Fast Pipeline Models for Simulation of Hydraulic Systems

In most cases it is justified to regard pipelines as lumped capacitances when hydraulic systems are simulated. In some cases, however, when the system is widely distributed the wave propagation effects in lines may become important and there exists very good models today to simulate these effects. The price to be paid is that of a much larger computational effort. In this paper, a numerically highly efficient model is presented which is just slightly more demanding than a model to represent a pure capacitance, yet it captures all the essential characteristics of a line, the finite wave propagation speed and the distributed frequency dependent friction. The model only calculates state variables at the ends of a line and not in any internal nodes as most models do. Despite this, the model gives good results both in the time and frequency domain which compared to more elaborate models. If for some reason internal state variables are wanted they can be obtained by representing a line with several line elements. The model is integrated in the library of the HOPSAN simulation package and has been used successfully for simulation of oil hydraulic systems as well as the human cardiovascular system.