JPH01310105A - Steam turbine - Google Patents

Abstract

PURPOSE:To improve cooling effect by making a packing movable in radius direction, and providing a gap adjusting mechanism moving the packing in accordance with steam pressure in high pressure side onto the packing. CONSTITUTION:A packing 6 is held movable in radius direction in a packing holder 5. A gap adjusting mechanism 12 consisting of a communicating hole 13, a cylindrical adapter 14 and a bellows 15 is provided between the packing holder 5 and the packing 6. Gap between the packing 6 and a rotor 7 can be adjusted thereby in accordance with high pressure of steam pressure, therefore cooling effect for the rotor 7 is not affected by steam condition in high pressure side, and yet it is possible to obtain optimum cooling effect over all loading area.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Field of Application) The present invention relates to a steam-cooled steam turbine, and in particular to a steam turbine that is capable of effectively cooling the entire load range. Regarding turbines.

(Prior art) Conventionally, in a steam turbine that has two stage groups, high-pressure side and low-pressure side, in the same cabin for opposing flow, packing for shaft-sealing both stage openings has been used as a means of suppressing the rise in rotor surface temperature. It is known that relatively low-temperature steam is fed into the gap between the rotor and the rotor from the high-pressure side to the low-pressure side, thereby providing a cooling effect to the rotor surface. The packing is held in a packing case fixed within the width via a packing holder. Conventionally, the packing is mechanically held against the packing holder by a leaf spring, so that the gap between the packing and the rotor is kept constant regardless of the load and main steam conditions. When the gap value between the packing and the rotor is constant in this way, the cooling effect is affected by the temperature conditions of the high pressure xi air, etc., and the rotor may not necessarily be sufficiently cooled u1.

Furthermore, in recent years, an increasing number of steam turbine plants are adopting variable pressure operation. In this variable pressure operating plant, the enthalpy of steam is higher at partial load than at rated load.

Therefore, if the gap between the packing and the rotor is relatively large, the temperature of the cooling steam at the low-pressure side inlet will be higher than the mainstream steam temperature, and the cooling fJI effect will disappear. It may have some effect.

(Problems to be Solved by the Invention) In conventional steam-cooled steam turbines, the gap value between the packing into which cooling steam is sent and the rotor is constant, so the cooling effect depends on the high-pressure side steam conditions, and variable-pressure operation There is a possibility of heating in the plant.

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a steam turbine that is not affected by the high-pressure side steam conditions and can perform an optimal rotor cooling 7f1 action over the entire load range. shall be.

[Structure of the invention]

(Means for solving one problem) The present invention provides two groups of high and low pressure stages in the same vehicle interior,
In a steam turbine in which steam for rotor cooling is sent from a high pressure side to a low pressure side into a gap between a shaft sealing packing arranged between both stage groups and the rotor, the packing is movable in the radial direction and the high pressure The present invention is characterized in that a gap adjustment mechanism is provided that moves the packing in the radial direction in accordance with the side steam pressure and expands or contracts the gap.

(Function) According to the present invention, the gap value between the packing and the rotor is controlled by the pressure of the high-pressure side, that is, the cooling steam source. For example, when the high-pressure side steam pressure decreases, the gap value also decreases and cooling is performed. The amount of steam sent is suppressed, and the rotor surface temperature at the low-pressure inlet portion is kept low. Furthermore, when the high-pressure side steam pressure becomes high, the gap value becomes large, and the amount of low-temperature cooling steam increases, improving the cooling effect. As a result, an optimum amount of cooling steam is ensured in accordance with the high-pressure side steam conditions and in the full load (pressure range), and the cooling effect is improved.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the entire configuration of the shaft seal of a steam turbine, and the second
The figure shows in detail one packing part that constitutes the shaft seal part.

In the steam turbine of this embodiment, as shown in FIG. 1, a packing casing 2 is fitted and fixed inside an outer casing 1, and this section divides the cabin into a high-pressure side steam chamber 3 and a low-pressure side inlet section 4. , each room forms a paragraph. A packing holder 5 is fixed to the inside of the packing casing 2 by bolting, and a plurality of packings 6 are held in a ring shape within the packing holder 5.

The packing 6 is disposed on the outer peripheral surface of the rotor 7 in a non-contact state, and the gap 8 between the packing 6 and the outer peripheral surface of the rotor 7 is 171 open to the high pressure steam chamber 3 side, so that high pressure steam is cooled from the high pressure steam chamber 3 side. It is sent into the gap 8 as u1 steam.

By the way, as shown in FIG. 2, the packing 6 is held by inserting the flange part 10 into the holding hole 9 of the packing holder 5, and with the flange part 10 in contact with the seat 11 in the drawing of the holding hole 9, a certain gap value is maintained. a has been set, and during this time 1li
It is movable in the direction in which the ii value a increases, that is, toward the outer circumference of the rotor 7.

A gap adjustment mechanism 12 is provided which moves the packing 6 in the radial direction in accordance with the high-pressure side steam pressure to expand or contract the gap value a.

The gap adjustment mechanism 12 generates high pressure steam v in the packing holder 5.
3, and this communication hole 13.
and a bellows 15, the inside of which communicates via a cylindrical adapter 14. This bellows 15 has an extensible part 17 in an outer case 16 fixed to the outer circumferential side of the packing 6. When the pressure inside the outer case 16 becomes higher than that in the holding hole 9 in the packing bolt 5, the outer case 16 expands. The elastic part 1 is pushed outward (upward in the figure).
7 is extended to move the packing 6 to the outer circumferential side of the rotor 7. The distance that the packing 6 can move is defined as the distance until the outer case 16 of the bellows 15 comes into contact with the outer peripheral surface of the holding hole 9.

According to this configuration, the inside of the bellows 15 becomes equal to the pressure of the high-pressure steam ¥3 through the adapter 14 and the communication hole 13, and when this pressure is greater than the outside of the bellows 15, the packing 6 is lifted and the packing 6 and rotor 7
The gap value can be controlled within the range of (a) to (a+b).

A method of setting this gap value will be explained with reference to FIGS. 3 and 4.

Figure 3 shows three examples of a steam turbine that adopts a variable pressure operation pattern.
This figure shows the relationship between the pressure side steam pressure X, the cooling steam temperature Y at the low pressure side inlet, and the mainstream steam temperature Z in the 0 to 90% zero load range. The cooling steam temperature Y depends on the high-pressure side steam pressure X and its temperature, and within the variable pressure range, the lower the high-pressure side steam pressure X is, the higher it becomes. If the low pressure side steam temperature is set to decrease on the low load side from the high pressure side steam pressure P3 as shown in 7, then the cooling steam temperature Y and the mainstream steam temperature 7 will change in height near 50% load. The opposite is true.

That is, below this load, the temperature Y of the cooling steam sent into the gap 8 becomes a heating source rather than a cooling source.

Therefore, as shown in Fig. 4, the material and shape of the bellows 15 are selected so that the bellows 15 begins to expand at a pressure of 13 degrees or more at which the cooling steam r1 degree and the mainstream steam temperature Z are reversed. The dimensions of the holding hole 9 of the packing holder 5 are set so as not to exceed the gap value (a + b).

If such settings are made, the gap 8 between the packing 6 and the rotor 7 will be kept at a relatively small value at pressures below P3, and by suppressing the cold 1i1 steam ω to a minimum, the low pressure inlet portion will be The rotor surface temperature can be kept as low as possible.

Further, in the pressure range of P3 or higher where the cooling effect appears, the gap 8 is enlarged, thereby improving the cooling effect.

Therefore, it becomes possible to secure an optimum cooling steam volume in the entire load range (pressure range).

〔Effect of the invention〕

As described above, according to the steam turbine of the present invention, the gap between the packing and the rotor can be adjusted according to the high-pressure steam pressure using the gap adjustment mechanism, so that the rotor cooling effect is influenced by the high-pressure side steam conditions. Moreover, the optimum cold 7J+ effect can be obtained over the entire load range.

[Brief explanation of the drawing]

FIG. 1 is an overall sectional view of a packing part showing an embodiment of a steam turbine according to the present invention, FIG. 2 is an enlarged view of a part of FIG. 1, and FIGS. 3 and 4 are for variable pressure operation. FIG. 4 is a characteristic diagram showing the relationship between the steam state value of each part and the gap setting value at a certain time. 3...High pressure side steam room, 4...Low memo side steam room, 6...
... Packing, 7... Rotor, 8... Gap, 12
...Gap adjustment mechanism. Representative Patent Attorney Rule Chika Kenji Ken Maru Diagram 1 p Diagram 2

Claims (1)

[Claims] A steam turbine that has two high-pressure and low-pressure stage groups in the same vehicle compartment, and sends rotor cooling steam from the high-pressure side to the low-pressure side into the gap between the shaft sealing packing and the rotor, which are placed between the two stage groups. A steam turbine characterized in that the packing is movable in the radial direction and is provided with a gap adjustment mechanism that moves the packing in the radial direction and expands or contracts the gap in accordance with high-pressure side steam pressure.