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Replacing n-heptane (chlamers mechanism) for ECN Spray Simulation |
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#1 |
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Hi all,
I am using Chalmers n- heptane mechanism (http://www.tfd.chalmers.se/~valeri/MECH.html ) for ECN reacting spray validation. I want to replace the mechanism with T. Lu's n-heptane mechanism (http://www.engr.uconn.edu/~tlu/mechs/mechs.htm). Except the mechanism part, the case setup is the same. The changes are as follows:
What could be the possible reason? Is it a problem with mechanism ? Any leads will be highly appreciated Thank You |
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#2 |
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Tobias
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Hi,
can you post further information regarding the mechanisms you used? Number of Elements: Number of Species: Number of Reactions: Maybe they differ in size? |
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#3 |
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#4 |
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Tobias
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Hi,
i guess this is T. Lu´s mechanism. What about the other that you replaced? I meant, if this Chalmers mechanism is more detailed (larger number of species and reactions), it might be that small reactions already occur, that are not present in the reduced mechanism of Lu. |
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#5 | |
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Thank you MFGT for the reply
I've replaced Chalmers mechanism with T Lu's mechanism. Yes it is a highly reduced mechanism. I am using this for ECN Spray simulation not for combustion (though I tried Lu's mechanism for combustion also ; it gave me the same result- no combustion) Quote:
Thank You |
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#6 |
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Tobias
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#7 |
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SAGE is activated.
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#8 |
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Saurav
Join Date: Dec 2015
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Hi alenp07,
I will be curious to know the magnitude of species concentrations with Chalmers mechanism. Are these hydrocarbons in the order of 1e-09~1e-10 Kg? If it is so, I will actually ignore those values, as they are comparably low when compared to ~10 mg of fuel injection. Different mechanism can lead to different pathways depending upon local temperature, and equivalence ratio as Tobias was referring to. Anyhow, keep us posted about your findings. Thanks Last edited by SauravMitra; August 18, 2016 at 10:13. |
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#9 |
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Thank You Saurav for your response. I agree with your point but what I am trying to say is after certain time step, say for example 1.5 ms, the OH radical formation is significant. I can observe this in Chalmers but not in Lu's mechanism. Also in Lu's mechanism , I cannot even observe traces of OH radical.
Is this problem due to mechanism alone? or I am making a mistake in case setup? Thank You |
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#10 |
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Saurav
Join Date: Dec 2015
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Hi alenp07,
How long does this take to run ? Can you send me the setup for both ? I can have a look at it. Thanks |
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#11 |
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Saurav
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Hi alenp07,
I noticed the mechanism of Lu might need special treatment. If you open chem.inp for 52 species reduced mechanism, you will notice that the reaction rates are zero out there. You have to specify custom reaction rates via UDF route by using the CKWYP routine. Refer to section 1.4 in the UDF manual regarding this. If you do not take the UDF route, CONVERGE will parse the mechanism file as it is, but you will not get combustion out of it as the rates are zero. Can you just double check for me, which reaction mechanism you are using ? Thanks |
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#12 |
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Hello Saurav,
Run time is lower for Lu's mechanism. Yes I can share the case setup with you |
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#13 |
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Hi Saurav,
Since we were facing difficulty with Lu's mechanism we started the simulation with n-heptane mechanism which comes with CONVERGE. Why we decided to go with Lu's mechanism because a literature was available and lesser number of reactions will have some advantage with runtime. At present we are using Chalmers mechanism. What is your suggestion in this case. using Lu's mechanism for our study or we should continue with Chalmers mechanism? |
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#14 |
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Saurav
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Hi alenp07,
Chalmers mechanism will do a good job for ECN Spray reacting flow. If you keep the oxygen concentration at 15% as specified here: http://www.sandia.gov/ecn/cvdata/tar...ion/sprayA.php you should be okay. You can refer to this work of Convergent Science for ECN Spray (reacting flow) simulations. http://proceedings.asmedigitalcollec...icleid=1721041 Thanks |
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#15 |
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Hi Saurav,
Thank you for the suggestions. I also felt that using Chalmers mechanism will give some reasonable results. I will keep you updated. Thank you once again |
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Tags |
chalmers, converge, ecn, n-heptane, spary |
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