Axial Fan Modal Analysis ANSYS

In summary, the conversation discusses using ANSYS modal analysis to find the bad frequencies and resonance of an axial fan in the lab. The speaker has a few questions, including the significance of the frequencies picked by ANSYS, the frequency and rotation relationship, and the meaning of a ruptured shape in higher modes. They also mention using a Static Structural module to add rotational velocity.
  • #1
dabest1
5
0
Hi,

We have an axial fan in the lab that apparently vibrates badly ("wobbles") at certain frequencies.

To find the resonance and the bad frequencies, I decided to do an ANSYS modal analysis.

I am still pretty new to it, and have a few questions.

1) Regardless of how many modes I pick, ANSYS picks certain frequencies. What is the significance of these frequencies?

2) I can't seem to input a rotational velocity into ANSYS. When I add a "Rotational Velocity" Modal, I try to input a 25 rad/s rotation but it does not go through...(I don't get the check mark to its left). So my question is, what is the frequency? Is that equivalent to rotation?

3) So I have just put a fixed point in the center of the fan, and run the analysis. I am getting different colors for the first 3 modes, but the shape seems intact. After mode 4, the entire shape gets ruptured...what does that mean? Let's say all the modes until 150hz had a smooth shape, and the next mode at 300hz is a ruptured shape. Does that mean that the "bad wobbly vibration" happens between 150hz and 300hz?

4) How do i find resonance frequency from these results?

Thanks!
 
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  • #2
So I just connected a Static Structural module and was able to add a rotational velocity using that...why couldn't I do it within modal?
 

1. What is Axial Fan Modal Analysis?

Axial Fan Modal Analysis is a type of analysis used in ANSYS, a computer-aided engineering software, to study the natural frequencies and mode shapes of an axial fan. This analysis helps in understanding the dynamic behavior of the fan and identifying potential issues such as resonance, vibration, and noise.

2. How is Axial Fan Modal Analysis performed in ANSYS?

Axial Fan Modal Analysis is performed by creating a finite element model of the fan in ANSYS and applying boundary conditions and loads. The software then uses the finite element method to calculate the natural frequencies and mode shapes of the fan. ANSYS also provides tools for visualizing and analyzing the results of the analysis.

3. Why is Axial Fan Modal Analysis important?

Axial Fan Modal Analysis is important because it helps in understanding the dynamic behavior of the fan, which is crucial for its optimal performance and reliability. It also helps in identifying potential issues that could lead to fan failure or inefficient operation, allowing for necessary design modifications to be made before production.

4. What are the benefits of using ANSYS for Axial Fan Modal Analysis?

ANSYS offers a powerful and accurate platform for performing Axial Fan Modal Analysis with its advanced finite element analysis capabilities. It also provides a user-friendly interface, extensive documentation, and a wide range of tools for post-processing and interpreting the results of the analysis.

5. Can Axial Fan Modal Analysis be used for all types of axial fans?

Yes, Axial Fan Modal Analysis can be used for all types of axial fans, including those with different blade geometries, materials, and operating conditions. However, it is important to have a thorough understanding of the fan design and operating conditions to ensure accurate results and proper interpretation of the analysis.

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