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cactilio86 June 24, 2010 09:16

Non-premixed comb. of two fuels through single inlet
Dear all,

I am trying to simulate something that can be simplified to the following case: a 2D axisym vessel with two inlets: one for air and one for fuel. The problem is that, in the fuel inlet, it is actually two different fuels that are entering the domain. My first approach has been mass-averaging the composition and temperature and treat it as a single fuel (and a single stream pdf) to correctly set the BC. However I am getting results far from the experimental data (about 300 K above).
My second approach was turning on the Secondary stream and then specify 1 for both mean mixture fractions at the fuel inlet (because mean mix frac is defined with respect the oxidizer, so no air is present in the fuel inlet, hence f=1). However I see a flaw in this approach and it is that fluent does not know how much of the mass flow corresponds to each fuel. In fact the reported fuel inlet composition is far from what I previously calculated. The solution is also non-converging and following the CFD principle crap-in, crap-out.

So now I have one extra option: Add an extra boundary embedded in the fuel inlet, so that either fuel enters the domain through a different boundary, and see what happens. but I think this represents different physics than the physics I should simulate.

What do you think ? I still believe that my first approach is correct but I am dissapointed with the results.


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