What is the general length of time taken for the power turbine component of an industrial gas turbine to reach design speed ?

Hi all,

Im running a CFD and transient mechanical analysis using ANSYS to simulate a gas turbine blade. Im wanting to run a simple transient structural analysis of the blade during the start-up sequence. I've read and observed a lot of material on the general start-up sequence but i cant seem to find any direct information on how long it takes for the power turbine itself to reach operation speed. I understand there is a period called the "warm up" phase where the turbine rotates at a lower constant rpm, and then it accelerates until full operation speed. Im interested in the general time taken to go from this intial/constant state, until it accelerates to full operational speed. Any rough time duration would be perfect as im only running a basic simulation for my thesis project.

Thanks !