JPH0849501A - Steam turbine - Google Patents

Abstract

PURPOSE:To improve the layout of stationary blades, give sufficient compressive strength to the stationary blades, reduce flow loss, and improve performance in the speed governing stages of a steam turbine. CONSTITUTION:The steam guided to a ring-like passage 6 from a steam inlet pipe 2 is guided to multiple speed governing stages of a steam turbine via multiple speed governing stage stationary blades 4a, 4b arranged in the peripheral direction. The layout in the peripheral direction of the speed governing stage stationary blades 4a in the region facing the steam inlet pipe 2 is made dense, and the layout in the peripheral direction of the speed governing stage stationary blades 4b in the region apart from the steam inlet pipe 2 is made coarser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine capable of improving the reliability and performance of a nozzle box and a speed control stage.

[0002]

2. Description of the Related Art In a conventional steam turbine, as shown in FIGS.
As shown in FIG. 1, after the high-pressure, high-temperature steam 1 supplied from the boiler is guided to the nozzle box 3 having the ring-shaped passage 6 through the steam inlet pipe 2, it is adjacent to the ring-shaped passage 6 integrally with the nozzle box 3. When passing through the speed-regulating stage stationary blades 4 and the speed-controlling stage moving blades 5, which are concentrically arranged with the ring-shaped passage 6, and the plurality of rows of stationary blades and the moving blades disposed downstream thereof. To
Turbine output is generated by reducing pressure and temperature.

[0003]

As shown in FIG. 5, the conventional speed-control vanes 4 are arranged with the same profile at equal pitches 8 in the circumferential direction. On the other hand, the nozzle box 3 has a ring-shaped passage 6 whose cross-section in the circumferential direction has a notch at the inlet of the speed control vane 4, but the steam inlet pipe 2 extends vertically in a part of the circumferential direction. Since they are joined, the joint portion of the ring-shaped passage 6 has a structure having an opening 7.

The nozzle box 3 having the ring-shaped passage 6 has a supercritical pressure turbine of about 240 kg / cm ² ,
Since high-pressure and high-temperature steam of 540 ° C. acts, the blade-height direction tensile force due to the internal pressure and the bending stress due to the expansion of the vapor also act on the speed-control vanes 4 structurally integrated with the nozzle box 3.

At the joint portion of the steam inlet pipe 2 of the nozzle box 3, the ring-shaped passage is partially open, so that the rigidity against internal pressure is weak and the steam inlet portion is provided. The steam force acting on is larger than that of the speed-control stage stationary blades 4b arranged in the other circumferential direction. Therefore, the speed control stage stationary blade 4a in the joint area of the steam inlet pipe 2 is stricter than the other speed control stage stationary blades 4b in terms of strength.

On the other hand, the speed control vane 4b in a region away from the joint with the steam inlet pipe 2 has a high rigidity because it has no opening and a small steam inflow amount, so the steam power is small. Moreover, as shown in FIG. 5, the steam 1a flows in directly to the speed control vanes 4a at the joint with the steam inlet pipe 2, whereas the ring-shaped passage 6 is surrounded by the circumference of the ring-shaped passage 6 in the region away from the joint. Since it branches left and right in the direction, the flow of the steam 1b having a large incident flows into the speed control vane 4b in this region without directly confronting it. Thus, when the flow of the steam 1b having a large incident flows into the speed control vane 4b,
As shown in FIG. 6, the flow loss (incident loss) in the speed control vane 4b increases. In addition, in FIG. 6, i shows the incident of the flow of steam.

Therefore, in the speed-control vanes 4a arranged at equal pitches, the speed-control vanes 4a in the joint region with the steam inlet pipe are severe in strength, and the speed-control vanes 4b in the region away from the joint have flow loss. It is feared that this will increase and adversely affect the reliability and performance of the turbine.

The present invention is intended to provide a steam turbine which can solve the above problems.

[0009]

According to the present invention, the steam introduced from the steam inlet pipe to the ring-shaped passage of the nozzle box is circumferentially arranged, and the speed is adjusted via a plurality of speed-control vanes integrated with the nozzle box. In the steam turbine guided to the stage rotor blades, the arrangement of the speed-control stage stationary blades in the circumferential direction is not dense in the region directly facing the steam inlet pipe, and is roughened as the distance from the steam inlet pipe increases.

[0010]

In the area directly facing the steam inlet pipe of the nozzle box, the number of speed-control stage stationary vanes is larger than in the conventional case in which the pitch is arranged. Therefore, each stationary vane is controlled by the internal pressure acting on the ring-shaped passage. The tensile force of the blade in the blade height direction is small,
In addition, the bending stress due to the expansion of steam is also reduced.

On the other hand, in the area away from the area directly facing the steam inlet tube, the load on the strength is conversely light as described above,
Even if the speed control stage stationary blades are arranged roughly, sufficient pressure resistance can be achieved, and since the pitch between the speed control stage stationary blades is large, the flow controllability is good even if there is an incident in the steam flow. The loss is small.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram in which a speed control vane according to the present embodiment is developed on a cylindrical surface at the same radial position.

In this embodiment, in the steam turbine shown in FIGS. 3 and 4, the speed control vanes are arranged as described below. The steam inlet pipe 2, the ring-shaped passage 6, the steam inlet pipe 2 and the nozzle are arranged. The opening 7 at the junction of the boxes is no different.

In this embodiment, the speed control vanes 4a in the region directly facing the steam inlet pipe 2 are arranged with a small pitch 8a so that the circumferential direction of the vanes 4a is dense, and a large number of blades are arranged. The pitch 8b is gradually increased and the number of blades is reduced so that the speed-control stage stationary blades 8b become coarser as the distance from the right and left increases. Specifically, the number of speed control vanes is about 10 to 10 as compared with the cases shown in FIGS.
It is set to reduce by 20%.

In the region directly facing the steam inlet pipe 2 in which the rigidity is lowered due to the presence of the opening 7 in a part of the ring-shaped passage 6 due to the existence of the steam inlet pipe 2, the number of the speed control vanes 4a is as described above. Since the rigidity is increased by increasing, the pressure resistance is increased, and the reliability of the nozzle box and the speed control stage can be improved.

On the other hand, since there is no opening 7 in the ring-shaped passage 6 in the region away from the steam inlet pipe 2, the rigidity is sufficiently high and the load acting on the speed control vanes is relatively small. Even if the number of the stationary vanes 4b is reduced by roughening the arrangement of the above, the pressure resistance can be sufficiently increased.

Further, in this region, the steam flow 1b has an incident that does not directly face the speed control vane 4b, but as shown in FIG. 5, by increasing the pitch 8b of the speed control vanes 4b, the flow of the flow is increased. Since the controllability is improved, FIG.
As shown in, there is an effect that the incident loss is reduced.

Further, according to the blade row experiment of the present inventor, the influence of the number of stationary blades (the number of nozzles) on the blade row performance in the steam turbine nozzle is as shown in FIG. According to this experimental result, it is shown that the blade row loss can be reduced by 1 to 2% if the speed control vane is reduced by 10%. Therefore, in the present embodiment, by disposing the speed control vane 4b roughly as it moves away from the area directly facing the steam inflow pipe 2, the flow loss due to the speed control vane 4b is reduced and the performance of the speed control stage is improved. be able to.

From the above results, in this embodiment, the reliability and performance of the speed control stage and the turbine as a whole can be improved.

[0020]

As described above, according to the present invention, the arrangement of the speed control vanes in the circumferential direction is made dense in the region directly facing the steam inlet pipe and becomes coarser as the distance from the steam inlet pipe increases. In addition, it is possible to secure the necessary pressure resistance around the ring-shaped passage and reduce the flow loss due to the speed control vanes, thus improving the reliability and performance of the speed control stage and the turbine as a whole.

[Brief description of drawings]

FIG. 1 is a development view of a portion of a speed control vane according to an embodiment of the present invention.

FIG. 2 is a graph showing how the number of stationary blades in a steam turbine nozzle affects blade row performance.

FIG. 3 is an elevation view showing a nozzle box and a speed control stage of a conventional steam turbine in a partial cross section.

FIG. 4 is a circumferential sectional view showing a nozzle box and a speed control stage of a conventional steam turbine.

FIG. 5 is a development view of a portion of a speed control vane of a conventional steam turbine.

FIG. 6 is a graph showing the relationship between the incident and the loss of the speed control vane.

[Explanation of symbols]

 1,1a, 1b Steam 2 Steam inlet pipe 3 Nozzle box 4,4a, 4b Speed control vane 5 Speed control blade 6 Ring passage of nozzle box 7 Ring passage opening 8,8a, 8b Pitch of speed control vane

Claims (1)

[Claims] 1. A steam turbine in which steam introduced from a steam inlet pipe to a ring-shaped passage of a nozzle box is circumferentially arranged and is introduced to a speed-control blade via a plurality of speed-control vanes integrated with the nozzle box. In the steam turbine, the arrangement of the speed control vanes in the circumferential direction is not dense in a region directly facing the steam inlet pipe, and is coarser as the distance from the steam inlet pipe increases.