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Old   June 4, 2006, 10:46
Default Fuel injection
  #1
Rams
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Hi friends am modelling combustion using non-premixed combustion modell,..... am using fuel injection to inject fuel in to the combustion chamber,... the problem am getting is the fuel injected in to combustion chamber is not getting evaporated completely,... what could be the reason for this,.. can any one help me,...

Thanks in Advance,........

mail me at gramesh1212@yahoo.com
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Old   June 4, 2006, 10:52
Default Re: Fuel injection
  #2
MANOJKUMAR
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FIRST TELL WHICH TYPE OF FUEL IS USED COAL OR LIQUID SETTING OF THE DISCRTE PHASE
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Old   June 5, 2006, 11:13
Default Re: Fuel injection
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Rams
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The Fuel am using is Liqued Fuel i.e., kerosene,... it is not getting evporated after injection even after many iterations,.....
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Old   June 5, 2006, 12:45
Default Re: Fuel injection
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joaquin
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try to increase the max number of steps, in the traking parameters of the discrete phase model
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Old   June 6, 2006, 03:46
Default Re: Fuel injection
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Rams
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ok,... i'll try the thing u suggested and let u know,.....

Thanks for the suggestion,...

Even some times if the fuel gets evaporated,... the pressure, temperature and mass flow rates,.. are not matching with the required experimental results,.. and am getting negative pressures,.. at the throat of the inlet and outlet nozzles,..

Am using Pre-Pdf for doing combustion,... is there any thing i need to change in my prepdf so that I get the correct results,.. with out getting negative pressures,...

Please Help Me,...

Waiting for Reply
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Old   June 7, 2006, 05:30
Default Re: Fuel injection
  #6
Sahin
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I found many times Fluent fails to model multi phase, but you can try by chnging the vapor UDF and changing the descritisation scheme to QUICK for vapor. Regards, Sachin sachin.pagnis@gmail.com
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Old   June 7, 2006, 05:36
Default Re: Fuel injection
  #7
bijan
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Hi having neg. press. is not unusual. you must first check the opperating cond.s of the problem the problem of neg. press. may be arisen from the low reaction rate. about the injection, you can check the temperature and also the diameter of droplets. if the total average of temp. in the combustion chamber is low, there would be no acceptable reaction rate and also poor vaporization. az a guess, you can use higher initial temp.s. however, alla these are true if you have a mesh enough fine to have accuracy in your results.
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Old   June 12, 2006, 10:20
Default Re: Fuel injection
  #8
Rams
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Hello friends,..

Thanks for u'r help

i have got good results in agreement with the experimental values for cold flow analyis,... but when am starting combustion on the same geometry,... am getting negative pressures at the throat of the inlet and oulet nozzles of the combustion chamber,... this negetive pressures is not dying down but going on increasing,...

am doing non-premixed combustion using mixture fraction/pdf model,...

am unable to locate where the problem lies,.. is it in the pre-pdf or any where else,...

My inlet boundry conditions for hotflow are

Pressure inlet : 60bar at inlet nozzle

Pressure oulet : 0bar (i.e atmospheric pressure ) at outlet nozzle

Wall Temperature : 500K

Operating pressure is 0 pa

Please help me in solving my problem,..

Thanks regards,..

Rams
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Old   June 15, 2006, 03:13
Default Re: Fuel injection
  #9
Jack
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Hi! I am also doing a modelling of liquid kerosene injection in a combustion chamber. Sorry I am not really familiar with the combustion modelling with Fluent especially with liquid fuel injection. Before I start asking question regarding my problem, I wish to ask how do you determine the fuel is not evaporated? My simulation shows only high fuel fraction near the nozzle, while the rest of the regions have almost zero mass fraction of fuel. So I dont think I have the same problem as yours. Now, my problem is how to model the liquid fuel injection? I have air and air-kerosene set under material section but how do I set the B.C. for the fuel nozzle? Does the mass fraction of kerosene = 1 mean liquid? Thanks.
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Old   June 16, 2006, 01:51
Default Re: Fuel injection
  #10
Rams
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Hi,..

First tell me whether u are using Discrete Phase model(DPM) or not,..

if u r not using that then u might be using species transpot model,.. for analysing combustion,....

fuel injection comes only when you use DPM,...

to know how to model liqued combustion see FLUENT Tutorials
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Old   June 16, 2006, 01:55
Default Re: Fuel injection
  #11
Jack
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Yes, I am using species transport model. Will try DPM immediately. Thanks
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Old   June 18, 2006, 04:31
Default Re: Fuel injection
  #12
Jack
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OK... now I start to have the same problem as yours. Initially I had my particles evaporated because my initial condition for temperature is 1500K. But when time elapses the whole chamber cools down and the evaporation stops. Ocassionally I get 1 or 2 evaporations, and the temperature is the same as ambient. Is this exactly your problem? I will have a few more trial and hopefully I will have the answer when I come back. Thanks.
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Old   June 20, 2006, 01:25
Default Re: Fuel injection
  #13
Jack
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Hi! Did you find anything new? I changed my fuel to liquid benzene and everything going very well. So I guess the problem must be the condition in the chamber doesnt help kerosene to evaporate. Please share with me your progress.
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