Power turbine cooling structure and aircraft engine

Abstract

The application discloses a power turbine cooling structure and an aero-engine, and belongs to the technical field of aero-engines.The impact cavity, the outer frame inner cavity, the support plate inner cavity and the inner frame inner cavity are sequentially communicated, and the inner frame surface is provided with an injection hole for communicating the airflow channel between the inner frame inner cavity and the support plate; the high-speed engine main flow between adjacent support plates sucks the gas in the inner frame inner cavity, so that the cooling airflow in the impact cavity is sequentially discharged from the injection hole after passing through the outer frame inner cavity, the support plate inner cavity and the inner frame inner cavity, the cooling of the outer frame, the support plate and the inner frame is realized, the cooling airflow comes from the engine nacelle, the cooling airflow does not consume the cooling gas of the engine itself, the temperature of the outer frame, the support plate and the inner frame in the working process can be effectively reduced, and a good thermal environment is provided for the sensors arranged in the exhaust frame.

Description

Technical Field

[0001] This invention relates to the field of aero-engine technology, specifically to a power turbine cooling structure and an aero-engine. Background Technology

[0002] Aero gas turbine engines typically bleed air from within the engine for cooling the power turbine casing and exhaust support plates. As the compressor pressure ratio increases, the temperature at the bleed air location also rises. When the total compressor pressure ratio exceeds 20, the temperature at the bleed air location used for cooling the power turbine casing and exhaust support plates from the low-pressure compressor outlet exceeds 300°C. A conventional power turbine casing has an annular channel along the axial direction, and the convective heat transfer coefficient of its inner channel is on the order of approximately 10–30 W / m. 2 The relatively high cold air temperature and low heat transfer coefficient result in poor overall cooling of the power turbine casing. When the engine is in the transition state, the turbine casing is in the mainstream side where the heat transfer level of the high-temperature gas is high. The heat transfer and cooling level of the internal channels of the casing is poor, which causes the power turbine casing to expand faster in the transition state. This is not conducive to the control of the turbine rotor blade tip clearance. At the same time, the high cold air temperature also has an adverse effect on the cooling design of the exhaust support plate. The turbine speed sensor is typically located at the rear, passing through a channel inside the support plate and leading to the outside of the engine, such as... Figure 1 The existing cooling scheme shown has the cooling airflow passing through the airflow channel between the outer casing and the inner casing before entering the inner casing and mixing with the main engine flow. At the same time, the inner cavity of the support plate is a dead flow cavity, which is subjected to heating by the external high-temperature combustion gas. The temperature inside the cavity is more severe than 370°C, which is not conducive to the placement of components such as speed sensors.

[0003] For example, Chinese invention patent application with publication number CN118881458A discloses an air bleed shroud device for a power turbine casing and an aero engine having the same. The air bleed shroud body is installed on the outer surface of the outer casing, and an inner annular cavity is formed between the air bleed shroud body and the outer casing. The outer casing is cooled by introducing cold air into the inner annular cavity. However, the aforementioned patent application does not improve the cooling effect of the exhaust support plate at the tail of the power turbine. The operating temperature of the exhaust support plate is still very high. The sensor installed in the exhaust support plate is in a high-temperature environment for a long time, which is not conducive to the safe use of the sensor and other components. At the same time, the aforementioned patent requires an additional ejector to eject the compressor airflow to cool the turbine casing, which has a certain impact on the weight and efficiency of the whole machine.

[0004] Based on this, the present invention designs a power turbine cooling structure and an aero-engine, which has the advantages of ejecting the atmosphere without consuming the engine air source and providing a suitable thermal environment for sensor placement through the cooling exhaust support plate channel. Summary of the Invention

[0005] This invention provides a power turbine cooling structure and an aero engine to solve the technical problem of excessively high temperature during the operation of exhaust support plates in the prior art.

[0006] According to one aspect of the present invention, a power turbine cooling structure is provided, characterized in that: it includes a turbine casing and an exhaust frame connected to the exhaust end of the turbine casing, wherein the outer circumferential surface of the turbine casing is provided with an impact cavity; the impact cavity is used to introduce external cold air to form a cooling airflow in the impact cavity to cool the turbine casing; the exhaust frame includes an outer frame, an inner frame and a plurality of support plates, wherein the outer frame, support plates and inner frame are connected sequentially from the outside to the inside in the radial direction of the exhaust frame, and the plurality of support plates are arranged at intervals along the circumference of the exhaust frame to form a channel for the main flow of the engine between adjacent support plates; the outer frame, support plates and inner frame are all hollow, and the impact cavity, the inner cavity of the outer frame, the inner cavity of the support plate and the inner cavity of the inner frame are sequentially connected, and an ejector hole is opened on the side of the inner frame where the support plate is installed to connect the inner cavity of the inner frame and the airflow channel, so that the cooling airflow in the impact cavity passes sequentially through the inner cavity of the outer frame, the inner cavity of the support plate and the inner frame and is then led out through the ejector hole and mixed with the main flow of the engine.

[0007] As a further embodiment of the present invention, the ejector hole is located in the throat of the airflow channel between two adjacent support plates in the axial direction of the inner frame.

[0008] As a further embodiment of the present invention, the ejector hole is provided with a turbulence protrusion protruding from the surface of the inner frame on the side near the turbine casing, and the height of the turbulence protrusion in the radial direction of the inner frame increases smoothly in the direction away from the turbine casing.

[0009] As a further embodiment of the present invention, a first air vent is provided on the outer circular surface of the outer frame. The first air vent is used to introduce air from the engine compartment into the outer frame and mix it with the cooling airflow entering the outer frame from the impact chamber.

[0010] As a further embodiment of the present invention, the turbine casing includes an outer casing and a heat shield. Both the outer casing and the heat shield are cylindrical. The heat shield is fitted onto the outer casing to form an impact cavity between the heat shield and the outer casing. The surface of the heat shield is provided with a plurality of impact holes, which are used to allow outside air to enter the impact cavity.

[0011] As a further embodiment of the present invention, both ends of the outer casing in the axial direction are formed with a first mounting edge extending radially outward along the outer casing, and both ends of the heat insulation cover in the axial direction are formed with a second mounting edge extending radially outward along the heat insulation cover, and the second mounting edge abuts against the first mounting edge in a one-to-one correspondence.

[0012] As a further embodiment of the present invention, an arc transition section is provided between the middle cylindrical portion of the heat insulation cover and the second mounting edges at both ends, and an impact hole is provided in the arc transition section. The impact hole in the middle cylindrical portion of the heat insulation cover is radially opened along the heat insulation cover, and the impact hole in the arc transition section is opened towards the first mounting edge.

[0013] As a further embodiment of the present invention, the turbine casing further includes an inner casing, the two ends of which in the axial direction are formed with third mounting edges extending radially outward along the inner casing. The third mounting edges are used to be fixedly connected with the first mounting edges. The outer surface of the inner casing is provided with connecting hooks for extending into the outer casing, and the inner surface of the outer casing is provided with connecting rings for extending into the inner casing. The connecting hooks and the connecting rings are inserted and engaged to control the deformation of the inner casing through the outer casing.

[0014] As a further embodiment of the present invention, the outer frame is fixedly connected to the first mounting edge and / or the third mounting edge. A second air vent is provided on the first mounting edge and the second mounting edge, which connects the impact chamber and the inner cavity of the outer frame. The second air vent is used to introduce cold air from the impact chamber into the outer frame. A third air vent is provided at the connection position between the outer frame and the support plate, which is used to introduce cold air from the outer frame into the support plate. A fourth air vent is provided at the connection position between the support plate and the inner frame, which is used to introduce cold air from the inner cavity of the support plate into the inner frame.

[0015] An aircraft engine, including the aforementioned power turbine cooling structure.

[0016] The present invention has the following beneficial effects: 1. This invention connects the impact chamber, the inner cavity of the outer frame, the inner cavity of the support plate, and the inner cavity of the inner frame in sequence, and opens ejector holes on the surface of the inner frame located in the inner cavity between adjacent support plates. The ejector holes are located at the throat of the airflow channel between two adjacent support plates in the axial direction of the inner frame. The mainstream flow velocity is the highest and the static pressure is the lowest when it passes through the throat of the inner frame of the adjacent support plate, thereby increasing the flow rate of the cooling airflow and improving the cooling effect of the cooling airflow on the outer frame, support plate, and inner frame. Furthermore, the ejector hole is provided with a turbulence protrusion protruding from the surface of the inner frame on the side near the turbine casing. The turbulence structure forms a local backflow zone at the outlet of the ejector hole, which can reduce the static pressure at the outlet of the ejector hole, thereby further increasing the ejector flow rate. Without affecting the main airflow of the engine or changing the overall structure of the power turbine, the flow rate of the cooling airflow passing through the support plate is increased. 2. Due to the special shape design of the support plate, the throats of two adjacent support plates are close to the front end of the support plate, that is, the end of the support plate facing the main engine flow. After the cooling airflow is discharged from the ejector hole, it can mix with the main engine flow and form a complete and stable cooling air film on the outer surface of the inner frame, effectively isolating the heat radiation and heat conduction of the main engine flow.

[0017] 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 figures. Attached Figure Description

[0018] 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: Figure 1 This is a schematic diagram of the existing technology structure; Figure 2 This is a schematic diagram of the overall structure of the present invention; Figure 3 This is a schematic diagram showing the installation position of the ejector hole between adjacent support plates in this invention; Figure 4 This is a schematic diagram of the internal frame structure in this invention; Figure 5 This is a schematic diagram of the injection holes between adjacent support plates in this invention; Figure 6 This is a schematic cross-sectional view of the ejector hole in this invention; Figure 7 This is a schematic diagram of the installation structure of the outer casing, heat shield, and inner casing in this invention; Figure 8 This is a static pressure cloud diagram of the airflow channel between two adjacent support plates. The numerical values ​​marked in the diagram are in kPa. Figure 9 The static pressure contour diagram of the ejector port without a turbulence boss is shown. The numerical values ​​marked in the diagram are in kPa. Figure 10 The static pressure contour diagram of the outlet of the ejector with a turbulence protrusion is shown. The numerical values ​​marked in the diagram are in kPa. Figure 11 This is a schematic diagram of the static pressure at the outlet of the ejector without a turbulence boss. The numerical values ​​in the diagram are in kPa. Figure 12 This is a schematic diagram of the outlet static pressure of an ejector with a turbulence protrusion. The numerical values ​​in the diagram are in kPa. Figure 13 The streamline diagram of the ejector outlet without the turbulence boss; Figure 14 A streamline diagram of the outlet of an ejector with a turbulence-inducing boss; Figure 15 This involves creating a one-dimensional model for the proposed solution.

[0019] Legend: 1. Turbine casing; 11. Impact chamber; 12. Outer casing; 121. First mounting edge; 122. Connecting ring; 123. Second air vent; 13. Heat shield; 131. Impact hole; 132. Second mounting edge; 14. Inner casing; 141. Third mounting edge; 142. Connecting hook; 21. Outer frame; 211. First air vent; 212. Third air vent; 22. Inner frame; 221. Ejector hole; 222. Baffle boss; 23. Support plate; 231. Fourth air vent. Detailed Implementation

[0020] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0021] Please see Figure 1-15 This invention provides a technical solution: a power turbine cooling structure, including a turbine casing 1 and an exhaust frame connected to the exhaust end of the turbine casing 1. The outer circumferential surface of the turbine casing 1 is provided with an impact chamber 11. The impact chamber 11 is used to introduce external cold air to form a cooling airflow within the impact chamber 11 to cool the turbine casing 1. The exhaust frame includes an outer frame 21, an inner frame 22, and multiple support plates 23. The outer frame 21, support plates 23, and inner frame 22 are sequentially connected from the outside to the inside in the radial direction of the exhaust frame. The multiple support plates 23 are spaced apart circumferentially along the exhaust frame. The arrangement is designed to form a channel for the main flow of the engine between adjacent support plates 23; the outer frame 21, support plates 23 and inner frame 22 are all hollow, and the impact chamber 11, the inner cavity of the outer frame 21, the inner cavity of the support plate 23 and the inner cavity of the inner frame 22 are connected in sequence. On the side of the inner frame 22 where the support plate 23 is installed, an ejector hole 221 is opened to connect the inner cavity of the inner frame 22 and the airflow channel, so that the cooling airflow in the impact chamber 11 passes through the inner cavity of the outer frame 21, the inner cavity of the support plate 23 and the inner cavity of the inner frame 22 in sequence and is then drawn out through the ejector hole 221 and mixed with the main flow of the engine. During operation, the mainstream flow has the highest velocity and lowest static pressure when passing through the throat of the inner frame of the adjacent support plate. Furthermore, due to the negative pressure suction effect of the ejector hole, a pressure gradient exists between the external ambient atmosphere and the outlet of the ejector hole 221. The outer ambient atmosphere enters the cavity through the impact hole 131, resulting in a cooling airflow entering the impact cavity 11 from the outside. This cooling airflow is used to cool the turbine casing 1. Meanwhile, the mainstream exhaust from the power turbine passes through the airflow channel between the support plates 23 at high speed. Therefore, a high-speed airflow exists between adjacent support plates 23. The engine mainstream flows through the inner frame 22, which has an ejector hole 221. The ejector hole 221 connects the airflow channel between the adjacent support plates 23 and the inner cavity of the inner frame 22. Under the suction of the engine mainstream, the gas in the inner frame 22 will be sucked out. Since the impact chamber 11, the inner cavity of the outer frame 21, the inner cavity of the support plate 23 and the inner cavity of the inner frame 22 are connected in sequence, the cooling airflow in the impact chamber 11 will be sucked into the inner cavity of the outer frame 21 and pass through the inner cavity of the outer frame 21, the inner cavity of the support plate 23 and the inner cavity of the inner frame 22 in sequence before being discharged from the ejector hole 221. This invention connects the impact chamber 11, the inner cavity of the outer frame 21, the inner cavity of the support plate 23, and the inner cavity of the inner frame 22 in sequence, and opens an ejector hole 221 on the surface of the inner frame 22 to connect the airflow channel between the inner cavity of the inner frame 22 and the support plate 23. The gas in the inner cavity of the inner frame 22 is drawn in by the high-speed engine mainstream between adjacent support plates 23, so that the cooling airflow in the impact chamber 11 passes through the inner cavity of the outer frame 21, the inner cavity of the support plate 23, and the inner cavity of the inner frame 22 in sequence and is discharged from the ejector hole 221. This achieves cooling of the outer frame 21, the support plate 23, and the inner frame 22. This cooling airflow comes from the engine nacelle and does not consume the engine's own cooling air volume. It can effectively reduce the temperature of the outer frame 21, the support plate 23, and the inner frame 22 during operation, and provide a good thermal environment for the sensor installed in the exhaust frame. Furthermore, the ejector hole 221 is located axially in the throat of the airflow channel between two adjacent support plates 23 in the inner frame 22; Typically, the exhaust gas from the rotor of a power turbine is radial, not entirely axial. To minimize flow losses, the inlet blade angle of the support plate 23 must align with the direction of the inlet airflow. Figure 3 As shown, the outlet airflow is completely guided into axial exhaust through the action of the support plate 23. To reduce flow losses, the support plate 23 uses thin blades, or to facilitate the arrangement of lubricating oil pipelines, it uses thick blades. Therefore, currently, support plates typically employ a combination of large and small blades, such as... Figure 6As shown, in the airflow channel between the support plates 23, the position with the smallest flow area perpendicular to the airflow direction is the throat. Since the flow rate of the entire flow channel is conserved, when the flow area is the smallest, the flow velocity is the highest and the static pressure is the lowest. The ejector hole 221 opened on the inner frame 22 is located at the throat of the airflow channel between two adjacent support plates 23, which can maximize the ejection pressure difference, enhance the ejection capability, and at the same time improve the mixing effect of the cooling airflow and the mainstream of the engine, and reduce the mixing loss. Because there is a certain pressure drop along the flow direction of the cooling airflow, the environmental pressure inside the engine compartment (pressure outside the heat shield) > the pressure inside the impact chamber > the pressure inside the outer frame > the pressure inside the inner frame > the pressure at the ejector exhaust position. Under the action of the pressure difference between the inside and outside, it can play the role of pressing the radial and axial joints of the heat shield, making the heat shield sealing effect better and preventing air leakage. Due to the special shape design of the support plate, the throats of two adjacent support plates are close to the front end of the support plate, that is, the end of the support plate facing the main engine flow. After the cooling airflow is discharged from the ejector hole, it can mix with the main engine flow and form a complete and stable cooling air film on the outer surface of the inner frame, effectively isolating the heat radiation and heat conduction of the main engine flow.

[0022] Specifically, multiple ejector holes 221 can be opened between each two adjacent support plates 23 to increase the ejector area and the ejector flow rate. In this example, three ejector holes 221 are opened between two adjacent support plates 23. Preferably, the number and size of the ejector holes 221 at different positions can be designed according to the heat load differences at each support plate position, so as to realize the distribution of cooling airflow as needed.

[0023] Specifically, such as Figure 4 As shown, the angle between the ejector hole 221 and the exhaust channel is in the range of 25 to 40° to reduce the mixing loss of the ejector gas on the mainstream.

[0024] Furthermore, the ejector hole 221 is provided with a turbulence protrusion 222 protruding from the surface of the inner frame 22 on the side near the turbine casing 1. The height of the turbulence protrusion 222 in the radial direction of the inner frame 22 smoothly increases from the end near the turbine casing 1 to the end away from the turbine casing 1. like Figure 4 As shown, a baffle 222 is provided on the side of the ejector 221 near the turbine casing 1. The height of the baffle 222 in the radial direction of the inner frame 22 smoothly increases from the end near the turbine casing 1 to the end away from the turbine casing 1, so as to form a slope at the top of the baffle 222. Figure 7-8 As shown, a turbulence structure is formed on the upper part of the ejector hole 221. The turbulence structure forms a local backflow zone at the outlet of the ejector hole 221, which can reduce the static pressure at the outlet of the ejector hole 221 and thus further increase the ejection flow rate. By utilizing the lowest throat pressure point in the airflow channel of the adjacent support plate 23 and setting a turbulence protrusion 222 structure above the ejector hole 221, the static pressure at the outlet of the ejector hole 221 is reduced as much as possible, and cold air is ejected from the aircraft cabin without consuming the engine's own bleed air volume. This achieves thermal deformation control of the power turbine casing and cooling of the exhaust support plate channel at a lower cost, with a lower impact on overall performance. Furthermore, a first air intake hole 211 is provided on the outer circular surface of the outer frame 21. The first air intake hole 211 is used to introduce air from the engine compartment into the outer frame 21 and mix it with the cooling airflow entering the outer frame 21 from the impact chamber 11. like Figure 2 As shown, a first air vent 211 is provided on the outer circular surface of the outer frame 21. During operation, outside air enters the inner cavity of the outer frame 21 through the first air vent 211 and mixes with the cooling airflow entering the inner cavity of the outer frame 21 from the impact chamber 11. This reduces the temperature of the cooling airflow and cools the outer frame 21. At the same time, it also makes the temperature of the cooling airflow lower when it enters the inner cavity of the support plate 23 and the inner cavity of the inner frame 22, resulting in a better cooling effect on the support plate 23 and the inner frame 22, and further reducing the working temperature of the outer frame 21, the support plate 23 and the inner frame 22. Specifically, the first air vent 211 is provided in multiple equidistant locations along the circumference of the outer frame 21; Specifically, the turbine casing 1 includes an outer casing 12 and a heat shield 13. Both the outer casing 12 and the heat shield 13 are cylindrical. The heat shield 13 is fitted onto the outer casing 12 to form an impact chamber 11 between the heat shield 13 and the outer casing 12. Several impact holes 131 are opened on the surface of the heat shield 13. The impact holes 131 are used to allow outside air to enter the impact chamber 11. like Figure 2 As shown, the turbine casing 1 includes an outer casing 12 and a heat shield 13. Both the outer casing 12 and the heat shield 13 are cylindrical. The heat shield 13 is used to fit onto the outer casing 12. When the heat shield 13 is fitted onto the outer casing 12, an impact chamber 11 is formed between the heat shield 13 and the outer casing 12. Several impact holes 131 are opened on the surface of the heat shield 13. Outside air enters the heat shield 13 through the impact holes 131 to cool the outer casing 12. Furthermore, the distance between the impact hole 131 on the heat shield 13 and the outer casing 12 is maintained between 4mm and 6mm, which ensures a compact structural space between the heat shield 13 and the outer casing 12 while ensuring the impact cooling effect. Furthermore, both ends of the outer casing 12 in the axial direction are formed with a first mounting edge 121 extending radially outward along the outer casing 12, and both ends of the heat shield 13 in the axial direction are formed with a second mounting edge 132 extending radially outward along the heat shield 13, and the second mounting edge 132 abuts against the first mounting edge 121 in a one-to-one correspondence. like Figure 5 As shown, the outer casing 12 has first mounting edges 121 at both ends in the axial direction. The first mounting edges 121 extend radially away from the axis of the outer casing 12. The heat shield 13 has second mounting edges 132 at both ends in the axial direction. The second mounting edges 132 are used to cooperate with the first mounting edges 121 to fix the heat shield 13 on the outer casing 12. The mounting edges are arranged so that the impact cavity 11 can completely cover the outer casing 12 in the axial direction, thereby improving the coverage of the cooling airflow on the outer casing 12 and improving the cooling effect of the cooling airflow in the impact cavity 11 on the outer casing 12. Specifically, in this example, the first mounting edge 121 and the second mounting edge 132 near the intake end of the power turbine are fitted with an interference fit, and the first mounting edge 121 and the second mounting edge 132 near the exhaust end of the power turbine are fastened with bolts.

[0025] Furthermore, an arc transition section is provided between the middle cylindrical part of the heat insulation cover 13 and the second mounting edges 132 at both ends, and an impact hole 131 is provided in the arc transition section. The impact hole 131 in the middle cylindrical part of the heat insulation cover 13 is opened radially along the heat insulation cover 13, and the impact hole 131 in the arc transition section is opened towards the first mounting edge 121. like Figure 5 As shown, an arc transition section is provided between the cylindrical part in the middle of the heat shield 13 and the second mounting edge 132, and an impact hole 131 is also provided on the arc transition section. The impact hole 131 provided in the cylindrical part in the middle of the heat shield 13 is opened radially along the heat shield 13. The cold air entering the impact chamber 11 from this part of the impact hole 131 is used for impact cooling of the outer casing 12. The impact hole 131 provided at the arc transition section is opened towards the first mounting edge 121. The cold air entering the impact chamber 11 from this part of the impact hole 131 is used to cool the first mounting edge 121, thereby improving the cooling effect of the outer casing 12.

[0026] Specifically, the turbine casing 1 also includes an inner casing 14. The two ends of the inner casing 14 in the axial direction are formed with third mounting edges 141 extending radially outward along the inner casing 14. The third mounting edges 141 are used to be fixedly connected with the first mounting edges 121. The outer surface of the inner casing 14 is provided with connecting hooks 142 for extending to the outer casing 12. The inner surface of the outer casing 12 is provided with connecting rings 122 for extending to the inner casing 14. The connecting hooks 142 and connecting rings 122 are inserted and engaged to control the deformation of the inner casing 14 through the outer casing 12. like Figure 2As shown, the inner casing 14 and the outer casing 12 exchange heat through the connecting hook 142 and the connecting ring 122. When the cooling airflow in the impact chamber 11 cools the outer casing 12, the cooling airflow controls the deformation of the inner casing 14 through the coordinated thermal deformation response of the connecting hook 142 and the connecting ring 122, thereby adjusting the gap. Specifically, the outer frame 21 is fixedly connected to the first mounting edge 121 and / or the third mounting edge 141. The first mounting edge 121 and the second mounting edge 132 are provided with a second air vent 123 that connects the impact chamber 11 and the inner cavity of the outer frame 21. The second air vent 123 is used to introduce cold air from the impact chamber 11 into the outer frame 21. A third air vent 212 is provided at the connection position between the outer frame 21 and the support plate 23. The third air vent 212 is used to introduce cold air from the outer frame 21 into the support plate 23. A fourth air vent 231 is provided at the connection position between the support plate 23 and the inner frame 22. The fourth air vent 231 is used to introduce cold air from the inner cavity of the support plate 23 into the inner frame 22. like Figure 2 As shown, in this example, the outer frame 21 is fixed on the third mounting edge 141. In order to enable the impact chamber 11 to communicate with the inner cavity of the outer frame 21, a second air vent 123 is opened on both the first mounting edge 121 and the third mounting edge 141. The cooling airflow in the impact chamber 11 is introduced into the inner cavity of the outer frame 21 through the second air vent 123. Then, the cooling airflow in the inner cavity of the outer frame 21 is introduced into the inner cavity of the support plate 23 through the third air vent 212. The cooling airflow in the inner cavity of the support plate 23 is introduced into the inner cavity of the inner frame 22 through the fourth air vent 231. Finally, the cooling airflow is led out to the space between two adjacent support plates 23 through the ejector hole 221 opened in the inner frame 22. This completes the movement of the cooling airflow from the impact chamber 11 to the inner frame 22, thereby achieving the cooling of the outer casing 12, the outer frame 21, the support plate 23, and the inner frame 22.

[0027] An aircraft engine includes the aforementioned power turbine cooling structure. By employing the aforementioned power turbine cooling structure, the temperature at the exhaust frame location at the tail of the power turbine can be effectively reduced, providing a good working environment for sensors installed at the tail of the power turbine.

[0028] The parameters of a certain type of aero-engine after adopting a rising power turbine cooling structure are as follows: The heat transfer calculation method for a single-row impact target surface is shown in Equation 1, and the heat transfer calculation method for a multi-row impact target surface is shown in Equation 2.

[0029] (1) (2) Where: px is the lateral spacing of the impact holes, py is the circumferential spacing of the impact holes, Z is the distance between the impact holes and the target surface, D is the diameter of the impact hole, Re is the intake Reynolds number of the impact hole, mc is the mass flow rate of the lateral flow, and mj is the mass flow rate of a single row of holes. Table 1 Correction Factors

[0030] Based on the AMESIM one-dimensional network model, the heat transfer coefficient of the outer casing surface and the cavity temperature of the support plate were compared under two air bleed schemes.

[0031] As can be seen from the calculation results in Table 2, the heat transfer coefficient of the turbine outer casing surface in the conventional bleed air scheme is 27 W / m. 2 ·K, the temperature of the induced airflow reaching the inner cavity of the support plate is approximately 315℃.

[0032] Figure 13 A one-dimensional model of this scheme is presented. Tables 3 and 4 show the calculated exhaust and structural parameters, and Table 5 presents the calculation results. The results show that, using the heat shield ejector scheme, the heat transfer coefficient of the outer casing surface is 445 W / m². 2 The K value is 15 times that of the conventional bleed air scheme, which can improve the thermal response of the outer casing during the transition state, reduce the turbine blade tip clearance, reduce the temperature rise of the cooling airflow impacting the outer casing by 176°C, and reduce the outlet temperature of the bleed airflow to 226°C. The flow rate is kept constant at 78 g / s. After mixing with the ejector airflow of 19.5 g / s and 50°C from the first bleed air hole, the mixing temperature in the channel inside the support plate is 191°C, which is about 120°C lower than the conventional bleed air scheme. The effect is significant, providing a suitable thermal environment for the arrangement of electronic components, sensors, etc.

[0033] Table 2 Parameter Table of Conventional Scheme

[0034] Table 3. Parameters of the present invention for exhaust and venting

[0035] Table 4 Hole Structure Dimensions of the Invention

[0036] Table 5 Calculation results of this invention

[0037] Table 6 presents a comparison of CFD calculations for conventional ejector holes and turbulence-structured ejector holes. The table shows that, under the condition that the main channel parameters and bleed pressure remain consistent, the ejector hole structure effectively reduces the static pressure at the ejector hole outlet compared to the conventional hole structure. Figures 11-13 Its air intake flow rate is 8.5 g / s, a significant improvement over the conventional ejector structure's 4.8 g / s. Meanwhile, from... Figure 11 As can be seen from the static pressure distribution cloud map, this scheme places the ejector hole at the oblique cut throat position in the channel of the lower edge plate of the support plate, which is beneficial for reducing the static pressure at the ejector hole outlet and increasing the air flow rate.

[0038] Table 6 Calculation results for conventional holes and ejector holes (single channel, 12 cycles in total)

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present 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 power turbine cooling structure, characterized in that: It includes a turbine casing (1) and an exhaust frame connected to the exhaust end of the turbine casing (1), wherein the outer circular surface of the turbine casing (1) is provided with an impact chamber (11). The impact chamber (11) is used to introduce external cold air to form a cooling airflow in the impact chamber (11) to cool the turbine casing (1); The exhaust frame includes an outer frame (21), an inner frame (22), and multiple support plates (23). The outer frame (21), support plates (23), and inner frame (22) are connected sequentially from the outside to the inside in the radial direction of the exhaust frame. The multiple support plates (23) are arranged at intervals along the circumference of the exhaust frame to form a channel for the main flow of the engine between adjacent support plates (23). The outer frame (21), the support plate (23), and the inner frame (22) are all hollow. The impact chamber (11), the inner cavity of the outer frame (21), the inner cavity of the support plate (23), and the inner cavity of the inner frame (22) are connected in sequence. On the side of the inner frame (22) where the support plate (23) is installed, an ejector hole (221) is opened to connect the inner cavity of the inner frame (22) and the airflow channel, so that the cooling airflow in the impact chamber (11) passes through the inner cavity of the outer frame (21), the inner cavity of the support plate (23), and the inner cavity of the inner frame (22) in sequence and is then drawn out through the ejector hole (221) and mixed with the main flow of the engine. The outer frame (21) has a first air vent (211) on its outer circular surface. The first air vent (211) is used to introduce air from the engine compartment into the outer frame (21) and mix it with the cooling airflow from the impact chamber (11) entering the outer frame (21). The ejector hole (221) is located in the throat of the airflow channel between two adjacent support plates (23) in the axial direction of the inner frame (22); The ejector hole (221) is used to draw gas from the inner cavity of the inner frame (22) by utilizing the low static pressure of the main engine flow at the throat of the airflow channel between two adjacent support plates (23), so that cold air from the outside can enter the impact chamber (11) and flow through the inner cavity of the outer frame (21), the inner cavity of the support plate (23) and the inner cavity of the inner frame (22) in sequence. The angle between the ejector hole (221) and the exhaust channel is 25° to 40°. The ejector hole (221) is provided with a turbulence boss (222) protruding from the surface of the inner frame (22) on the side near the turbine casing (1). The height of the turbulence boss (222) in the radial direction of the inner frame (22) increases smoothly in the direction away from the turbine casing (1). The turbulence boss (222) is used to form a local backflow zone at the outlet of the ejector hole (221) to reduce the static pressure at the outlet of the ejector hole (221) and increase the ejection flow rate.

2. The power turbine cooling structure according to claim 1, characterized in that: The turbine casing (1) includes an outer casing (12) and a heat shield (13). Both the outer casing (12) and the heat shield (13) are cylindrical. The heat shield (13) is fitted onto the outer casing (12) to form an impact cavity (11) between the heat shield (13) and the outer casing (12). The surface of the heat shield (13) is provided with a plurality of impact holes (131). The impact holes (131) are used to allow outside air to enter the impact cavity (11).

3. The power turbine cooling structure according to claim 2, characterized in that: Both ends of the outer casing (12) are formed with a first mounting edge (121) extending radially outward along the outer casing (12), and both ends of the heat shield (13) are formed with a second mounting edge (132) extending radially outward along the heat shield (13). The second mounting edge (132) and the first mounting edge (121) are respectively connected and abut against each other.

4. The power turbine cooling structure according to claim 3, characterized in that: The heat insulation cover (13) has an arc transition section between the middle cylindrical part and the two end second mounting edges (132), and the arc transition section has an impact hole (131). The impact hole (131) in the middle cylindrical part of the heat insulation cover (13) is opened radially along the heat insulation cover (13), and the impact hole (131) in the arc transition section is opened towards the first mounting edge (121).

5. A power turbine cooling structure according to claim 3, characterized in that: The turbine casing (1) also includes an inner casing (14). The inner casing (14) has a third mounting edge (141) extending radially outward at both ends in the axial direction. The third mounting edge (141) is used to fix and connect with the first mounting edge (121). The outer surface of the inner casing (14) is provided with a connecting hook (142) extending to the outer casing (12). The inner surface of the outer casing (12) is provided with a connecting ring (122) extending to the inner casing (14). The connecting hook (142) and the connecting ring (122) are inserted and engaged to control the deformation of the inner casing (14) through the outer casing (12).

6. The power turbine cooling structure according to claim 5, characterized in that: The outer frame (21) is fixedly connected to the first mounting side (121) or the third mounting side (141). The first mounting side (121) and the second mounting side (132) are provided with a second air vent (123) that connects the impact chamber (11) and the inner cavity of the outer frame (21). The second air vent (123) is used to introduce the cold air in the impact chamber (11) into the outer frame (21). The outer frame (21) is provided with a third air vent (212) at the connection position with the support plate (23). The third air vent (212) is used to introduce the cold air in the outer frame (21) into the support plate (23). The support plate (23) is provided with a fourth air vent (231) at the connection position with the inner frame (22). The fourth air vent (231) is used to introduce the cold air in the inner cavity of the support plate (23) into the inner frame (22).

7. An aircraft engine, characterized in that: Includes the power turbine cooling structure as described in any one of claims 1-6.

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