Pressure transients, commonly referred to pressure surges frequently occur in hydraulic systems. The pressure peak may become substantially higher than steady-state value, generate noise and/or cause damage to system components. And it sometimes exceeds the allowable stress of system components. If it exceeds the allowable stress level, the safety problem must be taken into account. Therefore identification of physical situation that can cause pressure surges, and method of limiting surges are essential consideration in successful system design.
In this thesis, the finite difference equation by method of characteristics are derived from the governing equations of unsteady flow in a pipe, and solved by using boundary conditions derived. Boundary conditions are derived at the ends of hydraulic elements in a pipe line such as servovalve, relief valve, hydraulic motor, cylinder, hydraulic accumulator etc. A computer program which can simulate general hydraulic systems is developed by using finite difference equations and boundary conditions derived. The simulated results by the developed computer program are in fair agreement with the experimental results.
The effect of such parameters as load inertia, pipe length, pipe material, valve closing time on the pressure transients is also studied. It is found that the peak pressure is drastically reduced by connecting a long flexible hose at downstream of actuator and by attaching a bypass valve across inlet and outlet of actuator.
