Protruding and rib combined structure for target surface cooling and double-wall impact cooling device

Abstract

The invention discloses a protrusion and rib combined structure for target surface cooling and a double-wall impingement cooling device, and relates to the technical field of blade heat exchange, the protrusion and rib combined structure comprises a plurality of combined structures, each combined structure comprises a protrusion and a flow guide rib, and each protrusion and each flow guide rib are used for being fixedly connected with the target surface, close to an impingement plate, of a target plate; the impact plate is provided with a plurality of impact holes, the target plate is provided with a plurality of air film hole groups, each air film hole group comprises at least three air film holes, and the air film holes of each air film hole group are arranged at intervals and define a cooling space; each bulge is fixedly connected in the cooling space of one target plate, each bulge is arranged opposite to one impact hole in the impact plate, and each bulge can enable airflow entering from the corresponding impact hole to flow in the direction close to the target surface and far away from the center line of the corresponding bulge; a flow guide rib is arranged between every two adjacent air film holes of each air film hole set, and each flow guide rib extends from one corresponding air film hole to the other corresponding air film hole. The overall heat exchange effect of the blade is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of blade heat exchange, in particular to a projection and rib combination structure for target surface cooling and a double-wall impact cooling device. Background Art

[0002] With the improvement of gas turbine performance, the turbine inlet temperature of some advanced gas turbines has exceeded 2000K. To ensure safe and reliable operation of the turbine, it is necessary to improve the temperature resistance of materials or to develop more efficient cooling methods. However, in recent years, the improvement in the temperature resistance of high-temperature materials has been far less than the increase in turbine inlet temperature. Simply relying on material improvements is difficult to meet the demanding requirements of turbine operation. Therefore, the cooling of high-temperature components in advanced gas turbines has been placed on a higher level. Efficient cooling measures are needed to protect turbine blades, afterburners, and nozzles from erosion by high-temperature gases.

[0003] Impingement cooling, a technique used in blade internal cooling, has been widely adopted due to its excellent heat transfer capabilities. Impingement cooling is applied to nearly all hot-end components in aircraft engines, including the combustion chamber, turbine guide vanes, rotor blades, shrouds, and even rotating disks. It is suitable for jet Reynolds numbers ranging from 10,000 to 500,000. However, when the jet exits the impingement hole and directly impacts the target surface at the impingement stagnation point, it is blocked by the target surface, causing the jet velocity to drop sharply to zero. This creates a significant pressure loss at this point, which affects the heat transfer coefficient near the impingement stagnation point. Summary of the Invention

[0004] The purpose of the present invention is to provide a combined structure of protrusions and ribs for target surface cooling and a double-wall impact cooling device to solve the problems existing in the above-mentioned prior art and significantly improve the overall heat exchange effect of the blade.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides a protrusion and rib combination structure for target surface cooling, comprising a plurality of combination structures, each of the combination structures comprising a protrusion and a guide rib, each of the combination structures being used to be arranged in a cooling cavity formed between an impact plate and a target plate of a double-wall impact cooling structure, each of the protrusions and each of the guide ribs being used to be fixedly connected to the target surface of the target plate near the impact plate; a plurality of impact holes are provided on the impact plate, a plurality of air film hole groups are provided on the target plate, each of the air film hole groups comprises at least three air film holes, all of the air film holes in each air film hole group are arranged at intervals and enclose a cooling space; each of the protrusions is fixedly connected to the cooling space of one of the target plates, each of the protrusions is arranged opposite to one of the impact holes on the impact plate, each of the protrusions can make the airflow entering from the corresponding impact hole flow in a direction close to the target surface and away from the center line of the corresponding protrusion; a guide rib is provided between two adjacent air film holes in each air film hole group, and each guide rib extends from a corresponding air film hole to a corresponding other air film hole.

[0007] Preferably, the diameter of the end of each protrusion away from the target surface is smaller than the diameter of the end of each protrusion close to the target surface, and the outer side wall of each protrusion is a concave curved surface.

[0008] Preferably, each of the protrusions is conical or truncated cone-shaped.

[0009] Preferably, each of the guide ribs extends along a line connecting the centers of the corresponding two air film holes.

[0010] Preferably, four air film holes are provided on the periphery of each protrusion, and the number of guide ribs in the combined structure is four.

[0011] Preferably, the height of each protrusion is 0.3 to 0.7 times the vertical distance from each protrusion to the air outlet of the corresponding impact hole.

[0012] Preferably, the height of each of the guide ribs is 0.3 to 0.7 times the vertical distance from the corresponding protrusion to the air outlet of the corresponding impact hole.

[0013] Preferably, the impact holes on the impact plate and the air film holes on the target plate are arranged alternately, and the protrusions correspond to the impact holes one by one.

[0014] Preferably, the two outer side walls of each guide rib in the width direction are concave curved surfaces, and the dimension of one end of each guide rib away from the target surface in the width direction of each guide rib is smaller than the dimension of the other end of each guide rib in the width direction of each guide rib.

[0015] The present invention also provides a double-wall impact cooling device, comprising an impact plate, a target plate, and a combination structure of protrusions and ribs for target surface cooling, each of the combination structures being arranged in a cooling cavity formed between the impact plate and the target plate of the double-wall impact cooling structure, each of the protrusions and each of the guide ribs being fixedly connected to the target surface of the target plate near the impact plate.

[0016] Compared with the prior art, the present invention has achieved the following technical effects:

[0017] The present invention provides a protrusion and rib combination structure for target surface cooling and a double-wall impact cooling device, comprising a plurality of combination structures, each combination structure comprising a protrusion and a guide rib, each combination structure being used to be arranged in a cooling cavity formed between an impact plate and a target plate of the double-wall impact cooling structure, each protrusion and each guide rib being used to be fixedly connected to the target surface of the target plate close to the impact plate; a plurality of impact holes are arranged on the impact plate, a plurality of air film hole groups are arranged on the target plate, each air film hole group comprises at least three air film holes, all the air film holes of each air film hole group are arranged at intervals and enclose a cooling space; each protrusion is fixedly connected in the cooling space of a target plate, each protrusion is arranged opposite to an impact hole on the impact plate, each protrusion can make the airflow entering from the corresponding impact hole flow in a direction close to the target surface and away from the center line of the corresponding protrusion; a guide rib is arranged between two adjacent air film holes of each air film hole group, and each guide rib extends from a corresponding air film hole to another corresponding air film hole.

[0018] After flowing into the impact duct inlet, the airflow enters the impact hole through the impact cavity within the impact plate, enters the cooling cavity through the impact hole, and impacts the protrusion arranged opposite the impact hole. The airflow is guided by the protrusion in a direction close to the target surface and away from the centerline of the corresponding protrusion. Then, under the guidance of the guide ribs, it flows toward the adjacent film hole and is finally discharged through the film hole. The provision of the protrusion can change the impact direction of the jet. After the jet is ejected from the impact hole, the guidance of the protrusion reduces the pressure loss caused by the jet vertically impacting the target surface and improves the heat transfer coefficient near the impact stagnation point. The height of the protrusion also reduces the impact distance, thereby improving the impact heat transfer effect. The arrangement of the guide ribs can effectively guide the airflow, so that the airflow flows along the guide direction and out of the specific film hole, preventing the jets ejected from the two impact holes from intersecting and causing huge impact losses. The good superposition of the effects of the protrusion and the guide ribs on the flow field significantly improves the overall heat transfer effect of the blade. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The overall model of the blade where the target surface cooling protrusion and rib combination structure provided in Example 1 is located, as well as a schematic diagram of the cold air flow direction;

[0021] Figure 2 A schematic diagram of a mid-section of the leading edge target surface provided in Example 1;

[0022] Figure 3 Schematic diagram of the target surface structure and airflow direction provided in Example 1;

[0023] Figure 4 A schematic diagram of the double-wall structure provided in Example 1;

[0024] Figure 5 Schematic diagram of the target surface structure provided in Example 1 Figure 1 ;

[0025] Figure 6 Schematic diagram of the target surface structure provided in Example 1 Figure 2 ;

[0026] Figure 7 A front view of the protrusion provided in Example 1;

[0027] Figure 8 for Figure 7 A top view of

[0028] Figure 9 A schematic cross-sectional view of the guide rib provided in Example 1;

[0029] Figure 10 A top view of the guide rib provided in Example 1;

[0030] Figure 11 The local Nusselt number distribution diagrams of the cooling structure with a smooth target plate (comparative example) and the target surface cooling protrusion and rib combination structure of this embodiment;

[0031] Figure 12 This is a comparison chart of the ratio of the total area average Nu of the target surface with the target surface cooling protrusion and rib combination structure of this embodiment and the smooth target surface of the comparative example;

[0032] Figure 13 The local Nu distribution and streamline diagram of the target surface of the target surface cooling protrusion and rib combination structure of this embodiment;

[0033] Figure 14 : This is a diagram showing the average Nu ratio of the target surface mapping area of ​​this embodiment and the comparative example;

[0034] Figure 15 Flow coefficient diagram of the cooling structure of this embodiment and the comparative example;

[0035] Figure 16 2 is a flow coefficient comparison diagram of the cooling structure of this embodiment and the comparative example;

[0036] In the figure: 100, a combined structure of projections and ribs for target surface cooling; 1, impact hole; 2, guide rib; 3, air film hole; 4, projection; 5, target plate; 6, impact plate; 7, leading edge double wall; 8, impact cavity; 9, cooling cavity; 10, target surface. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] The purpose of the present invention is to provide a combined structure of protrusions and ribs for target surface cooling and a double-wall impact cooling device to solve the problems existing in the above-mentioned prior art and significantly improve the overall heat exchange effect of the blade.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1

[0041] like Figures 1 to 16 As shown, this embodiment provides a target surface cooling protrusion and rib combination structure 100, including multiple combination structures, each combination structure includes a protrusion 4 and a guide rib 2, each combination structure is used to be arranged in a cooling cavity 9 formed between an impact plate 6 and a target plate 5 of a double-wall impact cooling structure, each protrusion 4 and each guide rib 2 is used to be fixedly connected to a target surface 10 of the target plate 5 close to the impact plate 6; a plurality of impact holes 1 are provided on the impact plate 6, and a plurality of air film hole groups are provided on the target plate 5, each air film hole group includes at least three air film holes 3, All the air film holes 3 of each air film hole group are arranged at intervals and enclosed by a cooling space; each protrusion 4 is fixedly connected to the cooling space of a target plate 5, and each protrusion 4 is arranged opposite to an impact hole 1 on the impact plate 6, and each protrusion 4 can make the air flow entering from the corresponding impact hole 1 flow in a direction close to the target surface 10 and away from the center line of the corresponding protrusion 4; a guide rib 2 is provided between two adjacent air film holes 3 of each air film hole group, and each guide rib 2 extends from a corresponding air film hole 3 to another corresponding air film hole 3.

[0042] After entering the impact duct inlet, the airflow enters the impact hole 1 through the impact cavity 8 within the impact plate 6. From there, it enters the cooling cavity 9 and impacts the protrusion 4 positioned opposite the impact hole 1. The protrusion 4 guides the airflow toward the target surface 10 and away from the centerline of the corresponding protrusion 4. The airflow is then guided by the guide ribs 2 toward the adjacent film hole 3, ultimately exiting through the film hole 3. The protrusion 4 alters the impact direction of the jet. After exiting the impact hole 1, the protrusion 4 guides the airflow, reducing the pressure loss caused by the jet's perpendicular impact on the target surface 10 and improving the heat transfer coefficient near the impact stagnation point. The height of the protrusion 4 also reduces the impact distance, thereby enhancing the impact heat transfer effect. The arrangement of the guide ribs 2 effectively guides the airflow, directing it along the guiding direction and exiting through a specific film hole 3, preventing the jets from two impact holes 1 from intersecting and causing significant impact losses. The combined effects of the protrusions 4 and the guide ribs 2 on the flow field significantly improve the overall heat transfer efficiency of the blade.

[0043] In some embodiments, the diameter of the end of each protrusion 4 away from the target surface 10 is smaller than the diameter of the end of each protrusion 4 close to the target surface 10, and the outer wall of each protrusion 4 is a concave curved surface. The outer wall of the protrusion 4 is preferably an arc surface.

[0044] In some embodiments, each protrusion 4 is conical or frustum-conical.

[0045] In some specific embodiments, each guide rib 2 extends along a line connecting the centers of two corresponding air film holes 3 .

[0046] In some specific embodiments, four air film holes 3 are provided on the periphery of each protrusion 4 , and the combined structure has four guide ribs 2 . The four guide ribs 2 enclose a cooling space, and the four guide ribs 2 surround one protrusion 4 .

[0047] In some specific embodiments, the height of each protrusion 4 is 0.3 to 0.7 times the vertical distance from each protrusion 4 to the air outlet of the corresponding impact hole 1 , so that the heat transfer coefficient near the stagnation point area is higher.

[0048] In some specific embodiments, the height of each guide rib 2 is 0.3 to 0.7 times the vertical distance from the corresponding protrusion 4 to the air outlet of the corresponding impact hole 1. The vertical distance from the air outlet of the impact hole 1 to the protrusion 4 directly opposite the impact hole 1 is the impact distance. It should be noted that when the target plate 5 and the impact plate 6 are not parallel to each other, the impact distances corresponding to different impact holes 1 may be different. The impact distance in this embodiment is the vertical distance between the protrusion 4 within the cooling space enclosed by the guide rib 2 and the impact hole 1 arranged opposite the protrusion 4.

[0049] In some specific embodiments, the diameters of the impact holes 1 and the air film holes 3 are 0.4 mm to 2 mm, which can better improve the heat transfer effect in the intersection area, increase the heat exchange area, and improve the impact heat transfer performance.

[0050] In some specific embodiments, the diameter of the top surface of the protrusion 4 is slightly larger than the diameter of the impact hole 1 .

[0051] In some specific embodiments, the impact holes 1 on the impact plate 6 and the air film holes 3 on the target plate 5 are arranged alternately, and the protrusions 4 correspond to the impact holes 1 one by one.

[0052] In some specific embodiments, the two outer side walls of each guide rib 2 in the width direction are concave curved surfaces, and the dimension of the end of each guide rib 2 away from the target surface 10 in the width direction of each guide rib 2 is smaller than the dimension of the other end of each guide rib 2 in the width direction of each guide rib 2. The two outer side walls of each guide rib 2 in the width direction are preferably arc surfaces.

[0053] In some specific embodiments, the target surface 10 is located at the leading edge of the turbine blade. The target surface 10 has a certain radius of curvature and is a smooth target surface 10 with multiple film holes 3 evenly arranged on its surface. The film holes 3 in two adjacent rows are staggered. Preferably, the midpoint of any two film holes 3 in the previous row directly faces a film hole 3 in the next row along the chord length. Four film holes 3 are evenly distributed around the periphery of the protrusion 4. These four film holes 3 form a rectangular area. A guide rib 2 is provided between two adjacent film holes 3. The four guide ribs 2, four film holes 3, and one protrusion 4 form an impact unit. Each impact unit corresponds to an impact hole 1. The impact station point of the jet entering through the impact hole 1 on the target plate 5 is located at the intersection of the diagonals of the rectangular area formed by the corresponding impact unit, that is, at the center of the four film holes 3 of the corresponding impact unit. The impact plate 6 has multiple impact holes 1 evenly arranged on it. The impact holes 1 in two adjacent rows are staggered, and each film hole 3 is located at the center of the four impact holes 1. In the arc length direction, the center lines of the impact hole 1 and the air film hole 3 form a certain angle.

[0054] Example 2

[0055] This embodiment provides a combined structure 100 of projections and ribs for target surface cooling. The geometric parameters of this embodiment are as follows: the diameter of the impact hole 1 and the air film hole 3 is d = 5 mm, the impact distance H = 2d = 10 mm, and the impact holes 1 and air film holes 3 are staggered. The impact hole 1 is located at the center of the four air film holes 3, and the air film hole 3 is located at the center of the four impact holes 1. The spanwise spacing Z between the impact hole 1 and the air film hole 3 is 10 d, and the angle between the centerlines of the two holes in the arc length direction is 60 degrees. The spacing between the air film holes 3 is S = 10 d, and the radius of curvature R = 10 d of the target surface 10. The projection 4 is a frustum with a curved outer wall. The projection 4 is located at the impact stagnation point. The bottom diameter of the projection 4 is 4 d, the top diameter is 1.2 d, the height h = 0.3 H, and the side surface is a smooth curved surface. The guide rib 2 is an inclined rib with a height of 0.3 H. It is arranged on the line connecting adjacent air film holes 3 and has a rib length L = 4 d. The cross-sectional dimensions of the guide rib 2 are: top width 0.25d, bottom width d, and side curvature R=5mm.

[0056] The heat transfer and flow characteristics of the smooth target plate 5 (comparative example) and the target plate 5 provided with the combined structure of this embodiment are analyzed. The experimental results of the local Nusselt number distribution of the comparative example are as follows: Figure 11 As shown in a, the experimental results of the local Nusselt number distribution of the target surface cooling protrusion and rib combination structure 100 of this embodiment are as follows Figure 11 As shown in FIG. 2 , by comparing the two cloud diagrams, it can be seen that the local Nusselt number distributions of the comparative example and the embodiment at different Reynolds numbers have the same regularity. Figure 12 The graph is a comparison of the ratio of the total area average Nu of the target surface 10 of the target surface cooling protrusion and rib combination structure 100 of this embodiment and the smooth target surface 10 of the comparative example under different Reynolds numbers. Figure 12 It can be seen that the ratio of the total area average Nu of the target surface 10 of this embodiment to the smooth target surface 10 of the comparative example is significantly improved, that is, the experimental value results of the target surface 10 of this embodiment are much better than those of the smooth target plate 5, which shows that the implementation effect of the protrusion and rib combination structure 100 for target surface cooling in this embodiment is very obvious.

[0057] Example 3

[0058] This embodiment provides a combined structure 100 of projections and ribs for target surface cooling. The geometric parameters of this embodiment are as follows: the diameter of the impact hole 1 and the air film hole 3 is d = 5 mm, the impact distance H = 2d = 10 mm, and the impact holes 1 and air film holes 3 are staggered. The impact hole 1 is located at the center of the four air film holes 3, and the air film hole 3 is located at the center of the four impact holes 1. The spanwise spacing Z between the impact hole 1 and the air film hole 3 is 10 d, the angle between the centerlines of the two holes in the arc length direction is 60 degrees, the spacing S between the air film holes 3 is 10 d, and the radius of curvature R of the target surface 10 is 10 d. The projection 4 is arranged at the impact stagnation point, with a bottom diameter of 4 d, a top diameter of 1.2 d, and a height h = 0.3 H. The side surface of the projection 4 is a smooth curved surface. The guide rib 2 has a height of 0.7 H and is arranged on the line connecting adjacent air film holes 3. The rib length is L = 4 d. The cross-sectional dimensions of the guide rib 2 are: the top width is 0.25d, the bottom width is d, and the side curvature R=5mm.

[0059] like Figure 13 As shown, the target surface cooling protrusion and rib combination structure 100 of this embodiment has a higher heat transfer coefficient near the stagnation area below the impact hole 1, and also has a high heat exchange area on the guide rib 2, combining the influence of the protrusion 4 and the guide rib 2 on the flow field, and the enhanced effect of the two on heat transfer is well superimposed.

[0060] The experimental verification was conducted using the impact target surface 10 protrusion 4 and the guide rib 2 combination structure with a rib height of 0.7H, and the results were as follows: Figure 14 The target surface 10 mapping area average Nu ratio diagram of this embodiment and the comparative example is shown as follows: Figure 15 The flow coefficient diagram of the embodiment and the comparative example shown in FIG. Figure 16 The flow coefficient comparison chart of this embodiment and the comparative example shows the following conclusions: The results show that the average mapped area Nu of the target surface 10 with protrusions 4 and guide ribs 2 is approximately 27% higher than that of the smooth target surface 10. Compared to Example 2, the combination of this embodiment improves heat transfer performance. The flow coefficients of the smooth target plate 5 of this embodiment and the comparative example are essentially the same, and the flow coefficient is higher than that of the comparative example. This embodiment improves heat transfer performance without increasing flow resistance, or even reduces it.

[0061] Furthermore, experimental verification shows that the flow coefficient of the target surface cooling protrusion and rib combination structure 100 of this embodiment is very close to that of the smooth target surface 10. When the Reynolds number and fin height are different, the deviation of the flow coefficient of the target surface cooling protrusion and rib combination structure 100 of this embodiment from that of the smooth target surface 10 is almost always within 4%. The presence of the protrusions 4 and the guide ribs 2 has little effect on the flow resistance of the channel and may even reduce it in certain circumstances.

[0062] Example 4

[0063] This embodiment provides a double-walled impact cooling device, including an impact plate 6, a target plate 5, and a combined structure 100 of protrusions and ribs for target surface cooling in Example 1. Each combined structure is arranged in a cooling cavity 9 formed between the impact plate 6 and the target plate 5 of the double-walled impact cooling structure, and each protrusion 4 and each guide rib 2 is fixedly connected to the target surface 10 of the target plate 5 near the impact plate 6.

[0064] In some specific embodiments, the double-wall impingement cooling structure is disposed in the leading edge region of the blade, specifically in the leading edge double-wall 7 region of the blade.

[0065] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A target surface cooling protrusion and rib combination structure, characterized in that:

18. The cooling fan as claimed in claim 17, wherein the cooling fan is mounted on a pair of support posts and a pair of support posts, wherein the support posts are connected along the length of the cooling fan to form a circle around the cooling fan. The cooling fan is mounted on a pair of support posts, and the support posts are connected along the length of the cooling fan to form a circle around the cooling fan.

2. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: The diameter of the end of each protrusion away from the target surface is smaller than the diameter of the end of each protrusion close to the target surface, and the outer side wall of each protrusion is a concave curved surface.

3. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: Each of the protrusions is in a cone or truncated cone shape.

4. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: Each of the guide ribs extends along a line connecting the centers of the corresponding two air film holes.

5. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: Four air film holes are provided on the periphery of each protrusion, and the number of guide ribs in the combined structure is four.

6. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: The height of each protrusion is 0.3 to 0.7 times the vertical distance from each protrusion to the air outlet of the corresponding impact hole.

7. The target surface cooling protrusion and rib combination structure according to claim 6, characterized in that: The height of each guide rib is 0.3 to 0.7 times the vertical distance from the corresponding protrusion to the air outlet of the corresponding impact hole.

8. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: The impact holes on the impact plate and the air film holes on the target plate are arranged alternately, and the protrusions correspond to the impact holes one by one.

9. The target surface cooling protrusion and rib combination structure according to claim 1, characterized in that: The two outer side walls of each guide rib in the width direction are concave curved surfaces, and the dimension of one end of each guide rib away from the target surface in the width direction of each guide rib is smaller than the dimension of the other end of each guide rib in the width direction of each guide rib.

10. A double-wall impingement cooling device, characterized in that: It comprises an impact plate, a target plate and a combined structure of protrusions and ribs for target surface cooling as described in any one of claims 1 to 9, each of the combined structures being arranged in a cooling cavity formed between the impact plate and the target plate of a double-wall impact cooling structure, and each of the protrusions and each of the guide ribs being fixedly connected to the target surface of the target plate close to the impact plate.

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