JPS6148613B2 - - Google Patents

Abstract

PURPOSE:To lower the temperature of gland steam, by providing a connection pipe to connect a halfway chamber defined on the halfway part of a labyrinth packing for a balance piston, to the halfway stage of a turbine cascade. CONSTITUTION:Leakage steam flows through a labyrinth packing 5 between a casing 4 and a balance piston 3 mounted on a turbine shaft 1. A halfway chamber 13 is defined on the halfway part of the labyrinth packing 5 for the balance piston 3. The halfway chamber 13 is connected to the halfway stage D of a turbine cascade 2 through a connection pipe 17. Since the steam of the halfway chamber 13 is replaced with bled steam of relatively low temperature from a main steam bleed pipe 18, the temperature of gland steam for a high-pressure gland 7 and a low-pressure gland 9 can be lowered to prevent the fall in the mechanical strength of the turbine shaft 1 and the casing 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present 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, which 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 the main steam led to the low pressure casing 14 via the blade row section 2 enters the condenser 15 through a pipe 16 and the like and is recovered. A main steam bleed pipe 18 bleeds main steam from an intermediate stage of the blade row section 2. 20 is a shaft-sealing main tube that connects the intermediate portions of the high-pressure side gland section 7 and the low-pressure side gland section 9, and 22 is a balance pipe that connects the rear end of the labyrinth packing 5 and the main steam bleed pipe 18. .

A part of the high-temperature, high-pressure main steam supplied to the high-pressure casing 10 through a steam-like piping system flows as leaked steam from the front end A of the labyrinth packing 5 in the direction of the arrow 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. Alternatively, it may be introduced into the main steam flow at an intermediate stage of the blade row section 2.

In this way, conventional gland steam is leaked steam that is discharged after being throttled by the labyrinth packing 5, so unlike main steam that has passed through the blade cascade section 2 and done expansion work, its temperature decreases. is extremely small, and high-temperature steam almost equal to the main steam temperature of the high-pressure casing 10 is supplied as it is to the high-pressure side/low-pressure side gland sections 7, 9 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 leakage of high-enthalpy main steam from the high-pressure casing 10 to the outside of the system, and deformation of the gland section of the casing 4 due to thermal stress, which increases the fin gap of the labyrinth seal 5, etc., impair the performance of the steam turbine. This was a contributing factor to the decline.

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 inside the high-pressure vehicle, 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 turbine blade cascade 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 reduce the amount of water and supply it.

[Summary of the invention]

According to the present invention, an intermediate chamber is formed in the middle of the casing side of the labyrinth packing, and the intermediate chamber communicates with the bleed pipe on the upstream side of the confluence of the balance pipe and the bleed pipe. Most of the leaked steam is returned to the bleed pipe through the intermediate chamber, mixed with the bleed air from the intermediate stage of the turbine blade row, and sent to the high-pressure side gland section via the balance pipe. This is achieved by supplying it to the low-pressure side ground section.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a grand steam pipe system diagram showing an embodiment of the present invention. Since the structure of the steam turbine and the arrangement of the shaft-sealed 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 explanation will be omitted.

In FIG. 2, reference numeral 13 denotes an intermediate chamber, which is located on the casing side of the labyrinth packing 5 between the balance piston 3 and the casing 4, and is located slightly toward the rear end of the labyrinth packing from the middle part thereof. An opening C is provided facing the balancing piston 3. A connecting pipe 17 connects the intermediate chamber 13 and the main steam bleed pipe 18, and is connected to a point I upstream of the confluence H of the balance pipe 22 and the main steam bleed pipe 18.

Therefore, most of the leaked steam introduced from the high-pressure casing 10 through the front end A of the labyrinth packing 5 is transferred to the intermediate chamber 13 from the opening C of the intermediate chamber 13.
It flows through the connecting pipe 17 in the direction of the arrow shown and merges with the bleed air in the main steam bleed pipe 18, so that the intermediate chamber 13
The amount of steam leaking between the opening C and the rear end B of the labyrinth packing 5 is extremely small. Therefore, if the pressure in the intermediate chamber 13 is P _C , the pressure in the intermediate stage D of the turbine blade row 2 is P _D , and the pressure at the rear end B of the labyrinth packing 5 is P _B , then the pressure relationship is P _C >P _D >P _B. The leaked steam that entered the main steam bleed pipe 18 via the connecting pipe 17 mixes with the relatively low-temperature bleed air that has undergone expansion work up to the intermediate stage of the blade row section 2, raising the temperature of the bleed air slightly, and then It flows through the balancing pipe 22 in the direction of the arrow in the figure and is supplied to the high-pressure side gland section 7, and is further supplied from the middle section of the high-pressure side gland section 7 to the low-pressure gland section 9 via the shaft seal main tube 20, so that the high-pressure side and low-pressure side ground part 7,
9 sealed steam.

In this way, almost all of the high temperature leaked steam introduced into the labyrinth packing 5 of the balancing piston 3 is recovered into the main steam bleed pipe 18 via the intermediate chamber 13, and the relatively low temperature Since most of the steam is diluted by the bleed air, high-temperature sealed steam is not supplied to the high-pressure side and low-pressure side gland sections 7 and 9.

Opening C of intermediate chamber 13 of labyrinth packing 5
Since almost no steam flow occurs between the rear end portion B and the rear end portion B, leaking steam during this period has extremely little influence on the temperature of the sealed steam in the gland portion.

The position of the opening C of the intermediate chamber 13 needs to be selected appropriately considering the relationship between the front end A of the labyrinth packing 5 and the opening C, and the labyrinth packing effect. It is desirable to set it at a position close to part B.

In the illustrated embodiment, the connecting pipe 17 is connected to the main steam bleed pipe 1.
8, but the connecting pipe 17 is connected to the pressure point of the same blade cascade separately from the main steam bleed pipe 18, and air is extracted from a slightly lower pressure side than the pressure point, and then connected to the balance pipe. Even if a conduit is provided, the same effects as described above can be obtained.

〔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, connects this intermediate chamber with the bleed pipe from the intermediate stage of the turbine blade row, It is configured to reduce the temperature of high-temperature leaked steam by diluting it with low-temperature steam that has undergone expansion work in the blade cascade. 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. It is possible to obtain the effect of improving both reliability 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. 1: Turbine axle, 2: Turbine blade cascade, 3:
Balance piston, 4: casing, 5: labyrinth packing, 7: high pressure side gland, 9: low pressure side gland section, 13: intermediate chamber, 17: connecting pipe, 18: main steam bleed pipe, 22: balancing 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 drained from the rear end of the labyrinth packing through the balancing pipe and into the bleed pipe from the intermediate stage of the turbine blade row. 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 in the middle of the labyrinth packing on the casing side, and the remaining leaked steam is connected to the intermediate chamber. A connecting pipe communicating with the bleed pipe is provided upstream of the confluence of the balancing pipe and the bleed pipe, and most of the leaked steam is returned to the bleed pipe via the intermediate chamber from the intermediate stage of the turbine blade row. A gland steam pipe device for a steam turbine, characterized in that the bleed air is mixed with the bleed air and sent to a high-pressure side gland section through the balancing pipe, and further supplied to a low-pressure side gland section.