Laminate cooling device for aero-engine flame tube

Abstract

The invention discloses a laminate cooling device for an aero-engine flame tube, the laminate cooling device comprises an upper layer plate and a lower layer plate which are attached to each other, the upper layer plate is provided with a plurality of cooling units, and each cooling unit comprises a rectangular impact groove, a rectangular turbulent flow groove and a gas film hole for spraying gas which are coaxially arranged and sequentially communicated; two L-shaped turbulent flow ribs parallel to the axis in the length direction are symmetrically arranged in the turbulent flow groove along the axis; the short ends of the turbulent flow ribs are close to the impact groove and are in a right triangle shape. The minimum distance between the two turbulent flow ribs is larger than the width of the impact groove. The lower-layer plate is provided with a through hole communicated with the impact groove; the device can strengthen convective heat exchange, improve the air film cooling performance and enhance the overall cooling effect in a high-temperature state.

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 control capability of fighter jets, the thrust-to-weight ratio of aircraft engines has been 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 temperature before the turbine. 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 temperature of the combustion chamber 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] At present, the combustion chamber cooling technology at home and abroad has developed from a single cooling method to a composite cooling method that integrates multiple cooling methods; the single cooling method includes convection cooling, impingement cooling, multi-inclined hole cooling, etc.; among them, convection cooling is an earlier application of flame tube cooling form, which is generally achieved by setting raised ribs on the flame tube wall to increase the convection heat transfer coefficient of the flame tube wall to further increase the heat transfer; but due to its limited cooling effect, its single form is only used in early combustion chambers with low temperature rise; impingement cooling uses a double-layer flame tube wall, and its cooling air enters from the outer wall perpendicular to the wall and impinges on the wall with higher temperature on the inner wall; high-speed jet impinges on the wall to form convection heat transfer, which is used to cool down a specific area; its advantage is that the convection heat transfer coefficient of the stagnation zone is extremely high, so it can effectively cool down the local high-temperature area, but the consumption of cold air is relatively large; multi-inclined hole cooling, by processing a large number of small holes on the flame tube wall at a certain inclination angle, the cooling air is introduced by using the internal and external pressure difference to achieve full air film coverage of the flame tube gas side wall.

[0004] Composite cooling refers to a cooling technology that simultaneously uses two or more of the aforementioned cooling methods. Although there are currently layer plate cooling devices that combine convection cooling and impingement cooling, the raised ribs that play a role in convection cooling cannot make the cooling gas form a stable unsteady flow, and the internal heat exchange effect is poor; secondly, as the temperature of the combustion chamber gradually increases, the cooling performance of the cooling gas ejected by the layer plate 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 the flame tube of an aircraft engine described in the present invention comprises an upper layer plate and a lower layer plate which are fitted together, the upper layer plate is provided with a plurality of cooling units, the cooling units comprise a coaxially arranged rectangular impact groove, a rectangular spoiler groove and an air film hole for ejecting gas which are connected in sequence, two L-shaped spoiler ribs which are parallel to the axis in the length direction are symmetrically arranged 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 coaxially arranged rectangular impact grooves, rectangular spoiler grooves and air film holes that are connected in sequence, two L-shaped spoiler ribs are symmetrically arranged along the axis in the rectangular spoiler groove, the short end of the L-shaped spoiler rib close to the impact groove is a special structure of a right triangle, and the minimum spacing between the two spoiler ribs is greater than the width of the impact groove. Under the action of the Coanda effect, the airflow from the impact groove will flow along the side walls of the two spoiler ribs, but because of the special structure of the 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. Such a cycle makes the airflow alternately flow on the side walls of the two spoiler ribs to form a periodic unsteady flow, which strengthens the convective heat transfer and enhances the internal cooling. At the same time, an air film outflow with a sweeping characteristic is formed to improve 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 axial 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 spacing between 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 spacing 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 ends 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 hole expands outward 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 expand outwards 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 satisfies the above range, which can ensure that an 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; and 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 a Ni-Ti based shape memory alloy which gradually bulges inwards when the temperature exceeds a critical value.

[0022] By setting the shape memory alloy, when the temperature exceeds the 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, adjust the sweeping characteristics of the air film outflow, and thus 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] Among them, 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 start temperature of martensitic transformation, the end temperature of martensitic transformation, the start temperature of austenitic transformation and the end temperature of austenitic transformation 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 impact groove end is greater than the impact groove width. Under these conditions, the airflow can 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 a reduction in the cooling effect due to temperature increase. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 It is the structural diagram of the upper plate;

[0029] Figure 3 It is the structural schematic diagram of the lower plate;

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

[0031] Figure 5 is a 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 FIG. Figure 6 a is a schematic diagram of the structure before the temperature exceeds the critical value; Figure 6 b is the structural schematic diagram 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 layer plate 1 and a lower layer plate 2 that are fitted to each other, the upper layer plate 1 is provided with a plurality of cooling units, 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, and two L-shaped spoiler ribs 6 whose length directions are parallel to the axis are symmetrically arranged along the axis in the spoiler groove 4; 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 layer plate 2 is provided with a through hole 7 connected to the impact groove 3.

[0034] The upper plate 1 may be provided with a plurality of 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, and the cooling gas flows into the cooling unit through the through hole 7 and then sprays 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 thereto, 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] Two L-shaped spoiler ribs 6 are provided in the rectangular spoiler groove 4. The specific shape of the spoiler ribs 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 angle side is integrally formed with the long end, and the other right angle 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 is in the range of 140° to 160°, that is, the angle range of the acute angle of the right triangle protruding in the axial direction is 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 spacing between the two spoiler ribs 6 meets 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 surface and the bottom surface 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 surface or top surface and the board 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 start temperature of martensitic transformation, the end temperature of martensitic transformation, the start temperature of austenitic transformation and the end temperature of austenitic transformation, respectively, which in this embodiment are 950K, 1150K, 1350K and 1550K, respectively; 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 temperature and airflow velocity are given for the mainstream, and the temperature and mass flow rate are given for the secondary flow; the secondary flow mass flow rate is obtained by calculating the blowing ratio, and the blowing ratio is defined as:

[0043]

[0044] In the formula, 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 and solved by 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] After calculation, it is found that the overall cooling efficiency of the traditional layer plate cooling device is relatively 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 air film cooled by the traditional layer plate cooling device in the span direction of the air film outlet is concentrated on the axis of the outlet, and the span-wise cooling effect 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 layer plate cooling device for an aircraft engine flame tube, comprising an upper layer plate (1) and a lower layer plate (2) attached to each other, characterized in that: The upper plate (1) is provided with a plurality of cooling units, the cooling units comprising a coaxially arranged and sequentially connected rectangular impact groove (3), a rectangular spoiler groove (4) and an air film hole (5) for ejecting gas, the spoiler groove (4) being 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).

2. The layer plate cooling device for an aircraft engine flame tube according to claim 1 is 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 is 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 1 is 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 is 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 is 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: Ni-Ti based shape memory alloys (8) which gradually bulge inwards when the temperature exceeds a critical value are provided on both sides of the inlet of the air film hole (5).

10. A layer plate cooling device for an aircraft engine flame tube according to claim 9, 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 of martensitic transformation start, martensitic transformation end, austenitic transformation start and austenitic transformation end, respectively. max is the maximum deformation of shape memory alloy.

Images