single heavy oil droplet

anon_f · July 19, 2013, 11:25

Hello everyone
I work on the combustion of a drop of heavy oil falling (single heavy oïl droplet). I use JetA Lequid on CFX, but I would define a drop of about 3mm diameter entering periodically in a combustion chamber with a given frequency (several times per minute).
How to define the injection mode I want to have in CFX-Pre?
Thank you for anyone who could help me.

ghorrocks · July 19, 2013, 18:20

You need to make a few decisions before your question can be answered.

How are you going to model this? There are several approaches and they are all very different:
1) Directly model the droplet with a free surface model. This can model the exact physics of the drop at a microscopic level, but means you will not be able to model much more than a single drop.
2) Model a cloud of drops with a eularian model. This is probably not a good approach if the aim is to track and burn droplets.
3) Model the droplets with a lagrangian particle tracking model. Then the droplet and its state is represented by a few key parameters (temperature, composition, size, density etc). You then need a model of the droplet drag, combustion and anything else you plan on modelling.

anon_f · July 19, 2013, 22:15

Hello and thank you for your reply.
For the evaporation model that seems appropriate is the easiest. What interests me is what is combustion with Eddy Dissipation model. My combustion chamber is a rectangle of 5 m depth where I inject several times a minute (about 50 times / min) a drop of oil of about 3mm, and there is an air inlet at about 900 ° C .
Theoretically, during the fall, the drop will evaporate and oil vapor mixed with air at a rate of 0.232 Oxygen burns and releases heat flux. The exact physics of gout does not seem necessary to me.
On pre-Cfx, using the library oil_combustion.ccl I can not set the injection conditions I want.
If you have any idea thank you for giving me advice.
sincerely

ghorrocks · July 20, 2013, 06:11

You have not answered the question - but I take it from your answer you think the lagrangian particle tracking approach is best.

Your initial post suggests you do not know how to start the droplets - have a look at the tutorials to explain this.

Your second post suggests you cannot set the injection conditions you want but you have not explained what injection conditions you are trying to achieve.

July 19, 2013, 11:25	single heavy oil droplet	#1
anon_f Disabled Join Date: Feb 2013 Posts: 16 Rep Power: 13	Hello everyone I work on the combustion of a drop of heavy oil falling (single heavy oïl droplet). I use JetA Lequid on CFX, but I would define a drop of about 3mm diameter entering periodically in a combustion chamber with a given frequency (several times per minute). How to define the injection mode I want to have in CFX-Pre? Thank you for anyone who could help me.

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July 19, 2013, 18:20		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,692 Rep Power: 143	You need to make a few decisions before your question can be answered. How are you going to model this? There are several approaches and they are all very different: 1) Directly model the droplet with a free surface model. This can model the exact physics of the drop at a microscopic level, but means you will not be able to model much more than a single drop. 2) Model a cloud of drops with a eularian model. This is probably not a good approach if the aim is to track and burn droplets. 3) Model the droplets with a lagrangian particle tracking model. Then the droplet and its state is represented by a few key parameters (temperature, composition, size, density etc). You then need a model of the droplet drag, combustion and anything else you plan on modelling.

July 19, 2013, 22:15		#3
anon_f Disabled Join Date: Feb 2013 Posts: 16 Rep Power: 13	Hello and thank you for your reply. For the evaporation model that seems appropriate is the easiest. What interests me is what is combustion with Eddy Dissipation model. My combustion chamber is a rectangle of 5 m depth where I inject several times a minute (about 50 times / min) a drop of oil of about 3mm, and there is an air inlet at about 900 ° C . Theoretically, during the fall, the drop will evaporate and oil vapor mixed with air at a rate of 0.232 Oxygen burns and releases heat flux. The exact physics of gout does not seem necessary to me. On pre-Cfx, using the library oil_combustion.ccl I can not set the injection conditions I want. If you have any idea thank you for giving me advice. sincerely

July 20, 2013, 06:11		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,692 Rep Power: 143	You have not answered the question - but I take it from your answer you think the lagrangian particle tracking approach is best. Your initial post suggests you do not know how to start the droplets - have a look at the tutorials to explain this. Your second post suggests you cannot set the injection conditions you want but you have not explained what injection conditions you are trying to achieve.