A steam turbine bearing chamber air seal

Abstract

The application discloses a steam turbine bearing box air-tight sealing device, which comprises a sealing body, the sealing body is composed of a device upper panel and a device lower panel to form an annular whole, a center through hole is arranged in the center of the sealing body, and an annular pressure equalizing chamber is arranged around the center through hole in the sealing body; a plurality of compressed air inlet pipes are arranged on the radial direction of the device upper panel, the inner end of the compressed air inlet pipe is communicated with the annular pressure equalizing chamber, the outer end is communicated with the outside, and a gas slit is arranged on the inner ring wall of the sealing body. Clean compressed air enters the annular pressure equalizing chamber through the circumferential multi-channel to stabilize the pressure and flow, and the stable annular positive pressure air film is formed by spraying the shaft from the inner ring slit; the bidirectional pressure difference airflow barrier formed by the air film blocks the outward leakage of oil mist and the inward infiltration of steam and water vapor, the internal structure of the bearing box does not need to be changed, there is no solid friction and wear, and the two core defects of traditional comb tooth oil leakage and water entering lubricating oil are solved.

Description

Technical Field

[0001] This invention relates to an airtight sealing device for a steam turbine bearing housing. Background Technology

[0002] Steam turbine bearing housings are generally equipped with comb-tooth type sealing oil baffles at both ends. Their core function is to prevent lubricating oil from leaking out of the housing and to prevent external dust and moisture from entering the bearing housing and contaminating the lubricating oil. However, existing comb-tooth oil baffles have two major drawbacks in long-term operation:

[0003] 1. Severe leakage of oil mist and lubricating oil: The turbine rotor has a large moment of inertia, which throws the lubricating oil in the oil tank at high speed during rotation. The oil is then broken up by the airflow inside the tank, forming a fine oil mist. Continuous operation of the unit will raise the oil temperature and bearing temperature, creating positive pressure inside the bearing housing. This pressure drives the oil mist to escape axially. Traditional seals use a rigid copper comb tooth structure. When the rotor starts and stops, there is radial runout, and during operation, there is shaft drift and continuous shaft vibration. To avoid scraping between moving and stationary parts, a large clearance needs to be reserved between the moving and stationary parts of the oil baffle. After long-term friction and wear between the copper comb teeth and the rotor, the clearance continues to expand, and there is no automatic compensation structure. This further aggravates the leakage of oil droplets and oil mist, contaminating the surrounding equipment and the ground, and increasing lubricating oil consumption.

[0004] 2. Deterioration of lubricating oil due to water ingress: The high-pressure and intermediate-pressure cylinder shaft seal is used to prevent high-pressure steam from leaking out along the rotor. The pressure difference between the inside and outside of the shaft seal is large. In order to prevent the moving and stationary parts from rubbing against each other, a gap must be reserved. It is impossible to completely eliminate steam leakage from the shaft seal. After the comb-tooth oil baffle wears, the gap increases. In addition, the lubricating oil tank maintains negative pressure operation. High-temperature and high-pressure steam leakage from the shaft seal will pass through the oil baffle along the rotor journal and enter the bearing box. After water vapor mixes into the lubricating oil, the water content in the oil exceeds the standard, causing lubricating oil emulsification, decreased lubrication performance, accelerated corrosion and wear of bearing shells and rotor journals, shortened unit maintenance cycle, and increased operation and maintenance costs.

[0005] In summary, the sealing performance of existing rigid comb-tooth oil baffles continuously deteriorates with operating time, and cannot effectively solve the problems of oil leakage and water ingress in turbine bearing housings in the long term. Summary of the Invention

[0006] To address the above-mentioned problems, the present invention provides a steam turbine bearing housing gas sealing device, which effectively solves the problems pointed out in the background art.

[0007] The technical solution adopted in this invention is:

[0008] A gas-tight sealing device for a turbine bearing housing includes a sealing body. The sealing body is formed by fitting an upper panel and a lower panel together to create an annular structure. The sealing body has a central through hole for a rotating shaft to pass through. An annular pressure equalization chamber is arranged around the central through hole inside the sealing body. Several compressed air inlet pipes are radially arranged on the upper panel. The inner end of each compressed air inlet pipe communicates with the annular pressure equalization chamber, and the outer end communicates with the outside. An outlet slit is formed in the inner annular wall of the sealing body, connecting the annular pressure equalization chamber and the central through hole. Clean compressed air from the outside enters the annular pressure equalization chamber through the compressed air inlet pipes, is pressurized, and then ejected from the outlet slit, forming an annular positive pressure air film on the outer wall of the rotating shaft.

[0009] Preferably, the upper panel and the lower panel of the device are separate, open-ended structures, and sealing gaskets are fitted to their mating surfaces.

[0010] Preferably, the upper panel and the lower panel of the device are provided with multiple bolt holes on their outer rings. These bolt holes are used to seal the body and fix it to the external shaft end of the turbine bearing housing.

[0011] Preferably, there are two compressed air inlet pipes, which are evenly distributed at equal angles along the circumference of the sealing body.

[0012] Preferably, the compressed air introduced into the compressed air inlet pipe is dry and clean compressed air that has undergone pretreatment to remove water, oil, and dust.

[0013] The beneficial effects of this invention are as follows:

[0014] 1. Double long-lasting seal, completely eliminating oil leakage and water ingress problems.

[0015] A dynamic air seal barrier is formed by an annular positive pressure air film on the surface of the shaft, which is unaffected by rotor runout, shaft vibration, and increased clearance due to comb tooth wear. It internally blocks oil mist leakage and externally isolates shaft seal steam, dust, and water vapor from intrusion, significantly reducing lubricating oil consumption, preventing lubricating oil emulsification and deterioration, extending the service life of bearings and rotors, and reducing the frequency of unit shutdown for maintenance.

[0016] 2. Modular external installation, requiring minimal modification work and facilitating maintenance.

[0017] The entire device is installed outside the bearing housing, without disassembling the internal components of the bearing housing, or altering the original oil circuit, comb tooth oil baffle, or bearing structure. The retrofit can be completed during a minor overhaul without shutting down the unit. The split upper and lower split structure means that the rotor does not need to be pulled out during disassembly; only the sealing body needs to be disassembled and installed separately, which greatly shortens the maintenance period and reduces the cost of modification and maintenance.

[0018] 3. Annular pressure equalization chamber structure ensures uniform and stable sealing air pressure.

[0019] Compressed air first enters a large-capacity annular equalizing chamber for pressure stabilization and buffering. Multi-point circumferential air intake eliminates local airflow pressure difference. A uniform air barrier film with consistent pressure is formed along the entire rotation shaft. There are no dead corners in the sealing. The sealing effect is uniform and stable, and it is suitable for the unit to start and stop, full load, and variable load operation under all working conditions.

[0020] 4. Compatible with various existing steam turbine units, highly versatile.

[0021] It only requires matching the corresponding specifications of the annular seal body according to the outer diameter of the turbine shaft, and the screw holes are adapted to the original mounting flange of the bearing housing. No customization or modification of the bearing housing body is required. It can be widely used for the modification of the bearing shaft end seal of thermal power generating units of different capacities and models. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 for Figure 1 AA sectional view. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0025] Example 1

[0026] like Figure 1-2 As shown, a turbine bearing housing gas sealing device includes a sealing body. The sealing body is formed by the upper panel 1-1 and the lower panel 1-2 of the device joining together to form an annular whole. The center of the sealing body is provided with a central through hole 6 for the rotating shaft 5 to pass through. The central through hole 6 and the rotating shaft 5 are provided with an annular gap, which is used for compressed air to be discharged from both sides of the sealing body. An annular pressure equalization chamber 4 is arranged around the central through hole 6 inside the sealing body. Several compressed air inlet pipes 2 are opened radially on the upper panel 1-1 of the device. The inner end of the compressed air inlet pipe 2 is connected to the annular pressure equalization chamber 4, and the outer end is connected to the outside. An air outlet slit 7 is opened on the inner annular wall of the sealing body to connect the annular pressure equalization chamber 4 and the central through hole 6. Clean compressed air from the outside enters the annular pressure equalization chamber 4 through the compressed air inlet pipe 2 and is stabilized before being ejected from the air outlet slit 7, forming an annular positive pressure air film on the outer wall of the rotating shaft 5.

[0027] The upper panel 1-1 and the lower panel 1-2 of the device are separate, open-ended structures, and sealing gaskets are fitted on their mating surfaces.

[0028] The upper panel 1-1 and the lower panel 1-2 of the device are provided with multiple bolt holes on their outer rings. These bolt holes are used to seal the main body and fix it to the external shaft end of the turbine bearing housing.

[0029] There are two compressed air inlet pipes 2, which are evenly distributed at equal angles along the circumference of the sealing body.

[0030] The compressed air introduced into the compressed air inlet pipe 2 is dry and clean compressed air that has undergone pretreatment to remove water, oil, and dust.

[0031] The working principle of this invention is as follows:

[0032] I. Foundation conditions for device installation

[0033] This device is an externally mounted, split-type annular sealing structure. The entire unit is fixed to the outer side of the turbine bearing housing and the outer journal position of the original comb-type oil baffle through the outer ring screw holes. All original factory components, such as the bearings, lubrication oil circuits, and original comb-type oil baffles inside the bearing housing, are not disassembled or modified throughout the process. The central through hole of the device is fitted onto the outer side of the turbine shaft. The upper and lower panels of the device are aligned to form a closed annular cavity. An independent annular pressure equalization chamber is set inside, and a clean compressed air source pipeline is provided externally.

[0034] II. Airflow Supply and Pressure Stabilization / Flow Equalization Process

[0035] 1. Pre-treatment air source input: The compressed air produced by the external air compressor is first dried, degreased, and dust-removed to obtain qualified compressed air that is free of moisture, impurities, and oil. It is then sent into the annular equalizing chamber inside the sealing body through multiple compressed air inlet pipes evenly arranged around the circumference of the sealing body.

[0036] 2. Annular pressure equalization chamber for stabilization and buffering: The annular pressure equalization chamber has a larger cavity volume, which is larger than the total ventilation cross-sectional area of ​​the inner ring outlet slit; after the compressed air from multiple circumferential intakes enters the pressure equalization chamber, the airflow impact and local pressure difference are buffered and eliminated by the cavity, and the air pressure in the entire annular cavity tends to be completely uniform, completely avoiding the problem of uneven local air pressure caused by unilateral air intake, and providing a stable pressure and uniform flow air source for the entire rotation of the shaft.

[0037] III. Annular Positive Pressure Air Membrane Forming Process

[0038] The stabilized compressed air is continuously injected inward along the axial outlet slit of the inner ring of the sealed body. The airflow continuously emerges from the annular gap between the inner ring of the sealed body and the outer wall of the shaft, forming a continuous, complete, annular positive pressure air barrier film on the outer surface of the shaft cylinder. The static pressure of this air film simultaneously satisfies two pressure difference conditions:

[0039] 1. The internal pressure of the air membrane is greater than the positive operating pressure inside the bearing housing;

[0040] 2. External pressure of the air membrane > pressure of steam leakage from the outer shaft seal and ambient atmospheric water vapor and dust.

[0041] IV. Bidirectional Dynamic Sealing and Barrier Principle (Core Sealing Function)

[0042] 1. Internal barrier: Prevents leakage of bearing housing lubricating oil and oil mist outwards.

[0043] During unit operation, the high-speed rotation of the rotor throws up the lubricating oil, forming oil mist. The internal positive pressure is generated in the bearing housing due to the increase in oil and bearing temperature, and the oil mist and fine oil droplets tend to escape outward along the shaft. The annular positive pressure air film on the outer layer of the shaft forms an air barrier. The high-pressure airflow direction is opposite to the direction of oil mist leakage, which in turn prevents the oil mist and lubricating oil droplets in the housing from passing through the sealing gap and overflowing outward. This solves the problems of oil leakage, oil throwing, and oil mist dispersion caused by the wear gap of the traditional comb-tooth oil baffle from the root. Even if the shaft jumps during unit start-up and shutdown, or if there is shaft vibration or shaft center drift during operation, the air film without physical contact will not wear, and there is no problem of gap compensation failure. The sealing effect is stable in the long term.

[0044] 2. External barrier: Prevents shaft seal steam, dust, and moisture from seeping into the bearing housing.

[0045] High-pressure steam leakage is inevitable in the shaft seals of the high-pressure and intermediate-pressure cylinders of steam turbines. High-temperature, pressurized steam moves along the rotor shaft towards the bearing housing. At the same time, dust and water vapor in the ambient air will also penetrate inward along the shaft gap. The annular positive pressure air film formed by this device continuously releases pressure outward, and the airflow flows outward, forming a reverse airflow barrier: on the one hand, it prevents the high-temperature steam from passing through the seal and entering the bearing housing, and prevents the steam from liquefying upon cooling and causing water to enter and emulsify the lubricating oil; on the other hand, it isolates external dust and water vapor from entering the lubricating oil system, avoids oil contamination and deterioration, and protects the bearing shells and rotor journals from water vapor corrosion.

[0046] V. Logic for Adaptation to All Operating Conditions of the Equipment

[0047] 1. During the start-up and shutdown phase of the unit: The shaft has a large radial runout. Traditional rigid comb teeth are prone to collision and wear. This invention relies on non-contact air film sealing, and there is no physical friction between moving and stationary parts, so the shaft and seals will not be damaged.

[0048] 2. Stable load-bearing phase of the unit: Continuous and stable pressure equalization air supply ensures constant air membrane pressure, unaffected by load changes or shaft vibration fluctuations;

[0049] 3. Maintenance conditions: The device has a split upper and lower structure, so there is no need to remove the turbine rotor. The upper and lower panels can be disassembled and cleaned by loosening the outer ring fastening bolts, making maintenance simple and efficient.

[0050] This invention uses clean compressed air to enter the annular pressure equalization chamber through multiple circumferential channels to stabilize and equalize the flow. It sprays air from the inner ring slits to wrap around the rotating shaft, forming a stable annular positive pressure air film. Relying on the bidirectional pressure difference airflow barrier formed by the air film, it blocks oil mist leakage inward and steam and water vapor infiltration outward. It does not require modification of the internal structure of the bearing box and has no physical friction and wear, effectively solving the two major defects of traditional comb oil seals: oil leakage and water ingress of lubricating oil.

[0051] Finally, it should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A gas sealing device for a steam turbine bearing housing, characterized in that, The device includes a sealing body, which is formed by the upper panel (1-1) and the lower panel (1-2) of the device. The sealing body has a central through hole (6) for the rotating shaft (5) to pass through. The sealing body is surrounded by an annular pressure equalization chamber (4). Several compressed air inlet pipes (2) are opened radially on the upper panel (1-1). The inner end of the compressed air inlet pipe (2) is connected to the annular pressure equalization chamber (4), and the outer end is connected to the outside. The inner ring wall of the sealing body has an outlet slit (7) that connects the annular pressure equalization chamber (4) and the central through hole (6). Clean compressed air from the outside enters the annular pressure equalization chamber (4) through the compressed air inlet pipe (2), is stabilized, and is then ejected from the outlet slit (7) to form an annular positive pressure air film on the outer wall of the rotating shaft (5).

2. The turbine bearing housing gas sealing device according to claim 1, characterized in that, The upper panel (1-1) and the lower panel (1-2) of the device are separate, open-ended structures, and sealing gaskets are fitted on their mating surfaces.

3. The turbine bearing housing gas sealing device according to claim 2, characterized in that, The outer ring of the upper panel (1-1) and the lower panel (1-2) of the device is provided with multiple bolt holes.

4. The turbine bearing housing gas sealing device according to claim 3, characterized in that, There are two compressed air inlet pipes (2), which are evenly distributed at equal angles along the circumference of the sealing body.

5. The turbine bearing housing gas sealing device according to claim 4, characterized in that, The compressed air introduced into the compressed air inlet pipe (2) is dry and clean compressed air that has undergone pretreatment of water removal, oil removal and dust removal.

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