combustion
 

hi

I am modeling n-octane injection inside a cylinder and it combustion.

i am injecting n-octane with cone injection inside the cylinder and i want to start combustion after injection. i am using species transport model.But combustion dont start in side the cylinder.I have tried inilization at 1000k and spark model but n-octane is not catching fire.

Re: combustion
 

hello what is the model of combustion u have selected?

Re: combustion
 

respected friend

thank you for your reply.as i have mentioned in first post tant i am using "SPECIES TRANSPORT MODEL".

for ignation i am using spark ignation model

please guide me how to select the model of combustion.

i shall be very thankful to you

mmacrb

Re: combustion
 

hi

I think one iformation was missing

for "turbulance-chemistry interaction" i am using "FINITE-RATE/EDDY-DISSIPATION" option.i hope this will answer your question regarding which combustion model i am using

mmacrb

Re: combustion
 

Hello sir

i also faced te similar problem, when contacted FLUENT support they suggested to go for eddy - dissipation model first then go for finite rate /eddy dissipation - no need of spark ignition

hope this will help u

Re: combustion
 

Respected friend

Thank you for your response. I think i am missing some very important setting in my simulation. due to this setting when i use spark model or i initialize it at high temperature (1000k)it don't ignite. If you like I can send you my case and data files so that you can have a look. I have already spent a lot time on finding it. Alternatively, if you can send me some case and data file in which liquid fuel is ignited using species and transport model. My email is bhuttathermo@yahoo.com

I will be very thank full to you

mmacrb

Re: combustion
 

please send me the case and data files my mail id is muggallasrinu@yahoo.com

it will be a nice pleasure for me to share these topics

Re: combustion
 

hi mmacrb, as u are injecting liquid fuel in to cylinder using cone injection, its a clear case of Non-premixed combustion,

but u can solve the problem using species trasport,

If u go for non-premixed combustion modeling u need to generate a look-up-table containing the mixture fraction, mixture fraction varience & enthalpy using pre-pdf module of Fluent

in the DPM model, make sure that u select the interaction of the discrete phase with contiuous phase,

to make the fuel burn simply increase the number of contiuous phase iteration per DPM iteration,

there is no need for the spark model if u consider fast chemistry i.e., mixed is burned approach,

Re: combustion
 

Hello

Can you please help me, I am doing combustion study of a single droplet fuel in a oxidizer medium. I have choosen a rectangular chamber in which a spherical drop is placed for its droplet study. Oxidizer is injected through the top face.

For this study, I have used species transport and eddy dessipation modeling. But the after iteration it is observed that combustion is not taken place..Can you please give any idea to proceed further..

Re: combustion
 

is the droplet stationary or is it moving, how are u injecting the fuel droplet, from where is the oxidiser inlet,

give me details of boundry conditions, domain type, injection type, fuel used etc

Re: combustion
 

First of all thanks for your response.Species are the fuel droplet(ANILINE) at centre , which is stationary and oxygen gas are entering from the top face. In fluent how to specify all this model, I am not able to understand...Can you please help in specifying it...I have given boundary for fuel drop as velocity inlet. Bottom face as pressure outlet.All four side face as hot wall.Actually I am not getting how to specify all other model...In model I selected solver as segeregated,unsteady; energy equation; viscous with K-e model and species transport with volumetric and eddy dessipation...Please specify other parameter I should consider for the droplet to combust..

Re: combustion
 

how did u specify fuel droplet to be stationary in domain in Fluent,

are u not injecting the fuel in to the domain,

if u are injecting the fuel in to the domain, then in the dpm model increase the number of contiuos phase iterations per dpm iteration to achieve combustion,

how did u decide upon the boundary conditions, have taken them frm any experiment, paper etc, or just r u giving it randomly, check whether they r right,

also check whether air fuel ratio u have given is in accordance with the stoichiometric air fuel ratio, if not there will be a problem

Re: combustion
 

Hai

Thank you....I am not injecting any drop..It is kept stationary and it is defined as velocity inlet....I have calculated this value by using formula given in heat and mass transfer book written by stefen turnes.Can you please explain how to define this model said as DPM model..

Re: combustion
 

how are u keeping it stationary in the domain, how r u defining it to be stationary.

DPM model is used when there is a secondary phase(fluid) whose volume fraction is less compared to the volume of the main phase (contiuous phase),

if the volume fraction is not negligible then u have to go for multiphase model,

in your case u can use dpm model, but i could not understand how u have set up the model n how u r making the droplet to be sationary in the domain,

for more details on dpm model just go through the user guide.

Re: combustion
 

hai

I have taken a rectangular chamber, in which a sphere is made which act as a droplet in the fluent.While solving,I am defining it as a either mass flow inlet or a velocity outlet...Or Can you suuggest another method to study a stationary drop in a oxidizer medium. Is their any method to inject only a single drop into the combustion chamber.Can give your email id so that I can send my set up that I have designed for this study...thank you in advance...

Re: combustion
 

Hi,

if u r making a sphere in a rectngular domain, then the fulid in the sphere should be that of liquid droplet n that in the rectangular domain should be air. we have to see how to define the fluid in sphere to be that of liquid drop.

other way is to make a single injection in the centre or any where in the domain, n model the evaporation

any how send me the setup to gramesh1212@gmail.com, i wud like to have a look at that,

regards, rams

hi.. can anyone take a look in my modeling.. i need to do a simulation on droplet combustion also.. and in facts, i does not know why i cant mesh it.. and how to do the simulation.. please reply.. i really need anyone expertise in this things. do emel me.. smi90_trg@yahoo.com.my