To increase the operating speed of machines which use hydraulics, it is necessary to increase the flow rate of hydraulic systems. As flow rate becomes larger, it becomes increasingly important at the design stage to take into account fluid transients in the fluid lines. In particular, column separation in the low-pressure return line generates a high surge pressure causing an undesirable noise and possible damage to components.
A number of studies have already been made of this phenomena. In the actual development of hydraulic systems however, there are problems in which the check valves are installed in the return line, or one of a variety of valve stroke patterns is used. These problems have not been sufficiently dealt with in the previous studies.
To analyze fluid transient phenomena in the fluid lines, a simulation program which combines the method of characteristics with numerical integration was developed. The results of the calculations with the program were verified by a comparison with the experimental results. Using this simulation program, the effect of various parameters on the surge pressure in the low-pressure return line investigated. These parameters include line dimensions, void ratio, check valve position, pressure loss, and timing of the valve control. Furthermore, to reduce the surge pressure, the use of two check valves mounted in a circuit was proposed. The effect of this proposed idea was verified with the numerical method and by experiments.
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