A MDOF (multi degrees of freedom) approximation has been set up for a pipeline network that connects a pump with two hydraulic cylinders. The network was excited by flow rate pulsations from the pump, and the MDOF model was used to simulate the resulting pressure pulsations in all system nodes. The eigenvalues and eigenvectors of the MDOF model revealed the natural frequencies and pressure mode shapes of the network. The high level of simulated pressure pulsations was explained by the fact that the network operated near a lightly damped resonance. Due to the existence of an equivalent mechanical MDOF model, heuristic methods from structural mechanics could be applied for effective system tuning. The relevant natural frequency was lowered by adding auxiliary pipelines at two pressure mode shape antinodes. Another simulation showed that the level of pressure pulsations was effectively reduced all over the network. Using the eigenvalue analysis, this could be done in a targeted way and a large number of trial simulations could be saved. A comparison of transcendental and approximated transfer functions showed good agreement in the frequency range of interest but disagreed in the lower frequency range. This was explained by the fact that for damped pipeline systems, the modal approximation of an individual pipeline becomes rather inaccurate in the frequency range below the first resonance. If such a frequency range is relevant, the MDOF model of the damped system will not be reliable and other methods have to be used for time-domain simulation. However, pressure mode shapes from a MDOF model of the undamped system can still be helpful for an interpretation of the dynamic system behaviour.


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    Title :

    A multi-degrees-of-freedom model for hydraulic pipeline systems


    Additional title:

    MDOF (multi degrees of freedom)


    Contributors:


    Publication date :

    2014


    Size :

    12 Seiten, Bilder, 7 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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