Combustion Problem

September 2, 2003, 16:45

I am completing an internship in the United States and I have been asked to simulate a simple combustion chamber in Fluent 6.1. However I am unsure if I am using the correct setup because the results seem to be inaccurate as when I run it in unsteady after 10 seconds the whole domain seems to be overheated too quickly. My chamber is 300mm by 70mm and the domain is 2000mm by 1000mm. I have the outer boundary of the domain set to an outflow.

The setup is basically a 2D rectangle, with fuel as n-heptane injected from the middle of the chamber as droplets. I setup n-heptane in PrePDF for the species I had read in a tutorial so I am pretty sure they are correct. For the injections I have choosen to have group injections so I can have a spray angle and I have the stochastic model turned on.

For the species in Fluent I choose non-premixed because I wish to inject air also. However I cannot find air in the list of inert injections so any suggestions on that would be helpful as I am currently injecting oxygen and nitrogen separately.

I am using the k-epsilon turbulence model with DPM turned on and also droplet collision and droplet breakup turned on.

I have everything set to 300K and I patch a surface in the combustion chamber for ignition. Which works perfectly well.

Can anyone give me any suggestions to how I could improve this or any settings I have missed out? I know you cannot give me individual values to use because that is dependent on the case itself and I will just have to figure those out alone such as injection speed, diameter, mass flow rate etc etc. I am just wanting to know if this setup is accurate or if I am missing things.

Also I orginally wished to use JP-4 aviation fuel but I could not figure out how I could specify this in PrePDF (I understand I could change the thermo.db in prePDF but I do not know what values to use or what other species are produced) and also how would I choose it as an injection in Fluent, I guess it is the same problem as choosing air as the injection.

Thank you

Andrew

September 3, 2003, 05:22

Have you acitvated the rdiation model? What is your wall boundary conditions?

September 2, 2003, 16:45	Combustion Problem	#1
Andrew Guest Posts: n/a	I am completing an internship in the United States and I have been asked to simulate a simple combustion chamber in Fluent 6.1. However I am unsure if I am using the correct setup because the results seem to be inaccurate as when I run it in unsteady after 10 seconds the whole domain seems to be overheated too quickly. My chamber is 300mm by 70mm and the domain is 2000mm by 1000mm. I have the outer boundary of the domain set to an outflow. The setup is basically a 2D rectangle, with fuel as n-heptane injected from the middle of the chamber as droplets. I setup n-heptane in PrePDF for the species I had read in a tutorial so I am pretty sure they are correct. For the injections I have choosen to have group injections so I can have a spray angle and I have the stochastic model turned on. For the species in Fluent I choose non-premixed because I wish to inject air also. However I cannot find air in the list of inert injections so any suggestions on that would be helpful as I am currently injecting oxygen and nitrogen separately. I am using the k-epsilon turbulence model with DPM turned on and also droplet collision and droplet breakup turned on. I have everything set to 300K and I patch a surface in the combustion chamber for ignition. Which works perfectly well. Can anyone give me any suggestions to how I could improve this or any settings I have missed out? I know you cannot give me individual values to use because that is dependent on the case itself and I will just have to figure those out alone such as injection speed, diameter, mass flow rate etc etc. I am just wanting to know if this setup is accurate or if I am missing things. Also I orginally wished to use JP-4 aviation fuel but I could not figure out how I could specify this in PrePDF (I understand I could change the thermo.db in prePDF but I do not know what values to use or what other species are produced) and also how would I choose it as an injection in Fluent, I guess it is the same problem as choosing air as the injection. Thank you Andrew

September 3, 2003, 05:22	Re: Combustion Problem	#2
kim Guest Posts: n/a	Have you acitvated the rdiation model? What is your wall boundary conditions?

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