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What are the main energy losses of centrifugal pumps?

Time of Release:

2023-11-03

In the process of converting mechanical energy into liquid energy, centrifugal pumps are accompanied by various losses, which are represented by corresponding efficiency. The internal losses of centrifugal pumps can be divided into three types: mechanical losses, volumetric losses, and hydraulic losses. The corresponding pump efficiency can also be divided into mechanical efficiency, volumetric efficiency, and hydraulic efficiency.

What are the main energy losses of centrifugal pumps?

         

  In the process of converting mechanical energy into liquid energy, centrifugal pumps are accompanied by various losses, which are represented by corresponding efficiency. The internal losses of centrifugal pumps can be divided into three types: mechanical losses, volumetric losses, and hydraulic losses. The corresponding pump efficiency can also be divided into mechanical efficiency, volumetric efficiency, and hydraulic efficiency.

  1: Mechanical loss and mechanical efficiency.

  The power P (shaft power) transmitted by the active engine to the pump shaft first needs to be consumed to overcome the bearings and sealing devices, and the remaining shaft force is used to drive the impeller to rotate. But the mechanical energy generated by the rotation of the impeller is not fully transmitted. A portion of the liquid flowing through the impeller needs to overcome the liquid friction between the front and rear cover surfaces of the impeller and the casing (pump chamber). This part of the loss is called disc friction loss. The bearing loss, sealing loss, and disc friction loss mentioned above. The sum of forces is called mechanical loss, denoted by P. The remaining power required to remove the mechanical loss of axial force in the representation method is used for the axis. Using the liquid of the impeller to do work is called input hydraulic power, using P. Representation.

  2: Capacity loss and capacity efficiency.

  Using water input power to do work on the liquid inside the impeller, so that the pressure of the liquid at the outlet of the impeller is higher than the pressure. The pressure difference between the inlet and outlet causes a portion of the liquid flowing through the impeller to enter the impeller seal ring gap from the pump chamber. By facing the flow at the inlet, the flow rate Q through the impeller, which is the theoretical flow rate of the pump, will not be completely transported to the outlet of the pump. The leaked liquid will consume the energy obtained from the impeller during the leakage flow process, which is under high pressure. The essence of volume loss is energy loss, volume loss. The magnitude of the loss is calculated by the volumetric efficiency v. The volumetric efficiency is achieved by removing the leaked liquid (actual flow rate) through the impeller. The estimation of volumetric efficiency based on the power and liquid flow rate (theoretical flow rate Q) of the impeller is quite complex and has many influencing factors. It is necessary to consider the size of the sealing ring gap, the number of pumps, mechanical performance, etc. Sealing series, etc. In addition, the leakage amount of the balance axial force device and sealing components of the pump should also be calculated in the volume loss of the pump.

  3: Hydraulic loss and hydraulic efficiency.

  The energy (H) obtained through the liquid (excluding leakage) from the impeller cannot be fully transmitted, because the liquid flow in the flow section of the pump is accompanied by hydraulic friction loss (resistance along the way) and hydraulic loss (local resistance), such as impact, flow separation, changes in velocity direction and magnitude, and therefore requires a portion of energy consumption. Due to the presence of hydraulic losses, the energy lost by the liquid per unit mass in the flow section of the pump is called the hydraulic loss of the pump. The energy (H) increased per unit mass of liquid lost through the pump is smaller than the energy (H) transmitted per unit mass of liquid through the impeller. The water loss of the pump is measured by the pump water efficiency m. Hydraulic efficiency is the power required to remove hydraulic fluid loss. The ratio of liquid power without hydraulic loss.
 



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