JPS6270603A - Steam turbine - Google Patents

Abstract

PURPOSE:To ensure the stable turbine output by, upon an over pressure running, throtting the part of a steam adjusting valve through a control device for controlling said valve due to the signal supplied from a pressure detecting device, thereby distributing the whole nozzle area in varying the effective nozzle number out of the nozzles in a first stage. CONSTITUTION:Upon an over pressure running where only a main steam pressure rises while a main steam from rate in not changed, the main steam pressure exceeding the rating pressure is detected by a pressure detecting device 8 and the obtained pressure signal is input to the comparator 11c of a second control circuit 9b. Then, in the comparator 11c, said pressure signal is compared with the set pressure signal output from a pressure setting device 10 so as to be output as a deviation signal. And, the deviation signal is multiplied by a pressure adjusting ratio in a multiplier 14 so as to be input to an opening setting device 12b and to be amplified by an amplifier 13b, thereafter being input to a second steam adjusting valve 3b for turning said valve 3b in the closing direction. Therefore, it is possible to control the valve 3b to be full open, upon the over pressure running where the main steam pressure becomes extremely higher.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a steam turbine, and more particularly to a steam turbine that improves the efficiency of the turbine during overpressure operation when the main steam pressure exceeds the upper limit.

[Technical background of the invention and its problems]

In general, there is a steam turbine in which the main steam flow rate supplied from the steam generation source to the steam turbine is kept constant during the rated operation of the turbine. Turbines are known.

The above-mentioned geothermal turbine has a steam well 1 as shown in FIG.
The main steam generated in the main steam stop valve 2 and the steam control valve 3
The water is supplied to the steam turbine 5 from a main steam line 4 having a main steam line 4, and after operating the steam turbine 5 to drive the power generation 11fi6, it is condensed in the condenser 7 to become water and is discharged outside the system. As shown in FIG. 6, the steam control valve 3 is controlled to be fully open when the main steam pressure reaches the rated pressure P1, and the steam control valve 3 supplies the steam to the steam turbine 5. The main steam flow rate G is increased in proportion to the opening degree of the steam control valve 3, and is controlled to be maximum and constant during rated operation when the steam control valve 3 is fully operated.

However, during rated operation of the geothermal turbine, the main steam pressure generated in the steam well 1 may rise above the rated pressure P1 due to changes in weather conditions. flowff1G
is constant, resulting in a decrease in main steam volume, and the decrease in volumetric flow rate due to this decrease in main steam volume increases the pressure loss of the main steam that occurs when passing through the steam control valve 3, which leads to a reduction in turbine output. was there. Figure 7 shows that as the main steam pressure increases from Pl to P2, the turbine output becomes overpressure operating output K than the rated output KwR.
Figure 8 shows the WB clothing line inside the steam turbine.During overpressure operation, the steam turbine nozzle inlet pressure (bowl pressure ) is P, p to P2F
As shown by the downward line 2P-38, the efficiency of the turbine decreases, indicating that it becomes difficult to maintain the rated output.

Therefore, during overpressure operation as described above, the steam control valve 3 is throttled down to compensate for the decrease in the volumetric flow rate of the main steam.
It was necessary to increase the nozzle inlet pressure to maintain the rated output. However, the throttling of the steam regulating valve 3 causes throttling loss, and even if a reduction in output can be prevented, the overall efficiency of the turbine remains the same as during rated operation. It was not a solution to improve efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a highly efficient steam turbine that can obtain stable output even during overpressure operation when the main steam pressure has exceeded the limit. be.

[Summary of the invention]

In order to achieve the above object, the present invention provides a pressure detector that detects the pressure of steam flowing in a main steam line, a main steam stop valve that shuts off the main steam line in an emergency, and a steam inflow into a steam turbine. m, and a plurality of steam control valve control devices that compare the signal from the pressure detector with a set pressure to adjust the opening degree of the steam control valve, Main steam pressure in the line increases A
- A part of the steam control valve is controlled by a signal from the steam control valve control device during vapor pressure operation, so that it is stable even during overpressure operation when the steam pressure increases by one step. This allows output to be obtained.

[Embodiments of the invention]

Hereinafter, embodiments of a steam turbine according to the present invention will be described with reference to FIGS. 1 to 5.

In Fig. 1, reference numeral 1 denotes a steam well that generates main steam.The main steam is supplied to a steam turbine 5 through a main steam line 4, operates the steam turbine, and is condensed in a condenser 7 to become water outside the system. It is designed to be discharged. The main steam line 4 branches into two lines in the middle, and the main steam line 4 on the upstream side of the branch point is provided with a pressure detector 8 and a main steam stop valve 2, and each main steam line on the downstream side of the branch point steam line 4
A and 4b are provided with a first steam regulating valve 3a and a second steam regulating valve 3b, respectively. Further, a first control circuit 9a and a second control circuit 9b are provided between the pressure detector 8 and each steam control valve 3a and 3b as a steam control valve control device for adjusting the opening degree of the steam control valve. There is. The first control circuit 9a includes a comparator 11a connected to a pressure setting device 10a, an opening setting device 12a for setting the opening of the first steam control valve 3a, and an amplifier 1 for amplifying the opening setting signal.
3a is provided. On the other hand, the second control circuit 9b branches into two systems a3 in the middle, one system is provided with a pressure setting device 10b and a comparator 11b, and the other system is provided with a pressure setting device 10C, a comparator 11C and a A multiplier 14 is provided, and the merging second control circuit 9b is further provided with an opening setting device 12b and an amplifier 13b/'fi.

The first stage nozzle 15, which is the inlet part of the steam turbine 5, has a two-atomization structure in which the nozzle 8Y is divided into two blocks 15a and 15b, as shown in FIG.

15b, the first and second steam control valves 3a.

3b is provided, and a nozzle governing system is adopted in which the number of nozzles used during turbine operation can be changed by opening the steam control valves 3a and 3b.

Next, the operation of the present invention will be explained.

Normally, during rated operation, the first and second steam control valves 3a, 3b are fully open, and the main steam supplied from the steam control valves 3a, 3b to the steam turbine 5 is as follows:
The pressure has reached the rated pressure P1 and the flow 6G is maximum and constant. Main steam is each steam control valve 3a
, 3b, each block 15a, 15b of the first stage nozzle
It starts expanding in each block and performs work in each stage of the turbine, and then is condensed in the condenser 7 to become water and is discharged outside the system. Further, the main steam pressure is constantly detected by a pressure detector 8 provided in the main steam line 4, and the pressure signal from the pressure detector 8 is
and is input to control circuits 9a and 9b that control the opening and closing of the second steam control valves 3a and 3b, and each comparator 11 in the circuit.
a.

The pressure is compared with the set pressure at 11b and 11c. and,
The opening degrees of the steam control valves 3a and 3b are adjusted by the deviation signals output from the comparators 11a, 11b, and 11c.

Therefore, when overpressure operation occurs where only the main steam pressure increases due to external factors such as changes in air contamination conditions and the main steam flow ff1G does not change, when the main steam pressure starts to rise above the rated pressure P1, the above pressure A pressure signal is detected by the detector 8, and this pressure signal is input to the comparator 11C of the second control circuit 9b, where it is compared with the set pressure signal output from the pressure setting device 10C, and then output as a deviation signal. be done. Further, this deviation signal is multiplied by the pressure adjustment rate in the multiplier 14 and input to the 17f1 degree setting device 12b. Further, the closing signal outputted from the opening setting device 12b is amplified by the amplifier 13b, and then the second steam control valve 3b is amplified by the amplifier 13b.
is input, and the second steam control valve 3b is rotated toward the closed position. Then, during overpressure operation where the main steam pressure is at its highest, P2, the second steam control valve 3b is controlled to be fully open.

Figure 3 shows the expansion line inside the steam turbine, 1P/IP
'-3D line indicates the first and second steam control valves 3a and 3b.
The line 2P-3C shows the overpressure operation with the second steam control valve 3b fully open. From this figure, when the second steam control valve 3b is fully opened during overpressure operation, the nozzle inlet pressure of the steam turbine increases to P2. 2P even though some throttling loss occurs due to throttling of the second steam control valve 3b.
As shown by the -3C line, it can be seen that the efficiency of the turbine is improved compared to the rated operation, and the pressure loss caused by the steam control valve that conventionally occurs during overpressure operation can be prevented.

In addition, Fig. 4 shows the turbine output when the main steam pressure exceeds P2 from Pl, and the turbine output is changed to the rated output by fully opening the second steam control valve 3b despite overpressure operation. It can be further improved.

In addition, in the example described above, a geothermal turbine was explained in which the turbine is operated by main steam generated from a steam well to drive the generator I13. It goes without saying that the present invention can be applied to any plant having an overpressure operation mode in which the pressure increases.

〔Effect of the invention〕

As is clear from the above description, the present invention provides a first nozzle for a steam turbine in an overpressure operation mode in which the main steam flow m is constant during rated operation and the main steam pressure rises above the rated pressure. It is formed into a plurality of blocks, each block is provided with a steam control valve, and a pressure detector is provided in the main steam line, and when the A-pressure is operated, a signal from the pressure detector is used to control the steam control valve through the steam control valve control device. Since the nozzle area is divided by narrowing down a part of the steam control valve and changing the number of nozzles used in the first stage nozzle, the nozzle inlet pressure of the steam turbine increases and the efficiency of the turbine is improved. Therefore, pressure loss caused by the steam control valve, which conventionally occurs during overpressure operation, can be prevented, and stable turbine output can be obtained even during overpressure operation.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram of a steam turbine according to the present invention, and FIG.
The figure is a schematic diagram showing the first stage nozzle of the steam turbine according to the present invention, Figure 3 is an enthalpy entropy diagram showing the expansion line of the steam turbine according to the present invention, and Figure 4 is a comparison between the output of the present invention and a conventional steam turbine. Figure 5 is an overall system diagram of a conventional geothermal turbine, Figure 6 is a diagram showing the relationship among the main steam pressure, main steam flow rate, and steam control valve opening of the steam turbine used in the geothermal turbine. 8 is a diagram showing the conventional relationship between main steam pressure and turbine output, and FIG. 8 is an enthalpy entropy diagram showing the expansion line of the conventional steam turbine. 1...Steam well, 2...Main steam stop valve, 3a...
First steam control valve, 3b...Second steam control valve, 4...
Main steam line, 5... Steam turbine, 6... Generator, 7... Condenser, 8... Pressure detector, 9a, 9b.
...Control circuit, 10a, 10b, 10c...Pressure setting device, 11a. 11b, 11C--Comparator, 12a, 12b--Opening degree setter, 13a, 13b--Amplifier, 14--Multiplier, 15--First stage nozzle. Applicant's agent Sato-Yuq Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 8 Z71'Of'''5

Claims (1)

[Claims] a pressure detector that detects the pressure of steam flowing in the main steam line; a main steam stop valve that shuts off the main steam line in an emergency; a plurality of steam control valves that adjust the amount of steam flowing into the steam turbine; a plurality of steam regulating valve control devices that compare the signal from the pressure detector and a set pressure to adjust the opening degree of the steam regulating valve, and overpressure the main steam pressure in the main steam line to an upper limit; A steam turbine characterized in that a part of the steam regulating valve is controlled by a signal from the steam regulating valve control device during operation.