Bleed air system and aeroengine
By incorporating a pressure stabilizing chamber and multiple bleed air vents into the aero-engine, the problem of combustion chamber performance degradation caused by bleed air methods has been solved, resulting in a more stable bleed air process and an improved cabin environment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- AECC HUNAN AVIATION POWERPLANT RES INST
- Filing Date
- 2023-04-27
- Publication Date
- 2026-05-29
AI Technical Summary
Existing bleed air methods lead to deterioration of combustion chamber performance, including changes in flow field structure, uneven airflow distribution, uneven combustion chamber temperature distribution, and high-frequency vibration of the combustion chamber and high-cycle fatigue cracks in thin-walled flame tubes caused by increased bleed air volume.
A bleed air system is designed by setting a pressure stabilizing chamber between the diffuser assembly and the combustor casing, and setting multiple bleed air holes on the diffuser assembly and the combustor casing to form a pressure stabilizing chamber and bleed air path, thereby reducing the impact on the airflow of the two channels in the combustion chamber and avoiding performance degradation when the airflow is excited and the bleed air volume is large.
It effectively reduces the negative impact of bleed air on combustion chamber performance, improves the nacelle ventilation and temperature environment, avoids cracks and spalling in the flame tube, improves the cleanliness and uniformity of bleed air, and reduces the adverse effects on combustion chamber performance.
Smart Images
Figure CN116517693B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aviation equipment technology, and in particular to an air bleed system and an aircraft engine. Background Technology
[0002] For conventional military and civilian aircraft, to improve cabin ventilation and temperature, a high-temperature, high-pressure gas is typically extracted from the aero gas turbine engine to provide compressed air for the aircraft's environmental control system, thus providing a safe and comfortable pressurized environment for passengers. For large civilian airliners and military fighter jets, bleed air is generally provided by the auxiliary power unit, using the air turbine starter that drives the main engine to start the engine on the ground or at high altitude. Bleed air from engines varies. Depending on the temperature and pressure requirements of the aircraft's environmental control system, bleed air is generally drawn from the engine compressor components or the combustion chamber components. Bleed air drawn from the compressor components is generally P2.5 bleed air, while bleed air drawn from the diffuser assembly outlet or the combustion chamber is generally P3 bleed air.
[0003] From the current engine bleed air configuration, there are two main ways to draw P3 air from the compressor outlet: such as Figure 1 As shown, one method involves drawing air from the two channels of the combustion chamber through an annular radial channel between the diffuser assembly and the combustor casing. The bleed air inlet is typically located on the diffuser casing or the combustor casing. Figure 2 As shown, another form mainly applies to tubular diffuser assemblies, where the bleed air inlet is located above the diffuser assembly. Air is drawn from the two channels in the combustion chamber primarily through the gap between adjacent tubular diffuser assemblies. The bleed air scheme within the diffuser assembly is as follows: Figure 3 As shown, this bleed air method involves creating a ring of holes near the outlet of the radial diffuser assembly and blocking the gap between the axial diffuser assembly and the combustor casing. During bleed air operation, the airflow from the radial diffuser assembly enters the narrow annular cavity formed between the diffuser assembly and the combustor casing through the openings on the diffuser assembly wall, and is finally supplied to the aircraft cockpit through the bleed air seat on the combustor casing.
[0004] like Figure 1 The method shown involves drawing P3 air from the diffuser assembly outlet. Because the air intake location is close to the mainstream outlet of the diffuser assembly, when the air intake flow rate is large, the airflow at the diffuser assembly outlet will be deflected due to the ducting effect. This will change the flow field structure in the two channels of the combustion chamber, especially the flow field in the outer two channels. This will cause changes in the total pressure distribution of the airflow in the two channels, which in turn will affect the intake flow rate of each row of air intake holes in the flame tube, change the flow distribution in the combustion chamber, cause the combustion chamber performance to deviate from the design value, and worsen the temperature field at the combustion chamber outlet.
[0005] for Figure 2The bleed air method shown, although the bleed air flow is not directly drawn from the diffuser assembly outlet, but is drawn from the gap between the two tubular diffuser assemblies, will cause uneven circumferential distribution of airflow in the two channels because there are often only 1 to 2 bleed air inlets in the circumferential direction. The bleed air position is close to the rear end of the flame tube and near the exhaust bend, which can easily reduce the intake airflow near the bleed air inlet, reduce the local cooling intake air in the exhaust bend, and cause the local wall temperature to be too high, or affect the uneven mixing of the circumferential intake air in the flame tube, resulting in a worse circumferential temperature distribution at the combustion chamber outlet.
[0006] refer to Figure 3 For the diffuser assembly bleed air method, since there is no obvious "air grabbing" phenomenon at the outlet of the axial-flow diffuser assembly, the airflow from the diffuser assembly is not significantly disturbed. When the bleed air volume is small, the OTDF value of the combustion chamber changes little, but the high-temperature zone of the combustion chamber will be biased towards the blade tip. When the bleed air volume is large, the OTDF value of the combustion chamber will deteriorate significantly. If the P3 bleed air of the auxiliary power unit is to directly draw air from the two channels of the combustion chamber from the combustor casing, it will have a more severe impact on the combustion chamber performance. This is mainly because the percentage of bleed air in the intake air is larger, the flow distribution in the combustion chamber will change significantly, and as the bleed air volume and velocity increase, the airflow excitation force inside the combustion chamber increases, which can easily cause high-frequency vibration of the thin-walled flame tube, leading to high-cycle fatigue cracks or even spalling. Summary of the Invention
[0007] This invention provides an air bleed system and an aero-engine to solve the technical problem that existing air bleed methods lead to the deterioration of combustion chamber performance.
[0008] The technical solution adopted in this invention is as follows:
[0009] A bleed air system is applied to an aero-engine, the aero-engine including a diffuser assembly and a combustion chamber, the diffuser assembly extending into the combustion chamber; the combustion chamber is connected to the diffuser casing, the diffuser assembly including a radial diffuser and an axial diffuser connected to each other, the bleed air system comprising:
[0010] The pressure stabilizing chamber includes a sealing structure disposed between the outer wall of the diffuser assembly and the combustion chamber near the outlet end of the diffuser assembly. The outer wall of the diffuser assembly, the combustion chamber, the diffuser chamber, and the sealing structure enclose the pressure stabilizing chamber, which is used to contain the introduced gas and stabilize its pressure.
[0011] The first gas bleed structure is located in the diffuser assembly and is used to introduce the gas from the diffuser assembly into the pressure stabilizing chamber.
[0012] The second bleed gas structure is disposed on the combustion chamber and communicates with the pressure stabilizing chamber, and is used to draw the gas in the pressure stabilizing chamber out to the engine compartment.
[0013] As a further improvement to the above technical solution, the first air intake structure includes a plurality of first air intake holes distributed circumferentially on the outer wall of the axial flow diffuser and second air intake holes on the inner wall of the axial flow diffuser that match the radial position of the first air intake holes, for introducing gas into the pressure stabilizing chamber through the second air intake holes and the first air intake holes and making the flow direction of the introduced gas perpendicular to the airflow direction at the outlet end of the diffuser assembly.
[0014] As a further improvement to the above technical solution, multiple first air intake holes are evenly distributed circumferentially and have different diameters. The diameter of the first air intake hole increases as the distance from the second air intake structure increases. The circumferential distribution position of the second air intake holes matches the first air intake holes, and the diameter of each second air intake hole matches the first air intake hole at the corresponding position.
[0015] As a further improvement to the above technical solution, multiple first air intake holes are distributed circumferentially and have the same diameter. The circumferential spacing of the first air intake holes decreases as the distance from the second air intake structure increases. The diameter of each second air intake hole is the same, and the circumferential distribution position of each second air intake hole matches that of the first air intake hole.
[0016] As a further improvement to the above technical solution, the second air intake structure is disposed on the outside of the combustion chamber and axially close to the sealing structure.
[0017] As a further improvement to the above technical solution, the second air intake structure is radially spaced from the first air intake structure.
[0018] As a further improvement to the above technical solution, the sealing structure includes a first mating surface formed on the outer wall of the diffuser assembly and a second mating surface formed on the combustion chamber. The first mating surface and the second mating surface cooperate to position the diffuser chamber axially and circumferentially on the combustion chamber.
[0019] As a further improvement to the above technical solution, the first mating surface is provided with a first mating protrusion, and the second mating surface is provided with a second mating protrusion for matching and embedding the gap between two adjacent first mating protrusions; the first mating protrusion has at least two sizes.
[0020] As a further improvement to the above technical solution, the combustion chamber casing is provided with a raised part at the pressure stabilizing cavity position to increase the capacity of the pressure stabilizing cavity.
[0021] According to another aspect of the present invention, an aircraft engine is also provided, which utilizes any of the above-described bleed air systems.
[0022] The present invention has the following beneficial effects: The diffuser casing of the bleed air system is connected to the combustion casing and the diffuser assembly extends into the combustion chamber. By setting a sealing structure, the outer wall of the diffuser assembly, the combustion casing, the diffuser casing, and the sealing structure are enclosed to form a pressure stabilizing chamber. The high-pressure airflow output by the centrifugal compressor enters the outer ring two channels of the combustion chamber through the radial diffuser and the axial diffuser. The airflow is introduced from the combustion chamber to the pressure stabilizing chamber through the first bleed air structure to stabilize the pressure, which reduces the impact of the bleed air on the airflow field of the two channels and avoids damage such as cracks and debris in the flame tube of the combustion chamber caused by airflow vibration. The airflow is then led out to the engine compartment through the second bleed air structure to improve the ventilation and temperature environment of the engine compartment. The second bleed air structure is set to lengthen the bleed air path, thereby further reducing the impact on the intake of the flame tube and the head of the combustion chamber.
[0023] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description
[0024] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:
[0025] Figure 1 This is a schematic diagram of the existing air intake structure;
[0026] Figure 2 This is a schematic diagram of the existing air intake structure;
[0027] Figure 3 This is a schematic diagram of the existing air intake structure;
[0028] Figure 4 This is a schematic diagram of a preferred embodiment of the present invention;
[0029] Figure 5 This is a schematic diagram of the sealing structure of a preferred embodiment of the present invention;
[0030] Figure 6 This is a schematic diagram of the first air intake hole structure in a preferred embodiment of the present invention;
[0031] Figure 7 This is a schematic diagram of another first air vent structure according to a preferred embodiment of the present invention;
[0032] 1. Diffuser casing 2. Second bleed air structure 3. Combustion casing 4. Diffuser assembly 41. Radial diffuser 42. Axial diffuser 5. Flame tube 61. Two-channel airflow 62. P3 bleed air 7. First bleed air structure 8. Sealing structure 9. First bleed air port Detailed Implementation
[0033] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0034] Reference Figures 4 to 7 A preferred embodiment of the present invention provides a bleed air system applied to an aero-engine. The aero-engine includes a diffuser assembly 4 and a combustion chamber, the diffuser assembly 4 extending into the combustion chamber; a combustion chamber 3 is connected to a diffuser chamber 1, and the diffuser assembly 4 includes a radial diffuser 41 and an axial diffuser 42 connected to each other. The bleed air system includes:
[0035] The pressure stabilizing chamber includes a sealing structure 8 located between the outer wall of the diffuser assembly 4 and the combustion chamber 3 near the outlet end of the diffuser assembly 4. The outer wall of the diffuser assembly 4, the combustion chamber 3, the diffuser chamber 1, and the sealing structure 8 enclose and form a pressure stabilizing chamber, which is used to contain the introduced gas and stabilize its pressure.
[0036] The first bleed structure 7 is disposed in the diffuser assembly 4 and is used to introduce the gas (P3 bleed gas) of the diffuser assembly 4 into the pressure stabilizing chamber;
[0037] The second bleed gas structure 2 is installed on the combustion chamber 3 and communicates with the pressure stabilizing chamber, and is used to draw the gas in the pressure stabilizing chamber to the engine compartment.
[0038] Understandably, the diffuser casing 1 of this bleed air system is connected to the combustion casing 3, and the diffuser assembly 4 extends into the combustion chamber. By setting a sealing structure, the outer wall of the diffuser assembly 4, the combustion casing 3, the diffuser casing 1, and the sealing structure 8 enclose a pressure stabilizing chamber. The high-pressure airflow output by the centrifugal compressor enters the outer ring two channels of the combustion chamber through the radial diffuser and the axial diffuser. The airflow is introduced from the combustion chamber to the pressure stabilizing chamber through the first bleed air structure 7 to stabilize the pressure, reducing the impact of the bleed air on the flow field of the airflow 61 in the two channels. This avoids damage such as cracks and debris falling off the flame tube 5 in the combustion chamber due to airflow vibration. The airflow is then led out to the engine compartment through the second bleed air structure 2 to improve the engine compartment ventilation and temperature environment. The second bleed air structure 2 is set to lengthen the bleed air path, thereby further reducing the impact on the intake of the flame tube 5 and the head of the combustion chamber.
[0039] In this embodiment, the combustion chamber casing is provided with a raised part at the pressure stabilizing cavity position to increase the capacity of the pressure stabilizing cavity and make it match the requirements of the working environment;
[0040] In this embodiment, the first bleed air structure 7 includes multiple first bleed air holes 9 distributed circumferentially on the outer wall of the axial diffuser 42 and second bleed air holes on the inner wall of the axial diffuser 42, which are matched with the radial position of the first bleed air holes 9. These are used to introduce gas into the pressure stabilizing chamber through the second bleed air holes and the first bleed air holes 9, and to make the flow direction of the introduced gas perpendicular to the flow direction of the airflow at the outlet end of the diffuser assembly 4. This can significantly reduce the impact on the flow field of the two channels, reduce the impact of bleed air on the large-hole jets such as the outer ring main combustion hole and mixing hole, and alleviate the deterioration of combustion chamber performance caused by large bleed air volume. The first bleed air holes 9 are located on the outer wall of the diffuser, and the second bleed air holes are located on the inner wall of the diffuser. The bleed air position is perpendicular to the diffuser outlet airflow and has a 90° bend and misalignment, which fully ensures the cleanliness of the bleed air, avoids fine dust or foreign objects in the airflow from entering the bleed airflow channel, improves the environmental control level of the engine room, and at the same time avoids dust and other particles from accumulating at the small holes and clogging the small holes after long-term bleed air.
[0041] In this embodiment, the second air intake structure 2 is disposed on the outside of the combustion chamber 3 and axially close to the sealing structure 8. The second air intake structure 2 is a single-hole air intake with a certain length to lengthen the air intake path. The axial position of the second air intake structure 2 matches that of the first air intake structure 7 to form a co-current air intake structure, thereby fully improving the air intake effect. The second air intake structure 2 and the first air intake structure 7 are radially spaced apart to prevent the first air intake structure 7 from colliding with the second air intake structure 2, making full use of the pressure stabilizing chamber for pressure stabilization and reducing the impact on the flow field of the two channels.
[0042] In addition, the second air intake structure should be positioned circumferentially away from the head of the combustion chamber to reduce the impact of the air intake on the flow field at the head of the combustion chamber.
[0043] The pressure stabilizing chamber is annular. The second air intake structure 2 uses a single-hole air intake method to draw air from the pressure stabilizing chamber, inevitably causing uneven circumferential air pressure distribution within the chamber. The closer to the second air intake structure 2, the greater the pressure difference between the pressure stabilizing chamber and the diffuser assembly 4, resulting in a larger flow rate from the air intake hole. Conversely, the further away from the second air intake structure 2, the smaller the pressure difference between the pressure stabilizing chamber and the diffuser assembly 4, resulting in a smaller flow rate from the air intake hole. This leads to uneven circumferential airflow distribution at the diffuser assembly 4 outlet, deteriorating combustion chamber performance. To ensure as uniform an airflow as possible at the diffuser 1 outlet, in this embodiment, as follows... Figure 6 As shown, multiple first air intake holes 9 are evenly distributed circumferentially with different diameters, and the diameter of the first air intake holes 9 increases with the increase of the distance from the second air intake structure 2; the circumferential distribution positions of the second air intake holes match the first air intake holes 9, and the diameter of each second air intake hole matches the corresponding position of the first air intake hole 9; in some embodiments, it can also be as follows: Figure 7As shown, multiple first air intake holes 9 are distributed circumferentially with the same diameter. The circumferential spacing of the first air intake holes 9 decreases as the distance from the second air intake structure 2 increases. The diameter of each second air intake hole is the same, and the circumferential distribution position of each second air intake hole matches that of the first air intake holes 9. By controlling the size of the local flow area through any of the above structures, the uneven air pressure distribution in the circumferential direction of the pressure stabilizing chamber is compensated, so that the air intake volume in the diffuser is basically equal along the circumferential direction, ensuring that the outlet air flow of the diffuser is uniform.
[0044] In this embodiment, the sealing structure 8 includes a first mating surface formed on the outer wall of the diffuser assembly 4 and a second mating surface formed on the combustion chamber 3. The first mating surface and the second mating surface cooperate to perform circumferential positioning and axial positioning of the diffuser chamber 1 on the combustion chamber 3 to prevent misinstallation.
[0045] Specifically, the first mating surface is provided with a first mating protrusion, and the second mating surface is provided with a second mating protrusion for matching and embedding into the gap between two adjacent first mating protrusions; the first mating protrusion has at least two sizes, such as Figure 5 As shown, by setting two sizes of first mating protrusions and second mating protrusions that only mate with each other at corresponding positions, misalignment during installation is prevented.
[0046] On the other hand, this embodiment also provides an aircraft engine that uses the above-mentioned bleed air system.
[0047] Example 1
[0048] The aero-engine application in this embodiment uses a preferred bleed air system. This bleed air method, based on compressor and combustion chamber performance calculations, results in relatively small changes in the combustion chamber's OTDF value and a certain degree of improvement in the RTDF value. In general, the blade-internal bleed air is not sensitive to combustion chamber bleed air distortion, and the degree of combustion chamber performance degradation is minimal.
[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A bleed air system applied to an aero-engine, the aero-engine including a diffuser assembly (4) and a combustion chamber, the diffuser assembly (4) extending into the combustion chamber; a combustion chamber casing (3) connected to the diffuser casing (1), characterized in that, The diffuser assembly (4) includes a radial diffuser (41) and an axial diffuser (42) connected to each other, and the bleed air system includes: The pressure stabilizing chamber includes a sealing structure (8) located between the outer wall of the diffuser assembly (4) and the combustion chamber (3) near the outlet end of the diffuser assembly (4). The outer wall of the diffuser assembly (4), the combustion chamber (3), the diffuser chamber (1), and the sealing structure (8) enclose and form the pressure stabilizing chamber, which is used to contain the introduced gas and stabilize its pressure. A first air intake structure (7) is disposed on the diffuser assembly (4) for introducing gas from the diffuser assembly (4) into the pressure stabilizing chamber. The first air intake structure (7) includes a plurality of first air intake holes (9) distributed circumferentially on the outer wall of the axial diffuser (42) and second air intake holes on the inner wall of the axial diffuser (42) matching the radial position of the first air intake holes (9). The gas is introduced into the pressure stabilizing chamber through the second air intake holes and the first air intake holes (9) and the flow direction of the introduced gas is perpendicular to the flow direction of the gas flow at the outlet end of the diffuser assembly (4). The second bleed gas structure (2) is disposed on the combustion chamber (3) and communicates with the pressure stabilizing chamber, and is used to draw the gas in the pressure stabilizing chamber out to the engine compartment.
2. The air extraction system according to claim 1, characterized in that, Multiple first air intake holes (9) are evenly distributed circumferentially and have different diameters. The diameter of the first air intake hole (9) increases as the distance from the second air intake structure (2) increases. The circumferential distribution position of the second air intake holes matches the first air intake hole (9), and the diameter of each second air intake hole matches the first air intake hole (9) at the corresponding position.
3. The air extraction system according to claim 1, characterized in that, Multiple first air intake holes (9) are distributed circumferentially and have the same diameter. The circumferential spacing of the first air intake holes (9) decreases as the distance from the second air intake structure (2) increases. The diameter of each second air intake hole is the same, and the circumferential distribution position of each second air intake hole matches that of the first air intake holes (9).
4. The air intake system according to any one of claims 1-3, characterized in that, The second air intake structure (2) is disposed on the outside of the combustion chamber (3) and axially close to the sealing structure (8).
5. The air intake system according to claim 4, characterized in that, The second air intake structure (2) is radially spaced from the first air intake structure (7).
6. The air extraction system according to claim 1, characterized in that, The sealing structure (8) includes a first mating surface formed on the outer wall of the diffuser assembly (4) and a second mating surface formed on the combustion chamber (3), the first mating surface and the second mating surface engaging to circumferentially and axially position the diffuser chamber (1) on the combustion chamber (3).
7. The air extraction system according to claim 6, characterized in that, The first mating surface is provided with a first mating protrusion, and the second mating surface is provided with a second mating protrusion for matching and embedding into the gap between two adjacent first mating protrusions; the first mating protrusion has at least two sizes.
8. The air extraction system according to claim 1, characterized in that, The combustion chamber casing has an elevated section at the location of the pressure stabilizing chamber to increase the capacity of the pressure stabilizing chamber.
9. An aircraft engine, characterized in that, The application has the air intake system as described in any one of claims 1-8.