There are six main parameters that characterize pump performance: flow, head, power, efficiency, speed, and allowable vacuum height (or required NPSH). These parameters are related to each other. When one of the parameters changes, other working parameters will change accordingly, but the law of the change depends on the structure and characteristics of the pump impeller.
Blade pump performance is represented by its performance parameters. There are six main parameters that characterize pump performance: flow, head, power, efficiency, speed, and allowable vacuum height (or required NPSH). These parameters are related to each other. When one of the parameters changes, other working parameters will change accordingly, but the law of the change depends on the structure and characteristics of the pump impeller. In order to study the performance of the vane pump in depth, we must first grasp the physical meaning of the vane pump performance parameters.
a, head (head)
The lift, denoted by the symbol h, refers to the energy gain obtained by the transported unit weight liquid flowing through the water pump, that is, the total energy of the pump actually delivered to the unit weight liquid, the unit of which is m (n·m / n = m) . Therefore, by the definition of the pump head, the head can also be expressed as the unit energy difference of the pump inlet and outlet sections.
　　 b, flow (flowrate, capacity, discharge)
The flow rate of the water pump refers to the volume or mass of liquid flowing out of the pump outlet section per unit time, which is called volume capacity and mass capacity, respectively. The volume flow rate is indicated by the symbol q, and the mass flow rate is represented by qm. The unit of volume flow is commonly used in liters per second (l/s), cubic meters per second (m3/s) or cubic meters per hour (m3/h); mass flow is commonly used in kilograms per second (kg/s) or Tons per hour (t/h). By definition, volume flow has a relationship with mass flow as follows: qm = Ïq, where Ï is the density of the liquid being transported (kg/m3).
Due to the different flow requirements of various applications, the vane pump design flow range is very wide, less than 1 liter per second, and large tens or even hundreds of cubic meters per second.
In addition to the pump flow described above, the concept of pump theoretical flow qt and leakage flow q is also encountered in the study of impeller theory.
The so-called theoretical capacity refers to the flow through the pump impeller. Leakage capacity refers to the gap between the rotating part of the pump and the stationary part, such as the gap between the impeller inlet ring and the pump casing, and the pump shaft and packing in the stuffing box. The gap between the balance and the balance hole in the axial force balance device or the gap between the balance plate and the outer casing flows back to the impeller inlet and out of the pump. It can be seen that there is the following relationship between pump flow, theoretical flow and leakage flow: qt = q + q
　
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