Model study Check

[Anonymous]

Hello again,

I made a designstudy which aren't very helpful. I designed a little axial turbine with the goal of a pressure difference.
The Inlet boundary is 5 bar, the oultet is a velocity of 3m/s.

After 100 iterations the pressure difference isnt' there. Everywhere is 5 bar besides the impeller. Only in the impeller the pressure decreases.

So I thought, maybe someone can look after my model an the boundary conditions and say why my results aren't good.

Thank you very much !!!

[Jon.Wilde]

I ended up testing a P=0 at either end, to see what sort of flow rate I get. It took a long time to ramp up though so I just started it with a bigger time step.

[Anonymous]

Sounds great 🙂

Your theorie, that the pressure starts to increase with a certain rotation was right. The turbine is able to decrease the pressure with free spinning. I made a little calculation on excel with big kaplan turbines as model, by using the similarity law and the result were very near to the simulation.

I also changed the geometry. Now it is way more aerodynamic and the rotation speed is getting higher.

Very exciting to see what a small change of the parameters can bring 🙂 Can understand why you are so in love with simulation 😄

[Jon.Wilde · Accepted solution]

I ran with a P=0 at the inlet and a 3 m/s at the outlet. This was at 30 deg/step, which might not be small enough to properly capture everything - perhaps 3 is better.

I do not get a huge pressure rise though, check out my screencast.

[Anonymous]

Wow thank you very much Jon for the screencast 😄 I ran many sumulations in the last few days and the pressure difference are most between 0,05bar and 0,1bar. So your simulation is a good view for me that the turbine isn't able to decrease the pressure about 0,5bar or even more.