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Old   March 30, 2005, 10:34
Default Combustion Problem
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My Problem:

I have a rotor with passages and I have one inlet on either side of rotor and 1 exit. From one side of inlet, I have fuel and air in constant proportion (0.1 percent of fuel and rest air of O2 and N2) coming in and from other inlet from other side; I have hot gas(O2 and N2) at high temperature and velocity coming (800 m/s and 1700K). This inlet is used to set up combustion parameters for the fuel air mixture coming from the other inlet. Mine is a high-speed compressible flow rotor with turbulence and shock waves and expansion waves taking place inside the rotor.

To complete the cycle, I need a simple combustion (turbulent combustion) of my fuel (ethylene-air mixture) by the hot gas coming from the other inlet. So now my question is what type of combustion should I use and what are the required parameters I should specify and what it should be.

1. Scheme definition:

Premixed/unpremixed-diffusion/partially premixed?

Which model- EBU standard/EBU

modwall/combined-user/single PPDF?

2. What reaction system should I use? I have to use only 1 step stoichiometric chemical reaction. What do you mean by mixture fraction value and how much should I use? Also should I use "products" in rate equation?

3. As my fuel will get combusted with the temperature of the hot gas coming from the other side, I think I need not specify anything in ignition menu. Am I correct? If no, then what do we mean by fraction burnt?

4. What should I specify as the mass fractions in additional scalar panels for boundary conditions?

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Old   April 1, 2005, 05:57
Default Re: Combustion Problem
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Your problem:

1. Partially premixed (do you really have only 0.1 % Fuel?). Try EBU-Standard first. 2. The reaction system comes from your combustion reaction (fuel + O2 -> products). the mixture fraction is calculated by the code. Use products in rate equation. You will probably have to tune Amix and Bmix to get reasonable results. 3. You have to set an ignition if you use EBU. Fraction burnt is the mass fraction of your fuel that is assumed to be burnt already. It is necessary to assume this to get the EBU Model kick-started. You will probably have to tune this value as well. 4. Those are your boundary conditions. You should know the mass fractions of your scalars (fuel ,O2, N2, CO2, etc) at the inlets. 5. I strongly recommend you read the manuals. Be prepared to fail a number of times before you get it right.

Good luck,

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Old   April 29, 2009, 08:13
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