[compu]

Hello experts. I am a student and have been reading the forum for years of uni now, and it is amazing how much problems it helped to figure. However, I am now facing a problem that I tried to solve for weeks and is completely stuck. Due to a shocking event I lost my supervisor who was basically the only CFX/steam/thermo experienced person in this uni, so I am a bit lost now.

So long story short, what I want to do is to do a CFX (17.2) of a Tesla Turbine. I have created the geometry for one gap and an intake (rotating wall). I managed to get it running with air (no inflation layers applied yet, have to do that still). It shows a nice power curve.

Now what is causing problems that I want to see the results with first dry, and then wet steam as a working fluid. Ideally, the condensation should happen due to the expansion. Point of this is to do a comparison between the power/efficieny of dry steam compared to a trubine that runs on wet steam. I wanted to calculate the isentropic efficiency from the enthalpy intake/outtake vs. steam table.

Problem is - since I introduced the steam model the simulation stops after one iteration with no result. I have chosen the material H2Ovl as a homogeneous binary mixture and set the redlich kwong equation of state.

The inlet pressure is pretty variable but basically should be related to the points in the steam table where I get an expansion of dry wet steam and see what the efficiency does.

I also tried to access the ansys tutorials but I couldn't log in, is that not for student access? What I also dont understand that how I can define the dryness of the steam., or if it is coming from the tables? Also, what do I need to set up to represent the condensation (and increase in wetness)?

I basically need any kind of steam running and ideally one that allows me to control inlet temp/pressure and makes it possible to define a wetness with either the input or as a constant fluid with just a continuous wetness. Can anyone suggest a suitable model, or help me to get the redlich kwong to run?

If someone could help me out this would save my thesis and my life. I can post any setup data/case file gemoetry etc. whatever you need to know. This really is my last resort of help

Thank you in advance

[ghorrocks]

You really need a tutorial example of modelling dry and wet steam. There are tutorial examples on the ANSYS customer webpage of exactly this - so I would try a bit harder to get onto the website. I understand it allows student accounts so if you have a valid university license you should be able to get a student login.

[compu]

I couldnt agree more with needing a tutorial. I have tried to create an account again but after using my customer number that came with the student licence it doesent let me create a customer account but prompts me to the ANSYS studen support page:

We now provide student users with access to self-guided support materials on ansys.com/academic, which includes:

Products installation & configuration guides and videos.
FAQ (PDF download).
Introductory level simulation videos and "how to" videos.
Links to external academic sites that provide curriculum material and tutorials
We trust that you'll find this new self-guided support material useful.

Unfortunately non of those covers a wet steam problem. I have tried many ways and times but I think students are not supposed to get access to the customer tutorials.

Isnt there a chance someone could tell me the settings for a simple steam model that does about what I need for getting the simulation running, read some enthalpy values and adjust the wetness? I basically set it up already according to the ANSYS user guide (I have read through all wet steam as far as I understand it), but I dont understand why it is not running at all

[ghorrocks]

Modelling wet steam is certainly beyond what most students would be doing. This page (http://www.ansys.com/products/academic/support-policy) says you will need to talk to faculty staff to get access to it, but they should have access to it.

You really want to get access to the customer page. There are a lot of settings to consider so it is not really appropriate to post, and I can't post a copy of the tutorial as that infringes copyright.

[turbo]

Try IAPWS in the binary mixture mode rather than R-K.

[compu]

I will try to speak to someone in uni. As I said my supervisor would have been able to get me started since he was CFX/steam pro (hence I picked the topic) but he passed away. The uni is only small so there is no one else to have time and understand to set up the wet steam model. So its really a call for help out of the odd.

I will try to get access to the tutorials via uni.

In case that doesent work.. I have a simulation running with air. Would there reasonable changes to the properties of air to get an approximation of (wet) steam? So for example from a known point in the steam table I could take the density, so at least something in the Reynolds number would be changed towards steam. This wouldn't allow me to read enthalpy since there is no condensation but at least power in comparison over different densities.

Is the above assumption about correct? I know its sketchy but I am kind of lost and if dont get it to run thats my options left.

Thanks so much

Edit: Just seen turbos post. Yes ok, will try that. RK was a suggestion by my supervisor but I dont have to go with that. Thank you too!