Adjusting method and structure of lubricating oil bearing cavity of gas turbine

Abstract

The invention relates to an adjusting method and structure of a lubricating oil bearing cavity of a gas turbine. When the gas turbine runs for a period of time and has a graphite sealing ring abrasion fault, meanwhile, sealing air in a bearing cavity is located outside a gas turbine body, and the gas turbine still needs to run continuously, adjustment can be conducted through the adjusting method provided by the invention. And if the lubricating oil consumption rate of the gas turbine is greater than a standard value, the bearing chamber at a certain position can be positioned to be untight in sealing by comparing the pressure of the bearing chamber with the lubricating oil return temperature. Adjustment can be achieved by adding a connecting pipeline of the bearing cavity and the static oil-gas separator and arranging a throttling orifice at the position where the pipeline is added. The method is of great significance to stable operation of the gas turbine.

Description

Technical Field

[0001] This invention relates to the field of gas turbine technology, and in particular to a method and structure for adjusting the lubricating oil bearing cavity of a gas turbine. Background Technology

[0002] As a high-speed rotating power plant, gas turbines operate under high-frequency variable conditions. When the rotor rotates at high speed and the rotor speed changes, a large amount of heat is generated between the bearings. In order to remove the hard inclusions formed between the mating surfaces in the bearing cavity, and to remove the heat generated by friction and the heat transferred to the lubricating oil from the high-temperature area, gas turbines require a lubricating oil system for lubrication.

[0003] However, after a gas turbine has been running for a period of time, especially when it is close to its overhaul life, the graphite sealing ring of the lubricating oil bearing chamber may be damaged. However, under certain circumstances, such as offshore oil platforms, the unit still needs to be operated even when the graphite ring is worn. This requires a lubricating oil bearing chamber adjustment method that can ensure the continued operation of the unit.

[0004] As the gas turbine operates, the lubricating oil consumption will exceed the specified value due to changes in the grate seal clearance and the graphite seal condition. To ensure the continuous and stable operation of the unit, a lubricating oil bearing cavity adjustment method is needed to ensure the continued operation of the unit. Summary of the Invention

[0005] This application addresses the shortcomings of the existing production technology by providing a method and structure for adjusting the lubricating oil bearing cavity of a gas turbine, which can quickly alleviate high temperature and high pressure conditions under extreme circumstances, enabling the gas turbine to continue operating.

[0006] The technical solution adopted in this invention is as follows: A method for adjusting the lubricating oil bearing cavity of a gas turbine is provided, applicable to situations involving graphite seal ring wear and abnormally increased lubricating oil consumption. When the graphite sealing ring fails due to wear, gradually reduce the amount of sealing air so that the lubricating oil return temperature gradually decreases at rated power. When the lubricating oil consumption rate increases abnormally, add a separator connecting branch pipe, adjust the pressure and flow rate in the separator connecting branch pipe, reduce the pressure in the bearing chamber, until the lubricating oil consumption rate returns to normal.

[0007] As a further improvement to the above technical solution: Before adding the separator connection branch pipe, locate the bearing chamber seal leakage point, and adjust the pressure and flow restriction at the seal leakage point.

[0008] When a graphite sealing ring fails due to wear, the specific adjustment steps are as follows: When a gas turbine has been running for a period of time and a graphite seal ring wear failure occurs, the bearing cavity return oil temperature rises, leading to an increase in the lubricating oil return temperature and triggering the gas turbine's limiting protection. Since the sealing air in this bearing cavity is outside the gas turbine body, and continued operation is still required, the following adjustments can be made: For sealed air pipelines, increase the sealing orifice plate and gradually reduce the diameter of the sealing orifice plate to reduce the amount of sealing air. Under rated power, the bearing lubricating oil return temperature will decrease until it is below the limiting protection value, at which point operation can continue.

[0009] The diameter of the sealing orifice plate is gradually reduced multiple times, with the same reduction amount each time, using a 1mm variable.

[0010] The sealing orifice plate is built into the sealing air pipeline.

[0011] When the lubricating oil consumption rate of the gas turbine exceeds the specified value, the specific adjustment steps are as follows: If the pressure in a bearing chamber increases and the temperature of the lubricating oil return at that location rises, then the bearing chamber seal at that location is located to indicate a leak. A separator connection branch pipe is added at the leak point. The separator connection branch pipe is the connecting pipe between the bearing chamber and the static oil-gas separator. A throttling orifice plate is installed at the separator connection branch pipe to reduce the pressure in the bearing chamber. Gradually increase the diameter of the throttling orifice plate until the lubricating oil consumption rate returns to normal and the bearing cavity return oil temperature at rated power decreases and meets the operating conditions.

[0012] The diameter of the sealing orifice plate was gradually increased multiple times, with the same increment each time, using a 1mm increment.

[0013] The sealing orifice plate is installed in series inside the separator connecting branch pipe.

[0014] A method for adjusting the lubricating oil bearing cavity of a gas turbine is applicable to gas turbine structures, including a sealed air structure and a lubricating oil return structure. After positive pressure is formed in the sealed air chamber, part of the positive pressure air in the sealed air chamber is discharged outward through the grate seal, and the other part acts on the graphite sealing ring to form an air seal barrier. The oil and gas mixture enters the static oil-gas separator through the separator connecting pipe to achieve separation.

[0015] The beneficial effects of this invention are as follows: When a gas turbine is nearing its overhaul life, the graphite seal ring in the lubricating oil bearing cavity wears, causing sealing air to enter the bearing cavity. This results in an increase in the lubricating oil return temperature and a limiting protection failure. In special circumstances, the unit still needs to be operated. By increasing the flow area of ​​the throttling orifice plate in the sealing air pipeline to reduce the sealing control quantity, the lubricating oil return temperature can be reduced to meet the operating requirements.

[0016] When a gas turbine experiences increased lubricating oil consumption and the faulty bearing chamber cannot be identified, the location of the problematic chamber can be pinpointed by comparing changes in the return oil pressure and temperature. This can be addressed by adding a connecting line between the affected bearing chamber and the static oil-gas separator, installing a throttling orifice plate at this new line to reduce the pressure within the bearing chamber. The diameter of the throttling orifice plate is gradually increased until the lubricating oil consumption rate returns to normal. This method is effective for adjusting all bearing chambers in a gas turbine. Attached Figure Description

[0017] Figure 1 The gas turbine structure to which the existing gas turbine adjustment method of this application is applicable.

[0018] Figure 2 The flowchart is for the adjustment method used in Case 1 of this application.

[0019] Figure 3 The flowchart is for the adjustment method used in Case 2 of this application.

[0020] The components include: 1. Sealed air intake pipeline; 2. Air intake pipeline connecting flange; 3. Sealed air flow channel; 4. Grate seal; 5. Graphite sealing ring; 6. Sealed air chamber; 7. Lubricating oil chamber; 8. Bearing; 9. Oil return pipeline; 10. Oil return booster branch; 11. Branch flange; 12. Separator connecting branch pipe; 13. Static oil-gas separator. Detailed Implementation

[0021] The specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0022] like Figure 1 The diagram shown is a schematic representation of the lubricating oil system of the present invention. As can be seen from the diagram, in the sealed air venting line 1 with the air venting line connecting flange 2, along... Figure 1 The direction of the middle arrow indicates the direction of the fluid. In this embodiment, the fluid is sealed air.

[0023] Figure 1 The structure of the sealed air system is shown in the figure: After the sealing air flows through the sealing air vent pipe 1 and the vent pipe connecting flange 2, it is distributed to the sealing air chambers 6 on both sides through the sealing air flow channel 3. The air forms a positive pressure in the sealing air chamber 6. Part of the positive pressure air in the sealing air chamber 6 is discharged outward through the grate seal 4, and the other part acts on the graphite sealing ring 5 to form an air seal barrier, preventing the lubricating oil in the lubricating oil chamber 7 from leaking outward.

[0024] This combination of air-sealed and contact-type dual seals is a classic design for preventing oil and gas mixture leakage in high-speed equipment. In case of any abnormality, it is necessary to investigate where the seal failure occurred.

[0025] Figure 1 The diagram also shows the lubricating oil and return oil structure: Bearing 8 is lubricated and cooled in the lubricating oil chamber 7. The heated lubricating oil is collected through the bearing return oil line 9. The newly added bearing return oil extension branch 10 is used to improve the return oil capacity under high load. The oil and gas mixture enters the static oil-gas separator 13 through the separator connection branch 12, realizing oil and gas separation and lubricating oil circulation and recovery. The branch flange 11 is used to provide an interface for pipeline connection.

[0026] The specific steps and methods for the investigation are as follows: Scenario 1: A gas turbine is nearing its overhaul period when a limiting protection fault occurs due to elevated oil return temperature at the compressor rear bearing. Disassembly and inspection revealed a worn graphite ring on the oil return pipe, indicating a fault in the graphite ring. Due to these special circumstances, the gas turbine still needs to operate for a period of time. Adjustments are made using the following methods.

[0027] At the flange 2 connecting the bleed air line from the compressor sealing air line 1, a sealing orifice plate of the same diameter as the bleed air line is installed; the compressor sealing air line 1 has a diameter of 30mm. The adjustment steps are as follows: Figure 2 As shown, gradually reduce the diameter of the sealing orifice plate to reduce the amount of sealing air. Each time the sealing orifice plate is replaced, the diameter is reduced by 1mm. For example, the first sealing orifice plate diameter is 29mm, the second is 28mm, and so on. When the sealing orifice plate diameter is 25mm, at rated power, the bearing lubricating oil return temperature decreases and falls below the limiting protection value. Then the adjustment is complete, and the machine can continue to operate stably for a period of time under these conditions.

[0028] The principle of reducing the lubricating oil temperature by reducing the diameter of the sealing orifice plate is: by throttling the sealing air through the sealing orifice plate, the flow rate of the sealing air is limited, reducing the heat transfer of the sealing air to the bearing cavity, thereby reducing the lubricating oil return temperature.

[0029] As a throttling element, when sealing air passes through the sealing orifice plate of the air intake pipe, the smaller the diameter of the sealing orifice plate, the smaller the cross-sectional area of ​​airflow, and the greater the airflow resistance will be, ultimately leading to a reduction in the flow rate of sealing air entering the bearing sealing cavity.

[0030] The air temperature in the compressor's sealing air pipeline is much higher than the normal operating temperature of the bearing cavity. When the diameter of the sealing orifice plate decreases, the sealing air flow decreases, the total heat carried into the bearing cavity by the sealing air decreases, and the heat generation rate of the lubricating oil is lower than the heat dissipation rate, causing the lubricating oil return temperature to decrease accordingly until it falls below the protection value.

[0031] Adjusting the diameter by 1mm each time can prevent damage to the equipment from sudden temperature changes.

[0032] Scenario 2: The lubricating oil consumption rate of the gas turbine is greater than the specified value.

[0033] After a period of operation, the lubricating oil consumption rate of a gas turbine exceeds the specified value. By comparing the pressure and temperature of the oil return pipes of each bearing cavity with those during normal operation, it can be found that the pressure in the bearing cavity after the compressor has increased and the lubricating oil return temperature at that location has risen compared to the past. Therefore, the bearing cavity at that location is not properly sealed.

[0034] Adjustment methods such as Figure 3 As shown, by adding a connecting pipe 10 between the bearing chamber and the static oil-gas separator 13, the diameter of the connecting pipe 10 is the same as that of the original branch 9; and by installing a throttling orifice plate at the flange 11 used to add the throttling orifice plate at the branch where the bearing oil return is added, the pressure in the bearing chamber is reduced. The diameter of the throttling orifice plate is gradually increased, starting from 1 mm and increasing by 1 mm each time. When the diameter of the throttling orifice plate is 10 mm, the lubricating oil consumption rate of the unit returns to the normal range, and the bearing chamber oil return temperature at rated power decreases to meet the operating conditions. After several months of operation, the gas turbine can operate stably.

[0035] The principle of reducing the lubricating oil consumption rate of the unit by increasing the diameter of the throttling orifice plate is that the throttling orifice plate adds an oil and gas discharge branch to the bearing cavity, which leads the oil and gas mixture to the separator and reduces the pressure in the bearing cavity.

[0036] The primary cause of excessive lubricating oil consumption is excessively high bearing cavity pressure. Reducing lubricating oil consumption requires lowering the pressure within the bearing cavity.

[0037] The smaller the orifice diameter of the throttling orifice plate, the greater the resistance and the slower the discharge rate of the oil-gas mixture; conversely, the larger the orifice diameter, the smaller the resistance and the faster the discharge rate. As the orifice diameter increases, the flow resistance within the branch gradually decreases, and the discharge efficiency of the oil-gas mixture gradually improves. The high-pressure oil and gas in the bearing cavity are continuously discharged to the static oil-gas separator, and the chamber pressure gradually decreases accordingly.

[0038] When the orifice diameter increases to 10mm, the flow capacity of the branch circuit perfectly matches the oil and gas production in the bearing cavity, and the chamber pressure is reduced to a safe threshold. At this point, the lubricating oil no longer has high pressure, nor can it leak due to internal high pressure. The leakage is significantly reduced, and the lubricating oil consumption rate returns to the normal range.

[0039] Increasing the diameter by 1mm each time can avoid the risk caused by a sudden drop in bearing cavity pressure.

[0040] Since all bearing chamber return oil lines are connected to the static oil-gas separator, the method in Case 2 is applicable to the adjustment of all bearing chambers.

[0041] The above description is an explanation of the present invention and not a limitation thereof. The scope of the present invention is defined by the claims. Within the scope of protection of the present invention, any form of modification may be made.

Claims

1. A method for adjusting the lubricating oil bearing cavity of a gas turbine, characterized in that: It is suitable for situations involving worn graphite sealing rings and abnormally increased lubricating oil consumption. When the graphite sealing ring fails due to wear, gradually reduce the amount of sealing air so that the lubricating oil return temperature gradually decreases under rated power. When the lubricating oil consumption rate increases abnormally, add a separator connecting branch pipe, adjust the pressure and flow rate in the separator connecting branch pipe, reduce the pressure in the bearing chamber, until the lubricating oil consumption rate returns to normal.

2. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 1, characterized in that: Before adding the separator connection branch pipe, locate the bearing chamber seal leakage point, and adjust the pressure and flow restriction at the seal leakage point.

3. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 1, characterized in that: When a graphite sealing ring fails due to wear, the specific adjustment steps are as follows: When a gas turbine has been running for a period of time and a graphite seal ring wear failure occurs, the bearing cavity return oil temperature rises, leading to an increase in the lubricating oil return temperature and triggering the gas turbine's limiting protection. Since the sealing air in this bearing cavity is outside the gas turbine body, and continued operation is still required, the following adjustments can be made: For sealed air pipelines, increase the sealing orifice plate and gradually reduce the diameter of the sealing orifice plate to reduce the amount of sealing air. Under rated power, the bearing lubricating oil return temperature will decrease until it is below the limiting protection value, at which point operation can continue.

4. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 3, characterized in that: The diameter of the sealing orifice plate is gradually reduced multiple times, with the same reduction amount each time, using a 1mm variable.

5. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 3, characterized in that: The sealing orifice plate is built into the sealing air pipeline.

6. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 1, characterized in that: When the lubricating oil consumption rate of the gas turbine exceeds the specified value, the specific adjustment steps are as follows: If the pressure in a bearing chamber increases and the temperature of the lubricating oil return at that location rises, then the bearing chamber seal at that location is located to indicate a leak. Add a separator connection branch pipe at the leak point and install a throttling orifice plate at the separator connection branch pipe to reduce the pressure in the bearing chamber; Gradually increase the diameter of the throttling orifice plate until the lubricating oil consumption rate returns to normal and the bearing cavity return oil temperature at rated power decreases and meets the operating conditions.

7. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 6, characterized in that: The diameter of the sealing orifice plate was gradually increased multiple times, with the same increment each time, using a 1mm increment.

8. The method for adjusting the lubricating oil bearing cavity of a gas turbine as described in claim 6, characterized in that: The sealing orifice plate is installed in series inside the separator connecting branch pipe.

9. A method for adjusting the lubricating oil bearing cavity of a gas turbine, applicable to a gas turbine structure, characterized in that: Including air-sealing structure and oil return structure, After positive pressure is formed in the sealed air chamber, part of the positive pressure air in the sealed air chamber is discharged outward through the grate seal, and the other part acts on the graphite sealing ring to form an air seal barrier. The oil and gas mixture enters the static oil-gas separator through the separator connection branch pipe to achieve separation.

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