engineFoam: combustionprogress too slow

astray · October 26, 2010, 03:52

Dear Foam users,

actually Im calculating a premixed PFI engine from a 4 cylinder engine with Weller's b-Xi combustion model. Everything seems to work fine but compared with the experiment the combustion progress is much too slow.
50 % progress is reached after 60 - 70 CA after ignition. Here is my setup:

Gulder
fuel IsoOctane
SuModel unstrained
euqivalenceRatio
XiModel transport
XiCoef 0.62
XiShapeCoef 1

diameter 0.003
start 690
duartion 20
strength 4
ft 0.062
Su 0.4

OF-1.5-dev

I also tried the XiModel algebraic but then the progress is much too fast. Now I can tune the model with XiShapeCoef and or other XiCoef in the Xi transport equation to augment the value of Xi or Su and then reach a faster combustion progress but I don't think this is the right way. I also read that the unstrained SuModel is good for engines. Can someone give me an advice?

Thanks a lot for helping me and best regards,
Benjamin

faithhidy · October 28, 2010, 08:09

I have the same problem，anyone can help？
I changed the uPrimeCoef in combustionProperties,it works.But is it legal to do that?

astray · October 28, 2010, 12:17

Yes that's what I want to know too. What is the meaning of this uPrimeCoeff? I don't want to tune a model with coefficient till I get my solutions that I like.
Why is there a uPrimeCoef for calculating the sub-grid turbulence intensity in bEqn.H?

Mr. Weller, I thought that you could help us out.

Thanks

Benjamin

October 26, 2010, 03:52	engineFoam: combustionprogress too slow	#1
astray New Member Benjamin B. Join Date: Nov 2009 Posts: 4 Rep Power: 16	Dear Foam users, actually Im calculating a premixed PFI engine from a 4 cylinder engine with Weller's b-Xi combustion model. Everything seems to work fine but compared with the experiment the combustion progress is much too slow. 50 % progress is reached after 60 - 70 CA after ignition. Here is my setup: Gulder fuel IsoOctane SuModel unstrained euqivalenceRatio XiModel transport XiCoef 0.62 XiShapeCoef 1 diameter 0.003 start 690 duartion 20 strength 4 ft 0.062 Su 0.4 OF-1.5-dev I also tried the XiModel algebraic but then the progress is much too fast. Now I can tune the model with XiShapeCoef and or other XiCoef in the Xi transport equation to augment the value of Xi or Su and then reach a faster combustion progress but I don't think this is the right way. I also read that the unstrained SuModel is good for engines. Can someone give me an advice? Thanks a lot for helping me and best regards, Benjamin Last edited by astray; October 26, 2010 at 03:52. Reason: tags

October 28, 2010, 08:09		#2
faithhidy New Member Josiah Xu Join Date: Jan 2010 Posts: 8 Rep Power: 16	I have the same problem，anyone can help？ I changed the uPrimeCoef in combustionProperties,it works.But is it legal to do that? Last edited by faithhidy; October 28, 2010 at 08:55.

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October 28, 2010, 12:17		#3
astray New Member Benjamin B. Join Date: Nov 2009 Posts: 4 Rep Power: 16	Yes that's what I want to know too. What is the meaning of this uPrimeCoeff? I don't want to tune a model with coefficient till I get my solutions that I like. Why is there a uPrimeCoef for calculating the sub-grid turbulence intensity in bEqn.H? Mr. Weller, I thought that you could help us out. Thanks Benjamin