[Diffidato]

Hi,

I want to model the combustion process inside a hybrid rocket engine that uses nitrous oxide as oxidizer and paraffin as fuel.

I'm trying to model the injection of nitrous oxide as fractions of gas phase and liquid (droplet) phase and to do so I have to add liquid nitrous oxide as a new material since only the gas phase is present in FLUENT database.

The models I'm using are the following:
- Energy (on)
- Viscous (standard k-eps, standard wall fn)
- Species transport (see attachmentScreenshot 2023-10-30 162516.jpg)
- Discrete phase (interaction with continuous phase on)

I'm using the following table to create the liquid nitrous oxide as a new materialScreenshot 2023-10-30 163037.png.

the translation for each parameter is:
- Reference state
- density
- specific heat
- specific enthalpy
- specific entropy
- dinamic viscosity
- latent heat of vaporization
- superficial tension
- boiling point

The table is taken from a paper in which the authors use these data to create the matrerial in FLUENT but I'm unable to find all the parameters in the create material window as seen in the images below.
Screenshot 2023-10-30 162248.jpg
Screenshot 2023-10-30 162258.jpg

Do you know how to set these parameters? Do I have to change some models settings?
I would really appreciate some help as this is my first simulation using ANSYS.

[Desmond Flanagan]

Hi Andrea!

Disclaimer
I am also looking at a similar situation. I am still pretty new at Ansys, however I will do my best to give you helpful feedback. It's possible some of my feedback may not help. If there is any additional information you can provide about your particular case, I would appreciate it!

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Questions

1. Why did you choose K-epsilon instead of K-omega? K omega is better for near-wall flow regions, where adverse pressure gradients are significant, which I would imagine is important for an atomizer, in your case. Though I did some quick reading and saw that K-epsilon had better reattachment through a nozzle.

2. Are you able to allow your liquid cp to stay constant for your particular case? If so, I successfully created a second (identical) nitrous-oxide Fluid in the materials tab, and then renamed it "liquid_nitrous_oxide" so that cp was constant.

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Sources:

K-Omega for Atomizers <https://link.springer.com/article/10.1007/s40831-021-00370-2>