slow down, and will it burn out?
The motor speed remains unchanged; an increase in power leads to an increase in the motor current, causing the motor to stop due to overcurrent
What would happen if its density were greater than that of water, but its viscosity were lower than that of water? :o:o:o
Isn’t it written clearly above? Can’t you understand it?
I’m here to learn *! ! ! ! ! ! ! !
I’ve learned about it; I didn’t understand before the impact of high viscosity. I understand now. Thank you for sharing.
For positive displacement pumps, the volumetric flow rate is theoretically constant, while the outlet pressure (head) varies depending on the pressure in the system downstream of the pump; therefore, the outlet pressure (head) is independent of viscosity. As viscosity increases, efficiency decreases as well, and shaft power increases.