A method of adjusting the pressure drop of a gas turbine contact seal

Abstract

The application belongs to the field of energy and power, and particularly relates to a gas turbine contact seal pressure drop adjusting method. The application actively adjusts the pressure difference on both sides of a graphite seal ring, ensures that the pressure difference on both sides of the graphite seal ring is within a specified range in the full working condition range of the gas turbine, greatly improves the service life of the graphite seal ring, and improves the reliability level of the gas turbine.

Description

Technical Field

[0001] This invention belongs to the field of energy and power, and specifically relates to a method for adjusting the pressure drop of the contact seal of a gas turbine. Background Technology

[0002] The selection of sealing materials for gas turbine bearing cavities is crucial to the successful design of sealing devices. For contact seals or seals where friction may occur during operation, the pairing characteristics of the materials involved in the friction are paramount when selecting sealing materials. Carbon graphite sealing materials, due to their excellent friction and wear resistance, self-lubrication, low coefficient of linear expansion, low density, high specific strength, and slight increase in strength and hardness with increasing temperature, are suitable not only for high-speed, high-temperature shaft seals but also for reciprocating motion seals at relatively high temperatures, making them the preferred material for gas turbine bearing cavity seals. However, to ensure the service life of graphite sealing rings, the pressure difference across the graphite sealing ring must be maintained within a specified range throughout the entire operating range of the gas turbine. Exceeding this pressure difference will accelerate the wear of the graphite sealing ring; the greater the pressure difference, the faster the wear, significantly reducing the service life of the graphite sealing ring. Therefore, it is essential to adjust the pressure difference across the graphite sealing ring within the specified range to improve its service life and thus enhance the reliability of the gas turbine. Summary of the Invention

[0003] The purpose of this invention is to provide a method for adjusting the pressure drop of the contact seal of a gas turbine, so as to ensure that the pressure difference on both sides of the graphite sealing ring in the bearing cavity of the gas turbine is within a specified range.

[0004] A method for adjusting the pressure drop of a gas turbine contact seal includes the following steps:

[0005] S1, measure the pressure of the oil-gas separator, that is, the pressure on the side of the graphite sealing ring bearing cavity is P0;

[0006] S2, the pressure of compressed air drawn from the gas turbine compressor stage for sealing the graphite sealing ring is P;

[0007] S3, the measured function relationship between the friction loss ΔP of the compressed air from the gas turbine compressor stages to the sealed side of the graphite sealing ring and the pressure P2 after the compressor is as follows:

[0008] △P=f(P2)

[0009] S4, the pressure P1 on the sealing side of the graphite sealing ring is calculated:

[0010] P1 = P - △P = Pf(P2)

[0011] S5, the pressure drop ΔP of the contact seal is calculated. 压差 :

[0012] △P 压差=P1-P0=P-P0-f(P2)

[0013] Since the pressure drop regulator is a constant differential pressure valve, P-P0 is a fixed value. The differential pressure value P-P0 of the pressure drop regulator is set by the change in friction loss ΔP, thereby ensuring the contact seal pressure drop ΔP of the gas turbine under all operating conditions. 压差 Within the prescribed scope.

[0014] The beneficial effects of this invention are as follows: This invention actively adjusts the pressure difference on both sides of the graphite sealing ring, ensuring that the pressure difference on both sides of the graphite sealing ring is within the specified range throughout the entire operating range of the gas turbine, greatly improving the service life of the graphite sealing ring and enhancing the reliability of the gas turbine. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0016] The present invention will now be further described with reference to the accompanying drawings.

[0017] like Figure 1 The diagram shown is a structural schematic of the present invention, which includes three subsystems: an oil supply subsystem, an oil return subsystem, and a ventilation subsystem.

[0018] The oil supply subsystem consists of an oil tank 1, a booster pump 2, a pressure regulating valve 3, an oil filter 4, a check valve 5, a front bearing chamber 6, and a rear bearing chamber 7. The booster pump 2 draws lubricating oil from the oil tank 1, the pressure regulating valve 3 can adjust the oil supply pressure, and the oil enters the front bearing chamber 6 and the rear bearing chamber 7 through the oil filter 4 and the check valve 5.

[0019] The oil return subsystem consists of an oil tank 1, a front bearing cavity 6, a rear bearing cavity 7, an oil-gas separator 9, an oil return pump 10, and an oil radiator 11. The lubricating oil after lubricating and cooling the gas turbine bearings enters the oil-gas separator 9 through the bottom of the front bearing cavity 6 and the rear bearing cavity 7, and is then pumped back by the oil return pump 10. After being cooled by the oil radiator 11, it enters the oil tank 1.

[0020] The ventilation subsystem consists of a front bearing chamber 6, a rear bearing chamber 7, a throttle valve 8, an oil-gas separator 9, a pressure drop regulator 12, and a static oil-gas separator 13. The oil-gas separator 9 is connected to both the front and rear bearing chambers 6 and 7. The lower part of the oil-gas separator 9 contains lubricating oil used to lubricate and cool the gas turbine bearings, while the upper part contains an oil-gas mixture. A gas line from the compressor interstage is drawn through the throttle valve 8 to pressurize the oil-gas separator 9. The oil-gas mixture in the oil-gas separator 9 enters the static oil-gas separator 13 via the pressure drop regulator 12. The other end of the pressure drop regulator 12 is connected to a specific compressor interstage to regulate the pressure in the oil-gas separator 9. The static oil-gas separator 13 separates the oil and gas; the separated lubricating oil enters the lubricating oil tank 1, and the separated gas is discharged to the exhaust duct.

[0021] A pressure drop regulator is installed to adjust the pressure of the oil-gas separator. One end of the regulator is connected to the oil-gas separator, and the other end is connected to the gas turbine compressor stage used for sealing the graphite sealing ring. The outlet of the regulator is connected to the static oil-gas separator and vented to the atmosphere. A pressurization path from the compressor stage to the oil-gas separator is provided to accelerate the response speed of adjusting the pressure difference on both sides of the graphite sealing ring, while also adding another adjustment method.

[0022] A method for adjusting the pressure drop of a gas turbine contact seal includes the following steps:

[0023] S1, measure the pressure of the oil-gas separator, that is, the pressure on the side of the graphite sealing ring bearing cavity is P0;

[0024] An oil-gas separator is installed to collect the lubricating oil from the bearing cavity after cooling the bearing. The lubricating oil in the oil-gas separator is pumped back by a return oil pump. The pumping capacity of the return oil pump is 2 to 3 times the amount of lubricating oil in the bearing cavity, ensuring that the oil-gas separator is a dry oil pool. In this way, the oil-gas separator is connected to the bearing cavity, and the pressure in the oil-gas separator and the bearing cavity is the same. That is, the pressure on the bearing cavity side of the graphite sealing ring is the pressure in the oil-gas separator.

[0025] S2, the pressure of compressed air drawn from the gas turbine compressor stage for sealing the graphite sealing ring is P;

[0026] S3, the measured function relationship between the friction loss ΔP of the compressed air from the gas turbine compressor stages to the sealed side of the graphite sealing ring and the pressure P2 after the compressor is as follows:

[0027] △P=f(P2)

[0028] S4, the pressure P1 on the sealing side of the graphite sealing ring is calculated:

[0029] P1 = P - △P = Pf(P2)

[0030] S5, the pressure drop ΔP of the contact seal is calculated. 压差 :

[0031] △P 压差 =P1-P0=P-P0-f(P2)

[0032] Since the pressure drop regulator is a constant differential pressure valve, P-P0 is a constant value. Therefore, the contact seal pressure drop ΔP 压差 The pressure difference value P-P0 of the pressure drop regulator is set as a function of the pressure P2 after the compressor, based on the change in friction loss ΔP, thereby ensuring the contact seal pressure drop ΔP of the gas turbine under all operating conditions. 压差 Within the prescribed scope.

[0033] Since the pressure P0 on the bearing cavity side of the graphite sealing ring is a passively adjusted value, the pressure P0 changes slightly slower when the gas turbine changes operating conditions, resulting in excessive pressure drop of the contact seal under changing operating conditions. To improve this situation, a pressurization path from the compressor stage to the oil-gas separator is set up. Since the pressure between the compressor stages is well synchronized with the pressure change after the compressor, the pressure P0 is better aligned with the gas turbine operating conditions.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for adjusting the pressure drop of a gas turbine contact seal, characterized in that, Includes the following steps: S1, measure the pressure of the oil-gas separator, that is, the pressure on the side of the graphite sealing ring bearing cavity is P0; S2, the pressure of compressed air drawn from the gas turbine compressor stage for sealing the graphite sealing ring is P; S3, the measured function relationship between the friction loss ΔP of the compressed air from the gas turbine compressor stages to the sealed side of the graphite sealing ring and the pressure P2 after the compressor is as follows: △P=f(P2) S4, the pressure P1 on the sealing side of the graphite sealing ring is calculated: P1 = P - ΔP = P - f(P2) S5, the pressure drop ΔP of the contact seal is calculated. 压差 : △P 压差 = P1- P0=P- P0- f(P2) Since the pressure drop regulator is a constant differential pressure valve, P-P0 is a constant value. The differential pressure value P-P0 of the pressure drop regulator is set by the change in friction loss ΔP, thereby ensuring the contact seal pressure drop ΔP of the gas turbine under all operating conditions. 压差 Within the prescribed scope; It includes three subsystems: oil supply subsystem, oil return subsystem, and ventilation subsystem; The oil supply subsystem consists of a lubricating oil tank, a booster pump, a pressure regulating valve, a lubricating oil filter, a check valve, a front bearing cavity, and a rear bearing cavity. The booster pump draws lubricating oil from the lubricating oil tank, the pressure regulating valve can adjust the oil supply pressure, and the oil enters the front bearing cavity and the rear bearing cavity through the lubricating oil filter and check valve 5. The oil return subsystem consists of a lubricating oil tank, a front bearing cavity, a rear bearing cavity, an oil-gas separator, a return oil pump, and a lubricating oil radiator. The lubricating oil after lubricating and cooling the gas turbine bearings enters the oil-gas separator through the bottom of the front and rear bearing cavities, and is then pumped back by the return oil pump. After being cooled by the lubricating oil radiator, it enters the lubricating oil tank. The ventilation subsystem consists of a front bearing chamber, a rear bearing chamber, a throttle valve, an oil-gas separator, a pressure drop regulator, and a static oil-gas separator. The oil-gas separator is connected to the front and rear bearing chambers. The lower part of the oil-gas separator contains lubricating oil that lubricates and cools the gas turbine bearings, while the upper part contains an oil-gas mixture. A gas line from the compressor stage is drawn through the throttle valve to pressurize the oil-gas separator. The oil-gas mixture in the oil-gas separator enters the static oil-gas separator through the pressure drop regulator. The other end of the pressure drop regulator is connected to a certain stage of the compressor to regulate the pressure of the oil-gas separator. The static oil-gas separator separates the oil and gas. The separated lubricating oil enters the lubricating oil tank, and the separated gas is discharged to the exhaust duct.

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