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-   -   Reversed Flow Outlet- Transient- Turbine (https://www.cfd-online.com/Forums/fluent/114422-reversed-flow-outlet-transient-turbine.html)

Gowrav March 11, 2013 02:35

Reversed Flow Outlet- Transient- Turbine
 
Hi,
I am doing transient analysis of Microturbine to evaluate fluid flow. 1.5 million elements. Using Sliding Mesh technique. Pr.Ratio- 4 atm. Rotating Speed 75krpm. I am able to get Convergence after 500 timestep of 2.2e^-6 s each. But am getting reversed flow at pressure outlet. As one of the suggestion mentioned in forum i have extended outlet volume length. Now my L/d ratio is 2. But problem nt resolved. Looking for help.

Thanks in Advance
Gowrav

blackmask March 11, 2013 04:17

Turn on Radial Equilibrium Pressure Distribution to see if it helps. It is not uncommon that reversed flow appear in the outlet after a strong vortex core formed. You can check the velocity contour of the outlet to see whether the reversed flow can be neglected. Sometimes they are of relatively small magnitude. Note that the only aim of extension of the computational domain is to facilitate the pressure outlet b.c. which resembles to sponge or buffer region in acoustics calculations. You can put a large-tank-like geometry after the outlet of your real geometry and specify pressure p.c. at the outlet of tank.

ali_mehrabi69 March 11, 2013 10:32

hey
 
hey Gawrev


Im working on a micro turbine with 100krpm too.I am trying to model it, as steady state
problem in different angles. but im not sure about it,
how did you design the mechanical parts?like turbine shape,blades and...
from which software did you use?

thank u

Gowrav March 12, 2013 02:41

Reply to Ali
 
Quote:

Originally Posted by ali_mehrabi69 (Post 413130)
hey Gawrev


Im working on a micro turbine with 100krpm too.I am trying to model it, as steady state
problem in different angles. but im not sure about it,
how did you design the mechanical parts?like turbine shape,blades and...
from which software did you use?

thank u

Hi, Ali
I am doing analysis part of MGT.. Design Even i am not sure, how it modeled.. It is a 8 blades -Twisted blade- axial turbine.. I have got ref. mat. for design of radial turbine for 40k,, its there in Google.. , i am also trying to find out its velocity triangles... Software as per my knowledge if you have dim. BladeGen will do.. If you can share some more info forum may give you right tip.
Bye

Gowrav March 12, 2013 02:43

Quote:

Originally Posted by blackmask (Post 413041)
Turn on Radial Equilibrium Pressure Distribution to see if it helps. It is not uncommon that reversed flow appear in the outlet after a strong vortex core formed. You can check the velocity contour of the outlet to see whether the reversed flow can be neglected. Sometimes they are of relatively small magnitude. Note that the only aim of extension of the computational domain is to facilitate the pressure outlet b.c. which resembles to sponge or buffer region in acoustics calculations. You can put a large-tank-like geometry after the outlet of your real geometry and specify pressure p.c. at the outlet of tank.

Hi Blackmask,
I am working on your suggestion..
Am also trying to increase the number of timesteps..
Thanks
Gowrav

ali_mehrabi69 March 15, 2013 13:33

hey
 
Quote:

Originally Posted by Gowrav (Post 413306)
Hi, Ali
I am doing analysis part of MGT.. Design Even i am not sure, how it modeled.. It is a 8 blades -Twisted blade- axial turbine.. I have got ref. mat. for design of radial turbine for 40k,, its there in Google.. , i am also trying to find out its velocity triangles... Software as per my knowledge if you have dim. BladeGen will do.. If you can share some more info forum may give you right tip.
Bye

im working on a radial turbine,a simple radial turbine,like a pelton turbine, with nozzles, and use air,for fluid.
i have problem with CFD analysis,
im working with fluent,

did u do CDF analysis?

tanx

Gowrav March 15, 2013 14:52

Reply to Ali
 
Hi ali,,
Yours your s quite interesting. If you can tell whats the difficulty, then i can give my opinion.. I am using Fluent-14, for analysis. Its Transient,, and using sliding Mesh..


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