Laminated plate cooling device for aircraft engine flame tube

Abstract

The present invention discloses a layer plate cooling device for an aircraft engine flame tube, comprising an upper layer plate and a lower layer plate fitted together, wherein the upper layer plate is provided with a plurality of cooling units, wherein the cooling units include a coaxially arranged rectangular impact groove, a rectangular spoiler groove and an air film hole for ejecting gas, which are connected in sequence, and two L-shaped spoiler ribs whose length directions are parallel to the axis are symmetrically provided in the spoiler groove along the axis; the short end of the spoiler rib is close to the impact groove, and the short end is a right triangle; the minimum spacing between the two spoiler ribs is greater than the width of the impact groove; the lower layer plate is provided with a through hole connected to the impact groove; the device can enhance convective heat exchange, improve air film cooling performance, and enhance the overall cooling effect under high temperature conditions.

Description

Technical Field

[0001] The present invention relates to a layer plate cooling device, in particular to a layer plate cooling device for an aircraft engine flame tube Background Art

[0002] Since the birth of aircraft engines, people's performance requirements have been gradually increasing, especially in fighter jets. In order to meet the technical requirements of high-performance military aircraft and enhance the air superiority of fighter jets, the thrust-to-weight ratio of aircraft engines has been continuously increasing. In order to improve the thrust-to-weight ratio, on the one hand, the cycle thermal efficiency is improved by increasing the compressor pressure ratio, and on the other hand, the unit thrust is increased by increasing the turbine inlet temperature. The combustion chamber outlet temperature of the latest generation of aircraft engines is as high as 2150-2400K. The problem caused by this is that the peak temperature of the gas in the flame tube far exceeds the melting point temperature of the flame tube material, and as the combustion room temperature continues to rise, the proportion of air participating in combustion increases, and the amount of air used for wall cooling becomes less and less. At the same time, as the compressor pressure ratio continues to increase, the inlet temperature of the combustion chamber continues to increase, and the cooling potential of the cooling gas decreases. Therefore, the cooling design of the flame tube faces huge challenges.

[0003] Combustion chamber cooling technology, both domestically and internationally, has evolved from a single cooling method to a composite cooling method that integrates multiple cooling methods. Single cooling methods include convection cooling, impingement cooling, and multi-angle hole cooling. Convection cooling is an earlier form of flame tube cooling. It generally increases the heat transfer rate by providing raised ribs on the flame tube wall to increase the convective heat transfer coefficient. However, due to its limited cooling effect, its single form is only used in early combustion chambers with lower temperature rise. Impingement cooling uses a double-layer flame tube wall. The cooling air enters the outer wall perpendicularly and impinges on the inner wall, which has a higher temperature. High-speed jets impinge on the wall, generating convective heat transfer, which is used to cool a specific area. Its advantage is that the convective heat transfer coefficient in the stagnation zone is extremely high, so it can effectively cool local high-temperature areas, but the cooling air consumption is relatively large. Multi-angle hole cooling uses a large number of small holes on the flame tube wall at a certain angle. The cooling air is introduced by utilizing the pressure difference between the inside and outside to achieve full air film coverage of the flame tube gas side wall.

[0004] Composite cooling refers to a cooling technology that simultaneously utilizes two or more of the aforementioned cooling methods. Although there are currently laminate cooling devices that combine convection cooling and impingement cooling, the raised ribs that provide convection cooling cannot form a stable unsteady flow of the cooling gas, resulting in poor internal heat exchange. Secondly, as the temperature of the combustion chamber gradually increases, the cooling performance of the cooling gas ejected from the laminate cooling device is low. Summary of the Invention

[0005] Purpose of the invention: The main purpose of the present invention is to provide a laminate cooling device for an aircraft engine flame tube that can enhance convective heat transfer, improve film cooling performance, and secondly enhance the overall cooling effect under high temperature conditions.

[0006] Technical solution: The layer plate cooling device for an aircraft engine flame tube described in the present invention includes an upper layer plate and a lower layer plate that are bonded to each other. The upper layer plate is provided with multiple cooling units. The cooling units include a coaxially arranged rectangular impact groove, a rectangular spoiler groove and an air film hole for ejecting gas that are connected in sequence. Two L-shaped spoiler ribs with their length directions parallel to the axis are symmetrically provided in the spoiler groove along the axis; the short end of the spoiler rib is close to the impact groove, and the short end is a right triangle; the minimum spacing between the two spoiler ribs is greater than the width of the impact groove; the lower layer plate is provided with a through hole connected to the impact groove.

[0007] Based on the above technical solution, cooling gas is circulated in the coaxially arranged rectangular impact groove, rectangular spoiler groove and air film hole which are connected in sequence, and two L-shaped spoiler ribs are symmetrically arranged along the axis in the rectangular spoiler groove. The L-shaped spoiler rib is a special structure of a right triangle near the short end of the impact groove, and the minimum distance between the two spoiler ribs is greater than the width of the impact groove. Under the action of the Coanda effect, the airflow coming from the impact groove will flow along the side walls of the two spoiler ribs. However, due to the special structure of this device, after a short time, the airflow will only flow along the side wall of any one spoiler rib, and most of it will flow in the spoiler rib. The end of the rib near the air film hole enters the air film hole and is ejected for cooling. A small part will continue to flow along the side wall of the spoiler rib back to the end of the spoiler rib near the impact groove and merge with the new airflow flowing into the impact groove. At this time, due to the disturbance of the returning gas, all the gas will flow along the side wall of the other spoiler rib, and continue the above process. This cycle repeats, making the air flow alternately adhere to the side walls of the two spoiler ribs to form a periodic unsteady flow, thereby strengthening convective heat transfer and enhancing internal cooling; at the same time, an air film outflow with a sweeping characteristic is formed, thereby improving the overall cooling effect of the device.

[0008] Preferably, the acute angle of the protrusion at the short end of the spoiler rib is greater than or equal to 50° and less than or equal to 70°.

[0009] Setting the acute angle of the right-angled triangle at the short end of the spoiler rib protruding toward the axis direction within this range can enhance the Coanda effect, thereby improving the spoiler cooling effect of the spoiler groove.

[0010] Preferably, the ratio of the impact groove width to the minimum distance between the two spoiler ribs is greater than or equal to 0.5 and less than or equal to 0.8.

[0011] Setting the ratio of the impact groove width to the minimum distance between the two spoiler ribs within the above range can ensure the formation of the periodic unsteady flow of the cooling gas to be achieved by the present invention.

[0012] Preferably, the air film hole inlet is rectangular, and the distance between the two spoiler ribs close to the air film hole end is greater than the width of the air film hole inlet.

[0013] The spacing between the spoiler ribs and the film hole ends is greater than the width of the film hole inlet, which can ensure that a sufficient amount of cooling gas will flow back along the spoiler ribs to form a periodic unsteady flow.

[0014] Preferably, the air film holes are outwardly expanding from the inlet to the outlet, connecting the spoiler groove and the top outside of the upper plate.

[0015] The air film holes are arranged to be outward-expanding so that the cooling gas can be sprayed more evenly over a wider range to the combustion chamber to form a cooling air film to protect the wall surface.

[0016] Preferably, the side walls of the air film hole expand outward, and the angle between the side walls is greater than or equal to 50° and less than or equal to 80°.

[0017] The two side walls expand outwards, and the angle between the two side walls meets the above range, which can ensure that the air film outflow with periodic sweeping characteristics is formed at the outlet of the air film hole, thereby improving the cooling air coverage of the downstream wall.

[0018] Preferably, the air film hole is an inclined hole, and the angle between the bottom surface of the air film hole and the surface of the upper plate is greater than or equal to 30° and less than or equal to 60°.

[0019] When the inclination angle of the air film hole meets the above range, a better air film can be formed to protect the wall surface.

[0020] Preferably, the height direction of the spoiler rib is perpendicular to the plate surface of the upper plate; the axis of the through hole is perpendicular to the plate surface of the lower plate.

[0021] Preferably, both sides of the air film hole inlet are provided with Ni-Ti based shape memory alloy which gradually bulges inwards when the temperature exceeds a critical value.

[0022] By setting up a shape memory alloy, when the temperature exceeds a critical value that will affect the cooling effect of the device, the shape memory alloy will bulge inward to reduce the inlet area of ​​the air film hole, regulate the sweeping characteristics of the air film outflow, and thereby improve the cooling performance of the device, avoiding the cooling effect of the device becoming worse and worse due to the gradual increase in the temperature of the combustion chamber.

[0023] Preferably, the relationship between the strain of the shape memory alloy and its temperature is:

[0024]

[0025] Wherein, F is the strain of the shape memory alloy, Ts is the temperature of the shape memory alloy, Mf, Ms, As and Af represent the temperatures at which martensitic transformation begins, martensitic transformation ends, austenitic transformation begins and austenitic transformation ends, respectively, and Fmax is the maximum deformation of the shape memory alloy.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant effects: by coaxially arranging a rectangular impact groove, a rectangular spoiler groove and an air film hole that are connected in sequence in the upper plate, two spoiler ribs of specific shapes are stacked along the axis in the spoiler groove, and the spacing between the spoiler ribs close to the end of the impact groove is greater than the width of the impact groove. These conditions enable the airflow to form a periodic unsteady flow in the spoiler groove under the action of the Coanda effect, thereby enhancing the internal convection heat transfer; and forming a cooling air film with a sweeping characteristic to improve the overall cooling effect; secondly, by arranging shape memory alloys on both sides of the air film hole inlet, when the temperature exceeds the critical value, the shape memory alloy will adjust the deformation amount with the temperature, thereby regulating the sweeping characteristics of the air film outflow, further improving the cooling effect of the device, and avoiding the reduction of the cooling effect due to temperature increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an overall perspective view of the device;

[0028] Figure 2 Schematic diagram of the structure of the upper plate;

[0029] Figure 3 Schematic diagram of the structure of the lower plate;

[0030] Figure 4 is a perspective view of a cooling unit;

[0031] Figure 5 Schematic diagram of the three-dimensional structure of the cooling unit;

[0032] Figure 6 for Figure 5 A partial enlarged schematic diagram is shown in the figure, Figure 6 a is a schematic diagram of the structure before the temperature exceeds the critical value; Figure 6 b is a schematic diagram of the structure after the temperature exceeds the critical value. DETAILED DESCRIPTION

[0033] As shown in the figure, the layer plate cooling device for the flame tube of an aircraft engine described in the present invention includes an upper plate 1 and a lower plate 2 that are bonded to each other. The upper plate 1 is provided with multiple cooling units, and the cooling units include a coaxially arranged rectangular impact groove 3, a rectangular spoiler groove 4 and an air film hole 5 for ejecting gas that are connected in sequence. The spoiler groove 4 is symmetrically provided with two L-shaped spoiler ribs 6 whose length direction is parallel to the axis along the axis; the short end of the spoiler rib 6 is close to the impact groove 3, and the short end is a right triangle; the minimum spacing between the two spoiler ribs 6 is greater than the width of the impact groove 3; the lower plate 2 is provided with a through hole 7 connected to the impact groove 3.

[0034] The upper plate 1 may be provided with multiple rows and columns of cooling units, and the lower plate 2 may be provided with a through hole 7 for the impact groove 3 of each cooling unit. The cooling gas flows into the cooling unit through the through hole 7 and then sprayed toward the inner wall of the combustion chamber for cooling.

[0035] The cooling unit includes a rectangular impact groove 3, a rectangular spoiler groove 4 and an air film hole 5 arranged along the same central axis, and the three are connected to each other; a through hole 7 is connected to the rectangular impact groove 3 to supply air therein, and the axis of the through hole 7 is perpendicular to the plate surface of the lower plate 2, and the plate surfaces of the upper and lower plates are arranged parallel to each other.

[0036] The rectangular spoiler groove 4 is provided with two L-shaped spoiler ribs 6. The specific shape of the spoiler rib 6 can be referred to Figure 4 and Figure 5 The long end of the spoiler rib 6 is a rectangular strip, and the height direction of the spoiler rib 6 is perpendicular to the plate surface of the upper plate 1; the short end of the spoiler rib 6 is a right triangle, one right-angled side is integrally formed with the long end, and the other right-angled side is integrally formed with the lower end of the long end in the same plane; the angle between the inclined surface of the right triangle and the contact surface of the long end ranges from 140° to 160°, that is, the angle of the acute angle of the right triangle protruding in the axial direction ranges from 50° to 70°, and this angle can be selected from 50°, 60° or 70°; the ratio of the width of the impact groove 3 to the minimum distance between the two spoiler ribs 6 meets the range of 0. 5~0.8, this ratio can be 0.5, 0.6, 0.7 or 0.8; that is, the ratio range of the width of the outlet of the impact groove 3 and the distance between the most protruding ends of the short ends of the two spoiler ribs 6 must meet the above requirements, which is equivalent to that after the airflow enters between the two spoiler ribs, the width of the flow channel is increased, and because of the special structure of the right-angled triangle of the short end of the spoiler rib 6, it will flow along the side wall of the spoiler rib 6 under the action of the Coanda effect. Initially, there is gas flow on the side walls of the two spoiler ribs 6 at the same time. After a period of time, the gas flows alternately on the side walls of the two spoiler ribs 6 to form a periodic unsteady flow.

[0037] The inlet of the air film hole 5 is rectangular, and the whole is outward-expanding from the inlet to the outlet, and the air film hole 5 connects the spoiler groove 4 and the space outside the top of the upper plate 1; specifically, the two side walls of the air film hole 5 expand outward, that is, the side walls on the left and right sides are inclined outward, and the angle between the two side walls is greater than or equal to 50° and less than or equal to 80°, and this angle can be 50°, 60°, 70° or 80°; the top and bottom surfaces of the air film hole 5 are parallel, and the range of the inclination angle of the air film hole 5, that is, the angle between its bottom or top surface and the surface of the upper plate 1 is greater than or equal to 30° and less than or equal to 60°, and this angle can be 30°, 40°, 50° or 60°; the spacing between the two spoiler ribs 6 near the end of the air film hole 5 is greater than the width of the inlet of the air film hole 5; the gas flows in from the through hole 7, flows through the impact groove 3, the spoiler groove 4 and the air film hole 5 in turn, and is finally ejected from the air film hole 5.

[0038] Shape memory alloys 8 are provided on both sides of the inlet of the air film hole 5, which gradually bulge inward when the temperature exceeds a critical value. The working process of the shape memory alloy is as follows: below the critical design temperature (i.e., the starting temperature of the martensitic phase transformation), the memory alloy adjustment structure presents an initial state; when the temperature exceeds the critical design temperature, the shape memory alloy deforms, the inlet area of ​​the air film hole is reduced, the air film sweeping characteristics are adjusted, and the downstream air film coverage performance is improved.

[0039] The relationship between the strain of shape memory alloy and its temperature is:

[0040]

[0041] Wherein, F is the strain of the shape memory alloy, Ts is the temperature of the shape memory alloy, Mf, Ms, As and Af represent the temperatures at which martensitic transformation begins, martensitic transformation ends, austenitic transformation begins and austenitic transformation ends, respectively, which in this embodiment are 950K, 1150K, 1350K and 1550K, respectively; and Fmax is the maximum deformation of the shape memory alloy.

[0042] In this implementation case, the calculation domain includes the high-temperature mainstream channel, the cooling secondary flow channel, and the layer cooling structure. The mainstream flow is given the mainstream temperature and airflow velocity, and the secondary flow is given the temperature and mass flow rate. The secondary flow mass flow rate is obtained by calculating the blowing ratio, which is defined as:

[0043]

[0044] Where m c 、A c is the mass flow rate of the secondary flow and the opening area of ​​the air film hole, m ∞ 、A ∞ are the mainstream mass flow rate and mainstream inlet area.

[0045] In this implementation case, the flow field and temperature field are calculated using the commercial computing software Ansys Fluent, and the comprehensive efficiency is defined as:

[0046]

[0047] Where, T ∞ is the mainstream temperature, T w is the spanwise average wall temperature of the hot side of the central cone, T c is the cooling air temperature.

[0048] Calculations show that the overall cooling efficiency of the traditional layer plate cooling device is low; by using the layer plate cooling device provided by the present invention, the cooling efficiency is increased by about 20% under the same blowing ratio; the traditional layer plate cooling device cools the air film in the span direction of the air film outlet and is concentrated on the axis of the outlet, and the span-wise cooling efficiency decreases rapidly; while the present device is more uniform in the span direction of the air film hole outlet, and the uniformity can be increased by 30%, and as the blowing ratio increases, the cooling range is wider.

[0049] After the shape memory alloy regulating structure is introduced at the air film hole inlet of the device, the comprehensive cooling efficiency is relatively improved by 5% compared with the case where the shape memory alloy regulating structure is not introduced.

Claims

1. A plate cooling device for an aircraft engine flame tube, comprising an upper plate (1) and a lower plate (2) bonded to each other, characterized in that: The upper plate (1) is provided with a plurality of cooling units, and the cooling units include a coaxially arranged rectangular impact groove (3), a rectangular spoiler groove (4) and an air film hole (5) for ejecting gas, and two L-shaped spoiler ribs (6) are symmetrically provided along the axis in the spoiler groove (4) and are parallel to the axis in length direction; the short end of the spoiler rib (6) is close to the impact groove (3), the long end of the spoiler rib (6) is a rectangular strip, and the short end is a right triangle, one of the right-angled sides is integrally formed with the long end, and the other right-angled side is integrally formed with the long end. The lower ends of the ends are located in the same plane and are integrally formed; the minimum spacing between the two spoiler ribs (6) is greater than the width of the impact groove (3); the lower plate (2) is provided with a through hole (7) connected to the impact groove (3); Ni-Ti based shape memory alloy (8) which gradually bulges inward when the temperature exceeds a critical value is provided on both sides of the inlet of the air film hole (5); the gas alternately flows on the side walls of the two spoiler ribs (6) to form a periodic unsteady flow; the shape memory alloy (8) deforms with temperature changes to adjust the air film sweeping characteristics.

2. The layer plate cooling device for an aircraft engine flame tube according to claim 1, characterized in that: The acute angle of the protrusion at the short end of the spoiler rib (6) is greater than or equal to 50° and less than or equal to 70°.

3. The layer plate cooling device for an aircraft engine flame tube according to claim 1, characterized in that: The ratio of the width of the impact groove (3) to the minimum spacing between the two spoiler ribs (6) is greater than or equal to 0.5 and less than or equal to 0.

8.

4. The layer plate cooling device for an aircraft engine flame tube according to claim 2, characterized in that: The inlet of the air film hole (5) is rectangular, and the distance between the two spoiler ribs (6) close to the end of the air film hole (5) is greater than the width of the inlet of the air film hole (5).

5. The layer plate cooling device for an aircraft engine flame tube according to claim 4, characterized in that: The air film hole (5) is outwardly expanding from the inlet to the outlet, and is connected to the spoiler groove (4) and the top of the upper plate (1).

6. The layer plate cooling device for an aircraft engine flame tube according to claim 5, characterized in that: The two side walls of the air film hole (5) expand outwards, and the included angle range of the two side walls is greater than or equal to 50° and less than or equal to 90°.

7. The layer plate cooling device for an aircraft engine flame tube according to claim 6, characterized in that: The air film hole (5) is an inclined hole, and the angle between the bottom surface of the air film hole (5) and the surface of the upper plate (1) is greater than or equal to 30° and less than or equal to 60°.

8. The layer plate cooling device for an aircraft engine flame tube according to claim 1, characterized in that: The height direction of the spoiler rib (6) is perpendicular to the plate surface of the upper plate; the axis of the through hole (7) is perpendicular to the plate surface of the lower plate (2).

9. The layer plate cooling device for an aircraft engine flame tube according to claim 1, characterized in that: The relationship between the strain of the shape memory alloy and its temperature is: Where F is the strain of the shape memory alloy, T s is the temperature of the shape memory alloy, M f 、M s 、A s and A f They represent the temperatures at which martensite transformation begins, martensite transformation ends, austenite transformation begins, and austenite transformation ends, respectively. max is the maximum deformation of shape memory alloy.

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