Hi all,

I would like to know the explanation of thermal expansion written on the generator manual.
GT model - GE Frame 9E
Generator model - GEC Alsthom T240-370

1. During turbine s/up - coupling face (between load shaft and generator) will shift toward turbine 7.46mm

2. During full load steady state - coupling face (between load shaft and generator) will shift toward generator 10.3mm and generator expansion is 6mm.

3. During turbine s/down - coupling face (between load shaft and generator) will shift toward generator 18.16mm

I don't understand this as GT thrust clearance is only 0.5-0.7mm.

 

The turbine rotor and the turbine casing expand together as the gas turbine heats up. Study how the turbine supports are connected to the base. I believe you will find it is firmly anchored at 1 point and free to slide at other support points. I don't have access to any of the drawings, and it is not my area of expertise, but I have heard this discussed in meetings once or twice.