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Simscape: Fan (MA) behavior with higher external flow

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Hello I'm trying to model in simscape a radiator of a car that is blown at by ram air and in addition has a fan. Using the Fan (MA) from the fluids addon the behavior is as expexted when the car is not moving, then the fan does what it should. However, if the car is driving fast and the ram air flow exceeds the fan air flow, I'm not sure if the fan behaves properly. It actually reduces the air flow. Normally the fan would have to freewheel in these cases, is that possible somehow with simscape components? Is it somehow possible to see the code behind the Fan (MA) block?
Fabian on 29 Jan 2024
Edited: Fabian on 29 Jan 2024
Sorry my mistake. Somehow I was only focused in adding simscape to the tags and not mentioning it. Edited my text now. Thanks for the hint.
Yifeng Tang
Yifeng Tang on 30 Jan 2024
I was lucky enough to see the original text of the question. @Fabian and @John D'Errico, thanks for the good laugh.
I'll try to help in the Answer section.

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Answers (1)

Yifeng Tang
Yifeng Tang on 30 Jan 2024
Hi Fabian,
In the radiator, the vehicle speed is converted to a ram pressure using a simple equation, and the air is also being driven, when necessary, by a fan downstream behind the condenser. I think the general modeling idea should apply in your case.
You may of course try to improve further by
  1. use a better correlation for the ram pressure calculation. Maybe a lookup table based on reference data?
  2. parametrize the fan block to define its behavior when the pressure difference is reversed over the fan. You may right-click on the block and select Fluids > Plot Fan Characteristics to see the fan curves.
  3. set up a test harness to examine how the air flow behaves in scenarios you described. Adjust parameters in test harness as well.
If you have any data that describe how the fan speed, air flow, pressure, and car speed should behave, feel free to share and I can take a look and provide more specific suggestions.
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Fabian on 31 Jan 2024
Hi Yifeng
Thanks for your response. I took that example as a reference and used the ram air block. It think it is a good representation. I also checked my fan characteristics and did a lot of tests before I wrote my question.
However, I'm doubting a bit the behavior of the fan when the airflow over it is being created by ram air.
Having this sentence "Fan behavior in the opposite shaft rotation is not defined and may not be accurate. " doesnt make me trust it more somehow.
No I don't have any data unfortunately.

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