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-   -   error: 126 Equivalence ratio of 0.000E+00 and error:076 negative desities found (https://www.cfd-online.com/Forums/star-cd/172778-error-126-equivalence-ratio-0-000e-00-error-076-negative-desities-found.html)

 Bücherknopf June 6, 2016 04:37

error: 126 Equivalence ratio of 0.000E+00 and error:076 negative desities found

Hello,

I'm relatively new to Pro-Star an I hope somebody can help me with the following problem. I'm trying to simulate a methane combustion in a pre-chamber.
I imported a static mesh from CCM+ and now I'm trying to get the simulation to run. I have two boundaries: a pressure outlet, which I define in a table(time).
The other boundary should be a massflow inlet. I had some problems with this, so I changed it to a velocity inlet, which is also defined by a table(time).
The next step would be to start the combustion but before that I have following problem: After the simulation(without combustion) is complete I can analyse the results. Here I get an expected picture of the CH4 fraction.But when I take a look at the N2 fraction, the picture shows me negative fraction of N2, on the places where CH4 was in the previous picture???
Maybe the origin of this problem ist the O2: Altough I define in the section "scalar boundaries", that my velocity boundary should have only CH4(so its value is 1, all the other species are 0), the O2 manages somehow to flow in, with the CH4.
After that the simulation calculates the fractions and sees that the value is above 1. I think thats why the N2 is negative, so that the total fraction stays at the value 1.
Now the question: How do I manage to stop the O2, but still have the CH4 to flow in?

And another question: I decided to try the combustion(premixed) anyway. But then I get for a EBU-model the error:076 negative desities found
or for the CFM-model the error: 126 Equivalence ratio of 0.000E+00 is outside.

What do this error messages mean and what should I improve then?

Has anybody suggestions what I can do here? I'm glad about every suggestions.

Regards

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