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Mehdi April 18, 2006 06:48

need help on premixed combustion
 
Hello,

I have simulated a premixed combustiom with EBU model. The Air to Fuel ratio is about 29 and according to expreimental data the bulk temperature in the combustion zone should be about 1800 K, but in my model I have reached to 1350 K. The other results for mass fractions show the inlet oxygen mass fraction is lower than my setting and aslo I have some fuel at the outlet. So there is incomplete combustion and it seems becasue of low oxygen, but my setting for inlet oxygen mass fraction is correct. Please help me if you know about this problem. I will be very tankful in advance for your help.

Best Regards, Mehdi

A Student April 18, 2006 07:32

Re: need help on premixed combustion
 
Hi,

I am also using the same model for 2-stroke engine. Try to refine your mesh and/or reduce time step. By the way did you find answers to your questions?

Good luck.

Mehdi April 18, 2006 09:22

Re: need help on premixed combustion
 
Hello, Thanks for your response. But I'm using steady state simulation. I have used the same model in my previous calculations and somehow the results was acceptable, but now I have installed 3.26 version and this is new simulation with this version. So you think I need a transient solver and fine mesh. I will keep this idea and if I couldn't solve the problem I will use it.

Thank very much, Mehdi

Ralphie April 18, 2006 10:03

Re: need help on premixed combustion
 
You could try and adjust the coefficients A and B in the EBU model. That should help with the incomplete combustion and might push your temperature as well. You could try using the heat of reaction option in 'Reaction Systems' for your reaction. I am not sure about the incorrect O2 concentration. The only reason I could think of is that all your scalar concentrations at the inlet sum up to more than 1. In this case the concentrations are normalised to 1 if I am not mistaken. This could happen for example if your mixture fraction is defined as an active scalar.

Hope that was of any help.

Good luck!

Mehdi April 18, 2006 10:29

Re: need help on premixed combustion
 
Hello, Maybe that is also helps, I mean setting of the A and B for the EBU model, but I don't know why this model shows the wrong Oxygen mass fraction at the inlet. I check and changed scalars BC many times and I'm realy confused. It does not work. the fuel mass fraction and N2 are the same with my inlet setting but the Oxygen is lower.

Thank you for your attention, Mehdi



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