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General thermoacoustic theory

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Viewing 8 posts – 1 through 8 (of 8 total)
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  • 2026-05-09 at 14:12 #293
    Ralf
    Participant

    Thermoacoustic theorie is quite complex and complicated.

    I designed the engines only with a few basic parameters:

    But the very important gas displacement amplitude which determines the maximum practical length of the heat exchangers is not exactly straightforward.
    I really must get to grips with this as soon as possible, but at the moment I’m having far too much fun with practical experiments!

    Any help and suggestions on this topic are very welcome!

    2026-05-09 at 16:42 #305
    jan_l
    Participant

    test message

    2026-05-09 at 18:53 #308
    minthemerciless
    Participant

    How did you use these basic parameters and what values did you use for your calculations?

    2026-05-09 at 18:55 #309
    minthemerciless
    Participant

    Also, what made you increase the length of your cold heat exchangers?

    2026-05-09 at 19:57 #311
    Ralf
    Participant

    I calculated thermal penetration depth to 0.5 mm and assumed viscous pd to be similar.
    I only estimated gas displacement amplitude which is really not optimal as this is a very important factor because of heat exchanger length!

    The length of the engine is typically a fraction (0.5 or 0.25 or 0.125? …) of lambda which is still quite long and I have to experiment further with the feedback loop length/volume.

    I increased the length of the coolers because the first ones were only half as long as heater/regenerator just because the heat transfer of the coolers was better.

    As far as I know, DeltaEC does not take into account the amplifying resonance effects of the feedback loop and therefore cannot be used to optimize the FBL without additional RPN code.
    Carmen Iniesta has written a number of freely available papers on this subject, and I’m not sure whether the RPN modules are in in the DeltaEC code from the book!

     

     

    2026-05-09 at 21:21 #312
    minthemerciless
    Participant

    There is a calculation for feedback loop loss, but there doesn’t seem to be any RPN calculations that feed into others, I.e. accounting for resonance.

    I’ll have to look into the missing resonating behaviour. Seems odd that an acoustics solver doesn’t do resonance!

    2026-05-09 at 22:14 #319
    Ralf
    Participant

    You have to add this feature by yourself as DeltaEC is designed for many different acoustic machines i think.

    It is really worth  to look at the papers of Carmen Iniesta, I can look the titles up or send the pdfs to you if you want!

    2026-05-09 at 23:01 #320
    minthemerciless
    Participant

    pdfs or paper titles would be excellent! If you have pdfs to share, you can send them via Discord.

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