Cold flow analysis on a AC generator

sainath.s@tdps.co.in · April 6, 2012, 05:49

I am trying to run a cold flow analysis on an A.C. Generator. The set up consists of both rotating and stationary bodies.

There is a rotor and a fan on the same axis and the direction of rotation is the same. Surrounding the rotor is a stator. All these components are placed inside a box open at the top. On the top of the box is another box to represent a cooler, but for this case there are no tubes and just a dummy box on top.

My aim is to determine the pressure drop inside the generator. The fan is a radial bi-directional fan rotating at a rpm of 1800. Both the rotor and fan are shaft mounted.

I have meshed the problem(5 million elements) and set up the problem. Only input from my side is the rpm and i have set a SST model for turbulence.

When i run it (in parallel), my solution diverges.

Is there any suggestions or steps that i need to take in order to help my solution converge.

kambireddy · April 6, 2012, 06:55

Check your mesh quality ?

sainath.s@tdps.co.in · April 6, 2012, 07:02

My mesh stats is as below.

+--------------------------------------------------------------------+
| Mesh Statistics |
+--------------------------------------------------------------------+
| Domain Name | Orthog. Angle | Exp. Factor | Aspect Ratio |
+----------------------+---------------+--------------+--------------+
| | Minimum [deg] | Maximum | Maximum |
+----------------------+---------------+--------------+--------------+
| Cooler | 81.6 OK | 1 OK | 1 OK |
| Fan | 21.1 ok | 7 ok | 14 OK |
| Frame | 15.2 ! | 36 ! | 26 OK |
| Rotor | 7.7 ! | 106 ! | 32 OK |
| Stator | 5.1 ! | 85 ! | 54 OK |
| Global | 5.1 ! | 106 ! | 54 OK |
+----------------------+---------------+--------------+--------------+
| | %! %ok %OK | %! %ok %OK | %! %ok %OK |
+----------------------+---------------+--------------+--------------+
| Cooler | 0 0 100 | 0 0 100 | 0 0 100 |
| Fan | 0 1 99 | 0 <1 100 | 0 0 100 |
| Frame | <1 1 99 | <1 <1 100 | 0 0 100 |
| Rotor | <1 3 97 | <1 1 99 | 0 0 100 |
| Stator | <1 5 95 | <1 1 99 | 0 0 100 |
| Global | <1 2 98 | <1 <1 100 | 0 0 100 |
+----------------------+---------------+--------------+--------------+

Is there something wrong?

Far · April 6, 2012, 07:06

Angles are not good.

kambireddy · April 6, 2012, 07:11

Mesh quality check
Orthog. Angle >20 deg
Max Exp Factor < 20

Please go through the documentation to know the importance of above parameters on solution

April 6, 2012, 05:49	Cold flow analysis on a AC generator	#1
sainath.s@tdps.co.in New Member Sainath Join Date: Mar 2012 Posts: 27 Rep Power: 15	I am trying to run a cold flow analysis on an A.C. Generator. The set up consists of both rotating and stationary bodies. There is a rotor and a fan on the same axis and the direction of rotation is the same. Surrounding the rotor is a stator. All these components are placed inside a box open at the top. On the top of the box is another box to represent a cooler, but for this case there are no tubes and just a dummy box on top. My aim is to determine the pressure drop inside the generator. The fan is a radial bi-directional fan rotating at a rpm of 1800. Both the rotor and fan are shaft mounted. I have meshed the problem(5 million elements) and set up the problem. Only input from my side is the rpm and i have set a SST model for turbulence. When i run it (in parallel), my solution diverges. Is there any suggestions or steps that i need to take in order to help my solution converge.

April 6, 2012, 07:02	Re:	#3
sainath.s@tdps.co.in New Member Sainath Join Date: Mar 2012 Posts: 27 Rep Power: 15	My mesh stats is as below. +--------------------------------------------------------------------+ \| Mesh Statistics \| +--------------------------------------------------------------------+ \| Domain Name \| Orthog. Angle \| Exp. Factor \| Aspect Ratio \| +----------------------+---------------+--------------+--------------+ \| \| Minimum [deg] \| Maximum \| Maximum \| +----------------------+---------------+--------------+--------------+ \| Cooler \| 81.6 OK \| 1 OK \| 1 OK \| \| Fan \| 21.1 ok \| 7 ok \| 14 OK \| \| Frame \| 15.2 ! \| 36 ! \| 26 OK \| \| Rotor \| 7.7 ! \| 106 ! \| 32 OK \| \| Stator \| 5.1 ! \| 85 ! \| 54 OK \| \| Global \| 5.1 ! \| 106 ! \| 54 OK \| +----------------------+---------------+--------------+--------------+ \| \| %! %ok %OK \| %! %ok %OK \| %! %ok %OK \| +----------------------+---------------+--------------+--------------+ \| Cooler \| 0 0 100 \| 0 0 100 \| 0 0 100 \| \| Fan \| 0 1 99 \| 0 <1 100 \| 0 0 100 \| \| Frame \| <1 1 99 \| <1 <1 100 \| 0 0 100 \| \| Rotor \| <1 3 97 \| <1 1 99 \| 0 0 100 \| \| Stator \| <1 5 95 \| <1 1 99 \| 0 0 100 \| \| Global \| <1 2 98 \| <1 <1 100 \| 0 0 100 \| +----------------------+---------------+--------------+--------------+ Is there something wrong?

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April 6, 2012, 06:55		#2
kambireddy New Member Redddy Join Date: Sep 2010 Posts: 25 Rep Power: 16	Check your mesh quality ?

April 6, 2012, 07:06		#4
Far Senior Member Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,560 Blog Entries: 6 Rep Power: 55	Angles are not good.

April 6, 2012, 07:11		#5
kambireddy New Member Redddy Join Date: Sep 2010 Posts: 25 Rep Power: 16	Mesh quality check Orthog. Angle >20 deg Max Exp Factor < 20 Please go through the documentation to know the importance of above parameters on solution