The axial thrust of the pump is generated when the pump rotating. For the cause of the axial thrust, many scholars have studied it in the past to improve the safety and reliable operation of the pump. Research shows that the reasons of the axial thrust of the pump are the following aspects:
1. The imbalanced liquid pressure of pump impeller at the front and back. When the pump is working and the impeller drives the liquid to rotate. In the process, liquid has passing through the front and the back of the rotating impeller, the liquid area of the suction inlet is not equal to the back of the impeller. The impeller suction inlet is low pressure and the back is high pressure. Due to the difference in air pressure between the front and back of the impeller, a pressure difference is formed between the front wheel cover and the rear wheel of the impeller, and the liquid pressure acting on the front cover and the rear cover can not be balanced out which caused an axial thrust.
2. The axial component of the fluid momentum changes. The liquid flows in from the impeller inlet and flows out from the impeller outlet, and the momentum component in the axial direction of the liquid changes. The reason is that the liquid acting on the front and back of the impeller not only changes its velocity, but also changes the direction of the velocity. According to the momentum theorem analysis, in the process of the liquid passing through the impeller, due to the change of the liquid momentum in the axial component, an impulse is generated in the axial direction, also called the reaction force.
3. Different pump bodies have different reasons of axial thrust. The weight of the internal rotor of the vertical pump will be part of the axial thrust during the operation, the gravity of the rotor inside the horizontal pump will not generate axial thrust to the pump.
Years of practice have shown that the balance of the axial thrust of the pump has become the key to its universal application. Regardless of the structural design of the pump or in practice, it is necessary to balance the axial thrust as much as possible to guarantee the reliable operation of the pump. The device for balancing the axial thrust of the water pump is designed according to the axial thrust itself. Most of the axial thrust can be balanced out by the balancing device, and a small part of the axial thrust is received by the mechanical device such as the thrust bearing inside the water pump. The effect of such axial thrust is eliminated and there is no threat to the safe operation of the pump.
