[Fat shady]

I would like to know how to import CFX PRE(Materials) for simulation calculation using mixture working medium.At present, I can only use RGP generator to generate methane pure matter file to import cfx pre to calculate, but my purpose is to simulate the mixed working medium of natural gas for simulation calculation.I really need your help.Thanks!

[ghorrocks]

By natural gas, do you mean a mixture of methane and ethane? Or some other mixture?

What are you trying to do in your simulation?

[Fat shady]

Natural gas consists of methane, ethane, propane and other alkanes.It also includes things like water, carbon dioxide, nitrogen.But methane accounts for about 90%, and other alkanes account for a small proportion. (So I want to make a mixture file as the material for the turbo expander). I am trying to simulate the real working conditions of the turbo expander in the simulation.But it is not known how to generate a material file of natural gas.

[ghorrocks]

That sounds like a multicomponent mixture. You generate all the components (methane, ethane, propane, water, CO2 etc) as stand-alone materials, and then make a material which is a variable composition mixture of all the components. You can then use the mixture as a fluid in your domain.

[Fat shady]

Yes,It's just a multicomponent mixture.But I don't know how to make this stand-alone materials.So far I can only make methane as a single material,the mixture has no idea.

[ghorrocks]

What fluid models are you intending to use for your components? Are they simple fluids with just viscosity and fixed specific heats or do you want more complex material models? Please describe the material models you intend to use for the components.

[Fat shady]

I intend to use the SST turbulence model as fluid model.Simple fluid with viscosity and fixed specific heats is enough,The main consideration of fluid temperature and pressure has a suitable range(The inlet pressure is over 10MPa and temperature range of-195℃ to 260℃).(Methane90%,Ethane1.3%,Propane0.33%,Nitrogen 7.8%,CO21.6%,H2O0.01%,Benzen0.01%,Toluene0.01%,Hel ium0.12%,Butane0.09%，Pentane0.13%，Mpentane，0.04%，M hexane0.03%，C7+ 0.14%.)

[ghorrocks]

What are you trying to model? What physics are involved?

[Fat shady]

Model:radial turbo expander(fluid is natural gas).
Involved physics:From a thermodynamic perspective,using exergy analysis to carry out the turbine system energy analysis.Using SRK model to calculate the thermal properties of mixture.Solve the Reynolds mean N-S equation.The turbulence model is SST model.(The change of enthalpy and entropy of expander was also analyzed)

[Opaque]

If your fluid is not condensing, nor reacting, you can get away with using a Fixed Composition mixture material.

Insert Material -> My Mixture

Start adding pure substances to the list, and their mass fractions

Fill as many of them with the existing materials.

Review how many are missing from your list

Determine if it is worth the effort to find the missing properties (Google search NIST database); otherwise, start your simulation with what is available, and reevaluate as you make progress into it.

You seem to be starting on this kind of simulation. Likely you will be encountering other issues; therefore, polishing each step is irrelevant at this point. You can polish every detail later once you have completed an end to end simulation and sorted out the basics.

[Fat shady]

Hello, thank you very much for your reply. I started following the steps you said and got some ideas. Thank you again for your answer!