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-   -   combustion doesn't occur need help plz (http://www.cfd-online.com/Forums/fluent/95568-combustion-doesnt-occur-need-help-plz.html)

roukaia December 22, 2011 09:55

combustion doesn't occur need help plz
 
i am working on 2D combustion chamber i achieved the cold flow and now i am working on combustion i used eddy dissipation model to model combustion but the rate reaction still 0 even with mass fraction of co2 and h2o =0
i use k epsilon for turblent model and group injection for diesel C10h22
my conditions boundary are pressure inlet -oulet
please does anyone have an idea why the combustion doesn't occur with eddy dissipation model

BMCombustor December 26, 2011 15:38

What is your initial temperature? Do you initialize your domain with a high temperature or not?

shk12345 December 26, 2011 21:01

hi
 
try to run the simulation for various higher temperatures.

roukaia December 27, 2011 10:28

re: cpmbustion doesn't occur
 
first of all thank you for replying
i initialize my temperature to 300 k but the temperature in the combustion chamber is about 900 k isn't enough for the combustion of diesel
i even try the patch but nothing that happens

roukaia December 27, 2011 10:33

thank's for replying
my initial temperature is about 300 k

shk12345 December 27, 2011 12:01

No combustion reaction occurs at 300
use higher temp as around 600- 1000 and see the various products

BMCombustor December 27, 2011 15:57

Quote:

Originally Posted by shk12345 (Post 337119)
No combustion reaction occurs at 300
use higher temp as around 600- 1000 and see the various products

I agree too; use 1000 k and let us know what happens.

roukaia December 28, 2011 04:13

response
 
this is the details of my case

•Select k-epsilon model (realizable) under Viscous Model
•Under Species & Transportation I select "Species Transport", Mixture properties "diesel-air" with everything else unchanged.
volumetric : eddy dissipation model
•Now I set up DPM. Enable "interaction with continous phase", enable "unsteady particle tracking", Number of Continous Phase Iterations per DPM Iteration set to 200.
?under Physical Models i enable "DRoplet Collision" and "Droplet Breakup Model". Under Break up constant I set "Breakup Parcel to 50".
?Under Tracking Tab I set Drag Law to "dynamic-drag"
?Particle time step set to 0.00001


•Injections: I create an injection. "group". Particle Type "Droplet". Material "Diesel Liquid". Flow Rate to be 3.22e-4 kg/s. crank angle 700, Stop Time 720.temperature diesel 310k
?Under Turbulent Dispersion I enable "Discrete Random Walk Model" and "Random Eddy Life"
•Under Solve-> Controls -> Solution I leave default settings and select OK
•Now I select Initialize.to 1600k.

when the iteration finished i go to track particle :and i have this summary

Fate Number Elapsed Time (s) Injection, Index
Min Max Avg Std Dev Min Max
---- ------ ---------- ---------- ---------- ---------- -------------------- --------------------
Evaporated 831 3.989e-02 4.000e-02 3.995e-02 0.000e+00 injection-0 0 injection-0 0

(*)- Mass Transfer Summary -(*)

Fate Mass (kg)
Initial Final Change
---- ---------- ---------- ----------
Evaporated 3.434e-08 0.000e+00 -3.434e-08

(*)- Energy Transfer Summary -(*)

Fate Energy (J) Change of Energy (J)
Initial Final Sensible Latent Total
---- ---------- ---------- ---------- ---------- ----------
Evaporated -9.046e-03 0.000e+00 -1.468e-03 1.051e-02 9.046e-03


number tracked = 7297, escaped = 0, aborted = 0, trapped = 0, evaporated = 0, incomplete = 7297, coalesced = 0, shed = 0, splashed = 0
one thing that i don't understand is why the evaporated ones are 0 and the incompleted ones are 7297
still nothing happen

pghoseju December 28, 2011 15:01

check the arhenius parameters from literature

roukaia December 29, 2011 04:06

re
 
thank you for replying
eddy dissipation model doesn't take in account the arhenus chemical reaction are you talking about finte rate / eddy disspiation model ?


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