JP2001221009A - Steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure the maximum output to the utmost even in the case of unavoidable lowering of output due to the cause from a well in a geothermal steam turbine. SOLUTION: In this turbine, the turbine stage by a combination of a turbine nozzle for taking the thermal energy of geothermal steam as output and a turbine moving blade is formed in plural stages. Among the turbine stages, an initial stage nozzle or the fitting angle of a nozzle plate in the initial stage nozzle and the second stage nozzle can be varied and controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steam turbine using geothermal steam as an energy source.

[0002]

2. Description of the Related Art Generally, a geothermal steam turbine uses steam generated by flashing hot water of geothermal energy or steam directly generated instead of a boiler as an energy source. Such geothermal steam is low-pressure steam, which corresponds to the inlet steam of a low-pressure turbine in general thermal power. Further, most of the steam is saturated steam and the condenser has a low degree of vacuum, so that the available heat drop is not large. Therefore, a slight change in the steam pressure at the inlet of the first stage nozzle greatly affects the output of the turbine. Also,
Because of the low-pressure steam, the volume flow rate of the inlet steam is large, and the valve diameter of the steam control valve is large, so that there is a limit in increasing the number of valves. Therefore, it is difficult to operate the turbine while keeping the performance of the turbine optimal in response to changes in the main steam pressure and the flow rate. Therefore, the geothermal steam turbine is generally designed to have one or two steam control valves, and to be operated at an opening close to the full control of the control valve.

[0003] Geothermal steam turbines are originally planned based on maximum output operation to ensure stable output, and are often actually operated as such. However, unlike a stable equipment such as a boiler, the steam source is steam from wells dug in the ground, so it is easily affected by the area and natural environment, and the steam pressure and steam flow must change over time. You. In particular, pressure and flow rate change greatly during the end of the stable period, several years after the start of operation. In addition, these characteristics often differ depending on the region and the well itself. In addition to these changes in the steam conditions at the well base, the area of the turbine passage decreases due to the scale accumulation due to the geothermal steam properties. In particular, the scale deposition on the first and second stage nozzle plates is remarkable, and varies depending on the region and the well itself.
Newly excavated wells have a higher scale content and decrease with operating years.

In a geothermal steam turbine power generation system having such characteristics, when the main steam pressure is reduced due to a well source, even if the steam control valve is fully opened, the weight flow rate of the steam taken in by the turbine is reduced and the output is reduced. Also, if the steam flow rate decreases without decreasing the main steam pressure, the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure) also decreases, and the effective heat drop also decreases at the same time, resulting in a significant decrease in turbine output. Would. Also, when the scale is deposited on the first and second stage nozzle plates and the nozzle throat area is reduced, the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure) increases, and the turbine swallows even if the steam control valve is fully opened. The steam flow decreases, and the output decreases accordingly.

[0005]

As described above, in the geothermal steam turbine power generation system, when the main steam pressure is reduced due to a well source, even if the steam control valve is fully opened, the weight flow rate of the steam taken in by the turbine is reduced and the output is reduced. There was a problem of doing it. Also, if the steam flow rate decreases without decreasing the main steam pressure, the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure) also decreases, and the effective heat drop also decreases at the same time, resulting in a significant decrease in turbine output. There was a problem that would. Also, when the scale is deposited on the first and second stage nozzle plates and the nozzle throat area is reduced, the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure) increases,
Even if the steam control valve is fully opened, there is a problem in that the turbine swallow steam flow rate is reduced and the output is reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a geothermal steam turbine which can secure the maximum output as much as possible even when the output is forced to decrease due to a well. I do.

[0007]

The invention according to claim 1 is
In a steam turbine in which a turbine stage in which a geothermal steam is used as an energy source and a turbine nozzle for extracting heat energy of the steam as an output and a turbine rotor blade are formed in a plurality of stages, the first stage nozzle or the first stage nozzle is included in the turbine stage. And the angle of attachment of the nozzle plate in the two-stage nozzle can be changed and adjusted.

According to a second aspect of the present invention, in the first aspect of the present invention, the nozzle plate is rotatably attached to the inner ring of the nozzle diaphragm and the outer ring of the nozzle diaphragm via central shafts provided on the nozzle plate, respectively. The center axis of each nozzle is connected to a drive ring that can be operated from the outside via a connecting rod.

The invention according to claim 3 is characterized in that, in the invention according to claim 1, the mounting angle of the nozzle plate is changed by the steam control valve opening signal and the generator output.

Further, the invention according to claim 4 is the invention according to claim 1.
In the invention according to the fifth aspect, the mounting angle of the nozzle plate is changed according to the steam pressure signal at the steam control valve outlet and the generator end output signal.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a schematic configuration of a geothermal steam turbine according to the present invention, in which a steam passage portion 1 expanding on both sides is combined into one turbine rotor (turbine shaft) 2 to form one turbine. The single-casing double-flow type housing accommodated in the casing 3 is shown.

The turbine rotor 2 is provided with a turbine stage 6 in which a turbine nozzle 4 and a turbine blade 5 are combined, and is a so-called axial type in which each turbine stage 6 is formed in a plurality of stages along the flow direction of steam. I have.

The turbine stage 6 formed by the turbine nozzle 4 and the turbine rotor blade 5 is an important component as a steam turbine for extracting heat energy of steam as an output. It acts to expand the prescribed steam to give velocity energy to the steam and change the direction of the flow to create momentum in the rotational direction.

The turbine nozzle 4 generally employs a two-piece nozzle diaphragm structure, which is constituted by a nozzle diaphragm outer ring 7, a nozzle diaphragm inner ring 8 and a nozzle plate 9, and the nozzle plate 9 is formed by a nozzle diaphragm outer ring 7 and a nozzle plate. It is fixed to the diaphragm inner ring 8 by welding. The nozzle throat area of the nozzle plate 9 is determined so as to be optimal with respect to a specified steam condition, and the mounting angle of the nozzle plate is also determined to a specified value.

In the geothermal steam turbine power generation system, when the main steam pressure decreases due to a well source, even if the steam control valve is fully opened, the nozzle throat area is fixed, so that the steam pressure at the inlet of the first stage nozzle and the steam pressure are reduced. The turbine intake steam flow rate, which is uniquely determined by the pre-adjustment valve pressure, decreases, and the output decreases.

When the steam flow rate is reduced without reducing the main steam pressure, the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure) is also reduced due to the fixed nozzle throat area, and the effective heat is reduced. The head also decreases at the same time, and the turbine output greatly decreases.

Further, when the scale is deposited on the first and second stage nozzle plates and the nozzle throat area is reduced, the steam pressure at the outlet of the steam control valve rises, and even if the steam control valve is fully opened, the steam flow rate into the turbine drops. Output will decrease.

The present invention has been made in view of such a point, and is capable of changing the mounting angle of the first stage nozzle plate.

FIG. 2 is a view showing the structure of the mounting portion of the nozzle plate 9.
a and 10b are integrally formed, the central axis 10a is pivotally supported by the nozzle diaphragm outer ring 7, the central axis 10b is pivotally supported by the nozzle diaphragm inner ring 8, and the nozzle plate 9 is formed.
Can rotate about the central axes 10a and 10b.

One end of a connecting rod 11 is connected to a center shaft 10a pivotally supported by the nozzle diaphragm outer ring 7, and the other end of the connecting rod 11 is divided into upper and lower halves to form a drive ring 12 concentric with the turbine shaft 2. Are connected by pins 12a. That is, as shown in FIG. 3, a plurality of connecting rods 11 corresponding to the respective nozzle plates 9 are swingably connected to the drive ring 12, and the connecting rods 1 provided at the tips of the connecting rods 11.
A notch slot portion 11a orthogonal to one axis is fitted to a parallel surface portion 10a1 formed on the outer surface of the central shaft 10a.

On the other hand, a drive rod 13 drawn out of the turbine casing 3 is connected to the drive ring 12, as shown in FIG. It is designed to be driven in the circumferential direction.

Accordingly, when the drive ring 12 is driven in the direction of the arrow in FIG.
Is tilted about the pin 12a, whereby the central shaft 10a and the nozzle plate 9 are rotated about the central axis of the central shaft 10a as shown by arrows by engagement of the notch slot portion 11a and the parallel surface portion 10a1. , Its mounting angle θ is changed.

As described above, in the present invention, when a factor that lowers the output specific to a steam turbine using geothermal steam as an energy source occurs, the mounting angle θ of the first stage nozzle plate 9 is changed from outside the turbine. In addition, the output of the steam turbine can be increased as much as possible to perform stable operation.

By the way, in the above embodiment, the mounting angle of the first-stage nozzle plate 9 is changed, but the mounting angle of the second-stage nozzle plate can be changed by a similar mechanism. So, in this case,
Compared to a case where only the mounting angle of the first stage nozzle plate is changed, it is possible to more effectively increase the steam turbine output as much as possible and to perform a stable operation.

FIG. 5 is a view showing another embodiment of the present invention. When geothermal steam is supplied to a geothermal steam turbine 16 via a steam control valve 15, the steam is supplied to the geothermal steam turbine 1.
The work is performed at 6, and the generator 17 is driven to generate power. On the other hand, steam that has performed work in the geothermal steam turbine 16 is condensed in the condenser 18.

By the way, the opening signal 19 of the steam control valve 15
The generator end output signal 20 is input to the controller 21, and the mounting angle of the first stage nozzle plate is controlled based on the steam control valve opening degree signal 19 so that the generator end output can be held to the maximum. It is like that.

That is, operating the steam control valve 15 in the fully open state is the most efficient for the steam turbine because the pressure loss before and after the steam control valve is minimized. , The weight flow rate decreases and the output decreases. Therefore, when the output is reduced when the steam control valve 15 is fully opened, the mounting angle of the nozzle plate is controlled in a direction in which the throat area of the first stage nozzle increases. Thus, by controlling the mounting angle of the nozzle plate, the amount of steam swallowed by the turbine is increased and the output is increased.

Further, the main steam amount decreases, and the steam control valve 1
When the opening degree of the nozzle 5 changes in the opening direction and the output decreases, the mounting angle of the first stage nozzle plate is controlled in a direction to reduce the throat area of the first stage nozzle. Thus, the steam control valve outlet pressure, that is, the first stage nozzle inlet steam pressure is increased, the steam control valve 15 is fully opened, the effective heat head is increased, and the output is increased by improving the steam turbine efficiency.
As described above, in the present embodiment, the mounting angle of the first stage nozzle plate is controlled during the operation of the turbine according to the steam control valve opening signal 19 and the generator end output signal 20, so that the geothermal steam is With respect to a factor that lowers the output specific to the steam turbine used as the energy source, the output of the steam turbine can be increased as much as possible and stable operation can be performed.

In the above embodiment, only the controller 21 controls the mounting angle of the first stage nozzle plate. However, the controller 21 controls the mounting angle of the second stage nozzle plate together with the first stage nozzle plate. You may. Thus, in this case, the output of the steam turbine can be more effectively increased as compared with the control of only the first stage nozzle plate.

FIG. 6 is a diagram showing still another embodiment of the present invention, in which an outlet steam pressure signal 22 of the steam control valve 15 is provided.
And the generator end output signal 20 are input to the controller 21 so that the mounting angle of the first stage nozzle plate is controlled in accordance with both signals.

That is, operating the steam control valve 15 in the fully open state is the most efficient because the pressure loss before and after the steam control valve is minimized for the steam turbine, but usually, the design margin and controllability of the equipment are taken into consideration. Thus, at the time of rated operation, the steam control valve is operated with the throttle slightly adjusted from the fully opened state. Therefore, when the scale is deposited on the first-stage and second-stage nozzle plates and the nozzle throat area is reduced, the steam pressure at the steam control valve outlet (first-stage nozzle inlet steam pressure) increases, and the steam is swept in order to secure the turbine intake steam flow. The control valve 15 operates in the opening direction, and eventually opens fully. Therefore, when the scale further accumulates and the steam pressure at the steam control valve outlet rises, the turbine intake steam flow rate decreases and the output decreases.

Therefore, when the tendency of increasing the steam pressure at the outlet of the steam control valve is sensed and the output is decreasing, the mounting angle of the first-stage nozzle plate is controlled by the controller 21 in a direction to increase the area of the first-stage nozzle throat. . Therefore, the steam pressure at the outlet of the steam control valve is reduced, the amount of steam taken in by the turbine is increased, and the output is increased. Thus, also in this case, the output of the steam turbine can be increased as much as possible. Also in this case, not only the first-stage nozzle plate but also the two-stage nozzle plate can be controlled in the mounting angle.

[0034]

As described above, in the steam turbine according to the present invention, since the mounting angle of the first stage or the first stage and the second stage nozzle plate can be changed, the nozzle throat area can be adjusted, and the geothermal steam turbine power generation system can be used. It is possible to prevent a decrease in the weight flow rate of the steam swallowed by the turbine when the steam control valve is fully opened due to a decrease in the main steam pressure due to the cause of the well, thereby suppressing a decrease in output. Also,
Scale builds up in the first and second stage nozzles, reducing the nozzle throat area and increasing the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure). It is possible to prevent the output from decreasing due to the decrease in the nozzle throat by adjusting the nozzle throat area. In addition, when the main steam pressure does not decrease and the steam flow rate decreases, the turbine output decreases due to the decrease in the effective heat drop due to the decrease in the steam pressure at the steam control valve outlet (first stage nozzle inlet steam pressure). Can be prevented.

In the steam turbine according to the present invention, when the mounting angle of the nozzle plate is controlled by the steam control valve opening signal or the steam pressure signal at the steam control valve outlet, the steam turbine is operated during the operation of the turbine. This control can be performed, and for a factor that lowers the output specific to a steam turbine using geothermal steam as an energy source, the output can be increased by the steam turbine as much as possible and a stable operation can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a steam turbine according to the present invention.

FIG. 2 is a partial sectional view showing a first embodiment of the steam turbine according to the present invention.

FIG. 3 is a sectional view taken along the line AA of FIG. 2;

FIG. 4 is a sectional view taken along the line BB of FIG. 2;

FIG. 5 is a schematic system diagram showing another embodiment of the steam turbine according to the present invention.

FIG. 6 is a schematic system diagram showing still another embodiment of the steam turbine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steam passage part 2 Turbine rotor (turbine shaft) 3 Turbine casing 4 Turbine nozzle 5 Turbine rotor blade 6 Turbine stage 7 Nozzle diaphragm outer ring 8 Nozzle diaphragm inner ring 9 Nozzle plate 10a, 10b Central axis 11 Connecting rod 12 Drive ring 13 Drive rod 15 Steam control valve 16 Geothermal steam turbine 17 Generator 18 Condenser 19 Steam control valve opening signal 20 Generator output signal 21 Controller 22 Steam pressure signal at steam control valve outlet

Claims (4)

[Claims] 1. A steam turbine in which a turbine stage combining a turbine nozzle for extracting geothermal steam as an energy source and extracting thermal energy of steam as an output and a turbine rotor blade is formed in a plurality of stages. A steam turbine, wherein a mounting angle of a nozzle plate between a first stage nozzle and a second stage nozzle can be changed and adjusted. 2. A nozzle plate is rotatably mounted on a nozzle diaphragm inner ring and a nozzle diaphragm outer ring via central axes provided on the nozzle plate, and the central axes of the nozzles are externally connected via connecting rods. The steam turbine according to claim 1, wherein the steam turbine is connected to an operable drive ring. 3. The steam turbine according to claim 1, wherein the mounting angle of the nozzle plate is changed by a steam control valve opening signal and a generator output. 4. The steam turbine according to claim 1, wherein the mounting angle of the nozzle plate is changed according to a steam pressure signal at a steam control valve outlet and a generator end output signal.