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Modelling the regenerator of a Stirling engine

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Loris Chavée
Loris Chavée on 10 Sep 2020
Hello everyone,
I'm currently working on the gamma stirling engine Simscape model pre-built by Matlab and I'm trying to modify the regenerator to get better performance.
Let's say I want to try to add a mesh of a certain material on the surface of the regenerator, what's the best way to do that ? Should I directly modify the source code of the "Pipe (G)" block (which is called "Regenerator pipe" on the image displayed below) or is it more efficient to directly model the regenerator using Simulink (not Simscape), then connect it to the Simscape model using a "Simulink to PS converter" ? Thank you for your answers.

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Answers (1)

Angel Gonzalez Llacer
Angel Gonzalez Llacer on 18 Sep 2020
Hi Loris! Thanks for your question
Could you please explain the purpose of the mesh you want to add? Is it placed in the outer surface or the inner surface?
I guess it's in the outer surface and the goal is to act like fins, increasing the heat exchanged (with the ambient I guess?)
In that case, you could achieve it in different ways: you could build a more detailed thermal network for the regenerator, add a Convective Heat Transfer block between the mass and the ambient (represented by an ambient temperature source) like in the picture below:
Or you could customize the Pipe (G) block to create your own pipe with a detailed modeling of heat exchange with a mesh.
In any case, I definitely NOT recommend to use a Simulink subsystem to represent a physical device in your Simscape system, because it can lead to performance issues as they are being solved simultaneously but using different solvers that might compete between each other for precision and resources. Simulink should be use for the control algorithms of your systems, after having interfaced with sensors and actuators.
Hope it helps!
Angel

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Loris Chavée
Loris Chavée on 18 Sep 2020
Hi Angel, thank you for your answer. It helped me. Indeed, the goal of the mesh is to act like fins.
But let's say I really want to control the model as much as possible, would it be interesting to recreate this model on Simulink instead of Simscape ? Or is it just more complicated and not so helpful ?
Thanks for your help !
Loris
Angel Gonzalez Llacer
Angel Gonzalez Llacer on 24 Sep 2020
Hi Loris,
You could potentially build a model based on differential equations expressed in Simulink blocks and transfer functions, but it probably would be difficult to understand, and always have same input and same output. In Simscape you can quickly change inputs and outputs (i.e. input can be angular speed and output could be the torque, or vice versa)
All the components in this block have the source code available. If you open one of the blocks (for instance the Passage Pipe) you will see a hyperlink "See source code" so you can see the variables, equations, and parameters used in this component. And you have total control of this equations via modification of the source code.
I hope it helps!
Regards,
Angel

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