An impact-air film structure based on a bending impact plate and a design method thereof

Abstract

The application discloses an impingement-air film structure based on a bending impingement plate and a design method, and belongs to the technical field of impingement cooling.The impingement-air film structure based on the bending impingement plate comprises multiple rows of air film holes located on pressure surfaces and suction surfaces of a fairing, an impingement cavity located at a leading edge of the fairing, and a cold air cavity located outside the impingement cavity.The impingement cavity is surrounded by the suction surface, the pressure surface and the inner wall surface of the bending impingement plate, and the impingement holes are formed in the bending impingement plate.The cold air cavity is surrounded by the suction surface, the pressure surface and the outer wall surface of the bending impingement plate.Cold air enters the cold air cavity, part of the cold air flows out through the air film holes on the suction surface and the pressure surface, and part of the cold air enters the impingement cavity through the impingement holes on the bending impingement plate, impinges on the inner wall surface of the leading edge of the fairing, and then flows out from the first two rows of air film holes on the suction surface side in the impingement cavity to participate in air film cooling outside the fairing.The inner and outer cooling jointly act on the fairing to cool the fairing.The application solves the problem that the prior art cannot cool the fairing.

Description

Technical Field

[0001] This invention belongs to the field of impact cooling technology, specifically relating to an impact-film structure and design method based on a bent impact plate. Background Technology

[0002] With the development of next-generation engine technology, the demand for high thrust-to-weight ratio, high stealth, and wide Mach range power technologies is becoming increasingly urgent. Turbine inlet temperature is increasing by 20°C annually, and the gas temperature after the turbine is also gradually rising. The airflow temperature entering the exhaust system has gradually reached over 1300K. The high-temperature, high-speed combustion gas passing through the turbine rear casing poses a challenge to the cooling of the exhaust system. The turbine rear casing is a crucial load-bearing component of the exhaust system. Currently, the material of the load-bearing support plate is insufficient to withstand such high temperatures, necessitating cooling of the support plate. One method is to add a fairing outside the load-bearing support plate to prevent direct contact between the combustion gas and the support plate. Cooling the fairing with external bypass air reduces the wall temperature of the fairing and the load-bearing support plate, decreases thermal stress, and extends the service life of the turbine rear casing.

[0003] Domestic and international research on exhaust manifolds mainly focuses on their flow field characteristics, processing and casting techniques, and their impact on combustion performance in the combustion chamber. Research on the cooling of the manifold itself is extremely limited, with most studies focusing on film cooling of the center cone and employing convective cooling for the manifold. For example, existing technologies have numerically studied the effects of different film cooling arrangements on the temperatures of the center cone and manifold. In the calculations, different film cooling arrangements were set at the front end of the center cone, with cold air introduced into the center cone from the outer casing through the manifold. The results showed that film cooling of the center cone significantly reduced the surface temperatures of both the center cone and the manifold. However, these film cooling holes were only arranged on the center cone. With the development of new-generation engines, the exhaust system manifolds face increasingly higher combustion gas temperatures. Therefore, finding suitable cooling methods is crucial for improving lifespan and preventing manifold erosion. Currently, research on fairings in China is still in its early stages, with limited cooling structures. Publicly available technologies, considering radiation, have conducted research on film cooling for the integrated design of the rear support plate, fairing plate, flame stabilizer, and center cone. Convection cooling is used for the rear support plate / fairing, while convection-film cooling is used for the center cone. Therefore, research on other cooling methods for fairings is urgently needed.

[0004] The fairing is similar in shape to turbine blades. For turbine blade cooling, a comprehensive cooling solution has been developed, combining internal cooling, external cooling, and surface thermal barrier coatings. Among these, impingement cooling is one of the most effective internal cooling structures for heat transfer. Because the leading edge region of the blade is relatively small, it is difficult to arrange ribbed structures, and the high-temperature, high-pressure combustion gases from the outside are directly trapped in the leading edge region, resulting in the highest temperature at the leading edge. Therefore, impingement structures are widely used in the leading edge region. For the fairing, since the leading edge is narrower than that of the turbine blades, it is necessary to use impingement cooling to cool the leading edge.

[0005] In impact cooling, the airflow impacts the target surface through impact holes, absorbing heat from the combustion gases on the outer surface, thus cooling the interior of the blades. After impacting the target surface, the airflow immediately deflects, forming a boundary layer that develops from the impact point. The boundary layer is thinner in the impact point region, resulting in the strongest heat transfer. In studies of impact heat transfer, the leading edge is usually simplified to a semi-cylinder, neglecting the influence of curvature on both sides. The impact plate is often a flat plate, and the film cooling system is mostly located near the stagnation point of the leading edge. However, for fairing structures, the leading edge radius is smaller, and the asymmetry on both sides has a significant impact on impact heat transfer. Furthermore, the pressure difference between the inside and outside of the leading edge is smaller, making it impossible to arrange the film cooling holes in the stagnation point region of the leading edge. Therefore, it is necessary to study the asymmetric impact-film cooling of the fairing leading edge structure. Summary of the Invention

[0006] The technical problem to be solved:

[0007] To overcome the shortcomings of existing technologies, this invention provides an impact-film structure based on a bent impact plate. Addressing the cooling problem at the leading edge of the fairing, an impact chamber is provided in the leading edge portion of the fairing. Cooling airflow enters the impact chamber through impact holes. Within the impact chamber, the airflow first flows towards the impact stagnation point on the inner wall of the leading edge of the fairing, then is guided by the inner wall surfaces on both sides of the leading edge to the lowest pressure point on the suction surface, and finally exits from the film cooling holes located in the impact chamber on the suction surface side. This invention solves the problem that existing technologies cannot effectively cool the fairing.

[0008] The technical solution of this invention is: a design method for an impact-film structure based on a bent impact plate, the specific steps of which are as follows:

[0009] Determine the leading edge position and aerodynamic stagnation point of the fairing;

[0010] Multiple exhaust film holes are opened on the pressure side and suction side of the fairing, with the first exhaust film hole on the suction side located at the lowest pressure point on the suction side;

[0011] A bending impact plate is provided on the inner side of the leading edge of the fairing. The bending impact plate and the suction surface and pressure surface of the fairing form an impact cavity. The impact cavity encloses the multiple exhaust film holes on the suction surface side.

[0012] An impact hole is formed in the bent impact plate, and the impact hole is coaxially opposite to the pneumatic stagnation point.

[0013] Obtain the impact-film structure of the cooling shroud.

[0014] A further technical solution of the present invention is: the bending impact plate includes two bends, one end of which is connected to the pressure surface side and close to the pneumatic stagnation point, and the other end of which is connected to the suction surface side and far away from the pneumatic stagnation point; so that the first row and the second row of exhaust film holes of the suction surface are enveloped in the impact cavity.

[0015] A further technical solution of the present invention is: both turning angles of the bending impact plate are 90°, and the outer end plates of the two turning angles are parallel to each other and perpendicular to the line connecting the impact hole to the impact stagnation point on the inner wall of the front edge of the fairing.

[0016] A further technical solution of the present invention is that the pneumatic stagnation point is located on the extension line of the line connecting the impact hole to the impact stagnation point on the inner wall of the fairing leading edge.

[0017] An impact-film structure based on a bent impact plate is characterized by: multiple air film holes located on the pressure and suction surfaces of the fairing, an impact cavity located at the leading edge of the fairing, and a cooling cavity located outside the impact cavity; the impact cavity is formed by the suction surface, pressure surface, and inner wall surface of the bent impact plate of the fairing, and the bent impact plate has impact holes; the cooling cavity is formed by the suction surface, pressure surface, and outer wall surface of the bent impact plate of the fairing.

[0018] Cold air enters the cooling chamber. Part of it flows out through the air film holes on the suction and pressure surfaces, while part of it enters the impact chamber through the impact holes on the bent impact plate. It impacts the inner wall of the leading edge of the fairing and then flows out from the two front air film holes on the suction side inside the impact chamber, participating in the external air film cooling of the fairing. The combined effect of internal and external cooling cools the fairing.

[0019] A further technical solution of the present invention is that the thickness of the bending impact plate is 0.5-1.5mm, and the diameter of the impact hole is d.

[0020] A further technical solution of the present invention is: the distance between the end of the bending impact plate located on the pressure surface side and the pneumatic stagnation point is 3-4d, that is, the impact distance H is 3-4d; the distance between the end located on the suction surface side and the pneumatic stagnation point is 12-13d.

[0021] A further technical solution of the present invention is that the first exhaust film hole on the suction surface side is located at the lowest pressure point of the suction surface.

[0022] A further technical solution of the present invention is that the air film pores are all 90-degree cylindrical pores with a diameter of 0.3-0.7d.

[0023] An exhaust system for an engine includes a cowl and an impact-film structure based on a bent impact plate disposed on the cowl.

[0024] Beneficial effects

[0025] The beneficial effects of this invention are as follows: This invention proposes an impact-air film structure based on a bent impact plate, which changes the planar impact plate into a bent shape and opens a hole at the point of lowest pressure on the suction surface. Specific advantages are as follows:

[0026] 1. An opening at the point of lowest pressure near the leading edge on the suction surface improves leading-edge cooling. The pressure difference between the inside and outside of the fairing is relatively small, making it impossible to open an opening in the stagnation region of the leading edge like turbine blades. However, since the leading edge directly contacts the high-temperature gas, its temperature is the highest, and cooling it is crucial. The pressure distribution on the outer surface of the fairing indicates a point of minimum pressure in the leading-edge region of the suction surface. Opening an opening at this point ensures film cooling, improving the cooling effect of the leading-edge region through external film cooling. Currently, there is no research on film cooling for fairings in existing technology.

[0027] 2. The use of bent impact plates enhances the impact cooling effect at the leading edge. The impact plate closer to the leading edge ensures the optimal impact distance for the corresponding impact orifice diameter, while the impact plate farther from the leading edge ensures an additional air film outflow within the impact chamber, increasing the impact flow rate and thus improving the impact cooling effect.

[0028] 3. A bent impact structure is adopted, which improves overall cooling efficiency near the leading edge of the pressure surface. Due to the asymmetry of the leading edge, designing a bent structure near the pressure surface would create a dead zone. Figure 5 The (impact chamber includes a zigzag bent impact plate for pressure surface film outflow) not only fails to improve the internal impact effect but also affects the pressure surface film outflow, resulting in a decrease in the film outflow near the leading edge of the pressure surface, thus making the overall cooling efficiency improvement at this location insignificant. In contrast, the bent impact structure in this invention ensures pressure surface film outflow while maintaining impact strength, thereby improving the overall cooling efficiency near the leading edge of the pressure surface.

[0029] In summary, the impact-film structure based on the bent impact plate can increase the impact flow rate to a certain extent, enhance the heat transfer inside the asymmetric leading edge of the fairing, and ensure the outflow of the pressure surface film, thereby significantly improving the overall cooling efficiency of the leading edge. Attached Figure Description

[0030] Figure 1 This is an enlarged view of the leading edge impact plate of an impact-air film structure based on a bent impact plate according to the present invention.

[0031] Figure 2 This is a diagram showing the relationship between the leading edge impact plate and the air film hole of an impact-air film structure based on a bent impact plate according to the present invention.

[0032] Figure 3 This is a comparison diagram of the overall cooling efficiency of the mid-section of the impact-film structure impact plate based on the bent impact plate of the present invention and the planar impact plate under the conditions of the embodiment.

[0033] Figure 4 This is a comparison diagram of the overall cooling efficiency of the mid-section of the impact-film structure based on the bending impact plate of the present invention and the first exhaust film hole structure at the lowest pressure point of the non-suction surface under the conditions of the embodiment.

[0034] Figure 5 This is a comparison diagram of the overall cooling efficiency of the mid-section of an impact-film structure based on a bent impact plate, wherein both the impact plate and the suction and pressure surfaces are bent in a zigzag shape under the conditions of the embodiment.

[0035] Explanation of reference numerals in the attached diagram: 1. Fairing 2. Bending impact plate 3. Impact hole 4. Film air hole 5. Impact chamber 6. Cooling air chamber. Detailed Implementation

[0036] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Given the existing technology for fairing structures, the small leading-edge radius and the significant impact of asymmetry on impact heat transfer due to the asymmetry on both sides, coupled with the small pressure difference between the inside and outside of the leading edge, prevent the placement of film cooling vents in the stagnation region of the leading edge. Therefore, it is necessary to study the asymmetric impact-film cooling of the fairing's leading-edge structure. This invention provides a design method for an impact-film structure based on a bent impact plate, with the specific steps as follows:

[0039] S1: Determine the leading edge position and aerodynamic stagnation point of the fairing;

[0040] S2: Multiple exhaust film holes are opened on the pressure side and suction side of the fairing, wherein the first exhaust film hole on the suction side is located at the lowest pressure point on the suction side;

[0041] S3: A bending impact plate is provided on the inner side of the leading edge of the fairing. The bending impact plate and the suction surface and pressure surface of the fairing form an impact cavity. The impact cavity encloses the multiple exhaust film holes on the suction surface side.

[0042] S4: An impact hole is made in the bending impact plate, and the impact hole is coaxially opposite to the pneumatic stagnation point;

[0043] S5: Obtain the impact-film structure of the cooling shroud.

[0044] Specifically, the bending impact plate includes two bends, with one end connected to the pressure surface side close to the pneumatic stagnation point and the other end connected to the suction surface side away from the pneumatic stagnation point; so that the first and second row of exhaust film holes on the suction surface are enveloped in the impact cavity.

[0045] Specifically, the two turning angles of the bending impact plate are both 90°, and the outer end plates of the two turning angles are parallel to each other and perpendicular to the line connecting the impact hole to the impact stagnation point on the inner wall of the fairing front edge.

[0046] Specifically, the pneumatic stagnation point is located on the extension of the line connecting the impact hole to the impact stagnation point on the inner wall of the fairing leading edge.

[0047] The fairing described in this invention is a simplified model of the fairing of the turbine rear casing of an aero-engine. The fairing profile is the cross-sectional profile of the original fairing, and the fairing height (perpendicular to the flow direction) is 200-240mm. The impact-film structure based on the bending impact plate obtained by the above design method includes multiple air film holes located on the pressure and suction surfaces of the fairing, an impact cavity located at the leading edge of the fairing, and a cold air cavity located outside the impact cavity. The impact cavity is surrounded by the suction surface, pressure surface, and inner wall surface of the bending impact plate of the fairing, and the bending impact plate has impact holes. The cold air cavity is surrounded by the suction surface, pressure surface, and outer wall surface of the bending impact plate of the fairing. Cold air enters the cold air cavity, part of which flows out through the air film holes on the suction and pressure surfaces, and part of which enters the impact cavity through the impact holes on the bending impact plate, impacting the inner wall surface of the leading edge of the fairing, and then flowing out from the first two air film holes on the suction surface side inside the impact cavity, participating in the external air film cooling of the fairing. The internal and external cooling work together to cool the fairing.

[0048] Specifically, the thickness of the bending impact plate is 0.5-1.5mm, and the diameter of the impact hole is d.

[0049] Specifically, the distance between the end of the bent impact plate located on the pressure side and the aerodynamic stagnation point is 3-4d, i.e., the impact distance is 3-4d; the distance between the end located on the suction side and the aerodynamic stagnation point is 12-13d. One end, closer to the pressure side, ensures the impact distance from the impact hole to the leading edge, while the other end, closer to the suction side, ensures that as many air film holes as possible are located within the impact chamber, thereby obtaining a larger impact flow rate.

[0050] Specifically, the first exhaust film hole on the suction surface side is located at the lowest pressure point on the suction surface.

[0051] Specifically, the air film vents are all 90-degree cylindrical vents with a diameter of 0.3-0.7d. The air film vents are located between the two rows of impact vents along the height direction of the fairing, and are arranged alternately with the impact vents.

[0052] This invention can cool the leading edge wall of the fairing, thereby improving the overall cooling effect of the fairing.

[0053] The above technical solution will be further explained below with reference to the accompanying drawings:

[0054] Reference Figure 1 As shown, the impact-film structure of the bending impact plate in this example is located on the fairing 1 with a height of 220mm. 50 film holes are arranged along the height direction. The diameter of the film holes is 0.6mm and the spacing between the film holes is 4mm. The lowest pressure point near the leading edge of the suction surface is the first exhaust film hole of the suction surface. There are a total of 15 exhaust film holes on the suction surface and 14 exhaust film holes on the pressure surface.

[0055] The bending impact plate structure is located at the leading edge of the fairing, see [link / reference]. Figures 1-2 The impact plate is 1mm thick, and the impact holes are located on the side of the impact plate near the leading edge, directly opposite the leading edge aerodynamic stagnation point. The side of the impact plate furthest from the leading edge is 15mm away from the leading edge impact stagnation point. The impact hole diameter is 1.2mm, the impact hole spacing is 4mm, the impact distance is 4mm, and the impact holes are located between two air film holes in the height direction, with a total of 50 impact holes.

[0056] The impact chamber contains two exhaust film holes in front of the suction surface. After the airflow enters the cooling chamber, it flows out from the 50 impact holes, impacts the inner wall of the leading edge of the fairing, and then flows out through the two exhaust film holes in front of the suction surface to participate in the external air film cooling, further cooling the suction surface near the leading edge.

[0057] Compared to flat plate impact, bending impact structures can significantly improve the overall cooling efficiency at the leading edge. See the comparison results below. Figure 3 (Arc length S = 0 represents the leading edge stagnation point, S < 0 represents the pressure surface, and S > 0 represents the suction surface). The thickness of the flat impact plate used for comparison is the same as that of the bent impact plate, which is 1 mm. The diameter of the impact hole is the same as the impact position. The impact plate position with an impact distance of 4 mm corresponds to the side of the bent impact plate closer to the leading edge, and the impact plate position with an impact distance of 15 mm corresponds to the side of the bent impact plate farther from the leading edge. By adopting an impact-film structure based on a bent impact plate, the impact flow rate can be increased while ensuring the impact distance, without affecting the first exhaust film outflow from the pressure surface. The combined effect significantly improves the overall cooling efficiency at the leading edge.

[0058] A comparison of the overall cooling efficiency of the cross-section of the first exhaust membrane hole with and without suction surface pressure at the lowest point is shown in the image. Figure 4 The two structures being compared are identical except for the first exhaust film hole on the suction surface. Arranging the air film hole at the lowest pressure point near the leading edge of the suction surface can significantly improve the overall cooling efficiency near the leading edge.

[0059] The side near the pressure surface is also designed with a bent structure, which, compared to the overall cooling effect of the bent structure in this invention, is as follows: Figure 5 The two structures are identical except for the impact plate structure. It can be seen that due to the asymmetry of the suction surface and the pressure surface, the Z-shaped impact plate will form a dead zone near the pressure surface, thus affecting the gas film outflow of the gas film holes on the pressure surface side. In contrast, the present invention can achieve better leading edge cooling effect.

[0060] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A design method for an impact-film structure based on a bent impact plate, characterized in that... The specific steps are as follows: Determine the leading edge position and aerodynamic stagnation point of the fairing; Multiple exhaust film holes are opened on the pressure side and suction side of the fairing, with the first exhaust film hole on the suction side located at the lowest pressure point on the suction side; A bending impact plate is provided on the inner side of the leading edge of the fairing. The bending impact plate and the suction surface and pressure surface of the fairing form an impact cavity. The impact cavity encloses the multiple exhaust film holes on the suction surface side. An impact hole is formed in the bent impact plate, and the impact hole is coaxially opposite to the pneumatic stagnation point. Obtain the impact-film structure of the cooling shroud.

2. The design method of an impact-film structure based on a bent impact plate according to claim 1, characterized in that: The bending impact plate includes two bends, with one end connected to the pressure surface side close to the pneumatic stagnation point and the other end connected to the suction surface side away from the pneumatic stagnation point; thus, the first and second row of exhaust film holes on the suction surface are enveloped within the impact cavity.

3. The design method of an impact-film structure based on a bent impact plate according to claim 2, characterized in that: The two turning angles of the bending impact plate are both 90°, and the outer end plates of the two turning angles are parallel to each other and perpendicular to the line connecting the impact hole to the impact stagnation point on the inner wall of the fairing front edge.

4. The design method of an impact-film structure based on a bent impact plate according to claim 3, characterized in that: The pneumatic stagnation point is located on the extension of the line connecting the impact hole to the impact stagnation point on the inner wall of the fairing leading edge.

5. An impact-film structure based on a bent impact plate, characterized in that: The impact-film structure based on a bent impact plate, as described in any one of claims 1-4, is designed and obtained. It includes multiple exhaust film holes located on the pressure and suction surfaces of the fairing, an impact chamber located at the leading edge of the fairing, and a cold air chamber located outside the impact chamber; the impact chamber is formed by the suction surface, pressure surface, and inner wall of the bent impact plate of the fairing, and the bent impact plate has impact holes; the cold air chamber is formed by the suction surface, pressure surface, and outer wall of the bent impact plate of the fairing. Cold air enters the cooling chamber. Part of it flows out through the air film holes on the suction and pressure surfaces, while part of it enters the impact chamber through the impact holes on the bent impact plate. It impacts the inner wall of the leading edge of the fairing and then flows out from the two front air film holes on the suction side inside the impact chamber, participating in the external air film cooling of the fairing. The combined effect of internal and external cooling cools the fairing.

6. The impact-air film structure based on a bent impact plate according to claim 5, characterized in that: The thickness of the bending impact plate is 0.5-1.5mm, and the diameter of the impact hole is d.

7. The impact-air film structure based on a bent impact plate according to claim 6, characterized in that: The distance between the end of the bending impact plate on the pressure side and the pneumatic stagnation point is 3-4d, that is, the impact distance H is 3-4d; the distance between the end of the bending impact plate on the suction side and the pneumatic stagnation point is 12-13d.

8. The impact-air film structure based on a bent impact plate according to claim 7, characterized in that: The first exhaust membrane hole on the suction surface side is located at the lowest pressure point on the suction surface.

9. The impact-film structure based on a bent impact plate according to claim 8, characterized in that: All air film pores are 90-degree cylindrical pores with a diameter of 0.3-0.7d.

10. An exhaust system for an engine, characterized in that: Includes a fairing and an impact-film structure based on a bending impact plate as described in any one of claims 5-9, disposed on the fairing.

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