ABSTRACT
As described in Sec. 3, Chapter 6, and Sec. 8, Chapter 9, steam whirl is a subsyn-
whirling rotor mode. As previously explained, steam whirl differs from its “close relative” oil whip in that steam whirl has an instability threshold dictated by increasing power output, not increasing rotor speed. Although steam whirl forces are present in all stages of steam turbines, when steam whirl occurs it is always in the high-pressure turbine, as explained in Sec. 3, Chapter 6.
