CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   FLUENT (http://www.cfd-online.com/Forums/fluent/)
-   -   PDF problem (http://www.cfd-online.com/Forums/fluent/28870-pdf-problem.html)

olivier August 29, 2001 12:38

PDF problem
 
Hi I would like to create a non adiabatique PDF case to simulate a solid combustion in Fluent v5. I briefly describe the problem I have. The fuel considered is known to consist of 46% volatiles and 54% char. There is no ash. I have a known mole fraction CHONS composition (C=39.4% ; H = 52.2 %; O = 6.9% ; N = 1.13% ; S = 0.430%)and I know the lower heating value (30 e+06 J/kg). I don't know the value of the heat capacity of the fuel but I let a value of 1000J/kgK. 1/ I assume that the equilibrium system consists of 13 species (CHONS, C(S), S(S), SO2,NO2,CO2,H2O, N2,O2). that means a simple form. 2/The "empirically defined streams" consist of a FUEL STREAM 3/ My operating conditions are 101000Pa for pressure, 400K for the fuel and 555K for the oxidiser. Min temp =300K ansd max temp = 3500K.

PROBLEM I cannot calculate the pdf case with my LCV (J/kg)and if I modify this value to 45 e+06J/kg I have no problems and I obtain values .

Could someone able to help me to resolve this problem Because it's the first time I use the "fuel stream option" , may be I have forgotten something... all informations about my problem will be very kind. Thanks

Jin-Wook LEE September 4, 2001 23:54

Re: PDF problem
 
1. Select more species which is possible even though it's life cycle may be very short. Possible species are, for example, CH4, C2H2, OH and so on.

2. Additional comments :

1) Simplify your problem. That is neglet minor species or less meaningful species in the fuel, if possible, such as S(S), SO2, N......, if possible. In general, they can be neglected.

2) NO and/or NO2 is not good choice because it's chemistry is not based on the equilibrium chemistry.

Sincerely, Jinwook

olivier September 5, 2001 03:45

Re: PDF problem
 
Thank you I will try your advice and give you the results. bye

Olivier


All times are GMT -4. The time now is 13:00.