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HurricaneHenry March 19, 2011 09:21

EDM Coefficients A and B
 
Hi,

i have some problems while modelling a combustion chamber. I use the coupled Eddy Dissipation Model (EDM) and Finite Rate Chemistry, because Eddy Dissipation Concept (EDC) ist not available in CFX12. The combustion chamber has two inlets, one with fresh air and one with a mixture of H2/CO/CH4/CO2/N2/O2. As reaction mechanism I use a global 3step Westbrook Dryer mechanism with 3, only forward, reactions for burning CH4, CO and H2. In Every reaction, arrhenius with temperature PDF is used (Don't know if it's better than normal arrhenius).

The aim is, to determine the leftover of CO at the outlet, but it's problematic, because during the simulation H2/CO/CH4 is fully burned. The mass fraction at the outlet of CO is 0.00000. So there's nothing to determine. In the simulations i used the standard values for the coefficients of the reactant and product limiters A and B in the Eddy Dissipation Model (A=4, B=-1,0 ?). In the tutorial "simulating a gas chamber" the values A=4,0 and B=0,5 are used.

Can anybody recommend me some Values for the coefficients of the reactant and product limiters A and B in the Eddy Dissipation Model for homogeneous gas phase combustion? What's about Chemical Time Scale?

Greetings,
Hurricane


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