6. Efficiency Hydraulic pumps, hydraulic motors and hydraulic cylinders will have certain energy losses when transmitting energy. These losses also determine the efficiency and need to be taken into account in the calculation. The overall efficiency is largely determined by the structure of the equipment, manufacturing accuracy, degree of aging of the equipment and other operating parameters. These parameters need to be considered in the actual calculation of hydraulic equipment. Today, some different concepts of efficiency have been defined and used. The volumetric efficiency ηv is related to the internal and external leakage of the hydraulic pump and hydraulic motor; the hydraulic mechanical efficiency ηhm is related to the friction loss of the hydraulic pump and hydraulic motor; the total efficiency ηt=ηv*ηhm refers to the overall loss of the hydraulic pump and hydraulic motor during power transmission. The efficiency η is generally given in a graph, and there are several different graphical displays. Each graph represents the relationship between the operating parameters, as shown below:
η is related to the pressure p at a fixed speed n
η is related to the speed n at a fixed pressure p
For variable displacement pumps: η is related to the output flow at a fixed pressure p and a fixed speed n
η is related to the viscosity of the fluid at a fixed pressure p and a fixed speed n.
