Displacement and flow: Displacement refers to the volume of the discharged (or input) liquid obtained by the change of the geometric size of the sealed cavity per revolution of the pump (or motor). The common unit is ml/r (ml/revolution). The displacement can be changed into a variable pump (or variable motor) by adjusting,hydraulic pump and the displacement cannot be changed into a fixed pump (or fixed motor).
The actual flow rate refers to the flow rate at the outlet (or inlet) when the pump (or motor) is working. Due to the internal leakage of the pump itself, its actual flow is less than the theoretical flow. Because the motor itself also has internal leakage,hydraulic pump to achieve the specified speed, in order to compensate for the leakage,hydraulic pump the actual input flow must be greater than the theoretical flow.
Volumetric efficiency, for hydraulic pumps,hydraulic pump refers to the ratio of actual flow to theoretical flow. For hydraulic motors,hydraulic pump it refers to the ratio of the theoretical flow to the actual flow. Mechanical efficiency, for hydraulic pumps,hydraulic pump refers to the ratio of its theoretical torque to the actual input torque. The actual output torque of a hydraulic motor is the torque after the theoretical torque overcomes the friction force, so its mechanical efficiency is the ratio of the actual output torque to the theoretical torque.
The total efficiency refers to the ratio of the output power of the pump (or motor) to the input power. The total efficiency is equal to the product of volumetric efficiency and mechanical efficiency.