Single quill shaft in gas turbine power transmission 1

[Meshry]

In Frame-5 Gas Turbine, Load gearbox is equipped with a single quill shaft drive. it is a FLENDRGRAFF gearbox.
I need to understand, what is the advantage of quill shaft power transmission? why cannot we use a normal parallel gear unit?
also could not under stand how the quill shaft is connected to the gear shaft (i.e. Hollow shaft). is it by means of spline or drive plate?

I need your help please.
Thanks

 

[Hoxton]

I know this configuration. For the GE Frame 5, the turbine is on its bed plate and the gearbox and generator is on a separate bedplate.

The gearbox reduces the turbine speed (5100 rpm) to generator speed 3000 rpm in most of the world, 3600 rpm in those 60Hz areas.

I cannot remember how the turbine is coupled to the gearbox, but the generator is coupled to the quill shaft, this passes through a concentric hole through the driven gear and is connected to the low speed gear at the other end of the gearbox to the generator, correct?

A quill shaft is one form of flexible coupling, there are many types and each has advantages and disadvantages. The quill shaft type allows some radial misalignment and the relatively long shaft can allow some tuning of the torsional response.

The fact that the coupling is buried inside the gearbox means that the system is very compact.

The Frame 5 was built by GE at Schnectady USA and also by several (I nearly wrote many!) Manufacturing Associates wold wide. These included:

AEG Germany
Alsthom France
John Brown Scotland
Hitachi Japan
Thomassen Holland
Kvaerner Norway.

Each could select their own generator and gearbox. So heir are many gearboxes out there from various manufacturers, but all, to my knowledge used the parallel gearbox, with internal quill shaft design.

I think that the quill shaft is attached to the gear by a solid coupling, but am not 100% share.

One other advantage of this system was that the generator could be operated as a synchronous compensator (condenser) by the relatively simple addition of a clutch at the gear end of the quill shaft.

 

[Meshry]

Thanks Hoxton for your reply.
herewith I have attached the drawing for better understanding.
In some manuals it is mentioned; the purpose of the quill shaft drive is to absorb the axial movement of both units. still this is not clear for me.
also cannot figure out how the quill shaft is connected to the hollow gear shaft!! is it spline coupling?
can you throw more light one the torsional response as advantage of the quill shaft arrangement?
Thanks

 

[Hoxton]

Sorry about some spelling mistakes in my earlier reply.

"the purpose of the quill shaft drive is to absorb the axial movement of both units". I do not think that this is the case. The gearbox will act as a locator (sorry cannot think of a better word) for both high speed (turbine) and low speed (generator) shafts.

High speed. If you look at item 305, someone has written 'tilt pads' on the drawing. these form a thrust bearing,320 and 305 are journal bearings which support the high speed pinion gear 1. The thrust bearing locates the high speed shaft system. It is located at the best point in the shaft system, since these gears are helical, which gives many advantages (google it!) but results in some thrust from the gear, so there needs to be a thrust bearing to locate the gear, as close to it as possible.

The turbine drive shaft is bolted to the flange at the left hand end of 320. So the turbine is also located by the tilting pad thrust bearing and will grow to the left.

Low speed. The generator driven flange is bolted to the drive flange at the right hand side of the low speed shaft (marked 'LS' on the drawing). The low speed shaft system is located at the bearing 315, someone has circled what I assume are the thrust faces.

Going back to your questions:

Why a quill shaft? No doubt someone sat down and looked at all the options and decided that this was the most effective way to do this. Please remember that this turbine has a firing temperature of about 800 C and an exhaust temperature of about 500 C. At rest it will be at say 20 C, As the turbine starts and reaches operating temperature, the turbine shaft will move upwards. The shaft system has to remain in alignment and so this is accounted for when the set is installed. The quill will absorb any minor misalignments. From memory, the whole shaft system is a catenary, and the gearbox is 'low' i.e. sits at the bottom of the curve, the generator non drive end bearing is 'high', as is the turbine non drive end bearing.

Spline coupling? I do not think so, looking at 210 and 212, I think that the drawing shows a parallel connection, i.e. 210 is heated up and shrunk fitted onto 212. (Don't try getting it off again!). I think 213 214 are an end plate and locking pin. there may be three pins.

I think that the diagram and table at the right hand side (above 'characteristiques') are the alignment instructions.

That’s about all I can deduce and remember. These shaft systems can be extremely complex system to engineer and can have some difficult operating problems.

As my Technical Director once said: “Anyone with high speed rotating shaft systems will have problems. The object is to get the customer to understand this!”

 

[Meshry]

Dear Hoxton,
For some reason, I have just seen your great reply.
Many thanks for the elaborated answer.

 

[Pete_K]

To me, the drawing indicates that 210 has internal spline and that the input shaft (with the integral flange at the right side) is allowed some axial movement. Found some reference to this allowing for the generator rotor to maintain magnetic center. Just my assumption/opinion from a quick look at your drawing, i have no experience with these units.