Ryan,
Based on your comments it sounds to me that you can simulate this with SimCFD, but you are going to have to be careful with the setup. I would suggest that you model your simulation with the defined inlet flow rate and see what the resulting turbine speed is instead of using a pressure setup. When defining the inlet flow rate make sure that you don't use a constant flow rate, but include a linear warm up/ramp up period that lasts over 50-100 iterations worth of the simulation.
Since it seems that the transient response isn't important at the moment, when you define you inertial value for your turbine (or the solid material type), make sure that you use a much larger value than what it really is. This will only effect your transient response and not your steady state speed. The outcome will be a much more stable analysis. If you were to use a light turbine, you would likely see a chatter in the RPMs and most likely divergence unless you use a very small timestep.
When doing these turbine simulation, I sometimes like to turn on intellignet solution control (ISC) for added stability.
Try to simplify your geometry as much as possible so that you can keep your mesh count reasonable.
-Royce
