JP2600955B2 - Double-flow steam turbine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a double-flow steam turbine in which steam flowing from a steam inlet of a casing is divided into two directions and flows through paragraphs on both sides of the steam inlet to expand. In particular, the present invention relates to the structure of a first-stage stationary blade row of a steam inflow section.

[Conventional technology]

The double-flow steam turbine is configured such that steam flowing from a steam inlet of a casing is divided into two directions, and a stationary blade of a stationary blade row provided on a casing on both sides of the steam inlet and a rotor blade of a rotor row provided on an axle. Work is performed by flowing through a plurality of stages of stages formed by the steam turbine. As a structure of the first stage stationary blade row portion of the steam inflow section, steam flowing into the first stage stationary blade row is FIGS. 3 (see Japanese Patent Application Laid-Open No. 1-163405) and FIG. 4 are known to prevent leakage from the gap between the front end of the vehicle and an axle facing the front end.

In FIG. 3, a plurality of rows of stationary blades including stationary blades 3 are provided in the casing 1 on both sides of the steam inlet 2 of the casing 1. The axle 4 is provided with a plurality of rows of moving blade rows including the stationary blades of the stationary blade row and the moving blades 5 forming a paragraph. 6,
Reference numeral 7 denotes a first-stage stationary blade row of the steam inflow section, and shroud plates 8 and 9 are attached so as to cover the tips of the stationary blades of the stationary blade rows 6 and 7, and a gap between the shroud plates 8 and 9 is provided. A bridge piece 12 is mounted over which is fastened with a bolt 11 via a spring 10.

With such a structure, the steam flowing from the steam inlet 2 is connected to the bridge piece 12 and the shroud plate connected thereto.
The steam is divided into two directions by 8, 9 and flows into the paragraphs on both sides of the steam inlet 2. At this time, the bridge piece 12 and the shroud plates 8, 9
From the gap between the tip of the first stage vane row and the axle,
This prevents the steam flowing into the stator blade row of the stage from leaking.

In FIG. 4, the shroud 13,
A labyrinth fin 15 is provided on 14 and this labyrinth fin is
A flow guide 17 is provided to cover the tips of the stationary blade rows 5 and 6 with a gap from the flow guide 17.

With such a structure, the steam flowing in from the steam inlet 2 is divided into two directions by the flow guide 17 and flows to the paragraphs on both sides of the steam inlet 2, and at this time, the labyrinth fin 15 leaks from the tips of the stationary blade rows 6 and 7. Seals steam.

[Problems to be solved by the invention]

In the prior art shown in FIG. 3, since the shroud plates 8, 9 and the bridge piece 12 are fastened via the spring 10, when the spring expands in the axial direction and the radial direction due to thermal expansion during the operation of the turbine, the spring is closed. The first stage stationary blade row 6,
There is a problem that it is transmitted to the stationary blade of No. 7 and adversely affects the strength and deformation of the stationary blade row and stationary blade.

In the prior art shown in FIG. 4, an appropriate gap must be provided between the labyrinth fin 15 provided on the shrouds 13 and 14 and the flow guide 17 in consideration of thermal expansion during turbine operation and thermal deformation of each member. However, there is a problem that steam leaks from this gap to cause loss of steam leakage, which is not preferable in terms of performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a double-flow steam turbine which does not adversely affect the first-stage stationary blade row even if it expands in the axial direction and the radial direction due to thermal expansion during turbine operation and can prevent steam leakage. It is to be.

[Means for solving the problem]

In order to solve the above-mentioned problem, according to the present invention, on both sides of a steam inlet of a casing provided with a plurality of stationary blade rows composed of stationary blades, the stationary blade is formed on the both sides of a steam inlet and a plurality of rotor blade rows provided on an axle. A double-flow steam turbine having a plurality of stages, wherein the steam flowing from the steam inlet is divided into two directions and flows through the two stages to expand. In the turbine, a shroud plate that covers the tip of each of the first-stage stationary blade rows on both sides, and a flow guide ring that closes between the two shroud plates via an L-shaped split airtight ring. Shall be provided.

[Operation] A steam inflow portion through which steam flows in from a steam inlet has a shroud plate that covers the tip of the first stage stationary blade row on both sides of the steam inlet in the casing, and between the two shroud plates. And a flow guide ring that closes the steam flow through an airtight ring, the steam flowing from the steam inlet is divided into two directions by the flow guide and the shroud plate and flows into the first row of stationary vanes on both sides. However, at this time, since the shroud plate and the flow guide ring are joined by an airtight ring, thermal expansion during turbine operation is absorbed by the airtight ring, and leakage of steam is prevented.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial sectional view of a steam inflow portion of a double-flow steam turbine according to an embodiment of the present invention. In FIG. 1 and FIG. 2, which will be described later, the same parts as those in the conventional example shown in FIGS. In FIG. 1, shroud plates 20 and 21 are attached so as to cover the tips of the first stage stationary blade rows 6 and 7, and a flow guide ring 22 is provided so as to close between the shroud plates 20 and 21. ing. As shown in FIG. 2, the shroud plates 20, 21 and the flow guide ring 22 have an annular groove formed in the shroud plate 21 with an L-shaped split airtight ring 23.
24 and an annular groove 25 provided in the flow guide ring 22 are inserted and joined. The shroud plate
An airtight ring 23 is provided on the 20 side in a similar structure. The flow guide ring 22 has a split structure, and is supported by the casing 1 by a support (not shown).

With such a structure, the steam flowing from the steam inlet 2 allows the shroud plates 20, 21 covering the tips of the first stage stationary blade rows.
And flow into the first stage stationary blade rows 6 and 7 on both sides by the flow guide ring 22, but there is no steam leaking without flowing into the stationary blade rows 6 and 7 by the airtight ring 23. Also, thermal expansion during turbine operation can be absorbed.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, the space between the shroud plates covering the tips of the first stage stationary blade rows on both sides of the steam inlet of the casing is closed by the flow guide ring via the airtight ring. Thus, the steam flowing from the steam inlet can eliminate leaked steam that does not flow into the first row of stationary blades by the hermetic ring, and thermal expansion in the axial and radial directions during turbine operation is absorbed. The soundness of the structure of the one-stage stationary blade row can be ensured.

[Brief description of the drawings]

1 is a partial sectional view of a double-flow steam turbine according to an embodiment of the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, FIG. 3 is a partial sectional view of a conventional double-flow steam turbine, FIG. The figure is a partial sectional view of a different conventional double-flow steam turbine. 1: casing, 2: steam inlet, 3: stationary vane, 4: axle, 5: rotor blade,
6, 7: stationary blade row, 20, 21: shroud plate, 22: flow guide ring, 23: airtight ring.

Claims (1)

(57) [Claims] 1. A stage having a plurality of stages formed by said stationary blades and a plurality of rotor blades of a plurality of rotor blade rows provided on an axle, on both sides of a steam inlet of a casing having a plurality of stator blade rows comprising stator blades. ,
In a double-flow type steam turbine in which steam flowing from a steam inlet is divided into two directions and flows through the paragraphs on both sides and expands, a shroud plate that covers the tip of each stationary blade row of the first stage on both sides, A double-flow steam turbine comprising a flow guide ring which closes between both shroud plates via an L-shaped split airtight ring.