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Yunnai May 9, 2022 23:38

Problems of calculating Torque
 
Hello,
I encountered some problems when using reports to calculate torque in starccm+.
The transient numerical simulation is about scroll compressor,which is a kind of positive displacement compressor.
Now I want to get the torque to calculate the power, but I got some negative value at some rotation angle,I think itís wrong because the torque should always be positive.
I'm confused about that. Can anyone help me?
Here are some figures. The red part is the object for calculating the moment,and it rotates around the center point([2.3,0,0]).
If anyone have problems about working process of the scroll compressor, I'm glad to explain it to you. Thank you very much!

https://www.helloimg.com/images/2022/05/10/RNlazu.png
https://www.helloimg.com/images/2022/05/10/RNlXtE.png
https://www.helloimg.com/images/2022/05/10/RNlevY.png

cwl May 10, 2022 02:16

Quote:

but I got some negative value at some rotation angle
Torque report is negative at some rotation angle - or is alway constant?

Quote:

I think it’s wrong because the torque should always be positive.
Torque (Moment Report) is a dot-product, i.e. sign depends on the axis orientation.

Yunnai May 10, 2022 10:20

Quote:

Originally Posted by cwl (Post 827710)
Torque report is negative at some rotation angle - or is alway constant?


Torque (Moment Report) is a dot-product, i.e. sign depends on the axis orientation.

Thank you for your reply.

Sorry,I don't understand what you mean. The torque I got is as follows:
https://www.helloimg.com/images/2022/05/10/RNNSGo.png (Not linked)

The torque is sometimes negative value,that's what I said at some rotation angle. But in my opinion,to calculate the power of the machine (torque multiplied by angular velocity),the torque should be positive.
The axis orientation is fixed as the correct direction of rotation.

By the way,If you have done similar numerical simulation, could you please tell me how to calculate the power consumed in starccm+?

Sorry for my English,I hope it won't make you confused.


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