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-   -   rotary atomizer (http://www.cfd-online.com/Forums/cfx/89172-rotary-atomizer.html)

eng_norouzi June 7, 2011 03:47

rotary atomizer
 
hi all
i want to model a spray dryer and my atomizer is a weel atomizer(disk atomizer)but cfx does not have it.cfx have just cone and sphere in atomizer type what should i do? plz help me i have a rotary atomizer with 16 injection points and 20000rpm velocity and cfx have preesure nozzle not rotary atomizer plz help me i am very confued.
thanks

ghorrocks June 7, 2011 18:56

The atomisers just produce droplets of a certain size and velocity distributions. If the built in models are not suitable then define a new size and velocity distribution to match your atomiser.

eng_norouzi June 11, 2011 03:05

hi ghorrocks thank you but my atomizer rotates with 20000 rpm and i think this velocity induce swril in air flow inlet and cause air flow pattern in the dryer changes it has 16 injection vanes and i simulate with 16 pressure nozzle but the air flow pattern is not correct could you please give me some suggestions that what is wrong
thank you

ghorrocks June 11, 2011 07:43

If you do not know what the injection shape and velocities are you are not going to get very far in your simulation, are you? If you guess the boundary conditions then the simulation output is just random numbers with pretty pictures.

eng_norouzi June 14, 2011 05:19

my result in some places is far from the correct answer.i want to simulate the effect of rotating of atomizer and this is my question can you give me some suggestions?

ghorrocks June 14, 2011 08:09

So what is your question? Are you trying to model the breakup of the atomiser (good luck), or is the spray from the atomiser in a larger simulation incorrect? Please post an image.

eng_norouzi June 21, 2011 05:58

i want to plot air velocity and tempreture in the dryer.if you give me your email i can send you the image of dryer and its atomizer.

ghorrocks June 21, 2011 20:09

In that case you have to characterise the atomiser. Either measure it yourself or get the manufacturer's specifications for the spray. Then you can apply this spray to your model.

sope111 August 14, 2012 05:48

Quote:

Originally Posted by ghorrocks (Post 311582)
If you do not know what the injection shape and velocities are you are not going to get very far in your simulation, are you? If you guess the boundary conditions then the simulation output is just random numbers with pretty pictures.

Hi,
i don't understand your idea.
Do you mean that if i care about the movement of droplets(assuming i konw the size and velocity distributions), should i must know what the injection shape is? I think the shape is calculated by cfx.

Now i'm also do a rotating disk simulation, but i don't konw the way to simulate
i'm trying to model the breakup of the atomiser ,but as i know it seems very different
Another question , as the oil is spary by the rim of the rotating speed , do
i must set the rim as 16(or more)pressure nozzles? If it correct ,the rim is a circle , but i don't know the way to set line as nozzle.

Thanks

sope111 August 14, 2012 05:52

Quote:

Originally Posted by eng_norouzi (Post 310799)
hi all
i want to model a spray dryer and my atomizer is a weel atomizer(disk atomizer)but cfx does not have it.cfx have just cone and sphere in atomizer type what should i do? plz help me i have a rotary atomizer with 16 injection points and 20000rpm velocity and cfx have preesure nozzle not rotary atomizer plz help me i am very confued.
thanks

Hi,

May i know the way to slove your problem?
I'm simulate a rotating disk spary ,but there are few tutorials .I have no idea to simulate.
Could you give me a hand?
My Email:wanran125@163.com
Thanks

ghorrocks August 14, 2012 07:46

The definition of a boundary condition is a location where you know enough about the condition of the flow that you can define it. So for a spray atomisation simulation you have to know the particle velocity and size distribution at the boundary or you cannot define a boundary.

sope111 August 14, 2012 09:49

Quote:

Originally Posted by ghorrocks (Post 377014)
The definition of a boundary condition is a location where you know enough about the condition of the flow that you can define it. So for a spray atomisation simulation you have to know the particle velocity and size distribution at the boundary or you cannot define a boundary.

You mean the simulation domain is the external of the nozzle , and particle velocity and size distribution are the results of internal of the nozzle?
And i must get the flow pattern( particle velocity and size distribution)by experimental or cfd before simulate the movements of paritcles?

ghorrocks August 14, 2012 19:14

My point was that you have to know the conditions at a boundary condition. If you do not know the conditions you cannot apply a sensible bonudary there.

Getting spray velocity and particle size distribution by CFD is diabolically difficult. So if this spray is to be part of a larger model then use experimental results to define your spray boundary.


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