JPS61218704A - Gland steam pipe device for steam turbine - Google Patents

Abstract

PURPOSE:To prevent reduction of the strength of an axle by communicating an intermediate chamber formed in a portion of a labyrinth packing adjacent to the casing and an intermediate stage of an array of turbine blades on the higher pressure side than the bleeding stage. CONSTITUTION:An intermediate chamber 13 is formed in a portion of a labyrinth packing 5 adjacent to the casing 4. The intermediate chamber 13 is communicated through a connecting pipe 17 with an intermediate stage E of an array of turbine blades on the higher pressure side than the bleeding stage D. This causes the bleed from the intermediate stage E to be leaked through the intermediate chamber 13 and mixed with steam, so that the temperature of gland steam is lowered, preventing reduction of the strength of the axle 1 due to heating thereof.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] This invention relates to a gland steam pipe device for a steam turbine, and the present invention relates to a gland steam pipe device for a steam turbine that mixes high-temperature leaked steam with low-temperature steam from a turbine blade cascade to lower the temperature of the gland steam. We will supply it to you in a timely manner.

[Prior art and its problems]

Generally, the part where the axle of a steam turbine passes through the casing is provided with a high-pressure side gland part and a low-pressure side gland part.
A labyrinth packing is usually used to prevent air from leaking or leaking in, and a part of the main steam is supplied as gland steam from the high-pressure side gland to the low-pressure side gland to create a complete airtight seal. I am trying to maintain my gender.

To explain the conventional gland steam pipe system in terms of the reaction type steam turbine shown in Fig. 1, in the reaction type steam turbine, the axial thrust generated by the blade row parts 2, etc. is transmitted to the axle l provided with the blade row parts 2 in multiple stages. Balance piston 3 for balancing purpose
is equipped with.

A labyrinth packing 5 is provided between the balance piston 3 and the casing 4 as an airtight device.

Reference numeral 7 denotes a high-pressure side gland part provided between the high-pressure part casing 6 and the axle l, and 9 denotes a low-pressure side gland part provided between the low-pressure part casing 8 and the axle l, each of which constitutes a labyrinth packing. There is. 10 is a high pressure casing, and main steam is supplied to the high pressure casing 10 from a pipe 12 via a main steam stop valve 1. 14 is a low pressure casing, and the blade row section 2
The main steam led to the low pressure casing 14 via the condenser 15 enters the condenser 15 through the pipe 16 and is recovered. A main steam bleed pipe 18 bleeds main steam from an intermediate stage of the blade row section 2. ■ is a shaft seal main tube that connects the intermediate parts of the high-pressure side gland section 7 and the low-pressure side gland section 9, and n is the labyrinth packing 5.
This is a balance pipe that connects the rear end of the main steam bleed pipe 18 to the main steam bleed pipe 18.

Through the piping system as described above, a part of the high-temperature, high-pressure main steam supplied to the high-pressure casing 10 flows as leaked steam from the front end A of the labyrinth packing 5 in the direction of the arrow shown in the figure and passes through the rear end B. The leaked steam flowing out from the rear end part B is branched and supplied to the high-pressure side gland part 7, and further, part of the leaked steam sent from the middle part of the high-pressure side gland part 7 to the shaft seal main pipe (9) is The remaining leaked steam is supplied to the middle part of the low-pressure side gland [9] and is used as sealing steam for the high-pressure side gland part 7 and the low-pressure side gland part 9, respectively. . Among the leaked steam that has flowed out from the labyrinth packing 5, the remaining amount of leaked steam that is not used as sealing steam between the high-pressure side and the low-pressure side gland section 7.9 is combined with the bleed air of the main steam bleed pipe 18 through the balance pipe n. Alternatively, it may be introduced into the main steam flow at an intermediate stage of the blade row section 2.

In this way, conventional ground steam is leaked steam that is discharged after being subjected to the throttling action by the labyrinth packing 5, so unlike the main steam that has passed through the blade cascade and performed expansion work, its temperature drop is extremely low. The high-temperature steam, which is small in size and has a temperature almost equal to the main steam temperature in the high-pressure casing, is then supplied to the high-pressure side and low-pressure side gland sections and the gland steam condenser.

Therefore, low cycle fatigue and creep occur due to expansion and contraction due to temperature differences on the outer peripheral surface and shaft center of the balancing piston 3, which has a larger diameter than the turbine axle l. There are problems in that the mechanical strength of parts that come in contact with high-temperature steam decreases, such as the end face and shaft center of the side axle receiving thermal shock and causing brittle fracture, and the gland part of the bent casing 4 becoming bent due to thermal stress. was there.

Furthermore, losses due to leakage of main steam with high enthalpy from the high-pressure casing to the outside of the system, and the gland of the casing becoming 9-shaped due to thermal stress, increasing the fin gap of the labyrinth packing, reduce the performance of the steam turbine. This was a contributing factor.

These problems are particularly noticeable when the main steam pressure and temperature conditions are high, and in single-casing steam turbines that have large geometries and do not have a speed stage. A speed gear is provided to reduce the pressure and temperature of the main steam in the high-pressure vehicle compartment, which is the source of leakage steam. However, with such means, a large amount of thermal energy is consumed in the governor stage, which has inferior performance compared to the 8-row section, which further adds to the factors that reduce the performance of the turbine. In addition, in order to lower the temperature of the sealed steam in the low-pressure side gland section 9, a method of cooling the sealing steam by injecting water into the shaft sealing main tube connecting the high-pressure side gland section 7 and the low-pressure side gland section 9 is also adopted. However, since the amount of water injected was extremely small, its effectiveness was limited, and there were problems with the operability and reliability of the steam turbine.

[Purpose of the invention]

This invention was made to solve the above-mentioned problems, and mixes low-temperature steam from the blade row with high-temperature leaked steam flowing into the labyrinth packing of the balancing piston to lower the temperature of the gland steam. It is designed to lower the amount of water and supply it to h.

[Summary of the invention]

According to the present invention, an intermediate chamber is formed on the casing side of the labyrinth packing, and a connecting pipe is provided that communicates the intermediate chamber with an intermediate stage on a higher pressure side than the bleed stage of the turbine blade row. The bleed air from the intermediate stage on the high pressure side passes through the intermediate stage, mixes with the steam leaking from the front end of the labyrinth packing, and flows to the rear end of the labyrinth, and connects the bleed air to the high pressure side gland section and the low pressure side. This is achieved by dividing the flow into the ground section.

Embodiments of the present invention will be described below with reference to the drawings. Second
The figure is a system diagram of a grand steam pipe showing an embodiment of the present invention. Since the structure of the steam turbine and the arrangement of the shaft seal header tube and the balance tube are the same as those of the conventional example shown in FIG. 1, they will be designated by the same reference numerals and detailed explanation will be omitted.

In FIG. 2, reference numeral 13 denotes an intermediate chamber, which is provided in the middle part of the labyrinth packing 5 between the balance piston 3 and the casing 4, with an opening C facing the casing 4 side and the balance piston 3 side. There is. 17 is a connecting pipe that communicates the intermediate chamber 13 with point E of the intermediate stage of the turbine blade row 2 which is closer to the high pressure side than the inlet @D of the main steam bleed pipe 18, and vents the bleed air from point E to the intermediate chamber 13. It is for. In this case, the pressure in the intermediate chamber 13 will be the same as the pressure at point E, and the pressure at the rear end B of the labyrinth packing 5 will also be approximately the same as that at point m2.

Now, the amount of leaked steam between the front end A of the labyrinth seal 5 and the opening C of the intermediate chamber 13 is Gl, and the amount of leakage steam between the opening C of the intermediate chamber 13 (!: between the labyrinth seal and the rear end B of the kin 5 Let G2 be the amount of leaked steam, and if Gt > G2, the amount of steam (Gl-G,) is returned from the intermediate chamber 13 to the intermediate stage of the row section 2 through the connecting pipe 17, Steam amount G2
The liquid flows from the opening C of the intermediate chamber 13 to the rear end B of the labyrinth packing 5. On the contrary, if Gz>Gt,
The amount of steam (Gz Gl) flows from point E of the intermediate stage on the high pressure side of the blade row section 2 through the connecting pipe 17 in the direction of the arrow shown in the figure, and flows into the intermediate chamber 1.
3, and the amount of steam G2 mixed with steam tGt flows to the rear end B of the labyrinth packing 5.

Therefore, in order to make G2>Gl, the following formula, which is generally known regarding the amount of steam leaking through the labyrinth packing, may be used.

Here, Gz leakage steam amount (Kf/S) φ = flow', coefficient F = annular area of the labyrinth (k) P, = steam pressure at the leakage starting point (N/rrP) P2 = steam pressure at the leakage point ( N7m) Z = Number of fins in the labyrinth ■ + = Steam specific volume at the point where leakage starts -V ~) The steam pressure at the front end A and rear end B of the labyrinth seal 5 of the balancing piston 3 is the main steam condition side and the main steam Since it is determined by the pressure at the inlet point E of the air bleed pipe, if the annular area of the labyrinth packing 5 is constant, the number of fins between the front end A and the rear end B from the opening C of the intermediate chamber 13 is selected as appropriate. If we set the position of the opening C and set the connection part between the connecting pipe 17 and the high-pressure intermediate stage E of the blade row section 2 to an appropriate pressure, then G2>Gl. You can configure settings like this.

Therefore, the position of the opening C of the intermediate chamber 13 is set so that the length between AC and C8 is smaller than the length between C8 and C8, as in the illustrated embodiment.

In this way, high-temperature leaked steam that has flowed from the high-pressure casing 10 through the front end A of the labyrinth packing 5 can be removed from the main steam that has flowed from the intermediate stage E of the blade row section 2 to the intermediate chamber 13 through the connecting pipe 17. It mixes with steam and flows to the rear end B of the labyrinth packing 5. Since the main steam passing through the connecting pipe 17 is relatively low-temperature steam that has undergone expansion work in the blade cascade, the wake from the opening C of the intermediate chamber 13 is leaked steam whose temperature has been reduced.
After this is supplied to the high-pressure side gland section 7, it is supplied to the low-pressure side gland section 9 via the shaft-sealed main pipe m, and the remainder is extracted together with the steam in each gland section via the balance pipe ρ. It is diverted to the trachea 18.

According to this embodiment, since the intermediate chamber 13 is always filled with low-temperature steam, by increasing the volume of the intermediate chamber, the influence of heating of the balance piston can be reduced.

〔Effect of the invention〕

As described above, this invention provides an intermediate chamber on the casing side of the labyrinth packing between the balancing piston and the casing, and connects this intermediate chamber with the intermediate stage on the high pressure side of the turbine blade row to prevent high-temperature leakage. The structure is such that the low-temperature steam that has undergone expansion work in the blade row section flows into the intermediate chamber, and flows from the intermediate chamber to the rear end of the labyrinth packing to reduce the temperature of the leaked steam. Therefore, according to the present invention, it is possible to lower the gland steam temperature in the high-pressure side gland section and the low-pressure side gland section, which not only solves the strength problems caused by heating of the balance piston and the low-pressure side axle. At the same time, it becomes possible to solve problems such as leakage of main steam with high enthalpy out of the system and a decrease in turbine performance due to an increase in the labyrinth fin gap in the gland part due to the shape of the casing arm. This has the effect of improving performance and reliability.

[Brief explanation of the drawing]

Fig. 1 is a conventional grand steam pipe system diagram, and Fig. 2 is a grand steam pipe system diagram showing an embodiment of the present invention. Hematsuginkeimetsukuchinen匈N
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Claims (1)

[Claims] 1) Part of the leaked steam passing through the labyrinth packing between the balancing piston and casing installed on the turbine axle is
The rear end of the labyrinth packing is connected to the bleed pipe from the intermediate stage of the turbine blade row through the balance pipe, and
In a steam turbine configured to supply remaining leakage steam to a high-pressure side gland section and a low-pressure side gland section, an intermediate chamber is formed on the casing side of the labyrinth packing, and an air extraction stage between the intermediate chamber and the turbine blade row is formed. A connecting pipe is provided that communicates with the intermediate stage on the higher pressure side, and the bleed air from the intermediate stage on the higher pressure side is mixed with the leaking steam from the front end of the labyrinth packing through the intermediate chamber, and the steam is removed from the labyrinth packing. 1. A gland steam pipe device for a steam turbine, characterized in that the air flows to a rear end portion and branches to the bleed pipe, the high-pressure side gland portion, and the low-pressure side gland portion.