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MANOJKUMAR November 22, 2005 06:55

Help: Radiation model
 
Respected sir,

I have constructed a rectangular combustion chamber of 1930 mm in length. it is having fuel inlet diameter of 97.5 mm and air inlet diameter of 110 mm.The flue gase exit diameter is 290 mm. The air fuel ratio is 1:1. air and fuel rate is 75 m3/hr. based on this, calculated air and fuel velocities are 10.61 m/s and 2.79 m/s resp. The fuel used is producer gas. i have used species transport combustion model.

My worry is i am getting the flame fully developed, but the maximum flame temperature at the core of flame is only 564 K, which is far far less than the actual possible case. Field trial shows that usual flame temp. for Producer Gas should be around 1000 C.

can you please give your valueable guidance. It appears there is some problem is setting up of the problem at Fluent. If you allow me i will send the details of the same to you. I have tried with the Rosseland radiation model. I have also used DO radiation model. but I donot have much information of DO model. please tell me if any information is available on internet about the DO model.Also tell if any other radiation model can work. Awaiting your positive responce.

Thanking you.

kiran November 22, 2005 07:25

Re: Help: Radiation model
 
hi manoj please send the data regarding inlet gas temperatures,producer gas temperatures. did you checked results without radiation model switched on?

MANOJKUMAR November 23, 2005 01:45

Re: Help: Radiation model
 
Thankyou kiran

inlet air and producer gas temp=300K

i have checked the result without radiation model the maximum temperature obtained is 564K and by using DO model the maximum temp obtained is 565K. i have doubt that i have not supplied proper inputs for DO model as i donot know much about it. I have used DO model because someone told me that it is best for combustion.but he was also not knowing much about it. so please give me some information about DO model if u have. if you have come across some paper in the journal please tell me the name of it so that i can refer it. thank you


kiran November 24, 2005 03:14

Re: Help: Radiation model
 
do combustion analysis without switching on the radiation model.if temperature reaches near the desired region then switch on the do model. you are saying temperature is not rising .it seems to be error in boundary conditions itself.check the velocity pattern. first run the cold model and then switch on the volumetric reaction .put all material properties constant.if temperature rises beyond 700k only give variable properties. let me know what steps you following for doing this analysis.

finally do predicts radiation reasonably well but without this also you should able to get high temperatures.check your gas properties(mixture) thank you


MANOJKUMAR November 24, 2005 03:45

Re: Help: Radiation model
 
Thanks kiran,

i understood my problem. there was problem in giving the boundary condition at the wall.Now i am getting the temp near to actual.


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