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Ansys 2D - Spring system

  1. Nov 18, 2015 #1
    Hi friends,

    I am working on a model of linear generator. I have modeled the linear generator in Ansys 2D. Now I want to attach a spring to one end of the rotor and see how it works with the spring attached to it. How do I model the spring?

    Also is there any proper way to determine the damping co-efficient of the system

    Any help or suggestions will be highly appreciated. Thanks
     
  2. jcsd
  3. Nov 18, 2015 #2

    Hesch

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    Gold Member

    First of all you have to determine what the input/output is to be in the model. Say that the input is some force, F, that affects the rotor, and that x is the position of the rotor, you will get a model like this:
    upload_2015-11-19_3-16-17.png
    m = mass of rotor
    a(s) = acceleration
    v(s) = velocity
    x(s) = position
    K = spring coefficient

    Using Masons rule, you will get a transfer function: x(s)/F(s) = 1 / ( m*s2 + K ) = ( 1/m) / ( s2 + K/m ).

    which can be rewritten

    x(s)/F(s) = ( 1/m ) / ( s2 + 2ζωns + ωn2 )

    Here the damping ratio, ζ = 0 , because the coefficient to s = 0. So in this model no damping takes places, but that's because there is no friction and no power loss due to the generator included in this model.
    So to calculate a realistic damping coefficient, ζ > 0, you must introduce friction/power loss in the model.
     
    Last edited: Nov 18, 2015
  4. Nov 19, 2015 #3
    Thank you very much for your answer. I know the stiffness of the spring to be attached to be 750pounds/inch. But i am not sure how I can introduce it into the ansys model.

    Thanks for your explanation on damping co-efficient. I know the efficiency of the generator. I will try to calculate the damping co-efficient of the system.
     
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