Hello everyone,
Has anyone please manage to write a code for the methane reduced mechanism mentioned in paczko's paper named "Reduced Reaction Mechanism for Meathne, Methanol and Propane Flames"? Because i don't know how to initialize the domain with zero concentrations of species H, H2O, CO, CO2, H2, M while they are needed in calcualting intermediate species.
It is unclear what exactly you mean by "code". A system of ordinary differential equations describing reaction rates? Why then would it be difficult to set the starting concentrations?
Engelbert Buxbaum Thank you sir, for your quick responce.
this reduced mechanism consits of 4 reactions - 8 species, they are CH4 , O2 , H2 , H2O , H , CO , CO2. If i want to initalize the domain by the stoichiometric ratio of the fuel/oxidizer, then other species rather than CH4 and O2 will be zeros, while these species are needed to calculate intermediate species concentrations as indicated in the two foloowing images:
Again, I don't see the problem. If you start burning a mixture of, say, pure CH4 and O2, intermediates like CO will be initially 0. They are formed only during the reaction. If you do not have pure CH4/O2, but other gases like CO are present (like in natural gas), then you can use the composition of the gas as starting values. Note that in the ODS you use the sum (not the product) of the current concentrations to calculate the rate of change, it thus doesn't matter if some of them are 0.
Consider the simple 2-step reaction A → B → C with reaction rate constants k1 and k2 and the starting values A=1, B=0, C=0. Then
- A' = -k1A,
- B' = k1A - k2B,
- C' = k2B
- A' + B' + C' = 0 (preservation of mass)
(with A' = dA/dt, etc.). In the first time interval k2B = 0. Nevertheless, the system will proceed because k1A > 0, producing B. In the second time interval, C will also appear.
Dear Engelbert Buxbaum ,
let's take an example, for calculatine wI = w11 + w12 - w16, where w12 = -K12 * CH4 * OH. We have the concentration of CH4, but for OH it is given to be
(H * H2O) / (H2 * Kc3). So, initially we have zero concentration for H2 then how can we calulate concentration of OH ?
Note that, the given mechanism is reduced not detailed , it is a 4 reactions mechanism each consists of combination of elementary reactions from the detailed one.
Assuming the equations are correct (?!), the problem is that the denominator becomes zero, which is of course undefined. You will have to think what logically will happen to your reaction in case of H2 = 0, and then do exception handling accordingly.
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