JPH03267508A - Steam turbine - Google Patents

Abstract

PURPOSE:To improve a partial load efficiency by providing the second step on which the steam from a steam governor passes due to the nozzle control below the specified load to the front step of the first step. CONSTITUTION:In the range from the specified partial load to the rated load, the steam from a steam governor 4 for controlling a throttle valve passes the first blade step 3. The second blade step 13 is provided to the front step of the blade step 3 so that the steam from a steam governor 10 for controlling a nozzle may pass when the load is below the specified partial load. In this constitution, throttle loss energy in throttle controlling the load below the specified partial load can be effectively utilized by controlling the nozzle at the blade step 13. Therefore, the efficiency of the partial load can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention mainly relates to the structure of a steam turbine in which the amount of steam is controlled and supplied by throttling control.

[Conventional technology]

A steam turbine is supplied with steam from a steam supply source such as a boiler, and the amount of steam supplied is controlled by a steam control valve according to the load of the turbine, and the steam is passed through the blade stages in the turbine and expanded. Perform work and generate power. In this case, the steam turbine shown in FIG. 4 uses a steam control valve to control the amount of steam in the entire load range up to the rated load by throttling control.

In Fig. 4, 2 indicates a turbine rotor having a plurality of rows of moving blades, and 2 a casing having a plurality of rows of stator blades. The rows of rotor blades form a plurality of blade stages 3. Reference numeral 4 denotes a steam regulating valve controlled by the throttle control i, and steam whose amount of steam is controlled by this steam regulating valve flows into the casing from a steam inlet 5 provided in the casing 2. t26
is the main steam stop valve. Further, la is a balun piston provided in the turbine port 1 to balance the shaft displacement thrust during turbine operation, and faces the casing 2 via the labyrinth packing 7.

28 is Labyrinth Spatskin.

With this structure, steam from the steam supply source passes through the main steam stop valve 6 which is in an open state, and the amount of steam corresponding to the load of the turbine is controlled by the steam control valve 4, and flows into the casing 2 from the steam port 5. This inflowing steam flows through the blade stages 3ζ, expands, and generates power. This power is converted into electric power by, for example, a generator (not shown) coupled to a steam turbine, and is supplied to an external load.

[Problem to be solved by the invention]

As mentioned above, the amount of steam is controlled by the steam control valve through throttling control over the entire rated load range of the turbine, and this amount of steam is passed through the blade stages and expanded to do work. At a partial load where the amount of load is small, the steam control valve is throttled, resulting in a large throttling loss, and as shown in the turbine efficiency characteristic diagram of FIG. 5, there is a disadvantage that the turbine efficiency decreases as the load amount decreases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a steam turbine that can improve turbine efficiency even when the turbine is partially loaded with a small amount of load.

[Means to solve the problem]

In order to solve the above problems, the present invention includes a first steam control valve that controls the amount of steam corresponding to the load from a predetermined partial load to the rated load of the turbine by throttling control; a first blade stage through which steam flows and expands; a second steam control valve that controls the amount of steam corresponding to a load below the predetermined partial load by nozzle control; The blade stage is disposed in front of the second blade stage, and the second blade stage is expanded by the flow of steam from the second steam control valve.

In addition, a plurality of steam control valves that control the amount of steam corresponding to the load from a predetermined partial load to the rated load of the turbine and the load below the predetermined partial load by throttling control, and the steam from each of the steam control valves are provided. and a wing stage that is inflated by flowing through each of them.

[Effect]

In the first means, for loads ranging from a predetermined partial load to a rated load, steam in an amount controlled by a throttle-controlled steam control valve with the rated load as the rating point flows through the first blade stage. The required turbine efficiency can be obtained because the turbine does its work.

On the other hand, for loads below a predetermined partial load, the amount of steam corresponding to the load is controlled by a second steam control valve for nozzle control whose rating point is the predetermined partial load. Steam flows from the second blade stage through the first blade stage and expands to generate power. Therefore, it is possible to effectively utilize the energy of throttling loss at loads below a predetermined partial load, which occurs when the entire load range up to the rated load is controlled by a throttle-controlled steam control valve, in the second blade stage. Therefore, the turbine efficiency is improved even when the load is less than a predetermined partial load.0 In addition, in the second means, for loads from a predetermined partial load of the turbine up to the rated load and for loads below the predetermined partial load, Steam 1, which is controlled by a plurality of throttle-controlled steam control valves whose rating points are the rated load and the predetermined partial load, respectively, flows through each blade stage provided therein, expands, and performs work. By doing this, for loads from a predetermined partial load to the rated load, the rated point is used as the rated load, so the required turbine efficiency can be obtained, while for loads below the predetermined partial load, the rated point is used as the rated load. Since the point is at a predetermined partial load of low load, the turbine efficiency is improved.

〔Example〕

Embodiments of the present invention will be described below based on the relevant aspects.

FIG. 1 is a partial cross-sectional view of a steam turbine according to an embodiment of the present invention. ri 26 , the same parts as in the conventional example shown in FIG. 1 and FIG. 2 and FIG. What is different from the conventional example shown in FIG. 1 is that in addition to the throttle-controlled steam control valve 4, a nozzle-controlled steam control valve 10 is provided, and the steam controlled by this steam control valve 10 is supplied to a nozzle. 11 is provided in the casing 2, and a control stage 13 is further provided in the turbine rotor 1 with rotor blades 12 into which the steam expanded by the nozzle 11 and becomes high-speed flows. In addition, the nozzle control steam control valve 10 selects the most preferable partial load for turbine operation, and controls the amount of steam corresponding to the load below this predetermined partial load.

With this structure, under a predetermined partial load, steam from the steam supply source is controlled by the steam control valve 10 for nozzle control and supplied to the nozzle 11, and steam ejected from the nozzle 11 is supplied to the rotor blades 12 of the control stage 13. and further into the rotor blade 12.
The steam discharged from the blade is passed through the blade stage 3 and expanded to do work.

Further, for loads ranging from a predetermined partial load to a rated load, the steam from the steam supply source is controlled by a steam control valve 4 that throttles the steam. In this case, the steam controlled by the nozzle-controlled steam control valve 10 is switched to the steam controlled by the throttle-controlled steam control valve 3 at a predetermined partial load, and from the predetermined partial load to the rated load, the steam controlled by the throttle-controlled steam control valve 3 is switched to the steam controlled by the throttle-controlled steam control valve 3 at a predetermined partial load. The amount of steam is controlled by the steam control valve 4, and this steam passes through the blade stage 3.
Inflate and do your work. 2. After switching, the steam control valve 10 for nozzle control is closed at a predetermined partial load or higher.

FIG. 3 is a diagram showing the turbine efficiency characteristics when the steam amount is controlled by the steam control valves 10 and 1.
Reference numeral 6 indicates the turbine efficiency for a load below the switching load point A of a predetermined partial load where the steam amount is controlled by the nozzle-controlled steam regulator 10+, and 17 indicates the throttle-controlled steam regulator 4.
The turbine efficiency from the switching load point A to the rated load is shown. From the figure, it can be seen that even at a partial load where the load amount is small, the turbine efficiency is improved by the shaded area B compared to the conventional turbine efficiency.

FIG. 2 is a partial cross-sectional view of a steam turbine according to a different embodiment of the invention. 2, the inner casing 20 is provided with a row of stator vanes and has annular steam inlet chambers 21 and 22.
and further facing the inlet chambers 21 and 22, respectively, and forming blade stages 23 and 24 with the stator blades of the stator blade row and the rotor blades of the rotor blade row of the turbine rotor l, surrounding the turbine rotor 1. I'm here.

Note that 25 and 26 are steam inlets communicating with the steam inlet chambers 21 and 22, respectively.

The outer casing 27 surrounds the inner casing 20 and comprises rotor blades located downstream of the blade stages 24 of the turbine rotor 1 and stator blades forming a blade stage 28 . External casing 2
7 are provided with steam inlets 29 and 30, the steam inlets 29 and 30 respectively
5 and 26 via airtight rings 31 and 32.

A labyrinth packing 233 is provided at a portion where the turbine rotor l passes through the outer casing 27.

Throttle-controlled steam control valves 35 and 36 are arranged in parallel downstream of the main steam stop valve 6 so that the steam controlled by the steam control valves 35 and 36 flows into the steam inlets 29 and 30. Note that the steam control valve 35 controls the amount of steam corresponding to a load below a predetermined partial load of the turbine, and the steam control valve 36 controls the amount of steam corresponding to a load below the rated load of the turbine by throttling control.
The blade stage 23 has a predetermined partial load at the rated point, and the blade stage 2
4 is manufactured by applying the rated load to the rated point l. 2. The predetermined partial load is selected to be the most preferable load for turbine operation.

With this configuration, when the steam from the steam supply source passes through the main steam stop valve 6 in the open state, the steam amount corresponding to the load is controlled by the throttle-controlled steam control valve 35 when the load is less than a predetermined partial load, and the steam amount is controlled according to the load. Steam flows into the steam inlet chamber 21 from the steam port 25 via the inlet 29 . The steam that has entered the steam inlet chamber 21 flows through the blade stages 23, expands and does work, passes through the outer casing 38 between the inner casing 20 and the outer casing 27, flows through the blade stages 28, and expands. After doing work, it is discharged downstream. The load from the predetermined partial load to the rated load is switched from the steam control valve 35 to the steam control valve 36 at the point of the predetermined partial load, and the amount of steam controlled by the steam control valve 36 passes through the steam inlet 30 to the steam control valve 36. 26 into the steam inlet chamber 22 . The steam that has entered the steam inlet chamber 22 passes through the blade stages 24 and expands, then flows through the blade stages 28, expands further, performs work, and is then discharged downstream.

In this way, at a load below a predetermined partial load, the steam controlled by the throttle-controlled steam control valve flows through the blade stage 23 whose rated point is the predetermined partial load, expands, and does work, so the turbine efficiency decreases. As shown in Figure @2, it improves for loads below a predetermined partial load.

8. In the above embodiment, two throttle-controlled steam control valves are provided, but by adding an internal casing and increasing the number of blade stages, it is possible to provide three or more throttle-controlled steam control valves. You can get the same effect.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in claim 1, from a predetermined partial load to a rated load, a steam control valve is controlled by throttling, and a first blade stage through which steam from the valve flows; At a load below a predetermined partial load, a steam control valve is controlled by a nozzle, and the steam from this valve flows through the predetermined portion by providing a second blade stage provided in the preceding stage of the first blade stage. Since the throttling loss energy when throttling control is performed for a load lower than the load is effectively utilized in the second blade stage by nozzle control, there is an effect of improving partial load efficiency.

In addition, in claim 2, by providing throttling control steam control valves with the rated load and predetermined partial load as rated points, and blade stages through which the steam from each valve flows respectively, the predetermined partial load can be achieved. At loads below the partial load, the amount of steam controlled by the throttle-controlled steam control valve flows through the blade stages with the rated point at the predetermined partial load of the low load to perform work. This has the effect of improving turbine efficiency.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a steam turbine according to an embodiment of the present invention, FIG. 2 is a partial cross-sectional view of a steam turbine according to a different embodiment of the present invention, and FIG. 3 shows the turbine efficiency characteristics of the steam turbine of FIG. 4 is a partial sectional view of a conventional steam turbine, and FIG. 5 is a turbine efficiency characteristic diagram of the steam turbine shown in FIG. 4. 4.35, 36: Throttle control steam control valve, 10: Nozzle control steam control valve, 3, 23, 24, 28: Blade stage, 1
1: Nozzle, 12: Moving blade. Figure 1 Figure 2 No missing element output ('/,) Figure Figure Figure

Claims (1)

[Scope of Claims] 1) A first steam control valve that controls the amount of steam corresponding to a load from a predetermined partial load to a rated load of the turbine by throttling control, and the steam from this steam control valve flows through it. a first blade stage that expands; a second steam control valve that controls the amount of steam corresponding to a load below the predetermined partial load by nozzle control; a second blade stage through which steam from the steam control valve flows and expands. 2) A plurality of steam control valves that control the amount of steam by throttling control corresponding to the load from a predetermined partial load to the rated load of the turbine and the load below the predetermined partial load, and steam from each steam control valve. 1. A steam turbine characterized in that the blade stages are each expanded by flowing through the blade stages.