JPH0366484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in steam turbine nozzle boxes.

In a steam turbine, a set of a stationary blade row and a rotor blade row constitutes a stage, and these are housed in a vehicle compartment.
The first stage of a steam turbine is called the governor stage.
The nozzles of the governor stage are generally divided into a plurality of groups, each group being connected to one or two steam control valves.

This is an essential structure for implementing a nozzle speed control system that can minimize the throttling loss of the steam control valve during partial loads and increase the efficiency of the speed control stage.

In the above nozzle speed regulating system, the number of steam control valves that open increases as the output of the steam turbine increases,
Along with this, the number of nozzle groups through which steam flows increases.

In this way, there are situations where steam flows to some groups of nozzles and not to other groups, so in order to prevent excessive thermal stress from occurring in turbines with high temperature and high pressure steam conditions, the nozzles are flexibility by making each group independent
It is made to have.

The portion of the inlet steam chamber containing a group of independent nozzles as described above is referred to as a nozzle box.

Examples of such nozzle boxes are shown in Figures 1a and b.
and shown in Figures 2a and b. FIGS. 1a and 1b show an 8-valve nozzle box, and FIGS. 2a and 2b show a 4-valve nozzle.

In FIG. 1, an inner compartment 7 is installed inside an outer compartment 13, and a flexible skirt 8 is installed inside the inner compartment 7.
through nozzle boxes 1, 2, 3, 4, 5, 6
is installed. and each nozzle box 1
- 6 are mutually independent from the other nozzle boxes 1 - 6 and the inner compartment 7. In addition, each nozzle box 1
Main steam inlet pipes 14, . . . are inserted into the nozzle boxes 1 to 6, and are connected to the nozzle boxes 1 to 6.

In FIG. 2, the vehicle compartment is divided into an upper vehicle compartment 15 and a lower vehicle compartment 16. Similarly, nozzle boxes 1, 2, 3, and 4 are installed inside the upper vehicle compartment 16 via a flexible skirt 8. Each nozzle box 1 to 4 is mutually connected to other nozzle boxes 1 to 4.
4, an upper compartment 15, and an lower compartment 16.
In addition, each nozzle box 1 to 6 has a main steam inlet pipe,
... are inserted and connected to nozzle boxes 1 to 4.

As mentioned above, since each nozzle box is independent from other nozzle boxes and the casing, it can thermally expand independently, reducing thermal stress.

On the other hand, the base point of thermal expansion of the nozzle boxes 1 to 6 is the tip of the flexible skirt 8 of the upper compartment 15 or the lower compartment 16, so the inner compartment 7 or the upper compartment 15 or the lower compartment 16 and nozzle box 1~
The difference in temperature causes a difference in thermal expansion, and the position of the nozzle differs between the cold state and the hot state.

In addition, in FIG. 1, upper and lower nozzle boxes 1 and 4, left and right nozzle boxes 2, 3, 5, 6,
In FIG. 2, in the case of the nozzle box on the exit compartment 16 side, the direction of relative displacement (difference in expansion) of the nozzle 11 with respect to the rotor 10 is different between the lower part 17 and the side part 18.

This causes problems in setting the clearance between the rotor 10 and the nozzle boxes 1 to 6 and in setting the step-up (radial step) between the nozzle 11 and the rotor blades 12. In other words, it is necessary to take this into consideration in the upper and lower nozzle boxes (1 and 4 in Fig. 1) or the lower part of the nozzle box (17 in Fig. 2), where there is a large difference in radial expansion in both play and step-up.
There is little need for consideration in the left and right nozzle boxes (2, 3, 5, 6 in FIG. 1) or the lateral portions of the nozzle box (18 in FIG. 2) where the difference in elongation occurs in the circumferential direction rather than in the radial direction.

However, since processing is uniformly carried out in a cold state, the play and step-up must be increased, resulting in a loss in performance.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a nozzle box for a steam turbine that allows the nozzle box to thermally expand around the turbine shaft without losing its flexibility.

In order to achieve the above object, the nozzle box for a steam turbine of the present invention is a steam turbine in which a plurality of nozzle boxes are provided inside the passenger compartment, and a main steam inlet pipe is inserted and fixed into the nozzle box. There is flexibility between the two, and
Each nozzle box is supported within the vehicle interior by an axially symmetrical flexible support.

Embodiments of the present invention will be described below with reference to the drawings. Note that parts that are the same as those shown in FIGS. 1 and 2 are designated by the same reference numerals.

As shown in FIGS. 3a and 3b, an inner compartment 7 divided into two parts is installed concentrically within an outer compartment 13 divided into two parts, and a nozzle box 1 divided into four parts is installed inside the inner compartment 7. , 2, 3, and 4 are provided. Note that the nozzle box may be divided into an appropriate number other than four.

Further, instead of the outer compartment 13 and the inner compartment 7, only a single compartment may be used.

Each of the nozzle boxes 1 to 4 maintains flexibility independently of the other nozzle boxes and the inner compartment 7.

Further, in the nozzle boxes 1 to 4, there are nozzle blocks 19 having nozzles 11 facing the rotor blades of the speed governor stage.
is installed.

As shown in FIG. 4a, a dummy ring 20 or a blade ring is installed inside the inner vehicle chamber 7, and each nozzle box 1 to 4 is connected to four flexible plates 21, 2.
2, 23, and 24 to attach it to the dummy ring 20 or the blade ring. Note that whether to attach the dummy ring 20 or the blade ring depends on whether or not the governor stage is reversed.

As shown in FIGS. 4b and 4c, the flexible plates 21, 22, 23, 24 are arranged symmetrically about the axis of the rotor 10. And flexible plate 2
1 and 22 position the nozzle boxes 1 to 4 in the circumferential direction. Here, the difference in elongation in the radial direction between the nozzle boxes 1 to 4 and the dummy ring 20 or blade ring is absorbed by the bending of the flexible plates 21 and 22. Further, the flexible plates 23 and 24 position the nozzle boxes 1 to 4 in the radial direction. And nozzle boxes 1 to 4 and dummy ring 20
Alternatively, the difference in elongation of the blade ring in the circumferential direction is absorbed by the flexible plates 23 and 24 being bent. Note that 33 is a tightening bolt for the nozzle block 19.

As another embodiment, instead of the four flexible plates 21-24, two
flexible plates 25, 26 and T-shaped groove 2
7 can also be combined.

That is, T-shaped grooves 27 are provided in the nozzle boxes 1 to 4, and T-shaped protrusions 2 are provided on the dummy ring 20 or the blade ring at positions corresponding to the T-shaped grooves 27 in each nozzle box 1 to 4.
8 will be provided. On the other hand, two flexible plates 25 and 26 are placed between each nozzle box 1 to 4 and the dummy ring 20 or the T-shaped groove 27 and T-shaped protrusion 28 of the blade ring, and are arranged symmetrically about the axis of the rotor 10 and in the radial direction. Set up

Then, the T-shaped groove 27 is fitted into the T-shaped protrusion 28 to fix the positions of the nozzle boxes 1 to 4 in the circumferential direction. Here, the difference in radial elongation between the nozzle boxes 1 to 4 and the dummy ring 20 or blade ring is absorbed by the T-shaped groove 27 and the T-shaped protrusion 28 sliding. Further, the flexible plates 25, 26 fix the radial positions of the nozzle boxes 1-4. The difference in elongation in the circumferential direction between the nozzle boxes 1 to 4 and the dummy ring 20 or blade ring is determined by two flexible plates 2.
5 and 26 are deflected.

In FIGS. 3a and 3b, each nozzle box 1 to
A hole 20 for the main steam inlet passage is provided at the center of the outer periphery of 4. The main steam inlet pipe 14 is installed in the radial direction passing through the outer casing 13 and the inner casing 7 (or the outer casing 13 if there is a single casing), and its tip is inserted into the hole 29 on the outer periphery of the nozzle box. , are sealed by piston rings 30. Further, the main steam inlet pipe 14 is attached via the flexible skirt 8 to a flange 31 provided on the outside of the outer compartment 13 with bolts 32.

If there is an inner casing 7, the main steam inlet pipe 14 passes through a radial hole 33 provided in the inner casing 7;
Sealed by piston ring 34.

Note that since the main steam inlet pipe 14 is installed in the radial direction, when assembling the turbine, the inner casing 7,
And after assembling the outer compartment 13, the main steam inlet pipe 14
Insert.

With the above configuration, steam is supplied to each nozzle box 1-4 through the main steam inlet pipe 14, as shown in FIGS. 3a and 3b. Each nozzle box 1 to 4 is completely independent, so when steam is introduced into the speed control stage, the nozzle box into which steam is introduced can thermally expand independently, and the nozzle into which steam is not introduced No thermal stress occurs due to the temperature difference with the box.

In addition, the nozzle boxes 1 to 4 are provided with four flexible plates 21 to 24 or two flexible plates as shown in FIG.
The flexible plates 25 and 26 are connected to the T-shaped groove 2.
7 is attached to the dummy ring 20 or the blade ring symmetrically to the axis of the rotor 10.
The center does not shift even when thermally expanded.

Furthermore, since the main steam inlet pipe 14 is installed radially symmetrically with respect to the outer casing 13, the inner casing 7, and the nozzle boxes 1 to 4, the main steam inlet pipe 14 and the nozzle boxes 1 to 4 are The relationship between the steam inlet hole 29 and the hole 33 of the inner casing 7 remains concentric with no difference even if thermal expansion occurs.

As mentioned above, the thermal expansion of each part becomes completely axially symmetrical, which has the effect of maintaining flexibility and forming a nozzle box without distortion, thereby improving the performance of the turbine.

[Brief explanation of drawings]

Figure 1a is a cross-sectional view of a conventional 8-valve nozzle box in a direction perpendicular to the turbine axis, and Figure 1b is a cross-sectional view of a conventional 8-valve nozzle box.
FIG. 2a is a partial sectional view of a conventional four-valve nozzle box in the direction perpendicular to the turbine axis, and FIG. 2b is a cross-sectional view taken along the turbine axis along line B-- B sectional view, FIG. 3a is a sectional view of a nozzle box according to an embodiment of the present invention in a direction perpendicular to the turbine axis, and FIG. 3b is a sectional view taken in the turbine axis direction C in FIG. 3a.
-C sectional view, Figure 4a is an exploded perspective view showing how to attach the nozzle box using four flexible plates, and Figure 4b is a partial front view showing the flexible plate attached to the nozzle box.
Fig. 4c is a partial sectional view in the axial direction of the turbine showing the relationship between the nozzle box, the flexible plate, and the dummy ring or blade ring, and Fig. 5 is a sectional view taken along the line D-D in Fig. c. FIG. 7 is an exploded perspective view of another embodiment showing a method of attaching a nozzle box using a plate. 1, 2, 3, 4, 5, 6... nozzle box,
7...Inner compartment, 8...Flexible skirt, 9
... Tip of the flexible skirt, 10 ... Rotor, 11 ... Nozzle, 12 ... Moving blade, 13 ... Outer casing, 14 ... Main steam inlet pipe, 15 ... Upper casing,
16... Getting off chamber, 17... Lower part of nozzle box, 18... Side part of nozzle box, 19... Nozzle block, 20... Dummy ring, 21, 22,
23, 24, 25, 26...Flexible plate, 27...T-shaped groove, 28...T-shaped protrusion, 29,
33... Hole, 30, 34... Piston ring, 3
1...Flange, 32...Bolt, 33...Bolt.

Claims (1)

[Claims] 1. Install multiple nozzle boxes on the inside of the vehicle,
In a steam turbine in which a main steam inlet pipe is inserted and fixed in the nozzle box, the nozzle boxes are flexible, and each nozzle box is supported within the cabin by an axially symmetrical flexible support. A steam turbine nozzle box characterized by: