[Pham Van Chien]

Dear Experts,

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