Initial values of Species

MahdiSeddiq · February 28, 2017, 01:18

Hello
Does anybody know how to set the values of initial species when using EGR ?
I am using n-Butanol/PAH-Mechanism with 45% EGR and I set the values for it but the peak of pressure of combustion considerably increased about 4 MPa upper than experimental data!
I think the problem is the value of the n-butanol mass fraction and I dont konw how to set the values!

Thanks

jaychhatbar · April 23, 2017, 06:39

It depends on how you are inject your fuel and what simulation are you doing.
If you are doing port fuel injection and simulation of only combustion chamber then you have to give mass fraction with respect to inlet air with egr. It is easier to give equlance ratio in this condition.
But if you are doing direct injection then you have to give only the egr at initial conditions.

Sent from my Redmi Note 3 using CFD Online Forum mobile app

Pham Van Chien · April 20, 2020, 04:43

Dear all,

This discussion was organized in 2017, but because there were some things related to my problem which I have been facing now, so I would like to leave some text here hoping to get some help.

I have a question related to changing initial conditions, if you have experience with this, please give me a few minutes to give me some advice. Any help will be helpful to me and I will very much appreciate it.

I am simulating the combustion of a dual-fuel engine using AVL FIRE, in which the gaseous fuel (CH4) will be injected into the intake port to mix with fresh air generating a premixed mixture prior to supply to the cylinder, while diesel fuel (pilot fuel) will be injected into the cylinder as usually in order to ignite the gaseous mixture fuel at the end of the compression process.
Please refer to the figure below.

Image.png

My simulation will be conducted from IVC to EVO, which does not include intake port and exhaust port simulation. That is, at the start of the simulation, the fluid property inside the engine cylinder must be a mixture of CH4 + fresh air, not only FRESH air as default, therefore I will have to change the species components when setting up the initial conditions.
Specifically, I want to add CH4 to fresh air (O2 + N2) which was contained in the engine cylinder when setting the initial conditions, but I didn't know how to do that. Please give me some advice!

Thanks in advance!

PV Chien

February 28, 2017, 01:18	Initial values of Species	#1
MahdiSeddiq New Member Mahdi Seddiq Join Date: Aug 2016 Location: Iran Posts: 4 Rep Power: 9	Hello Does anybody know how to set the values of initial species when using EGR ? I am using n-Butanol/PAH-Mechanism with 45% EGR and I set the values for it but the peak of pressure of combustion considerably increased about 4 MPa upper than experimental data! I think the problem is the value of the n-butanol mass fraction and I dont konw how to set the values! Thanks

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April 23, 2017, 06:39		#2
jaychhatbar New Member engine_sim Join Date: Apr 2017 Posts: 10 Rep Power: 9	It depends on how you are inject your fuel and what simulation are you doing. If you are doing port fuel injection and simulation of only combustion chamber then you have to give mass fraction with respect to inlet air with egr. It is easier to give equlance ratio in this condition. But if you are doing direct injection then you have to give only the egr at initial conditions. Sent from my Redmi Note 3 using CFD Online Forum mobile app

April 20, 2020, 04:43		#3
Pham Van Chien New Member Pham Van Chien Join Date: Oct 2018 Location: Korea Posts: 9 Rep Power: 7	Dear all, This discussion was organized in 2017, but because there were some things related to my problem which I have been facing now, so I would like to leave some text here hoping to get some help. I have a question related to changing initial conditions, if you have experience with this, please give me a few minutes to give me some advice. Any help will be helpful to me and I will very much appreciate it. I am simulating the combustion of a dual-fuel engine using AVL FIRE, in which the gaseous fuel (CH4) will be injected into the intake port to mix with fresh air generating a premixed mixture prior to supply to the cylinder, while diesel fuel (pilot fuel) will be injected into the cylinder as usually in order to ignite the gaseous mixture fuel at the end of the compression process. Please refer to the figure below. Image.png My simulation will be conducted from IVC to EVO, which does not include intake port and exhaust port simulation. That is, at the start of the simulation, the fluid property inside the engine cylinder must be a mixture of CH4 + fresh air, not only FRESH air as default, therefore I will have to change the species components when setting up the initial conditions. Specifically, I want to add CH4 to fresh air (O2 + N2) which was contained in the engine cylinder when setting the initial conditions, but I didn't know how to do that. Please give me some advice! Thanks in advance! PV Chien