JPS60145404A - Steam turbine - Google Patents

Abstract

PURPOSE:To shorten starting time by connecting the counterflow side of a gland steam chamber of a steam turbine to a steam seal header through a gland steam stop valve. CONSTITUTION:The counterflow side 8' of the gland steam chamber of a steam turbine is connected to a steam seal header 18 through a gland steam stop valve 19, and the counterflow side 7' of a high pressure gland chamber is connected to the steam seal header 18 through gland steam stop valves 22 and 23. And generation of thrust force at a preheating time is restrained by controlling pressure of the counterflow side of the gland steam chamber. Thus, pressure of preheated steam can be increased and starting time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a steam turbine in which thermal stress caused by a temperature difference between main steam and a rotor surface is kept low, particularly during a cold start.

[Technical background of the invention and its problems] Generally, when cold starting a steam turbine, the rotor is preheated to a certain temperature in a turning state, and after preheating, main steam is introduced to increase rotation and load. let When the main steam flows in, thermal stress is generated on the rotor surface due to the temperature difference between the main steam and the rotor surface, and this thermal stress limits the rate of increase in rotation. Further, this generated thermal stress is closely related to the lifespan of the rotor, and the higher the thermal stress, the greater the rotor's lifespan consumption rate. Therefore, by increasing the rotor preheating temperature and keeping the temperature difference between the main steam and the rotor surface low after the main steam inflows, it is possible to shorten the startup time and extend the life of the rotor. Increasing the rotor preheating temperature is one of the important issues for steam turbines.

In Fig. 1, in the high-pressure stage of the steam turbine, in order to reduce the thrust force during steady operation, the main steam flowing in from the main steam pipe 1 is divided into two by the nozzle box 2, and one is divided into two by the main stream side first stage. One flows to the blade 3, and the other flows to the first stage blade 3' on the reverse flow side, passes through both first stage blades 3, 3', merges, and flows to the downstream stage on the mainstream side. In order to reduce the thrust force caused by the downstream stage on the mainstream side, a thrust stage 5 is provided in the rotor 4 at the outlet of the first stage blade 3' on the reverse flow side.

The high-pressure casing 6 includes a high-pressure gland chamber 7゜7' that is connected to an intermediate-pressure bleed point via a three-way blowdown valve, and a steam seal header that is maintained at a pressure slightly higher than atmospheric pressure by a nondo steam regulator. Grand steam room 8.8'
There is also a grand negative chamber 9.9' connected to a grand dehydrator that maintains a pressure slightly lower than atmospheric pressure. A labyrinth packing is provided between each of these chambers, and high pressure steam, which is a working fluid, is sealed in the shaft. The rotor 4 is also provided with a rotor stage 10.8 located in the gland steam chamber 8.8' to reduce the leakage area. I+)' is provided.

The method for preheating the high pressure stage of the steam turbine constructed in this way is carried out by the preheating system shown in FIG. That is, in FIG. 2, first, the gland steam regulator 11 and the gland condenser 12 are put into operation and the shafts are sealed. At this time, the high pressure gland chamber 7.
The connection between 7' and the medium pressure bleed point is broken. Therefore, the pressure in the high pressure gland chamber 7.7' is equal to the pressure in the high pressure casing 6.
The pressure is intermediate between the pressure inside the vessel and the pressure in the grand steam chamber 8.8'. The main steam stop valve 14 provided in the main steam pipe 1 is fully closed, and the drain valves provided in each part of the high pressure casing 6 are fully opened.

The rotor 4 is in a turning state at a low rotational speed.

A warming valve 16 provided between the auxiliary steam system 15 and the high-pressure outlet section is opened to allow preheated steam to flow into the high-pressure casing 6, thereby filling the high-pressure casing 6 with the preheated steam. Since the rotor surface temperature is lower than the saturation temperature of the preheated steam, the preheated steam condenses on the rotor surface, and the condensed water is discharged by the drain valve. The rotor 4 is rapidly heated by this condensed heat transfer.

However, when the rotor surface temperature reaches the saturation temperature of the preheated steam, the heat transfer from the preheated steam to the rotor becomes convective heat transfer.

Since the amount of heat transferred by this convective heat transfer is smaller than the amount of heat transferred by condensation heat transfer, the temperature rise of the rotor becomes gradual. Therefore, the degree of preheating of the rotor is largely dependent on the saturation temperature or pressure of the preheated steam. The higher the pressure of the preheating steam, the higher the saturation temperature, and the preheating temperature of the rotor can be increased.

However, when the high-pressure casing 6 is filled with preheated steam, a thrust force Fl is applied to the rotor 4 as shown in FIG.
occurs. In other words, the thrust stage 5 receives preheating steam pressure, and the part facing it has a ground steam adjustment pressure slightly higher than atmospheric pressure, and the projected area of the thrust stage 5 on a plane perpendicular to the axial direction is AI + Let A2 be the projected area of the mainstream downstream stage on a plane perpendicular to the axial direction, and A8 be the projected area of the reverse rotor stage 10' on a plane perpendicular to the axial direction.

A thrust force Fl of the following formula is generated.

Thrust force Fl = (preheating steam pressure) x person l - (ground steam adjustment pressure) x (As - AS ) -----
--- (1) At this time, the rotor 4 is in a turning state with a low rotational speed, and the oil film thickness of the thrust bearing is thin, so that it cannot receive an excessive thrust force Fl.

For the above reasons, the current preheating steam pressure is approximately 5 at
The preheating temperature of the rotor 4 is 150°C at most. Since the main steam temperature is 500° C. or higher, this preheating temperature of 150° C. is insufficient, and from the viewpoint of shortening startup time and extending the life of the rotor, a steam turbine that can preheat the rotor to a lower temperature is desired.

[Object of the Invention] An object of the present invention is to provide a steam turbine that suppresses thermal stress generated in the rotor after main steam inflows to a low level, and also enables shortening of start-up time and extension of four-day life. be.

[Summary of the Invention] The steam turbine according to the present invention enables pressure control of one of the opposing grand steam chambers, thereby preheating with higher pressure preheating steam, increasing the rotor preheating temperature, and increasing the rotor preheating temperature after the inflow of royal steam. The rotor is characterized in that it is configured to suppress thermal stress generated in the rotor to a low level.

[Embodiments of the Invention] Examples of the present invention shown in the drawings will be described below. The main body of the steam turbine according to the invention is identical to that shown in FIG.
．． 3, which shows the preheating steam system used in the present invention, will be described. In FIG. 3, the same reference numerals as those in FIGS. 1 and 2 indicate the same parts, so the explanation thereof will be omitted.

In the present invention, as shown in FIG. 3, a gland steam stop valve 19 is provided between the backflow side gland steam chamber 8' and the steam seal header 18, and a gland steam stop valve 19 is provided between the backflow side gland steam chamber 8' and the steam seal header 18. and the auxiliary steam system 15 are connected via a ground steam regulating valve 20.

A high pressure gland steam stop valve 22 is provided between the backflow side high pressure gland chamber 7' and the high pressure gland system 21, and this stop valve 2
2 and the backflow side high pressure gland chamber 7' and the steam seal header 18 are connected via a high pressure gland steam stop valve 23.

A warming pressure measuring device 24 is provided on the downstream side of the warming valve 16 to output a signal P1, and a steam seal header pressure measuring device 2 is provided in the steam seal header 18.
5 is provided as the output signal PsI, and downstream of the grand steam regulating valve 20, a grand steam regulating pressure measuring device 26 is provided as the output signal P8.

Then, if the two river force signals Pl and P2 are led to the arithmetic circuit 27 and the output signal PB' is assumed, the following relational expression (2) holds O Ps'=(PIXA1+P2X4)/As -----
---(2) Here, A, , A2 and A8 are the projected areas of the thrust stage and rotor stage in the above equation (1) onto a plane perpendicular to the axial direction. The output signal P8' and the output signal P8 are guided to the grand steam regulator path, and the grand steam regulating valve 20 is controlled so as to make the signal difference between them zero.

In the steam turbine according to the present invention constructed in this way, as shown in FIG. 1, in which the preheating steam system shown in FIG. 3 is attached, the following procedure is used to preheat the steam turbine. That is, in FIG. 3, the gland steam valve 19 is fully closed, the high pressure gland steam stop valve 22 is fully closed, and the high pressure gland steam stop valve 23 is fully open. The gland steam regulating valve 20 is kept closed until the output signal P8' of equation (2) becomes greater than the steam seal header pressure P2, and from the point when the output signal P8' becomes greater than the output signal P2, the output signal P8 is closed. Make sure to keep it under control.

With the above preparations in place, in the groove where the warming valve 16 bends during preheating, the internal pressure of the high pressure casing 6 is a vacuum because the drain valve is fully open. At this time,
Since Ps'<Ps, the gland steam regulating valve 19 is fully closed, and the internal pressure of the backflow side gland steam chamber 8' is slightly higher than atmospheric pressure, which is the internal pressure of the high pressure gland chamber 7'. This is an intermediate value between the internal pressure of the grand negative pressure chamber 9', which is slightly lower than atmospheric pressure. At this time, as shown in FIG. 1, a thrust force F2 acts from the reverse flow side to the upstream side. However, the conventional thrust force is
Although the pressure of 0.10' was the same, according to the present invention, the pressure of the rotor stage 10' is slightly lower than the pressure for the rotor stage, so that the thrust force due to the vacuum in the high pressure casing 6 is reduced.

When the warming valve 16 is opened and the internal pressure of the high pressure casing 6 is increased, p8'>p2 and the grand steam 8
The glue box 20 is activated. Since equation (1) is satisfied, no thrust force acts on the rotor. Also P8'〉P
2, the steam in the backflow side gland steam chamber 8' flows through the labyrinth, one to the backflow side high pressure gland 7' and the other to the backflow side gland negative pressure chamber 9'. Since both the backflow side high pressure gland chamber 7' and the backflow side gland negative pressure chamber 9' are kept at a constant pressure (-), the flow rate is adjusted by the gland steam regulating valve 20 based on the relationship between the flow rate and pressure of the labyrinth backing. Then, the output signal P8f'i can be definitely controlled.

In this way, even if the warming valve 16 is opened to a certain degree and the internal pressure of the high-pressure casing is increased, the gland steam regulating valve 2 ( ) is configured such that the thrust force reduces the internal pressure of the backflow side gland chamber 8' to zero. It is also possible to operate the preheating steam pressure higher than before.

Next, in the embodiment shown in FIG. 4, another grand chamber 30 is provided between the backflow side grand steam chamber 8' and the backflow side grand negative chamber 9', and this grand chamber 30 and the steam seal header 18 are connected to each other. The features are that the ground steam regulating valve 20 is connected to the downstream side of the warming valve 16 instead of the auxiliary steam system 15, and the other configuration is as shown in FIG. 3. The lineage and the [mouth one.

According to this configuration, when the inside of the high-pressure casing is under negative pressure, the gland steam regulating valve 20 is connected to the warming valve 1.
6, it became possible to control the backflow side gland steam chamber 8' to negative pressure so as to cancel out the thrust force due to the negative pressure in the high-pressure Köhlen, and also by providing the gland chamber 30. The shaft is sealed by. Even when the high pressure casing pressure is high, the pressure in the gland steam chamber 8' at a point downstream of the warming valve 16 is sufficient, and it is possible to reduce the thrust force to zero.

Furthermore, in another embodiment shown in FIG.
A thrust force measuring device 33 such as a load cell is provided at the pump, and the output signal thereof is used to control the grand steam regulating valve 20 so as to reduce the thrust force to zero.

[Effects of the Invention] As described above, according to the present invention, in order to suppress the generation of thrust force during preheating, one side of the opposing grand steam chambers is configured for pressure control, thereby increasing the pressure at a higher pressure. By preheating with preheating steam, the rotor preheating temperature can be raised to a high level, and the thermal stress generated in the rotor after the inflow of live steam can be lowered, thereby making it possible to shorten startup time and extend the rotor life.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the high-pressure stage section of the steam turbine;
3 is a preheating system diagram showing an embodiment of the preheating system applied to the steam turbine according to the present invention, and FIGS. It is a preheating system diagram showing an example. 1...Main steam pipe 2...Nozzle box 3...Main stream side first stage blade 3'...Reverse flow side first stage blade 4...
Rotor 5...Thrust stage 6...High pressure casing 7...Mainstream side high pressure gland chamber 7'...Reverse flow side high pressure gland chamber 8...Mainstream side gland steam pipe 8...Reverse flow side gland steam pipe 9...Mainstream side ground negative pressure chamber 9...Reverse flow side grand negative pressure chamber IO...Mainstream side rotor stage 10 saw Reverse flow side rotor stage 11
...Ground steam regulator 15...Auxiliary steam system 1
6...Warming valve 18...Steam seal header 19...Gland steam stop valve 20...Gland steam W1 regulating valve 21...^Pressure gland system 22.23...High pressure gland steam stop valve 24 Warming pressure meter 111 25 Steam seal header pressure meter 26 Grand steam adjustment pressure meter 27 Arithmetic circuit 28 Grand regulator 30
...Gland chamber 32...Thrust bearing 33...
Thrust force measuring device agent Patent attorney Yoshiaki Inomata (1 person) 2nd
figure/? 3rd figure 1? 4th figure 1? Figure 5 I?

Claims (1)

[Claims] (1) A steam turbine characterized in that the main stream 1 [IH and the reverse flow side of the gland steamer facing each other on the reverse flow side are connected to a steam seal header having high pressure steam pressure via a gland steam stop valve ( 2) It has a valve that switches the connection of the high-pressure gland chamber from the high-pressure gland system to the steam seal header, a warming downstream pressure measuring device, and a steam seal header pressure measuring device, and furthermore, the rotor thrust force is determined from the output signals of these pressure measuring devices. A calculator that calculates the ground steam chamber pressure to be zero, and the output of this calculator (i
The steam turbine according to claim 1, characterized in that the steam turbine is equipped with a grand steam regulating valve that is controlled by the auxiliary steam system and guides steam from the auxiliary steam system to the grand steam chamber.