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Old   April 6, 2014, 10:29
Exclamation FLUENT Compression Ignition model
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anonymous
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Dear all. Urgently need some help here.

My work is to use two chemkin mechanisms (lets name them A and B) and test them in fluent CI engine setup with species-transport EDC combustion model (chemkin-cfd).

My case starts at inlet valve closes (-143 before TDC). The density should be around 1.2kg/m3 as thats the density of air in atmosphere.

For mechanism A, the initial density output is 1.2kg/m3 which i think is correct. Pressure, density and temperature output along the compression stroke is also sensible. However it stopped at -20 before TDC due to divergence.
I am lowering the URF and see if its working, so i am not sure yet if the case is being correctly set.

Then i tried with mechanism B. This time the initial density at inlet valve closes is around 4kg/m3!!! I dono why it's not air's density(1.2kg/m3).
The pressure and temperature output is not sensible throughout the simulation (this time no divergence occurs).

I dono why the initial density is not 1.2kg/m3. I tried to use the case of mechanism A to import mechanism B again (confirming that both cases are identical). But the result is still the same.
Maybe it is because the case was not set properly in the first place?

URGENT! MUCH MUCH THANKS IN ADVANCE!
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Old   September 18, 2014, 00:47
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zdx
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maybe you should try the material's density as “ideal gas”
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Old   September 18, 2014, 01:01
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also,I have encountered a problem,when i simulate the IC engine's combustion with EDC model(file/import chemkin mechanism),it shows that there burning only very very short time just after ingniton(setting ingnition at 15 BTDC),and the burned zone is very small,the flame seems not going to spread farther no matter how long time is gone,although this zone's temperature reachs 3000K,and some CO2/H2O is produced.
I appricitae your advices very much,thanks a lot.And,I'm from Asia,so my english is poor.
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Old   April 19, 2015, 11:14
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sanjeet Limbu
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I am using the ignition delay model for combustion by compression stroke of cylinder... simulation to rapid compression machine. The mixture fuel is inside the cylinder compressed at 30 millisec. The dynamic mesh used to show compression- for 30 millisec and combustion is expected after 30 millisec

I am able to run the dynamic mesh using the chem kin file for combustion . I got some results...
But I expected the combustion to make temperature rise steadily , but it rise at 30ms abruptly
If possible can u suggest if I entered any wrong input in initialization or model dialog box.. say mixture fraction part ... i m new to that


Please suggest for solving

1. Pressure not rising during the compression stroke
2. tremperature not rising till 30ms and getting raised at instantly- abrupt
Attached Images
File Type: jpg temp profile.jpg (27.1 KB, 4 views)
File Type: jpg mixture fraction and variance.jpg (21.7 KB, 5 views)
File Type: jpg Temp and Presuree.jpg (22.9 KB, 3 views)
File Type: jpg fuel mole fraction and reaction progress.jpg (28.9 KB, 3 views)
File Type: jpg Referance mesh needed.jpg (35.9 KB, 4 views)
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