JPS6410642B2 - - 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.

[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 to prevent air leakage and inflow, but this gland packing is usually a labyrinth packing. Part of the main steam is supplied as gland steam from the high-pressure side gland section to the low-pressure side gland section to maintain complete airtightness.

A conventional gland steam pipe system will be explained with reference to the reaction type steam turbine shown in FIG.
A balancing piston 3 is provided for the purpose of balancing the axial thrust generated by the blade row section 2 and the like.
A labyrinth packing 5 is provided between the balance piston 3 and the casing 4 as an airtight device.
Reference numeral 7 indicates a high-pressure side gland section provided between the high-pressure section casing 6 and the axle 1, and 9 indicates a low-pressure section casing 8.
and the axle 1, each forming a labyrinth packing. 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 11. Reference numeral 14 denotes a low pressure casing, and main steam led to the low pressure casing 14 via the blade row section 2 enters the condenser 15 through a pipe 16 and is recovered. A main steam bleed pipe 18 bleeds main steam from an intermediate stage of the blade row section 2. Reference numeral 20 designates a shaft-sealing main pipe that connects the intermediate portions of the high-pressure side gland portion 7 and the low-pressure side gland portion 9, and 22 represents a balance pipe that connects the rear end of the labyrinth packing 5 and 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 a part of the leaked steam fed into the shaft seal main pipe 20 from the middle part of the high-pressure side gland part 7 is further diverted. The remaining leaked steam is introduced into a gland steam condenser (not shown) and collected, and the remaining leaked steam is supplied to the intermediate portion of the low-pressure side gland section 9 to serve as sealing steam for the high-pressure side gland section 7 and the low-pressure side gland section 9, respectively. Among the leaked steam that has flowed out from the labyrinth packing 5, the remaining leaked steam that is not used as sealing steam for the high-pressure side and low-pressure side gland sections 7 and 9 passes through the balance pipe 22 and merges with the bleed air from the main steam bleed pipe 18. or 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 throttled 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 supplied as is to the high-pressure side and low-pressure side gland sections and the gland steam condenser.

For this reason, low-cycle fatigue and creep occur on the outer peripheral surface and shaft center of the balancing piston 3, which has a larger diameter than the turbine axle 1, due to expansion and contraction due to temperature differences. There are problems in that the mechanical strength of parts that come in contact with high-temperature steam is reduced, 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 casing 4 being deformed due to thermal stress. Ta.

Furthermore, losses due to main steam with high enthalpy leaking out of the system from the high-pressure casing, and deformation of the gland section of the casing due to thermal stress, increasing the fin gap of the labyrinth seal, are factors that reduce the performance of the steam turbine. It was becoming.

These problems are particularly noticeable in single-casing steam turbines that have large shapes and dimensions and do not have a governor stage when main steam pressure and temperature conditions are high. established,
Measures are taken to reduce the pressure and temperature of the main steam in the high-pressure vehicle interior, which is the source of leakage steam. but,
With such means, a large amount of thermal energy is consumed in the governing stage, which has inferior performance compared to the blade row, and thus the factors that reduce the performance of the turbine are further aggravated. 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 shaft sealing main tube 20 that connects the high-pressure side gland section 7 and the low-pressure side gland section 9 by injecting water is also adopted. There are, but
Because 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 before supplying it.

[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. Bleed air from the intermediate stage on the high pressure side is passed through the intermediate stage,
This is achieved by mixing the steam leaking from the front end of the labyrinth packing, flowing it to the rear end of the labyrinth, and then branching it to the bleed pipe, the high-pressure side gland section, and the low-pressure side gland section.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a system diagram of a gland steam pipe showing an embodiment of the present invention. Since the structure of the steam turbine and the arrangement of the shaft-sealing main tube and balance tube are the same as those of the conventional example shown in FIG. 1, they are designated by the same reference numerals and detailed description thereof 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. 1
Reference numeral 7 denotes a connecting pipe that communicates the intermediate chamber 13 with a point E in 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 bleeds air from the point E to the intermediate chamber 1.
This is for ventilation to 3. 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 the former two.

Now, the amount of leaking steam between the front end A of the labyrinth packing 5 and the opening C of the intermediate chamber 13 is _G1 , and the amount of leaking steam between the opening C of the intermediate chamber 13 and the rear end B of the labyrinth packing 5 is G1. If the quantity is G ₂ , then G ₁ >
In the case of G ₂ , the amount of steam (G ₁ - _{G 2} ) is returned from the intermediate chamber 13 to the intermediate stage of the blade row section 2 through the connecting pipe 17, and the amount of steam G ₂ is returned to the opening C of the intermediate chamber 13. From there, it flows to the rear end B of the labyrinth packing 5. On the other hand, if G ₂ > G ₁ , the amount of steam (G ₂ - _{G 1} ) flows into the blade row section 2 from point E of the intermediate stage on the high pressure side through the connecting pipe 17 in the direction of the arrow shown in the figure, and flows into the intermediate chamber. 13, steam volume
The amount of steam G ₂ mixed with G ₁ is labyrinth packing 5
It will flow to the rear end B of.

Therefore, in order to satisfy G ₂ >G ₁ , the following formula, which is generally known regarding the amount of steam leaking through the labyrinth packing, may be used.

Here, G = Leakage steam amount (Kg/S) φ = Flow coefficient F = Labyrinth annular area (m ² ) P ₁ = Steam pressure at the leakage start point (N/m ² ) P ₂ = Steam at the leakage point Pressure (N/m ² ) Z = Number of fins in the labyrinth V ₁ = Steam specific volume at the starting point of leakage (m ³ /Kg) The steam pressure at the front end A and rear end B of the labyrinth seal 5 of the balancing piston 3 is Since it is determined by the main steam conditions and the pressure at the inlet point E of the main steam bleed pipe, if the annular area of the labyrinth packing 5 is constant, there is a gap between the opening C of the intermediate chamber 13 and the front end A and the rear end B. The number of fins is appropriately selected and the position of the opening C is set, and the connection pipe 17 and the blade row section 2 are
If the connection part with the intermediate stage E on the high pressure side is set to have an appropriate pressure, it is possible to set G ₂ > G ₁ .

Therefore, the position of the opening C of the intermediate chamber 13 is set so that the length between AC is smaller than the length between CB, 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 into the intermediate chamber 13 from the intermediate stage E of the blade row section 2 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 seal main tube 20, and together with the sealing steam of each gland section,
The remainder is diverted to the bleed pipe 18 via the balance pipe 22.

According to this embodiment, the intermediate chamber 13 is always filled with low-temperature steam, so 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, the temperature of the gland steam in the high-pressure side gland section and the low-pressure side gland section can be lowered, and the strength problems caused by heating of the balance piston and the low-pressure side axle are solved. This makes it possible to simultaneously solve problems such as leakage of main steam with high enthalpy out of the system and deterioration of turbine performance due to increased labyrinth fin gaps in the gland due to deformation of the casing, and improve operability of the steam turbine. and can have the effect of improving reliability.

[Brief explanation of drawings]

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. 1: Turbine axle, 2: Blade row section, 3: Balancing piston, 5: Labyrinth packing, 7: High pressure side gland section, 9: Low pressure side gland section, 10: High pressure casing, 13: Intermediate chamber, 17: Connection Pipe, 18: Main steam bleed pipe, 20: Shaft-sealed main pipe, 22: Balance pipe.

Claims (1)

[Claims] 1. A part of the leaked steam passing through the labyrinth packing between the balancing piston and the casing installed on the turbine axle is transferred from the rear end of the labyrinth packing to the bleed pipe from the intermediate stage of the turbine blade row via the balancing pipe. In the steam turbine in which the remaining leaked steam is supplied to the high-pressure side gland section and the low-pressure side gland section, an intermediate chamber is formed on the casing side of the labyrinth packing, and the intermediate chamber and the turbine A connecting pipe is provided that communicates with an intermediate stage on a higher pressure side than the bleed air stage of the blade row, and the bleed air from the intermediate stage on the high pressure side is mixed with the steam leaking from the front end of the labyrinth packing through the intermediate chamber. A gland steam pipe device for a steam turbine, characterized in that the flow is conducted to the rear end portion of the labyrinth packing, and is branched to the bleed pipe, the high-pressure side gland portion, and the low-pressure side gland portion.