details.htm

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Turbine/Generator Details

This page provides details of turbine3 as it was disassembled for normal maintenence overall. First of all, here is the link of the photo from the Power Plant Home Page in case you want to review it at any time (turbine3).

Steam flow can be shut off to the turbine. For example, here is the stem from the shut-off valve for turbine3.

Overall Schematic

Here is an artist's rendering of the cross-section of a general turbine.

In the drawing, the steam enters on the right and flows to the left. Many close-ups of the parts in this drawing will be shown for turbine3 later on this page. (Turbine3 is not exactly like this drawing, but the basic features are the same). Details to look for:

The speed of the turbine is held closely to 3600 rpm in order to create 60 cycle alternating current. The speed governer is on the right of the picture and connected to the inlet valve. MSU uses electronic speed governers.
The steam passes through inlet gas nozzles to convert the enthalpy to high velocity.
In between each turbine blade are stators. In the drawing, you can see them spanning the space between the housing and the shaft. Stators are filled with curved nozzles to convert the enthlpy of the low velocity steam coming off the blade back into kinetic energy before implelling on the next blade.
In this drawing, steam passes through four turbine blades on the rotor, and then can be extracted from the large valve on center of the housing. The rate of steam extraction is controlled by the throttle valve. (You won't see this extraction valve on turbine3 pictures later because it doesn't have steam extraction).
After the extraction valve, steam passes through ten more turbine blades.
The outlet of a turbine is often at very low pressure, especially in a condensing turbine, and the outlet is very large to avoid creating pressure drop. The condenser would be attached directly below the outlet.
The shaft of the turbine passes out the right end of the turbine housing, and would be connected to a generator.

Rotor and Turbine Blades

Blades. You might be interested in first seeing the turbine blades.
Blades - in this photo, look for the12 blade sets from the outlet end. The inlet end is on the left. The blades are on the outer edge on the outer edge of the rotor only. With the exception of the first disc, the rotor discs increase in size from the inlet to the outlet. Also note that the size of the blades and spacing increases from left to right.
Inlet view - note the blades look a little different from this view because they are curved.
Blade closeup - The increase in size of the downstream blades is obvious, although the curvature is hard to discern. Because of the curvature, each blade was individually machine before being assembled on the disc!

Inlet End. The shaft at the inlet end is highly polished were it turns on bearings and is sealed. The smaller diameter region that is covered by a cloth is where the bearings will go. The screw pitch on the end drives a gear connected to the oil pump that continuously pumps oil to the bearings. The brass knob that you see is an overspeed key that will pop out by centrifugal force if the turbine goes overspeed. This will shut the steam flow and disengage the turbine allowing it to run free as it speeds down.

Outlet End. The shaft at the outlet end is very long to accomodate the large steam exit. At the very end is the flange where the generator rotor will be bolted. The flange has gear teeth that aren't engaged at high speed. The gear teeth are used when the turbine is taken off-line but is still hot. The turbine is slowly rotated to prevent the rotor from developing warpage!

Lubrication. The rotor rides on bearings. The rotor rides on a layer of oil that is continuously pumped through them. The oil pump runs from the screw pitch on the rotor shaft as described above on the Inlet End section. The bottom of the picture shows the screened inlet of the pump that is normally immersed in an oil reservoir. The outlet of the centrifugal pump is the flange just above the screened inlet.

Turbine Housing and Stators

Housing. Before looking at the turbine housing apart, review this photo from the Power Plant Home page looking down on the totally assembled turbine3 from the second level. When turbine3 was taken apart, the shroud and top half of the housing was removed, and this is the view from about the same spot of the lower housing. The stators have been removed but the channels where they fit are visible. The steam outlet is protected by a gray covering to keep things from dropping into the condenser and will be more visible in the picture of the upper housing.
Governor - This closeup shows the speed control device.
Lower Channel Closeup - Notice the wide channel for the first blade, and the size of the bolts used to close the housing. All stators have been removed in this photo.
Upper Channel Closeup - The first stator is still in the housing (note nozzle openings) although the others have been removed, giving a good idea of how the rest would look in place. Compare the first channel with the Lower Channel Closeup.
Upper Housing - A view from a few feet away showing the overall appearance and the steam outlet.
Steam Outlet - A closeup of the steam outlet on the upper housing.

Stators. The stators shown here are removed from the turbine and are resting on wooden pallets. The stator that is shown is the smallest one near the outlet of the turbine. The stators are split in half to enable them to be inserted in the housing before the two halves are closed over the rotor.
Inlet - The leading edge of the nozzles are rounded.
Inlet Closeup - The rounded leading edge and the curvature of the nozzles are apparent.
Outlet - The outlet side of the same stator. Note the outlet flow is directed to the side to impel on the turbine blades at the correct angle at high velocity. Although not apparent from the photos, the nozzles converge as they curve to the outlet side which leads to the acceleration of the steam.
Outlet Closeup - Shows more detail of the outlet.

Throttle Valves. Inlet flow to the turbine is regulated with a series of staged throttle valves on a cam shaft. The cams are aligned so that as the shaft turns, the valves are succesively raised. The valve stems can be seen more clearly in the closeup. Note the differences in size of the stems. You might review the overhead photo of assembled turbine3 to see them as they sit when assembled.

Generator

Coil - The rotor from the generator has been removed in this shot, which shows the coils.
Coil End View - looking down the "tunnel" of the coils.
Rotor - The generator rotor. The turbine shaft bolts on at the far end.
Rotor End Closeup - The flange where the turbine shaft bolts on.

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