There are two kinds of losses when the hydraulic pump works, one is volume loss, and the other is mechanical loss.


1.The main cause of volume loss

①. Although the suction and discharge chambers of the positive displacement hydraulic pump are separated in the pump, there is always a certain gap between the relative movement, so the oil in the high-pressure area of ​​the pump must leak to the low-pressure area through the gap. . The lower the viscosity of the hydraulic oil and the higher the pressure, the greater the leakage.

②. During the oil suction process of the hydraulic pump, the suction of the pump will be caused due to too much oil suction resistance, too viscous oil or too high pump shaft speed, so that the sealed working volume cannot be filled with oil. The working space is not fully utilized.

Due to the above reasons, the hydraulic pump has a volume loss. However, as long as the pump is designed correctly and used reasonably, the loss caused by the second reason can be overcome, that is, the volume loss of the pump can be reduced. However, the volume loss caused by the leakage of the hydraulic pump during operation is unavoidable, that is, the volume loss of the pump can be approximated as all caused by the leakage, so that the actual flow of the hydraulic pump is always smaller than the theoretical flow. The ratio of the actual flow rate to the reduced flow rate is called volumetric efficiency, which represents the degree of volume loss of the hydraulic pump. The volumetric efficiency of the hydraulic pump indicates the degree of volume loss of the hydraulic pump.


2. Main reasons for mechanical loss

①. When the hydraulic pump is working, there is mechanical friction between the relative moving parts, such as between the bearing and the shaft, between the shaft and the seal, between the blade and the inner wall of the pump body, resulting in loss of friction resistance. This loss is related to the output pressure of the hydraulic pump. The higher the output pressure, the greater the frictional resistance loss.

②. When the oil flows in the pump, viscous resistance due to the viscosity of the liquid will also cause mechanical loss. This loss is related to the viscosity of the oil and the speed of the pump. The more viscous the oil and the higher the speed of the pump, the greater the mechanical loss.

Due to the above reasons, the actual input power of the pump is greater than the theoretically required power. The ratio of the theoretical input power to the actual input power of a hydraulic pump is called mechanical efficiency, and it indicates the degree of power loss. The ratio of the output power of the hydraulic pump to the input power is called the total efficiency of the hydraulic pump.

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