JPS648162B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling internal casing horizontal flange fastening bolts in an ultra-high temperature steam turbine.

BACKGROUND ART Conventionally, a method as shown in FIG. 1 has been generally used to cool horizontal flange tightening bolts of an inner casing in a steam turbine having a double casing structure of an inner casing and an outer casing.

This figure shows a state in which the internal casing 13 has been disassembled into upper and lower parts, the upper half has been removed, and the turbine rotor has been removed. In order to connect the upper and lower halves of the internal casing 13, bolt holes 29 are provided on both sides of the horizontal flange 37 of the internal casing 13, sandwiching the center line AB of the turbine shaft.
a, 29b...29g are provided, and tightening bolts 28a, 28b...28 are provided through a relatively large play.
g is inserted.

In the figure, side A is the high-pressure steam inflow side, and side B is the exhaust side. A cooling steam intake hole 30 is provided in the middle of the steam flow path from the A side to the B side, and after passing through the bolts 28c, 28d, . A cooling steam flow path is provided which exits into the chamber.

As can be easily understood from the above structure, the bolts 28a and 28b near the turbine exhaust side are not cooled. The reason why such a structure is used is as follows.

(a) The driving steam of the turbine flows from side A to side B, and its pressure and temperature drop. Therefore, the members that make up the turbine are high temperature on the A side and low temperature on the B side, and the tightening bolts are also 28a, 28b, etc. from the left.
...The temperature increases in the order of 28g. Therefore, the tightening bolts 28a and 28b near the left end require less cooling.

(b) In order to take in cooling steam from the cooling steam intake hole 30 and release it into the external compartment 11 from the cooling steam outlet 32, the cooling steam intake hole 30 is heated to a pressure slightly higher than the pressure inside the external compartment 11. It must be connected to the location. That is, since the pressure of the steam on the exhaust side of this turbine is equal to the pressure inside the external casing 11, even if an attempt is made to use the turbine exhaust for cooling, the exhaust does not have the differential pressure necessary to flow to the cooling steam outlet 32. .

Conventionally, for general high-temperature steam turbines, the tightening bolt cooling method shown in Figure 1 described above was practically sufficient, but with the recent development of ultra-high temperature turbines of 570°C or higher, This method of cooling the tightening bolts was insufficient, and it became necessary to cool all the horizontal flange tightening bolts in the internal casing with exhaust steam. The circumstances are briefly explained below.

For example, main steam temperature 650℃, exhaust temperature approximately 530℃
In ultra-high temperature and high pressure turbines, the main steam pressure is 350Kg/ ^cm2・g, compared to the conventional 246Kg/cm2・g.
This is approximately 1.4 times the pressure of a high-pressure turbine (kg/ ^cm2.g ), and the stress generated in the tightening bolts is also greater.

On the other hand, improvements have been made to the materials of heat-resistant, high-tensile strength bolts, but at present the maximum temperature that they can practically withstand is approximately 570°C. Therefore, as mentioned above, in order to use ultra-high temperature steam with a main steam temperature of about 650℃,
Conventional cooling methods (Fig. 1) are not sufficient.

The above-mentioned ultra-high temperature and high pressure turbine is used as a component of a power generation plant as shown in FIG.

The super high temperature and high pressure steam is supplied from the super heater 1 to the super high temperature and high pressure turbine 2 . This ultra high temperature high pressure turbine 2 includes a high pressure turbine 4, an intermediate pressure turbine 6,
It is directly connected coaxially with the low pressure turbine 7 to drive the generator 9.

The exhaust gas of the ultra-high temperature and high pressure turbine 2 is sent to the first stage reheater 3.
The exhaust gas is supplied to a high pressure turbine 4 via a second stage reheater 5, and then to an intermediate pressure turbine 6, and then to a low pressure turbine 7, and the exhaust gas is led to a condenser 8.

Ultra high temperature and high pressure turbine 2 used as described above
It is most desirable to use the exhaust gas of the turbine 2 as the cooling steam. For example, if you try to extract high-pressure, low-temperature steam from the inlet of the superheater 1 as shown by arrow C and use it as cooling steam for the ultra-high-temperature, high-pressure turbine 2, the structure of the piping system and the internal structure of the ultra-high-temperature, high-pressure turbine 2 will be complicated. This is not desirable.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to tighten all the internal casing horizontal flange tightening bolts in a steam turbine having a double casing structure using the exhaust gas of the turbine. The purpose of this invention is to provide a method that can perform effective cooling with a simple configuration.

FIG. 3 is a longitudinal sectional view showing the overall structure of an ultra-high temperature and high pressure turbine to which the present invention is applied, as will be described later with reference to FIGS. 4 and 5.

350Kg/cm ²・g, 650℃ steam is main steam inlet pipe 1
0, penetrates the wall of an external chamber 11 made into a spherical shape for heat resistance, and is guided to a nozzle box 14 provided in an internal chamber 13.

The steam accelerated by the nozzle box 14 and the diaphragm 17 consisting of several stages rotates the rotor blades 16 and gives rotational energy to the rotor 15.
Exhaust gas with a temperature of approximately 530°C flows into the external compartment 11,
It flows from the exhaust port 25 to the next device (first stage reheater). 12 is an expansion joint, 18, 19, 20 is a shaft gland, 21, 22 is a main bearing, 23, 2
4 is a mechanical seal.

In order to achieve the above object, the present invention uses the exhaust steam of the turbine as cooling steam, and sequentially flows this from the exhaust side tightening bolt of the horizontal flange tightening bolt to the main steam inlet side tightening bolt. By communicating the steam that has passed through the exhaust side tightening bolt to the shaft gland intermediate extraction line of the turbine rotor, a pressure difference necessary for flow is created between the outlet and inlet of the cooling steam flow path. , all horizontal flange tightening bolts in the internal compartment are cooled with low-temperature exhaust steam.

Next, an embodiment of the present invention will be described with reference to FIGS. 4 and 5.

FIG. 4 is a vertical cross section including a cooling steam flow path portion configured to apply the cooling method according to the present invention to the ultra-high temperature and high pressure steam turbine shown in FIG. 3;
Figure 5 is a plan view of the rotor with the upper half of the outer compartment and the upper half of the internal compartment removed and the central part of the rotor cut out, and corresponds to Figure 1 using the conventional cooling method. be.

In the present invention, the exhaust gas that has finished driving the turbine is used as the cooling steam without extracting the steam that is driving the turbine from the middle. That is, in a steam turbine having a double-structured casing, steam that has completed its work in the inner casing and flows out into the outer casing is used as cooling steam.

In the conventional method, as shown in FIG. 1, cooling was performed by separating steam from the middle of the paragraph, so by opening the cooling steam outlet 32 into the external compartment 11, a cooling steam flow was generated. However, in the present invention, as mentioned above, in order to use the exhaust gas inside the external vehicle compartment as cooling steam, the end of the cooling steam flow path is connected to a location where the pressure is lower than that in the external compartment. Otherwise, the differential pressure necessary for the flow of cooling steam cannot be obtained. In the present invention, the steam that has been cooled is allowed to flow out into the shaft gland intermediate extraction line of the turbine rotor to generate the above-mentioned differential pressure.

An example of the above method will be specifically explained with reference to FIG. 5 as follows. The packing of the shaft gland on the high pressure side is generally No. 1 packing 1.
9a and No. 2 packing 19b, and an intermediate leak extraction port 36 is provided in a steam reservoir 35 formed in the middle to adjust the differential pressure. In this example, the cooling steam outlet 32' is connected to the intermediate leak extraction port 36 by a connecting pipe 33 and a steam passage 34. As a result, the above-mentioned No. 1 Packing 19
The differential pressure handled by a is the cooling steam intake 30'
and the cooling steam outlet 32', and a portion of the steam in the outer casing 11 flows to the intermediate leak steam extraction port 36 via a cooling passage described in detail below. In this example, the steam flowing out from the steam extraction port 36 is used to preheat the feed water, thereby improving the heat economy.

The present invention directs the cooling vapor flow flowing under the differential pressure obtained as described above to the internal casing horizontal flange 37.
The flow is made to flow through all the tightening bolts sequentially from the exhaust side tightening bolt 28a to the main steam inlet side tightening bolt 28g.

In this example, seven tightening bolts are arranged in two rows from tightening bolts 28a, 28a to 28g, 28g, so for each example, the tightening bolts 28a on the exhaust side are 28b, 28
c,... and finally tightening bolt 2 on the main steam inlet side.
A flow path was formed to cool 8 g.

The cooling steam flow supplied to each tightening bolt is blown in the tangential direction of the bolt in the horizontal plane as shown by the arrow in Fig. 5, creating a rotational flow, and in the vertical plane as shown by the arrow in Fig. 4. As shown, the flow alternately flows upward and downward along the length of the tightening bolts, sufficiently contacting each tightening bolt to cool it.

The closer the tightening bolts in each row are to the main steam inlet side, the higher the ambient temperature is, and the tightening bolts 28a to 28g receive high heat in this order. In this example, since the cooling steam is flowed in the same order as above, cooling is performed as follows. For example, the steam that cooled the tightening bolt 28b is
The heat of the bolt is absorbed and the temperature rises, and the above temperature rise is slightly alleviated by the temperature drop caused by the expansion, and then the bolt is blown onto the next tightening bolt 28c. This tightening bolt 28c is the tightening bolt 28b of the previous stroke.
Since the heat is higher than that of the bolt 28b, it is reasonable from the overall balance point of view to cool it with the steam that has slightly risen in temperature when it touches the tightening bolt 28b in the previous process. In this way, each tightening bolt is cooled in a way that is appropriate for the overall balance.

As explained above, the present invention provides a steam turbine having a dual structure of an inner casing and an outer casing, in which exhaust steam of the steam turbine is used as a cooling steam source for horizontal flange tightening bolts in the inner casing. ,
The above exhaust steam is made to flow sequentially from the exhaust side tightening bolt of the horizontal flange to the main steam inlet side tightening bolt, and the steam that has passed through the above exhaust side tightening bolt is sent to the shaft gland intermediate extraction line of the turbine rotor. By creating a pressure difference to cause the cooling steam to flow,
With a simple configuration, all the tightening bolts on the horizontal flange of the internal casing can be effectively tightened using the exhaust gas of the steam turbine.
Moreover, it can be cooled economically.

[Brief explanation of the drawing]

Figure 1 is an exploded plan view of a steam turbine commonly used in the past, Figure 2 is a system diagram of a power generation plant using an ultra-high-temperature, high-pressure steam turbine, Figure 3 is a longitudinal cross-sectional view of an ultra-high-temperature, high-pressure turbine, and Figure 4 The figure is a longitudinal cross-sectional view of an ultra-high-temperature, high-pressure steam turbine configured to implement the bolt cooling method according to the present invention, and FIG. 5 is an exploded plan view, partially cut away, of the same. 11...External compartment, 13...Internal compartment, 18,
19...High pressure side shaft gland, 19a...High pressure side shaft gland No.1 packing, 19b
...Same No. 2 packing, 20...Low pressure side shaft gland, 28a, 28b to 28g...Horizontal flange tightening bolt, 29a, 29b to 29g...Same bolt hole, 30, 30'...Cooling steam intake ,3
2, 32'... Cooling steam outlet, 33... Communication pipe,
36...Intermediate leak steam extraction port, 37...Horizontal flange.

Claims (1)

[Claims] 1. In a steam turbine having a double casing structure of an inner casing and an outer casing, the exhaust steam of the steam turbine is used as cooling steam for horizontal flange tightening bolts of the inner casing, and the exhaust steam is The steam is made to flow sequentially from the exhaust side tightening bolt of the horizontal flange to the main steam inlet side tightening bolt, and the steam that has passed through the exhaust side tightening bolt is allowed to flow out to the shaft gland intermediate extraction line of the turbine rotor. 1. A method for bolt cooling in a steam turbine, characterized in that all horizontal flange fastening bolts in an internal casing are cooled with exhaust steam by creating an appropriate differential pressure between the outlet and inlet of a cooling steam flow path.