Gap control system and air entraining device

Abstract

The clearance control system and the air entraining device are used for meeting different cooling air requirements of a high-pressure turbine active clearance control system and a low-pressure turbine active clearance control system. The air entraining device is used for entraining air from the outer duct and comprises an air entraining pipe and a partition plate; the air entraining pipe comprises a wall body, and an air entraining channel is enclosed by the wall body; the partition plate is located in the air entraining pipe and divides the air entraining channel into a low-pressure air entraining channel and a high-pressure air entraining channel, the low-pressure air entraining channel is used for entraining air to a low-pressure turbine case, and the high-pressure air entraining channel is used for entraining air to a high-pressure turbine case. The circulation sectional area of the low-pressure air entraining channel is larger than that of the high-pressure air entraining channel.

Description

Technical Field

[0001] This invention relates to a clearance control system and bleed air device for turbofan engines, specifically to a control system and bleed air device that bleeds air from the outer bypass duct to cool the turbine casing, thereby controlling the clearance between the turbine casing and the turbine rotor. Background Technology

[0002] In aero-engines, the clearance between the outer ring of the turbine casing and the tips of the turbine rotor blades has a significant impact on turbine efficiency and engine fuel consumption. Due to the clearance between the blade tips and the turbine casing, the pressure difference between the pressure and suction surfaces of the blades causes gas leakage, reducing engine efficiency and increasing fuel consumption. Therefore, from the perspective of reducing engine fuel consumption, the blade tip clearance should be controlled to be as small as possible. However, excessively small blade tip clearance can lead to friction between the blades and the turbine casing, reducing engine lifespan. During aero-engine operation, various factors such as temperature and centrifugal force cause different degrees of expansion between the blades and the turbine casing, resulting in variations in the blade tip clearance. Furthermore, different operating conditions of the aero-engine can also alter the blade tip clearance.

[0003] To maintain the blade tip clearance within the ideal range during aero-engine operation, controlling the thermal expansion of the turbine casing is essential, which is often achieved through an active clearance control system. Active clearance control systems are mostly thermodynamic, typically drawing air from the outer bypass duct behind the fan as cooling air to the periphery of the turbine casing. This cooling air impacts the turbine casing through cooling pipes, controlling its temperature and thus its thermal expansion, which in turn controls the clearance between the outer ring of the turbine casing and the blade tips of the turbine rotor.

[0004] The tip clearance between the high-pressure turbine casing and the high-pressure turbine rotor blades, and the tip clearance between the low-pressure turbine casing and the low-pressure turbine rotor blades, need to be controlled separately. Therefore, a high-pressure turbine active clearance control system and a low-pressure turbine active clearance control system are often installed. Both systems typically draw air from the same location in the bypass duct and share a common bleed air device. The high-pressure bleed air duct supplying air to the high-pressure turbine active clearance control system and the low-pressure bleed air duct supplying air to the low-pressure turbine active clearance control system have the same flow area, as illustrated in US Patent Application Publication No. US7717667B2. Figure 3 The air intake devices shown in Figures 4 and 5 have an evenly distributed flow area that cannot meet the different cooling gas requirements of the high-pressure turbine active clearance control system and the low-pressure turbine active clearance control system. Summary of the Invention

[0005] The purpose of this invention is to provide a gap control system and an air bleed device to adapt to the different cooling gas requirements of the high-pressure turbine active gap control system and the low-pressure turbine active gap control system.

[0006] In a first aspect, the present invention provides an air intake device. According to an embodiment of the present invention, the air intake device is used to draw air from an outer bypass duct. The air intake device includes an air intake pipe and a partition. The air intake pipe includes a wall that encloses an air intake channel. The partition is located inside the air intake pipe and separates the air intake channel into a low-pressure air intake channel and a high-pressure air intake channel. The low-pressure air intake channel is used to draw air to a low-pressure turbine casing, and the high-pressure air intake channel is used to draw air to a high-pressure turbine casing. The flow cross-sectional area of ​​the low-pressure air intake channel is larger than the flow cross-sectional area of ​​the high-pressure air intake channel.

[0007] In one or more embodiments, the flow cross-sectional area of ​​the low-pressure air intake channel is four times that of the flow cross-sectional area of ​​the high-pressure air intake channel.

[0008] In one or more embodiments, the partition extends axially along the outer duct so that the low-pressure bleed air passage and the high-pressure bleed air passage are located in the same axial position.

[0009] In one or more embodiments, the wall includes a front sidewall located upstream of the outer duct relative to the other walls, the front sidewall having a rounded corner at the inlet of the air intake.

[0010] In one or more embodiments, the inlet of the air duct is provided with a flange that protrudes from the inlet of the air duct to secure the air duct device to the outer surface of the casing, and the axial section profile of the inlet of the air duct and the flange is the same as the axial section profile of the outer surface of the casing.

[0011] In one or more embodiments, the front sidewall is an arc-shaped wall.

[0012] In one or more embodiments, a grid is provided in both the low-pressure air intake channel and the high-pressure air intake channel. The grid includes multiple airfoil elements arranged along the axial direction of the outer bypass duct, and each airfoil element connects the partition and the wall.

[0013] In one or more embodiments, the downstream end of each airfoil is located behind the upstream end and thus tilted backward, with the tilt angle of the downstream airfoil being smaller than that of the upstream airfoil along the axial direction of the outer bypass duct.

[0014] In one or more embodiments, each of the airfoils is arc-shaped from the upstream end to the downstream end.

[0015] Secondly, the present invention provides a clearance control system. According to an embodiment of the present invention, the clearance control system includes a high-pressure turbine active clearance control system and a low-pressure turbine active clearance control system. The high-pressure turbine active clearance control system includes a high-pressure bleed air pipeline for bleeding air into the high-pressure turbine casing, and the low-pressure turbine active clearance control system includes a low-pressure bleed air pipeline for bleeding air into the low-pressure turbine casing. The clearance control system further includes the aforementioned bleed air device. The high-pressure bleed air channel of the bleed air device is connected to the high-pressure bleed air pipeline, and the low-pressure bleed air channel of the bleed air device is connected to the low-pressure bleed air pipeline.

[0016] The embodiments of the present invention possess at least one of the following beneficial effects:

[0017] The flow cross-sectional area of ​​the low-pressure bleed air passage is larger than that of the high-pressure bleed air passage. Given that the bleed air flow rate required by the low-pressure turbine casing is greater than that required by the high-pressure turbine casing, the flow capacity of the bleed air device is rationally allocated to the high-pressure and low-pressure bleed air passages. This maximizes the utilization of the bleed air device's flow capacity, improves the bleed air flow capacity of the low-pressure bleed air passage, reduces the total bleed air pressure loss to the low-pressure turbine casing, increases the total bleed air pressure recovery coefficient to the low-pressure turbine casing, meets the bleed air flow rate requirements of the low-pressure turbine casing, improves the cooling effect on the low-pressure turbine casing, and enhances the control effect on the blade tip clearance. Attached Figure Description

[0018] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0019] Figure 1 This is a schematic diagram of the clearance control system;

[0020] Figure 2 A schematic diagram showing the installation location of the bleed air device;

[0021] Figure 3 This is a perspective view of the air intake device.

[0022] Figure label:

[0023] 1-Outlet guide vane;

[0024] 2-Outer bypass duct;

[0025] 3-Core engine room;

[0026] 4-High-pressure turbine active clearance control system;

[0027] 5-Low-pressure turbine active clearance control system;

[0028] 6-High-pressure turbine casing;

[0029] 7-Low-pressure turbine casing;

[0030] 8- Air intake device;

[0031] 9-Inhalation tube;

[0032] 10-Wall;

[0033] 11-Air intake channel;

[0034] 12-High-pressure bleed air channel;

[0035] 13-Low-pressure bleed air channel;

[0036] 14-Partition;

[0037] 15 - Anterior sidewall;

[0038] 16-Rounded corners;

[0039] 17-Flange;

[0040] 18-grid;

[0041] 19-Airfoil;

[0042] 20 - Downstream end of the airfoil;

[0043] 21 - Upstream end of the airfoil;

[0044] 22-High-pressure bleed air main;

[0045] 23-High-pressure bleed air flow control valve;

[0046] 24-High-pressure bleed air distribution pipe;

[0047] 25-High-pressure gas collection box;

[0048] 26-High-voltage cover plate;

[0049] 27-High-pressure impact cooling pipe;

[0050] 28 - Low-pressure bleed air main;

[0051] 29 - Low-pressure bleed air flow control valve;

[0052] 30 - Low-pressure bleed air distribution pipe;

[0053] 31-Low-pressure gas collection box;

[0054] 32 - Low-pressure impact cooling pipe. Detailed Implementation

[0055] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0056] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0057] A turbofan engine, in terms of airflow direction, includes a fan, booster stage, low-pressure compressor, high-pressure compressor, combustion chamber, high-pressure turbine, and low-pressure turbine. The low-pressure compressor and low-pressure turbine are connected to the low-pressure shaft, and the high-pressure compressor and high-pressure turbine are connected to the high-pressure shaft. Circumferentially and axially, all these engine components are enclosed by a segmented casing, which is housed within the core engine compartment, and the entire engine is housed in a nacelle. During operation, the airflow, after passing through the fan, is split by a splitter ring on the outer periphery of the low-pressure compressor. A portion of the airflow enters the inner duct, is compressed by the compressor, and then flows into the combustion chamber to mix and burn with fuel. The combustion gases drive the high-pressure turbine and low-pressure turbine; the high-pressure turbine drives the high-pressure compressor, and the low-pressure turbine drives the fan. Figure 2 As shown, another portion of the air enters the outer bypass duct 2 through the outlet guide vane 1 behind the fan, and is ejected rearward through the outer bypass duct 2 between the nacelle and the core engine room 3 to generate thrust.

[0058] Figure 1 and Figure 2 An implementation of a gap control system is also shown. For example... Figure 1 As shown, the clearance control system includes a high-pressure turbine active clearance control system 4 and a low-pressure turbine active clearance control system 5. The high-pressure turbine active clearance control system 4 draws cooling air from the high-pressure turbine casing 6 to control the temperature of the high-pressure turbine casing 6, thereby controlling the thermal expansion of the high-pressure turbine casing 6, and consequently controlling the tip clearance between the high-pressure turbine casing 6 and the high-pressure turbine rotor blades. The low-pressure turbine active clearance control system 5 draws cooling air from the low-pressure turbine casing 7 to control the temperature of the low-pressure turbine casing 7, thereby controlling the thermal expansion of the low-pressure turbine casing 7, and consequently controlling the tip clearance between the low-pressure turbine casing 7 and the low-pressure turbine rotor blades.

[0059] like Figure 1 and Figure 2 As shown, the gap control system is equipped with an air bleed device 8, which is used to bleed air from the outer bypass duct 2. Further refer to... Figure 3The gas eliminator 8 includes a gas eliminator pipe 9 with a wall 10 that encloses a gas eliminator channel 11 located at the center of the gas eliminator pipe 9. The gas eliminator 8 also includes a partition 14 located within the gas eliminator pipe 9, dividing the gas eliminator channel 11 into a low-pressure gas eliminator channel 13 and a high-pressure gas eliminator channel 12. The partition 14 and a portion of the wall 10 enclose the low-pressure gas eliminator channel 13, and the partition 14 and another portion of the wall 10 enclose the high-pressure gas eliminator channel 12. The flow cross-sectional area of ​​the low-pressure gas eliminator channel 13 is larger than that of the high-pressure gas eliminator channel 12. The partition 14 can be offset relative to the central plane of the gas eliminator pipe 9, unequally dividing the flow cross-sectional area of ​​the gas eliminator channel 11, such that the flow cross-sectional area of ​​the low-pressure gas eliminator channel 13 is larger than that of the high-pressure gas eliminator channel 12 at all points along the gas flow path.

[0060] Further integration Figure 1 The high-pressure turbine active clearance control system 4 includes a high-pressure bleed air pipeline for bleeding air into the high-pressure turbine casing 6. The high-pressure bleed air passage 12 of the bleed air device 8 is connected to the high-pressure bleed air pipeline and is used to bleed air into the high-pressure turbine casing 6. The low-pressure turbine active clearance control system 5 includes a low-pressure bleed air pipeline for bleeding air into the low-pressure turbine casing 7. The low-pressure bleed air passage 13 of the bleed air device 8 is connected to the low-pressure bleed air pipeline and is used to bleed air into the low-pressure turbine casing 7.

[0061] Because the low-pressure turbine has more stages, the bleed air flow rate required by the low-pressure turbine casing 7 is greater than that required by the high-pressure turbine casing 6. A bleed air device with an evenly distributed flow cross-sectional area (such as the one described in US patent application publication number US7717667B2) is used. Figure 3The air intake systems shown in Figures 4 and 5 cannot accommodate the different bleed air flow requirements of the low-pressure turbine casing 7 and the high-pressure turbine casing 6. This often results in excessive bleed air flow capacity in the high-pressure bleed air passage 12 and insufficient bleed air flow capacity in the low-pressure bleed air passage 13, wasting the flow capacity of the bleed air device 8. Consequently, the total bleed air pressure recovery coefficient for bleed air into the low-pressure turbine casing 7 is lower than that for bleed air into the high-pressure turbine casing 6. Furthermore, the length of the low-pressure bleed air pipe leading to the low-pressure turbine casing 7 is greater than the length of the high-pressure bleed air pipe leading to the high-pressure turbine casing 6, further exacerbating the total bleed air pressure loss in the low-pressure turbine casing 7. This prevents the bleed air flow requirements of the low-pressure turbine casing 7 from being met, reducing the cooling effect on the low-pressure turbine casing 7 and decreasing the control effect on the blade tip clearance. The flow cross-sectional area of ​​the low-pressure bleed air passage 13 is larger than that of the high-pressure bleed air passage 12. Since the bleed air flow rate required by the low-pressure turbine casing 7 is greater than that required by the high-pressure turbine casing 6, the flow capacity of the bleed air device 8 is rationally allocated to the high-pressure bleed air passage 12 and the low-pressure bleed air passage 13. This maximizes the utilization of the flow capacity of the bleed air device 8, improves the bleed air flow capacity of the low-pressure bleed air passage 13, reduces the total pressure loss of bleed air entering the low-pressure turbine casing 7, improves the total pressure recovery coefficient of bleed air entering the low-pressure turbine casing 7, meets the bleed air flow rate requirement of the low-pressure turbine casing 7, improves the cooling effect of the low-pressure turbine casing 7, and improves the control effect of the blade tip clearance.

[0062] The flow cross-sectional area of ​​the low-pressure bleed air passage 13 can be four times that of the high-pressure bleed air passage 12. At all points along the gas flow path, the flow cross-sectional area of ​​the low-pressure bleed air passage 13 can be four times that of the high-pressure bleed air passage 12. In a turbofan engine, the bleed air flow rate required by the low-pressure turbine casing 7 is at most four times that required by the high-pressure turbine casing 6. Therefore, the flow cross-sectional area of ​​the low-pressure bleed air passage 13 is four times that of the high-pressure bleed air passage 12, rationally allocating the flow capacity of the bleed air device 8 to the high-pressure bleed air passage 12 and the low-pressure bleed air passage 13, maximizing the utilization of the flow capacity of the bleed air device 8. The design operating condition for the clearance control system of a turbofan engine is generally the economic cruise condition. Under the economic cruise condition, simulations were performed on the following conditions: the flow cross-sectional area of ​​the low-pressure bleed air passage 13 separated by the diaphragm 14 is four times the flow cross-sectional area of ​​the high-pressure bleed air passage 12, and the flow cross-sectional area of ​​the low-pressure bleed air passage 13 separated by the diaphragm 14 is equal to the flow cross-sectional area of ​​the high-pressure bleed air passage 12. Table 1 is obtained from these simulations.

[0063] Table 1

[0064]

[0065] In Table 1, the total pressure recovery coefficient of the high-pressure bleed channel 12 is the ratio of the total pressure at the outlet of the high-pressure bleed channel 12 to the total pressure at the inlet of the high-pressure bleed channel 12, and the total pressure recovery coefficient of the low-pressure bleed channel 13 is the ratio of the total pressure at the outlet of the low-pressure bleed channel 13 to the total pressure at the inlet of the low-pressure bleed channel 13. As shown in Table 1, compared to the case where the flow cross-sectional area of ​​the low-pressure bleed air passage 13 separated by the baffle 14 is equal to that of the high-pressure bleed air passage 12, the flow cross-sectional area of ​​the low-pressure bleed air passage 13 separated by the baffle 14 is four times that of the high-pressure bleed air passage 12. The total pressure recovery coefficient of the low-pressure bleed air passage 13 increases significantly by 7%, indicating that the flow loss of the low-pressure bleed air passage 13 is significantly reduced, thus improving the cooling effect on the low-pressure turbine casing 7. Meanwhile, since the bleed air flow required by the high-pressure turbine casing 6 is relatively small, the total pressure recovery coefficient of the high-pressure bleed air passage 12 decreases only slightly by 1%, indicating that the flow loss of the high-pressure bleed air passage 12 increases slightly. The increase in the flow loss of the high-pressure bleed air passage 12 is significantly less than the decrease in the flow loss of the low-pressure bleed air passage 13. Furthermore, the flow rate of the low-pressure bleed channel 13 increased significantly by 14%, while the flow rate of the high-pressure bleed channel 12 decreased only slightly. The decrease in the flow rate of the high-pressure bleed channel 12 was significantly less than the increase in the flow rate of the low-pressure bleed channel 13, resulting in a total flow rate increase of approximately 10% for both the high-pressure and low-pressure bleed channels 12 and 13. This indicates that the flow capacity of the bleed device 8 is more rationally allocated to the high-pressure and low-pressure bleed channels 12 and 13, and the flow capacity of the bleed device 8 is better utilized. While slightly reducing the bleed capacity of the high-pressure bleed channel 12, the bleed capacity of the low-pressure bleed channel 13 and the entire bleed device 8 is significantly improved.

[0066] like Figure 3 As shown, the baffle 14 can extend along the axial direction of the outer bypass 2 so that the low-pressure air intake channel 13 and the high-pressure air intake channel 12 are located in the same axial position. The gas flows in the outer bypass 2 along the axial direction of the outer bypass 2. The baffle 14 extends along the axial direction of the outer bypass 2 so that the low-pressure air intake channel 13 and the high-pressure air intake channel 12 are adjacent in the circumferential direction of the outer bypass 2 and located in the same axial position. Both the low-pressure air intake channel 13 and the high-pressure air intake channel 12 can be set at the optimal position for recovering the dynamic pressure head of the airflow in the outer bypass 2, so as to recover the dynamic pressure head of the airflow in the outer bypass 2 as much as possible, increase the kinetic energy of the introduced airflow, and thus improve the cooling effect on the high-pressure turbine casing 6 and the low-pressure turbine casing 7.

[0067] like Figure 3As shown, the wall 10 may have a front sidewall 15, which is located upstream of the outer bypass 2 compared to the other walls 10 of the intake pipe 9. The front sidewall 15 has a rounded corner 16 at the inlet of the intake pipe 9 to reduce airflow separation losses. In the illustrated embodiment, all the front sidewalls 15 of the intake pipe 9 are arc-shaped walls with rounded corners 16, and the arc-shaped protrusions face the gas flow direction of the outer bypass 2. This conforms to the gas flow direction of the outer bypass 2, recovers the dynamic pressure head of the airflow in the outer bypass 2 as much as possible, and increases the kinetic energy of the introduced airflow, thereby improving the cooling effect on the high-pressure turbine casing 6 and the low-pressure turbine casing 7.

[0068] like Figure 3 As shown, the inlet of the air duct 9 may be equipped with a flange 17, which protrudes from the inlet of the air duct 9 to fix the air duct device 8 to the outer surface of the casing, further combining... Figure 2 The inlet of the bleed air duct 9 and the axial section profile of the flange 17 are the same as the axial section profile of the outer surface of the casing. The axial section is a section passing through the central axis of the turbofan engine. The same axial section profile makes the axial streamline of the bleed air device 8 consistent with the axial streamline of the outer surface of the casing, which can reduce the flow loss of airflow. The flange 17 can be bolted to the outer surface of the casing. The bleed air device 8 can be fixed to the outer surface of the support ring behind the outlet of the bypass fan, thereby recovering the dynamic pressure head of the airflow in the bypass duct 2 as much as possible, increasing the kinetic energy of the introduced airflow, and thus improving the cooling effect on the high-pressure turbine casing 6 and the low-pressure turbine casing 7.

[0069] like Figure 3 As shown, grids 18 can be installed in both the low-pressure bleed air channel 13 and the high-pressure bleed air channel 12, and the grids 18 are fixedly installed in the low-pressure bleed air channel 13 and the high-pressure bleed air channel 12. The grids 18 include multiple airfoil elements 19, which are arranged along the axial direction of the outer bypass duct 2. The airflow of the outer bypass duct 2 flows through the airfoil elements 19 into the bleed air channel 11. The airfoil elements 19 guide the bleed air flow and reduce airflow loss. Each airfoil element 19 is connected to the partition plate 14 and the wall 10 for installation and fixation.

[0070] like Figure 3As shown, the downstream end 20 of each airfoil 19 can be located behind the upstream end 21, thus tilting the airfoil 19 backward. The downstream end 20 of the airfoil 19 is located downstream of the gas flow path into the air intake channel 11, and the upstream end 21 of the airfoil 19 is located upstream of the gas flow path into the air intake channel 11. Gas flows along the axial direction of the bypass 2. Compared to the upstream end 21 of the airfoil 19, the downstream end 20 of the airfoil 19 is located downstream of the gas flow direction of the bypass 2. The airfoil 19 tilts backward from the upstream end 21 to the downstream end 20, which conforms to the gas flow direction of the bypass 2 and reduces airflow loss. Along the axial direction of the bypass duct 2, the backward tilt angle of the downstream airfoil 19 is smaller than that of the upstream airfoil 19. As the gas flows along the axial direction of the bypass duct 2, the backward tilt angle of the downstream airfoil 19 in the gas flow direction of the bypass duct 2 is smaller than that of the upstream airfoil 19 in the gas flow direction of the bypass duct 2. Along the gas flow direction of the bypass duct 2, the backward tilt angles of multiple airfoils 19 in a grid 18 gradually decrease, which conforms to the gas flow direction of the bypass duct 2 and reduces the flow loss of the airflow.

[0071] like Figure 3 As shown, each airfoil 19 can be arc-shaped from the upstream end 21 to the downstream end 20, with the arc-shaped protrusion facing the gas flow direction of the outer bypass 2. This conforms to the gas flow direction of the outer bypass 2 and reduces the flow loss of the airflow.

[0072] like Figure 3 As shown, the air intake device 8 can be integrally molded, such as by additive manufacturing. The edges of the airfoil 19 and the baffle 14 can be rounded to reduce airflow loss. A flange can be installed at the outlet of the air intake pipe 9 to be bolted to the downstream high-pressure air intake pipe and low-pressure air intake pipe.

[0073] like Figure 1 As shown, the high-pressure turbine active clearance control system 4 may further include a high-pressure bleed air main pipe 22, a high-pressure bleed air flow control valve 23, an annular high-pressure bleed air distribution pipe 24, a circumferentially distributed high-pressure air collection box 25, and a high-pressure cover plate 26 and a high-pressure impact cooling pipe 27 located inside the high-pressure air collection box 25. The bleed air device 8 collects the total pressure of the airflow from the outer bypass duct 2. A portion of the airflow is drawn through the high-pressure bleed air channel 12 and the high-pressure bleed air main pipe 22 to the high-pressure bleed air distribution pipe 24. The high-pressure bleed air flow control valve 23 regulates the bleed air flow rate of the high-pressure bleed air main pipe 22. The annular high-pressure bleed air distribution pipe 24 evenly distributes the airflow to the circumferentially distributed high-pressure air collection box 25. The airflow flows from the high-pressure air collection box 25 into the high-pressure impact cooling pipe 27, and performs impact cooling on the high-pressure turbine casing 6 through the impact cooling holes on the high-pressure impact cooling pipe 27.

[0074] like Figure 1As shown, the low-pressure turbine active clearance control system 5 may further include a low-pressure bleed air main pipe 28, a low-pressure bleed air flow control valve 29, an annular low-pressure bleed air distribution pipe 30, a circumferentially distributed low-pressure air collection box 31, and a low-pressure impact cooling pipe 32 located inside the low-pressure air collection box 31. The bleed air device 8 collects the total air pressure of the airflow from the outer bypass duct 2, and another part of the airflow is drawn through the low-pressure bleed air channel 13 and the low-pressure bleed air main pipe 28 to the low-pressure bleed air distribution pipe 30. The low-pressure bleed air flow control valve 29 regulates the bleed air flow of the low-pressure bleed air main pipe 28, and the annular low-pressure bleed air distribution pipe 30 evenly distributes the airflow to the circumferentially distributed low-pressure air collection box 31. The airflow flows from the low-pressure air collection box 31 into the low-pressure impact cooling pipe 32, and performs impact cooling on the low-pressure turbine casing 7 through the impact cooling holes on the low-pressure impact cooling pipe 32.

[0075] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention.

Claims

1. An air bleed device for bleeding air from an outer duct, characterized in that... include: An air intake tube, including a wall that encloses an air intake channel; as well as A baffle plate, located inside the air intake pipe, separates the air intake channel into a low-pressure air intake channel and a high-pressure air intake channel. The low-pressure air intake channel is used to draw air into the low-pressure turbine casing, and the high-pressure air intake channel is used to draw air into the high-pressure turbine casing. The flow cross-sectional area of ​​the low-pressure air intake channel is larger than that of the high-pressure air intake channel.

2. The air extraction device according to claim 1, characterized in that: The cross-sectional area of ​​the low-pressure air intake channel is four times that of the high-pressure air intake channel.

3. The air extraction device according to claim 1, characterized in that: The baffle extends axially along the outer duct so that the low-pressure air intake channel and the high-pressure air intake channel are located in the same axial position.

4. The air extraction device according to claim 1, characterized in that: The wall includes a front sidewall, which is located upstream of the outer duct compared to the other walls, and the front sidewall has a rounded corner at the inlet of the air intake pipe.

5. The air extraction device according to claim 1, characterized in that: The air intake pipe has a flange at its inlet, which protrudes from the inlet to secure the air intake device to the outer surface of the casing. The axial section profile of the inlet of the air intake pipe and the flange is the same as that of the outer surface of the casing.

6. The air extraction device according to claim 4, characterized in that: The front sidewall is an arc-shaped wall.

7. The air extraction device according to claim 3, characterized in that: Both the low-pressure air intake channel and the high-pressure air intake channel are equipped with grids. Each grid includes multiple airfoil elements, which are arranged along the axial direction of the outer duct. Each airfoil element connects the partition and the wall.

8. The air extraction device according to claim 7, characterized in that: The downstream end of each airfoil is located behind the upstream end and is tilted backward. Along the axial direction of the outer bypass, the backward tilt angle of the downstream airfoil is smaller than that of the upstream airfoil.

9. The air extraction device according to claim 7, characterized in that: Each of the airfoils is curved from the upstream end to the downstream end.

10. A clearance control system, comprising a high-pressure turbine active clearance control system and a low-pressure turbine active clearance control system, wherein the high-pressure turbine active clearance control system includes a high-pressure bleed air pipeline for bleeding air into the high-pressure turbine casing, and the low-pressure turbine active clearance control system includes a low-pressure bleed air pipeline for bleeding air into the low-pressure turbine casing, characterized in that: The gap control system further includes a bleed air device as described in any one of claims 1 to 9, wherein the high-pressure bleed air channel of the bleed air device is connected to the high-pressure bleed air pipeline, and the low-pressure bleed air channel of the bleed air device is connected to the low-pressure bleed air pipeline.

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