Rotary kinetic fluid motors or pumps – With shaft connected fluid abutment member in sealing fluid...
Reexamination Certificate
1999-10-21
2001-06-12
Verdier, Christopher (Department: 3745)
Rotary kinetic fluid motors or pumps
With shaft connected fluid abutment member in sealing fluid...
C415S111000, C415S112000, C415S168400, C415S230000
Reexamination Certificate
active
06244816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a gland portion deformation preventing structure of a low pressure steam turbine and more particularly to a structure for preventing thermal deformation of the gland portion that is exposed to wet steam coming from an exhaust chamber.
2. Description of the Prior Art
FIG. 3
is a cross sectional view of a half portion of a double flow type low pressure steam turbine, which is known in the prior art. In
FIG. 3
, numeral
1
designates a rotor and numeral
2
designates a gland portion periphery of the rotor
1
. Numeral
3
designates a gland casing, which surrounds the gland portion periphery
2
of the rotor
1
. Within the gland casing
3
, there is formed a passage (not shown) through which sealing steam for sealing the gland portion periphery
2
flows in or flows out. Numerals
4
,
5
designate a seal portion, which comprises a labyrinth seal, etc. and is disposed so as to oppose the gland portion periphery
2
. Thus, a gland portion is formed by the gland portion periphery
2
of the rotor
1
, the gland casing
3
and the seal portion
4
,
5
.
Numeral
6
designates a casing, which forms therein an exhaust chamber
7
. Numeral
8
designates a final stage stationary blade and numeral
9
designates a final stage moving blade. Numeral
10
designates a cavity, which is formed annularly between the exhaust chamber
7
and the rotor
1
. Two apparatuses consisting each of the mentioned parts and components are disposed symmetrically in the right and left direction of the rotor
1
in the figure and steam
20
flows therein from the central portion to flow separately into steam paths of the right and left blade portions for rotation of the respective rotors
1
.
That is, in the low pressure steam turbine constructed as mentioned above, the steam
20
of low pressure flows into the turbine portions from the central portion to flow through the steam paths wherein stationary blades and moving blades are disposed in multi-stages, including the final stage stationary blade
8
and the final stage moving blade
9
. While the steam
20
so flows through the steam paths, it works to rotate the rotor
1
and then flow out into the exhaust chamber
7
and further into a condenser (not shown) to be condensed to water.
In the mentioned low pressure steam turbine, in order to seal an inside of the casing
6
, where the steam flows, against an outside thereof in the gland portion periphery
2
of the rotor
1
at a downstream end portion of the casing
6
, sealing steam is led into the gland casing
3
to maintain a predetermined pressure therein and then the sealing steam flows out into the cavity
10
via the seal portion
4
,
5
, as shown by the arrows which indicate the steam
22
. Thereby the steam in the casing
6
is prevented from leaking outside along the gland portion periphery
2
.
On the other hand, while the steam, which has passed through the final stage stationary blade
8
and moving blade
9
and finished its work, flows out into the exhaust chamber
7
, a portion of the steam in the form of wet steam
21
may enter the cavity
10
through a gap
11
between the rotor
1
and a stationary portion of the exhaust chamber
7
, etc. This wet steam
21
, which has finished the work, is a low temperature steam having a high moisture content and cools portions of the seal portion
4
,
5
and the gland casing
3
which are heated by the sealing steam in the vicinity of the gland portion in order to cause deformation of the gland casing
3
, which, according to the extent of the deformation, causes the seal portion
4
,
5
to come into excessive contact with the gland portion periphery
2
of the rotor
1
so as to generate vibration there.
As mentioned above, in the prior art gland portion of the low pressure steam turbine, the wet steam
21
that has finished the work may enter the gland portion via the cavity
10
and partially cool the gland casing
3
and the seal portion
4
,
5
so as to cause the deformation of the gland portion, by which there arises the problem that the rotor
1
and the seal portion
4
,
5
make excessive contact with each other, as the case may be, thereby generating vibration at this location.
SUMMARY OF THE INVENTION
In view of the problem in the prior art, it is an object of the present invention to provide a countermeasure in a low pressure steam turbine for preventing wet steam, which may enter a cavity upstream of a gland portion, from further entering the gland portion so that a gland casing and a seal portion will not be cooled by the wet steam.
In order to achieve the mentioned object, the present invention provides the following means.
A gland portion deformation preventing structure of a low pressure steam turbine that is of a type in which a gland portion comprising a seal device and a gland casing for leading therein a sealing steam is provided between a rotor and an exhaust chamber and a wet steam flowing from the exhaust chamber through a gap at a base portion of a final stage moving blade is prevented from leaking outside from the gland portion. The present invention is characterized in that there is provided a ridge projecting in a predetermined width and height on and around an entire periphery of said rotor at a position between the gland portion of the rotor and the gap at the base portion of the final stage moving blade such that the wet steam flowing through the gap is prevented from flowing toward the gland portion so that deformation of the gland portion due to cooling by the wet steam may be prevented.
Also, the ridge has a cross sectional shape in a plane passing through an axis of the rotor of any one of a shape having smooth curved lines descending toward both sides from a top thereof, a semi-circular shape, a triangular shape having one apex in a top thereof and a quadrangular shape.
In the gland portion deformation preventing structure according to the present invention, there is provided the projecting ridge having a predetermined width and height on and around the entire periphery of the rotor at the position between the gap at the moving blade base portion and the gland portion and the wet steam which is going to enter the rotor side from the exhaust chamber side through the gap to flow toward the gland portion, which includes the gland casing and the seal portion, and strike the ridge of the rotor. Also, there is a centrifugal effect following the rotation of the rotor, and thereby the wet steam flows in a swirling pattern in front of the ridge and does not reach the gland portion. Also, water in the wet steam, attached to the ridge, scatters therearound due to the rotation of the rotor before it reaches the gland portion and is discharged outside via a drain.
In the prior art gland portion, the wet steam flows into the gland casing and the seal portion of the gland portion, and thereby the gland portion, which is heated by the sealing steam is partially cooled by the water contained in the wet steam to cause a deformation thereof so that the seal portion and the rotor may contact excessively with each other to generate vibration. In the present invention, the ridge is provided, and thereby the wet steam is prevented from flowing to the gland portion and the vibration caused by the deformation of the gland portion can be prevented.
REFERENCES:
patent: 0 752 515 (1997-01-01), None
patent: 0 919 698 (1999-06-01), None
patent: 2 594 176 (1987-08-01), None
patent: 63-205404 (1988-08-01), None
Mitsubishi Heavy Industries Ltd.
Verdier Christopher
Wenderoth , Lind & Ponack, L.L.P.
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