High-thrust reversing gas turbine sliding thrust bearing with silver coating

Abstract

The invention provides a high-thrust backing-up gas turbine sliding thrust bearing with a silver coating. The high-thrust backing-up gas turbine sliding thrust bearing comprises a shell, an oil supply isolating ring and tiles. An oil supply isolating ring is mounted on the shell; the tile blocks are mounted in the oil supply isolating ring; the tile block is provided with an inclined surface and can be rotationally adjusted around a fulcrum; the tile block pouring is made of lead bronze, and silver is plated on the surface of the lead bronze. The coating material of lead bronze and silver plating is adopted, the manufacturability of the coating material is improved, the working temperature of the sliding bearing is greatly increased, and the stability and firmness of the coating at the high temperature are guaranteed. The sliding bearing can realize forward and reverse rotation under the conditions of high temperature, high speed and large load, has very high stability and reliability, fills the blank of the design of the sliding bearing of the domestic high-power gas turbine capable of reversing, and provides a reference and a design thought for the design of the gas turbine with higher power in the future.

Description

Technical Field

[0001] The invention belongs to the field of gas turbines and aero engines, and in particular relates to a high-thrust reversible gas turbine sliding thrust bearing with a silver-plated coating. Background Art

[0002] Compared with rolling bearings, sliding bearings are more suitable for working environments with large thrust loads and high speeds; and sliding bearings are less sensitive to damage from water, dust and impurities; sliding bearings tend to wear gradually and have a long service life. Even if the sliding bearing fails, the machine can continue to work for a period of time to avoid accidents caused by sudden shutdowns. The manufacturing accuracy, difficulty and cost of sliding bearings are all superior to rolling bearings. In theory, sliding bearings are more suitable for the high-speed and high-thrust working environment of gas turbines. However, there are few sliding bearings in gas turbines at home and abroad. This is mainly based on the following reasons: on the one hand, the structure of gas turbines is very compact and the working temperature is extremely high. The working temperature environment in the bearing area is very harsh, and sliding bearings are easily damaged at high temperatures; on the other hand, gas turbines are used on ships, and the working load environment is harsh. They are often affected by ocean waves, resulting in complex operating environments such as pitch, roll, bow swing, sway, sway, heave, etc., which make the bearings bear complex alternating loads and cause them to fail.

[0003] With the continuous expansion of gas turbine demand and the development of gas turbines, the initial temperature of gas turbine power is constantly increasing, and the power is constantly increasing. Therefore, the working temperature of the sliding bearing is constantly increasing, and the load is constantly increasing. The design of the sliding bearing has become one of the bottlenecks in the design of reversible gas turbines. The following problems and difficulties have arisen in the design and application of sliding bearings for reversible gas turbines:

[0004] Question 1: The load of conventional sliding bearings used in steam turbines and various common machines is small, usually not exceeding 10 tons. However, the axial thrust of the turbine rotor of a gas turbine power plant cannot usually be balanced and eliminated inside the machine, so the thrust of the sliding bearing is very large. The thrust of a medium-sized gas turbine is basically in the order of more than 20 tons, or even up to 40 tons. On the other hand, gas turbines have high power and compact structure, and work at high temperatures and high speeds. The working environment of sliding bearings is very harsh, above 100°C, up to 120°C, or even higher. Therefore, the design of sliding bearings in reversible gas turbines is difficult.

[0005] Improvement of the existing technology: In the design of gas turbine bearings, mature tilting pad sliding bearings are usually selected in China, and babbitt alloy pads are used. The working temperature of babbitt alloy is usually lower than 80°C, and it will melt and fail when working at 100°C. Improvements have also been made to the pad materials, using materials such as lead bronze to increase the working temperature of the pads.

[0006] One of the deficiencies of the existing technology is that by selecting the common tilting pad sliding bearing forms and structures at home and abroad, the common sliding bearings often wear out in the edge area of ​​the pad under the high temperature, high speed and high thrust of the gas turbine, and gradually extend to the entire pad, resulting in the failure of the bearing. The main reason is that the conventional bearing uses a nozzle or pad to supply oil, and the oil supply area can only cover the middle position of the pad, such as Figure 1 As shown, the edge area often lacks oil, causing wear at the edge.

[0007] The second insufficiency of existing technology improvement: conventional sliding bearings use bus alloy coatings to basically meet the use requirements of conventional mechanical bearings, and lead bronze sliding bearings are rarely used. Lead bronze can theoretically meet the use requirements, but due to the relatively weak development of domestic gas turbines, the application technology of lead bronze is not mature under high temperature, high speed and high thrust load working conditions. The lead bronze tiles used in China will crack on the surface and fall off when the temperature exceeds 120℃.

[0008] Problem 2: The reversible gas turbine rotor not only needs to work at high temperature and high speed, but also requires the rotor to be able to achieve forward and reverse rotation. It is very difficult for the sliding bearing to achieve stable operation under forward and reverse conditions under high load, high speed and high temperature environment. When the sliding bearing is working, due to friction and the viscosity of the lubricating oil, the journal drives the lubricating oil to form a wedge-shaped oil film between the journal and the pad, such as Figure 2 As shown in Figure 1, the rotor axial thrust is transmitted to the pads through the oil film. The oil film pressure distribution along the arc length of the pad surface is shown in Figure 1. Figure 3 As shown, the maximum oil film pressure point is approximately located at 60% of the arc length on the oil inlet side, and the point of action of the resultant force of the oil film is also located near 60% of the arc length on the oil inlet side. For tilting pad sliding bearings, the most ideal state of the pad support point is to coincide with the axial position of the oil film resultant force point on the pad. In this state, the sliding bearing runs most stably; on the contrary, the greater the deviation between the pad support point and the oil film resultant force point in the axial position, the greater the pad deflection during operation, and the more unstable it is. Therefore, under normal circumstances, the fulcrum of the sliding bearing pad is generally located at about 60% of the arc length on the oil inlet side of the pad.

[0009] However, for a rotor that can rotate forward and reverse, if a conventional sliding bearing is used (the fulcrum is located at 60% of the arc length), the rotor can run stably when rotating forward, but when reversing, the effect of the pad is as follows: Figure 4 As shown, the oil film thrust on the pad is far away from the pad fulcrum, and the pad will rotate, which may easily cause the pad to become unstable and cause damage.

[0010] A first improvement method of the prior art: For machines that can rotate forward and reverse, rolling bearings are usually used because the working state of rolling bearings is the same when they work forward and reverse.

[0011] The first disadvantage of the existing technical improvement method is that the bearing capacity of the rolling bearing is too low to meet the large load requirement of the reversible gas turbine.

[0012] Existing technology improvement method 2: For gas turbines that can rotate forward and reverse, the most common method is to set the support point of the sliding bearing pad in the middle of the pad, such as Figure 5 shown.

[0013] The second improvement method of the prior art is insufficient: for a gas turbine that can rotate forward and reverse, the fulcrum of the sliding bearing pad is set in the middle position of the pad, such as Figure 5 As shown, the working state of the pad is roughly the same for forward and reverse rotation. However, the oil film thrust on the pad and the pad fulcrum cannot always be in the same position. When the axial force is small, this bearing can operate normally. However, under large thrust load, the sliding bearing is also very easy to become unstable and cause failure. Summary of the invention

[0014] The object of the present invention is to provide a high-thrust reversible gas turbine sliding thrust bearing with a silver coating.

[0015] A high-thrust reversible gas turbine sliding thrust bearing with a silver coating comprises a housing, an oil supply isolation ring and a tile; the housing is provided with an oil supply isolation ring; the tile is installed inside the oil supply isolation ring; the tile is provided with an inclined surface, and the tile can be rotated and adjusted around a fulcrum; the tile is cast using lead bronze material, and the lead bronze surface is silver-plated.

[0016] Furthermore, grooves are cut on the surface of the tile base before pouring the lead bronze, and the groove direction is perpendicular to the rotation direction.

[0017] Furthermore, the tile is supported by a round head.

[0018] Furthermore, an elastic support plate structure is added behind the round head support, and the elastic support plate material adopts spring steel 60Si2CrA.

[0019] Furthermore, the elastic support plate structure includes an elastic plate and a retaining spring; the elastic plate is mounted on the housing via the retaining spring, and a thrust pad is provided at the front end of the elastic plate.

[0020] Furthermore, the oil supply isolation ring is provided with 8 oil supply pipes. The lubricating oil first enters the first oil supply pipe of the isolation ring through the oil supply isolation ring inlet, and then enters the lubricating oil ring cavity of the inner ring through the first oil supply pipe. The lubricating oil enters the remaining 7 oil supply pipes through the ring cavity. Oil spray ports are evenly arranged on both sides of each oil supply pipe along the radial direction, so that the lubricating oil is sprayed to both sides of the oil supply pipe through the oil spray ports.

[0021] The beneficial effects of the present invention are:

[0022] (1) The present invention is the first in China and abroad to adopt a structural form that combines an inclined-plane thrust bearing and a tilting pad bearing, which improves the stability of the bearing under large loads and high speeds and has unique innovation in structural form.

[0023] (2) The present invention is the first in China and abroad to adopt a double-sided inclined surface structure to ensure that the bearing has high stability in both forward and reverse working conditions.

[0024] (3) The lead bronze + silver-plated coating material used in the present invention improves its processability, greatly increases the working temperature of the sliding bearing, and ensures that the coating can be stable and firm at high temperatures.

[0025] (4) The present invention adopts elastic support, which can ensure that the bearing blocks are more evenly stressed under heavy load, thus avoiding unbalanced loading of the blocks and further improving the overall stability of the bearing.

[0026] (5) The present invention has been innovatively optimized so that the oil inlet and outlet of the bearing block can be more fully and evenly lubricated and cooled, thereby improving the stability of oil film formation when the bearing operates under variable conditions, improving the cooling effect of the bearing block, and increasing the applicable temperature of the bearing.

[0027] (6) The present invention can realize forward and reverse rotation under high temperature, high speed and heavy load, and has high stability and reliability. It has been verified through experiments, filling the gap in the design of sliding bearings for high-power reversible gas turbines in China, and providing a reference and design idea for the design of higher-power gas turbines in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a map of the area where the prior art tile slots are used for oil supply and the nozzles are not able to supply oil sufficiently;

[0029] Figure 2 It is a schematic diagram of the working principle of the sliding bearing in the prior art;

[0030] Figure 3 It is a distribution diagram of the pressure on the pad surface of the prior art sliding bearing along the length of the pad surface arc;

[0031] Figure 4 This is the working principle diagram of conventional bearing when it is reversed;

[0032] Figure 5 It is a diagram showing the working forward and reverse states of the intermediate support tile in the prior art;

[0033] Figure 6 This is a model diagram of the present invention;

[0034] Figure 7 It is a cross-sectional view of the present invention;

[0035] FIG8( a ) is a schematic diagram A of a tile of the present invention;

[0036] FIG8( b ) is a schematic diagram B of a tile of the present invention;

[0037] FIG8( c ) is a schematic diagram C of a tile of the present invention;

[0038] Fig. 9 This is a working principle diagram of the bearing of the present invention when it rotates forward;

[0039] Fig.10 This is a working principle diagram of the bearing of the present invention when it is reversed;

[0040] Fig.11 This is a schematic diagram of the surface coating of the tile of the present invention;

[0041] FIG. 12( a ) is an elastic support plate structure A of the present invention;

[0042] FIG. 12( b ) is an elastic support plate structure B of the present invention;

[0043] FIG. 12( c ) is an elastic support plate structure C of the present invention;

[0044] Fig.13 This is a diagram showing the expansion of the tiles in the circumferential direction of the present invention;

[0045] FIG14( a) is a cross-sectional view of the oil supply isolation ring of the present invention;

[0046] FIG14( b ) is a model diagram of the oil supply isolation ring of the present invention;

[0047] Fig.15 It is the oil supply route diagram of the oil supply isolation ring of the present invention;

[0048] Fig.16 This is a structural diagram of the oil supply isolation ring nozzle of the present invention;

[0049] Fig.17 This is an overall diagram of the bearing test piece of the present invention;

[0050] Fig.18 This is a diagram showing the appearance of the bearing after a 200-hour bench test of the present invention;

[0051] Fig.19 This is a state diagram of the thrust bearing of the present invention after 600 hours. DETAILED DESCRIPTION

[0052] The present invention is further described below in conjunction with the accompanying drawings.

[0053] A high-thrust reversible gas turbine sliding thrust bearing with silver coating, the overall structure is shown in Figure 6-Figure 7, including a shell 1, an oil supply isolation ring 2 and a tile 3; the shell 1 is equipped with an oil supply isolation ring 2; the tile 3 is installed inside the oil supply isolation ring 2; the tile 3 is provided with an inclined surface, and the tile 3 can be rotated and adjusted around a fulcrum; the tile 3 is cast with lead bronze material, and the lead bronze surface is silver-plated.

[0054] The pad 3 draws on the structure of the inclined-plane thrust bearing, and an inclined surface is opened on the surface of the pad as shown in Figure 8 (a, b, c); at the same time, a fulcrum structure of a tilting pad is adopted, and the bearing pad can be rotated and adjusted around the fulcrum. Therefore, the bearing has the advantages of stable load-bearing and strong load-bearing capacity of the inclined-plane thrust bearing, and the advantage of automatically adjustable load-bearing capacity of the tilting pad sliding bearing, so the rotor is more stable and reliable.

[0055] As shown in Figure 8 (a, b), the tile surface is divided into three areas (I, II, III), with a double-sided inclined structure (I, III), and the middle II area is a flat surface. Its working principle is as follows:

[0056] First, when the gas turbine rotates forward, the tile surface is slightly tilted, such as Fig. 9 As shown (the oil film angle is magnified for illustration), a continuous wedge-shaped oil film is formed in areas Ⅰ and Ⅱ. Due to the existence of the inclined surface in area Ⅲ, the clearance of the lubricating oil through this area increases, and the lubricating oil pressure suddenly decreases, making it impossible to form an effective oil film. Therefore, the pad surface in area Ⅲ does not participate in the work during forward rotation. Therefore, the effective working length of the oil film on the pad surface is L. Although the fulcrum position is located in the middle of the pad (50% L'), the fulcrum is located at 60% L of the effective length of the pad surface, that is, the fulcrum position basically coincides with the position of the resultant force point of the oil film, which can ensure that the pad can work stably under large loads.

[0057] Secondly, when the gas turbine is reversed, the tile surface is slightly tilted, forming a continuous wedge-shaped oil film in the III and II regions, such as Fig.10 As shown (the oil film angle is magnified for illustration), due to the existence of the inclined surface in zone I, the clearance of the lubricating oil through this area increases, the lubricating oil pressure suddenly decreases, and an effective oil film cannot be formed. Therefore, during reversal, the pad surface in zone I does not participate in the work, so the effective working length of the pad surface is L. Although the fulcrum position is located in the middle of the pad (50% L'), the fulcrum is located at 60% L of the effective length of the pad surface, that is, the fulcrum position is basically the same as the position of the resultant force point of the oil film, which can also ensure that the pad can work stably under large loads.

[0058] Therefore, the following relationship exists between the angles of the inclined plane and the flat plane in the tile:

[0059] 0.5L′=0.6L (1)

[0060] The arc length of the tile is:

[0061] L′=(2α+β)R (2)

[0062] The actual working effective arc length of the tile is:

[0063] L=(α+β)R (3)

[0064] Where R is the tile radius;

[0065] Substituting formula 2 and 3 into formula 1, we can get

[0066]

[0067] Simplifying gives:

[0068] 4α=β (5)

[0069] The wrap angle of a single tile is θ, then the following relationship exists:

[0070] 2α+β=θ (6)

[0071] Formulas 5 and 6 can be used to obtain:

[0072] α=θ / 6

[0073] β=2θ / 3

[0074] This type of bearing, as long as the inclined area of ​​the pad surface is reasonably set, can ensure that the bearing support point is located at 60% of the pad working surface when the gas turbine is rotated forward and reversely, and ensure that the resultant point of the thrust formed by the oil film on the pad surface basically coincides with the position of the bearing support point, which can greatly improve the stability of the bearing when working forward and reversely.

[0075] The coating of the bearing pads commonly used in engineering is Babbitt alloy. This alloy material is relatively soft and the domestic process is very mature. It has a good lubrication effect under low working conditions and relatively low temperatures (80°C). However, the gas turbine has a compact structure and a high operating temperature. The oil film temperature of the sliding bearing reaches 130° or even higher. The Babbitt alloy will melt and deform, causing the bearing to fail. In order to increase the temperature of the bearing, domestic materials with high temperature resistance such as lead bronze or aluminum bronze are usually used. These materials are relatively harder than Babbitt alloy, but slightly softer than the bearing base material. They are also used in China, but they are very rare. In the early design and test process, it was found that lead bronze bearings can also meet the conditions of 120°C for bearings, but with the increase of temperature and time, cracks and shedding will occur on the surface of the lead bronze. After a lot of analysis and testing, the main reason for the cracks is the temperature gradient on the surface of the lead bronze bearing, and the poor bonding between the lead bronze and the bearing when casting the lead bronze. Therefore, a layer of silver plating is added after casting the lead bronze, such as Fig.11As shown. Silver has a higher thermal conductivity and is very soft, with good stability at high temperatures. After adding the silver layer, the bearing surface temperature is more uniform, reducing the stable gradient on the surface of the bearing. At the same time, silver has better self-lubricating properties, which can further improve the bearing reliability and protection performance when the bearing is started and stopped or when the oil supply is insufficient due to a fault, and can greatly increase the allowable operating temperature of the bearing surface and the reliability of the gas turbine bearing.

[0076] The present invention also makes innovations in the process of pouring the lead bronze coating. In previous experiments, the lead bronze was directly poured on the surface of the tile. After the temperature rises and the long-term operation, the lead bronze and the substrate fall off. Innovative improvements are made to address the above problems.

[0077] First, grooves are cut on the surface of the bearing base before pouring lead bronze. The groove direction is perpendicular to the rotation direction, such as Fig.11 As shown, the direction of the friction force generated by the oil film on the surface of the tile is perpendicular to the direction of the groove, which greatly improves the bonding strength between the lead bronze and the substrate.

[0078] Secondly, the melting point of lead bronze is relatively high. Adding borax as a flux to lead bronze can help melt the bronze. At the same time, it can significantly reduce the generation of bubbles in the lead bronze and make the cast lead bronze denser.

[0079] Through the above two aspects, the lead-bronze bonding strength is improved, and the problem of lead-bronze falling off during the working process is completely solved;

[0080] In addition to the traditional round head support, the support of the pad 3 can ensure that the pad can be adaptively rotated around the round head support under different working conditions, so that it has the adaptive adjustment ability of the tilting pad sliding bearing; secondly, an elastic support plate structure is added behind the round head support, as shown in Figure 12 (a, b, c), and the elastic support plate material is spring steel 60Si2CrA. Its working principle is as follows Fig.13 As shown, when the axial thrust of the gas turbine is large, assuming that the force on the entire circle of pads is uneven, and a certain pad is subjected to a larger force, the pad subjected to a larger force will compress the elastic support plate, causing the pad to move away from the journal, thereby increasing the oil film gap between the pad and the shaft and reducing the thrust force on the pad subjected to a larger force. Therefore, the above structural form can ensure that the entire circle of 8 pads can be subjected to uniform force, and the phenomenon of individual pad failure and the failure of the entire bearing due to uneven thrust distribution of the pads will not occur. In summary, this structure not only has the ability of conventional sliding bearing pads to freely adapt to axial forces and perform swing adjustment, but also, under large thrust loads such as gas turbines, can ensure a more even distribution of axial force between the entire circle of 8 pads, making the bearing operation more stable and reliable, and improving the bearing's overall load-bearing capacity;

[0081] The present invention has made an innovation in the oil supply method and adopted an oil supply isolation ring structure, as shown in FIG. 14 (a, b), and its working principle is as follows:

[0082] like Fig.15 As shown, the lubricating oil first enters the first oil supply pipe of the isolation ring through the oil supply isolation ring inlet, and then enters the lubricating oil ring cavity of the inner ring through the first oil supply pipe. The lubricating oil enters the remaining 7 oil supply pipes through the ring cavity. Oil injection ports are evenly arranged on both sides of each oil supply pipe along the radial direction, as shown in FIG. Fig.16 As shown, the lubricating oil is sprayed to both sides of the oil supply pipe through the oil injection port. By adjusting the angle α and position size L of the oil injection holes on both sides of the oil supply pipe, the lubricating oil on one side is directly sprayed into the oil inlet of the tile, directly participating in the formation of the oil film of the tile, which greatly improves the film formation stability of the tile under the working environment of start-stop and complex alternating loads; the lubricating oil coming out of the oil injection port on the other side is just sprayed to the edge of the tile and the oil film position of the oil outlet, which is the position with the highest temperature of each tile and the oil film, which greatly improves the cooling effect of the tile and greatly reduces the working temperature of the tile of the gas turbine sliding bearing. When the gas turbine is reversed, the holes on the oil inlet side and the oil outlet side of the tile surface interchange their functions, ensuring the uniform oil inlet and sufficient cooling of the sliding bearing when the gas turbine is reversed.

[0083] Common oil supply methods such as nozzles and tile slots in sliding bearings only set nozzles or oil inlets in the middle of the tile oil inlet. The upper and lower corners of the tile oil inlet will produce insufficient lubricating oil supply, which is easy to wear. The wear of the tile edge causes damage to the entire tile casting and leads to failure. Compared with the traditional oil supply structure, the tile oil inlet is provided with oil nozzles along the radial direction, making the tile oil film formation more stable and reliable. At the same time, the oil outlet position of the tile is also provided with cooling lubricating oil direct spray along the radial direction, which greatly improves the cooling effect of the tile and significantly reduces the working temperature of the tile. It can adapt to the high-temperature working environment of the gas turbine and the forward and reverse working requirements.

[0084] Based on the above design, test pieces were produced, such as Figure 17-Figure 19 The test was carried out on a sliding bearing test bench and in a gas turbine. The bench test lasted more than 200 hours and the whole machine was operated for more than 600 hours. The maximum load was 33 tons of axial force, the maximum speed reached 5000rpm, and the temperature of the pad reached 130℃. The test piece was in good condition after operation. Fig.18 , Fig.19 As shown, it has been verified through experiments that the bearing capacity of the present invention is greatly improved, the operating temperature is greatly increased, the reliability is high, and the forward and reverse working requirements of the gas turbine can be met.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A high-thrust reversible gas turbine sliding thrust bearing with a silver coating, characterized in that: The invention comprises a shell (1), an oil supply isolating ring (2) and a tile (3); the shell (1) is provided with an oil supply isolating ring (2); the tile (3) is installed inside the oil supply isolating ring (2); the tile (3) is provided with an inclined surface, and the tile (3) can be rotated and adjusted around a fulcrum; the tile (3) is cast using a lead bronze material, and the lead bronze surface is silver-plated.

2. A high-thrust reversible gas turbine sliding thrust bearing with a silver coating according to claim 1, characterized in that: The grooves are cut on the surface of the tile (3) base before pouring the lead bronze, and the groove direction is perpendicular to the rotation direction.

3. A high-thrust reversible gas turbine sliding thrust bearing with a silver coating according to claim 1, characterized in that: The tile (3) is supported by a round head.

4. A high-thrust reversible gas turbine sliding thrust bearing with a silver coating according to claim 3, characterized in that: An elastic support plate structure is added behind the round head support, and the elastic support plate material is spring steel 60Si2CrA.

5. A high-thrust reversible gas turbine sliding thrust bearing with a silver coating according to claim 4, characterized in that: The elastic support plate structure comprises an elastic plate (4) and a retaining spring (6); the elastic plate (4) is mounted on the housing (1) via the retaining spring (6), and a thrust pad (5) is provided at the front end of the elastic plate (4).

6. A high-thrust reversible gas turbine sliding thrust bearing with a silver coating according to claim 1, characterized in that: The oil supply isolation ring (2) is provided with 8 oil supply pipes. The lubricating oil first enters the first oil supply pipe of the isolation ring through the inlet of the oil supply isolation ring (2), then enters the lubricating oil ring cavity of the inner ring through the first oil supply pipe, and then enters the remaining 7 oil supply pipes through the ring cavity. Oil injection ports are evenly arranged on both sides of each oil supply pipe along the radial direction, so that the lubricating oil is sprayed to both sides of the oil supply pipe through the oil injection ports.

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