Rubbing stationary blade structure and rubbing brake lifting method after shaft failure

Abstract

The rub-impact stationary blade structure comprises an outer diameter area, an intermediate diameter area and an inner diameter area, and the blade thickness of the outer diameter area, the blade thickness of the intermediate diameter area and the blade thickness of the inner diameter area are sequentially decreased. And the front edges of the outer diameter area, the intermediate diameter area and the inner diameter area are thickest areas of each blade profile section of the blade. By means of the structure, deformation and failure of the rub-impact position structure can be effectively delayed, and therefore the rotor and the stator are promoted to continuously generate high-efficiency rub-impact energy consumption. The invention further provides a rub-impact brake lifting method after shaft failure.

Description

Technical Field

[0001] The present invention relates to the field of aero engines, and in particular to the field of shaft failure protection solutions. Background Art

[0002] In actual operation, turbine-driven engines may suffer shaft failure due to over-torque, resonance, fatigue, corrosion, material defects, manufacturing errors or other indirect events. Although the probability of shaft failure is very small, once it occurs, it may lead to harmful consequences.

[0003] For twin-rotor engines, low-pressure shaft failure is common. After the low-pressure shaft fails, the turbine rotor is decoupled from the front load, such as the compressor, and driven by the high-energy gas discharged from the combustion chamber, the speed rises instantly or enters the overspeed state. When the speed rises to a certain level, the wheel stress reaches a critical point and breaks, and the high-energy fragments of the rupture have the risk of penetrating the engine. Therefore, limiting the turbine overspeed after shaft failure is a constraint that must be followed in the design of turbine engines.

[0004] In known twin-rotor engines, the rotor speed is generally monitored directly or converted by installing a speed sensor. The speed sensor is generally installed at the front end of the engine and cannot monitor the increase in the rear turbine speed caused by shaft failure. Even if a sensor is added to the turbine end, for large civil turbofan engines, the entire process from the control system monitoring and determining the occurrence of a shaft failure to the oil cut response takes a long time, which is about an order of magnitude slower than the time required for the turbine speed to rise to the critical speed. Therefore, the speed limit after the low-pressure shaft failure through the control system alone has stringent requirements on the response time of the control system.

[0005] Compared with the response time of the control system, the duration of a shaft failure event is very short. Therefore, civil aviation engines generally use a combination of mechanical and control systems to limit the low-pressure turbine speed after a shaft failure. Before the control system responds, the mechanical braking effect must be guaranteed. Otherwise, the low-pressure turbine wheel will rupture before the control system fully responds.

[0006] In view of this, it is necessary to propose a structure that increases the friction effect and thus quickly limits the turbine speed. Summary of the invention

[0007] An object of the present invention is to provide a friction-impacting stator blade structure that can effectively delay the deformation and failure of the friction-impacting position structure, thereby promoting continuous and efficient friction energy consumption of the rotor and stator.

[0008] In order to achieve the above-mentioned purpose, the outer diameter area, middle diameter area and inner diameter area of ​​the rubbing stationary blade structure have blade thicknesses that become thinner in sequence; wherein the leading edges of the outer diameter area, middle diameter area and inner diameter area are the thickest areas of each blade profile section of the blade.

[0009] In one or more embodiments, the outer diameter area is the area from the blade edge to 1 / 3 of the blade body height, the mid-diameter area is the area from 1 / 3 of the blade body to 2 / 3 of the blade body height, and the outer diameter area is the area from 2 / 3 of the blade body to the blade tip.

[0010] In one or more embodiments, the area from the leading edge of the blade to 1 / 3 of the chord length of the blade is a thickened structure.

[0011] Another object of the present invention is to provide a friction brake lifting method after shaft failure, in which one or more stages of stationary blades adopt the above-mentioned friction stationary blade structure.

[0012] In one or more embodiments, the method includes the following steps: S1. evaluating the friction participation degree of blade structures of different levels and the imbalance level after friction; S2. selecting the blade level with a higher friction participation degree and the lowest friction imbalance level; S3. adopting the friction stationary blade structure as described in any one of claims 1-3 for the blade level determined in step S2.

[0013] In one or more embodiments, the evaluation is performed by finite element methods.

[0014] The above-mentioned friction-impact stator blade structure retains the basic functions of blades at all levels, and designs the stator blades with variable thickness, gradually increasing the blade thickness along the blade height direction, and increasing the thickness of the leading edge of the blade at the same time. On the one hand, it can prevent the stator blades that are rubbed from rapid deformation and failure, resulting in rupture and flying out after the rotor-stator blades are violently rubbed, and on the other hand, it can prevent other inefficient blade positions from entering the friction after the bent stator blades are bent and deformed. Therefore, the friction blade can prolong the resistance torque during the friction, promote the consumption of friction energy, and then quickly reduce the turbine speed and improve the energy consumption efficiency of the rotor-stator friction brake. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0016] Figure 1 is a schematic diagram of an embodiment of a twin rotor turbine engine;

[0017] Figure 2 It is to put the stationary blade and moving blade structure in the state of friction;

[0018] Figure 3 It is a schematic diagram of the blade friction area;

[0019] Figure 4 It is a schematic diagram of the appearance of the friction blade structure;

[0020] Figures 5A-5C It is the blade profile of a certain section at the outer diameter area, middle diameter area and inner diameter area of ​​the blade;

[0021] Figure 6 It is a comparative schematic diagram of the stator blade before and after deformation;

[0022] Figure 7 It is a flow chart of a specific embodiment of the friction brake lifting method after shaft failure.

[0023] Symbols and Markings

[0024] 1. Roller bearing 2. Ball bearing 3. Ball bearing 4. Roller bearing 5. Roller bearing 11. Low-pressure shaft 12. High-pressure shaft 21. Fan 22. Boost stage 22a. Low-pressure compressor rotor component 22b. Boost stage stator component 23. High-pressure compressor 23a. High-pressure compressor rotor component 23b. High-pressure compressor stator component 24. High-pressure turbine 24a. High-pressure turbine rotor component 24b. High-pressure turbine stator component 25. Low-pressure turbine 25a. Low-pressure turbine rotor component 25b. Low-pressure turbine stator component 26. Combustion chamber 31. Front bearing casing 32. Turbine interstage bearing casing 33. Rear bearing casing 41. Fan casing 51. Support plate 61. Fracture position 89. Trailing edge area 90. Leading edge area 100. Turbine engine DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0026] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0027] Figure 1A simplified schematic diagram of a twin-rotor turbine engine is shown. The turbine engine 100 includes a fan 21, a low-pressure compressor 22, a high-pressure compressor 23, a combustion chamber 26, a high-pressure turbine 24, and a low-pressure turbine 25. The low-pressure compressor 22 is driven by the low-pressure turbine 25, and the two are connected through the low-pressure shaft 11, and the high-pressure compressor 23 is driven by the high-pressure turbine 24, and the two are connected through the high-pressure shaft 12.

[0028] The low-pressure compressor 22 includes a low-pressure compressor rotor component 22a and a low-pressure compressor stator component 22b. The high-pressure compressor 23 includes a high-pressure compressor rotor component 23a and a high-pressure compressor stator component 23b. The high-pressure turbine 24 includes a high-pressure turbine rotor component 24a and a high-pressure turbine stator component 24b. The low-pressure turbine 25 includes a low-pressure turbine rotor component 25a and a low-pressure turbine stator component 25b.

[0029] The low-pressure compressor rotor component 22a, the high-pressure compressor rotor component 23a, the high-pressure turbine rotor component 24a, and the low-pressure turbine rotor component 25a constitute the rotor unit in the engine 100; the low-pressure compressor stator component 22b, the high-pressure compressor stator component 23b, the high-pressure turbine stator component 24b, and the low-pressure turbine stator component 25b constitute the stator unit in the engine.

[0030] The working process of the turbine engine is as follows: after the high-temperature and high-energy combustion gas is discharged from the combustion chamber 26, it passes through the high-pressure turbine 24 and the low-pressure turbine 25 successively, driving the high-pressure turbine rotor component 24a and the low-pressure turbine rotor component 25a to rotate, the high-pressure turbine rotor component 24a drives the high-pressure compressor rotor component 23a at the front end to rotate, and the low-pressure turbine rotor component 25a drives the low-pressure compressor rotor component 22a and the fan 21 to rotate.

[0031] The compressor connection end of the low-pressure shaft 11 is supported by roller bearings 1 and ball bearings 2, and the turbine connection end is supported by roller bearings 5. The compressor connection end of the high-pressure shaft 12 is supported by ball bearings 3, and the turbine connection end is supported by roller bearings 4.

[0032] The roller bearing 5 is mainly used to transmit radial force, and the ball bearing 3 can transmit axial force and radial force at the same time. The axial force or radial force on the roller bearing 1, the ball bearing 2 and the ball bearing 3 is mainly transmitted outward through the front bearing casing 31, and the forces on the roller bearing 4 and the roller bearing 5 are respectively transmitted outward through the turbine interstage bearing casing 32 and the rear bearing casing 33 in the low-pressure turbine stator component 25b.

[0033] The outside of the fan 21 is a fan casing 41 , and the rear end is a guide support plate 51 .

[0034] Figure 1A possible fracture position 61 of shaft failure is shown. The rotor at the axial rear side close to the fracture position 61 will collide with the stator at the axial rear side close to the rotor under the action of its own rotation speed and the airflow in the working state. Figure 1 The A area in the figure gives the possible location where axial friction may first occur. Figure 2 An enlarged view of the rubbing process of the low-pressure turbine rotor component 25a and the low-pressure turbine stator component 25b in region A is provided, wherein region B is the key position region of the rubbing.

[0035] Known shaft failure over-speed protection structures include bent and swept stator blades, which are designed to first rub against the rotor blades after shaft failure occurs, and the rubbing produces a braking effect, thereby limiting the maximum over-speed speed that the rotor can reach. For high bypass ratio turbofan engines, the low-pressure turbine generally includes a multi-stage rotor structure with a large moment of inertia, and the aerodynamic force acting on the low-pressure turbine rotor unit body after shaft failure is extremely high, which may cause the bent and swept stator blades to quickly fail due to large-scale structural deformation after concentrated rubbing, and the stator's limiting effect on the rotor speed after deformation and failure decreases. In addition, when the stator blades bend backward under the axial impact of the rotor, it will cause other relatively small clearance positions but low friction-reducing efficiency rotors and stators to enter rubbing, further affecting the limiting effect of the bent and swept stator blades on the turbine rotor speed.

[0036] like Figure 2 As shown, the low-pressure turbine rotor component 25a, that is, Figure 2 The low-pressure turbine rotor blades 251 are of conventional ordinary straight blade design; the low-pressure turbine stator component 25b, i.e. Figure 2 The low-pressure turbine stator blades 252 are of conventional swept blade design.

[0037] In this design structure, the low-pressure turbine stator blade 152 is connected to the casing through a hook 82. Under normal operating conditions, there is a certain axial gap 81 between the low-pressure turbine rotor blade 251 and the low-pressure turbine stator blade 252. When the low-pressure shaft 11 breaks and fails, the low-pressure turbine rotor blade 251 moves backward while rotating and accelerates and rubs against the stator blade 252. Under the action of the axial force, the trailing edge 89 of the low-pressure turbine rotor blade 251 and the leading edge 90 of the low-pressure turbine stator blade 252 will have an axial overlap area 92, such as Figure 3 As shown, due to the concentrated high level of friction force, the axial overlap area 92 is very susceptible to deformation failure.

[0038] Therefore, the rubbing stator blade structure described in the present application is used to delay the deformation and failure of the rubbing position. By increasing the structural thickness of the overlapping area, on the one hand, it can increase the resistance generated in the overlapping area, and on the other hand, it can delay the deformation and failure of the swept stator blades, prolong the action time of the high resistance torque, and thus promote the rapid release of turbine energy.

[0039] like Figure 4 As shown, the stationary blade structure includes an outer diameter region 83, a middle diameter region 84 and an inner diameter region 85, and the blade thickness of the outer diameter region 83, the middle diameter region 84 and the inner diameter region 85 becomes thinner in sequence. The term "thin" refers to the thickness from the suction surface of the blade to the pressure surface of the blade. Among them, the leading edges of the outer diameter region 83, the middle diameter region 84 and the inner diameter region 85 are the thickest areas of each blade section of the blade.

[0040] That is, on the one hand, the leading edge region 90 of the low-pressure turbine stator blade 252 adopts an overall thickened design; on the other hand, the low-pressure turbine stator blade 252 adopts a variable thickness design along the blade height direction.

[0041] For example, the cross section of the outer diameter region 83 of the low-pressure turbine stator blade 252 is thickened, and the cross section of the outer diameter region 83 is as follows: Figure 5A The first blade profile 86 shown in FIG5A ; the cross-sectional thickness of the mid-diameter region 84 of the low-pressure turbine stator blade 252 is medium, and the cross-sectional shape of the mid-diameter region 84 is the second blade profile 87 shown in FIG5B ; the cross-sectional thickness of the inner diameter region 85 of the low-pressure turbine stator blade 252 is relatively thin, and the cross-sectional shape of the inner diameter region 85 is the second blade profile 88 shown in FIG5C . Figures 5A to 5C It can be seen that the thickness of the blade gradually decreases.

[0042] In some embodiments, the "inner diameter region" refers to the region from the blade edge to 1 / 3 of the blade body height, the "mid-diameter region" refers to the region from 1 / 3 of the blade body to 2 / 3 of the blade body height, and the "outer diameter region" refers to the region from 2 / 3 of the blade body to the blade tip.

[0043] In some embodiments, the leading edge region 90 is the range from the leading edge of the blade to 1 / 3 of the blade chord length, and the range is designed to be thickened. It can be understood by those skilled in the art that the leading edge region 90 includes but is not limited to the above range, and can be changed according to the specifications and aerodynamic parameters of different engines without affecting the basic functions of the blades at each level.

[0044] The thickness of the outer diameter region 83 , the middle diameter region 84 and the inner diameter region 85 transitions uniformly.

[0045] The above design can not only delay the deformation failure of the axial overlapping portion 92 of the stator blade, maintain high-efficiency friction energy consumption, but also limit the occurrence of the following after the friction of the low-pressure turbine stator blade 252: Figure 6 The deformation shown prevents the pre-collision stator blades 91 from being located at the position of the post-collision stator blades 92 after deformation, and prevents other inefficient rotor-stator structures from rubbing against each other and causing adverse effects.

[0046] In addition, the outer diameter area 83 of the low-pressure turbine stator blade 252 is thickened to improve its rigidity, which can prevent the failure of the entire stator blade caused by a huge axial impact, thereby avoiding other adverse effects caused by friction, such as preventing the low-pressure turbine stator blade 252 from flying out after failing as a whole after a collision.

[0047] Combined with the above introduction to the friction stator blade structure, we can also understand a friction brake lifting method after shaft failure, which strengthens the swept blades by adopting the friction stator blade structure as described above for one or more stages of stator blades. This method retains the basic functions of the stator blades and designs the stator blades to have variable thickness, gradually increasing the blade thickness from the inner diameter to the outer diameter, and increasing the leading edge thickness of the blades at the same time. On the one hand, it can prevent the stator blades from rapid deformation and failure after the rotating stator blades have severe friction, and on the other hand, it can prevent the swept stator blades from bending and deforming and other inefficient positions from entering friction, thereby achieving the purpose of improving the friction-induced rotation efficiency.

[0048] Specifically, refer to Figure 7 As shown, the method includes the following steps: first, step S1 is performed to evaluate the friction participation degree of blade structures of different levels and the imbalance level after friction. For example, the finite element method is used to evaluate the blades of each level. Subsequently, the blade level with a higher friction participation degree and the lowest friction imbalance level is selected, and the blade level determined in the above step adopts the above friction stationary blade structure.

[0049] Under the premise of ensuring the original function of the blades, the above method can delay the deformation failure of the bent and swept stator blades by predetermining the parts of the shaft that are prone to breakage and specifically designing the blade stage with a high degree of friction participation and the lowest level of friction imbalance, and promote the continuous and efficient friction energy consumption of the rotor, thereby improving the efficiency of the turbine rotor speed limit after shaft failure and promoting the rapid release of rotor energy. It can also reduce the degree of bending deformation of the bent and swept stator blades, ensure that friction occurs concentratedly at the bent and swept stator blades, and prevent the whole blade from flying out due to the failure of the bent and swept stator blades after concentrated friction.

[0050] It should be noted that the above content uses words such as "first", "second", and "third" to limit components, which is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0051] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0052] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A friction-impacting stationary blade structure, characterized in that: The structure includes: The outer diameter region, the middle diameter region and the inner diameter region, the blade thickness of the outer diameter region, the middle diameter region and the inner diameter region becomes thinner in sequence; wherein the leading edges of the outer diameter region, the middle diameter region and the inner diameter region are the thickest regions of each blade section.

2. The rubbing stationary blade structure according to claim 1, characterized in that: The outer diameter area is the area from the blade edge plate to 1 / 3 of the blade body height, the mid-diameter area is the area from 1 / 3 of the blade body to 2 / 3 of the blade body height, and the outer diameter area is the area from 2 / 3 of the blade body to the blade tip.

3. The rubbing stationary blade structure according to claim 1, characterized in that: The area from the leading edge of the blade to 1 / 3 of the blade chord length is a thickened structure.

4. A friction brake lifting method after shaft failure, characterized in that: In this method, one or more stages of stationary blades adopt the rubbing stationary blade structure as described in any one of claims 1-3.

5. The friction brake lifting method after shaft failure as claimed in claim 4 is characterized in that: The method comprises the following steps: S1. Evaluate the degree of friction participation of blade structures of different levels and the magnitude of imbalance after friction; S2. Select the blade stage with the highest friction participation and the lowest friction imbalance level; S3. The blade stage determined in step S2 adopts the rubbing stationary blade structure as described in any one of claims 1 to 3.

6. The friction brake lifting method after shaft failure as claimed in claim 5, characterized in that: In step S1 , an evaluation is performed using the finite element method.

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