How to model marine exhaust system using Simscape.
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I want to create a simulation for marine exhaust systems for large vessels but I'm not sure how to set everything up.
I have values for temperature (from turbo), ambient temp (engine compartment), k values, h values, various exhaust pipe diameters, lengths, and thermal properties (stainless steel, aluminum, etc.).
Sections of the exhaust use a multilayer multi product insulation. I know the diameters at each layer, h and k values of the different layers, and thermal resistances of the layers.
Eventually, I want to include where the exhaust gas mixes with sea water in a mixing chamber.
My end goal is to create a model that can find the surface temperature, the internal temperature, and the internal pressure at any location of the exhaust system.
Can someone help with creating a basic model to start with?
2 Commenti
Yifeng Tang
il 30 Set 2024
Do you have a diagram of some kind to explain what you are trying to model?
The air flow part, i.e. pressure, temperature, flow rate, heat transfer, etc., can be handled reasonably well at the system level using Simscape and Simscape Fluids. The mixing with sea water, however, can be exponentially more difficult, depending on what kind of physical effects you are trying to include.
Anyway, more clarification will help.
Risposte (1)
Yifeng Tang
il 4 Ott 2024
Hi @Jonathan
Thanks for sharing the picture. That helps.
Whether MathWorks tools, in particular Simscape, can help model this depends on what you want to use the model for. Simscape and Simscape Fluids are designed to do 1D system-level modeling, often as the plant model of a feedback control system. For example, if you want to analyse how certain valve control strategy will impact the overall system performance, yes, you may build a model in Simscape and it'll be useful.
If you are trying to analyze the flow field inside the pipe, or maybe vary the connector design and see the impact on the pressure drop, Simscape isn't the right tool and you need a CFD package instead. You requirement on "want to know at any location ..." seems to suggest this level of detailed modeling. If true, I'm afraid the physical modeling tools from MathWorks aren't the right choice.
8 Commenti
Yifeng Tang
il 22 Ott 2024 alle 18:56
Lots of these information will be useful when modeling the pipe.
The Pipe (G) block models the gas inside, the flow resistance, and the heat transfer between the gas and the INNER WALL of the pipe. The pipe material and the insulation is not part of this block but can be added easily. Below is an example.
The diameter, thickness, and thermal conductivity of the metal and insulation will go into the conductive heat transfer blocks. The density, specific heat, and total mass of the pipe material will go into the thermal mass. The outside temperature can be prescribed using a temperature source.
I took a look at your model. Some comments:
(1) thermal reference represents 0 K. I don't think that's what you intended. Use a temperature source instead.
(2) You need to set the unit for each of the PS-Simulink converters. Leaving them as inherit will get you SI unit (Pa, K, etc.). Looks like that's NOT what you wanted.
(3) when measuring a temperatue and using units like degC or degF, make sure you check the apply affine conversion. See this doc page for more information.
(4) you probably need to use the measured pressure and temperature to compare to your reference data to understand whether you need to tune parameters like "aggregate equivalent length for local resistance" and "hydraulic diameter" to get the right amount of pressure drop and/or heat transfer.
Good luck and happy modeling.
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