Heat exchange plate

Abstract

The utility model discloses a heat exchange plate, belongs to the field of air preheaters, solves the problem that better heat exchange efficiency cannot be obtained when a plate sheet with higher hardness is used in the prior art, and mainly adopts the technical scheme that the heat exchange plate is formed by welding two thin plates which are arranged front and back through a plurality of linear welding parts, the non-welded parts on the two thin plates are far away from each other to form an air cavity for flowing air, the left side of the air cavity is an air inlet side, the right side of the air cavity is an air outlet side, and the linear welding part is in an up-and-down fluctuating wave shape. The heat exchange plate is mainly used for improving the heat exchange efficiency while ensuring the strength of the heat exchange plate.

Description

TECHNICAL FIELD

[0001] The application relates to the field of air preheaters, in particular to a heat exchange plate. BACKGROUND

[0002] In terms of energy utilization, the exhaust gas after industrial fuel combustion contains a large amount of heat energy. In the early stage, due to the lack of recovery means, such as the large heat loss of traditional boiler exhaust gas, the heat energy is wasted. With the development of industry and the improvement of energy awareness, improving energy utilization rate is the key, and the air preheater emerges as the times require and is popularized. It relies on the principle of heat exchange to transfer the waste heat to the air, improve the combustion efficiency and reduce fuel consumption. From the early simple pipe structure of small-scale furnace to the advanced types such as rotary and plate types suitable for large-scale heavy industry, its technology is constantly innovated. The increasingly stringent environmental protection requirements further promote the development of air preheaters, which can reduce the exhaust gas temperature and reduce greenhouse gas emissions, and become an important equipment for energy saving and emission reduction in many industries such as power, steel and chemical industry, and is widely used and continuously optimized in the industrial field, and has great significance in the process of energy efficient utilization and environmental protection.

[0003] In some plate air preheaters with relatively high hardness of the plate (such as 2205 / 2507, etc.), the point-shaped welding ring cannot be inflated to form the required wave height, because the hardness of such plate is relatively large, and the ductility is also poor, so it is difficult to balance the strength of the heat exchange plate and the flow space of the flow cavity when manufacturing the heat exchange plate. If the flow cavity needs a large space, a smaller number of point-shaped welding rings are used to expand the distance between the point-shaped welding rings, but this also leads to a decrease in the strength of the middle part of the heat exchange plate. Pursuing the strength of the middle part of the heat exchange plate will increase the number of point-shaped welding rings, which will reduce the distance between the point-shaped welding rings and reduce the height of the plate, resulting in a decrease in the space of the flow cavity and the flow of air, and a decrease in the overall heat exchange efficiency. In the prior art, the welding points are changed into welding seams with a longer length, which can solve the problem of the height of the heat exchange plate and the size of the air cavity space, and the strength of the heat exchange plate. However, because the channels formed between the two adjacent welding seams are relatively independent, the gas in the channel cannot exchange with the gas in the adjacent channel, and the channel surrounded by the welding seam is a smooth space without turbulence effect, which leads to the formation of a boundary layer of air with low flow speed in the single channel near the surface of the heat exchange plate, which hinders the heat transfer. CONTENT OF THE UTILITY MODEL

[0004] The application provides a heat exchange plate to overcome the low heat exchange efficiency of the heat exchange plate with high hardness and long welding seams in the prior art, which can ensure the strength of the heat exchange plate while improving the heat exchange efficiency.

[0005] In order to achieve the above object, the technical scheme adopted by the present application is as follows: a heat exchange plate is formed by welding two thin plates arranged in front and back through a plurality of linear welding portions, the positions not welded on the two thin plates are away from each other to form an air cavity for flowing air, the left side of the air cavity is an air inlet side, the right side is an air outlet side, and the linear welding portions are in a wave shape rising and falling up and down.

[0006] After the above technical scheme is adopted, the present application has the following advantages: during the heat exchange process, a boundary layer is formed near the surface of the heat exchange plate, and the air flow speed in the boundary layer is low, which hinders the heat transfer. The wave-shaped welding portions of the present application first form a turbulent protrusion of the air cavity, can generate a turbulent effect on the air in the air cavity, make the flow path of the air in the air cavity become complex, which makes the air generate a convection effect, and the contact opportunity of the relatively cold air inside the air cavity with the heat exchange plate is significantly increased, and secondly, the original air cavity forms a wave-shaped channel, and the turbulent flow generated by the wave-shaped channel can effectively destroy the boundary layer, so that the heat transfer between the air and the heat exchange plate is no longer limited by the boundary layer, and the heat can be more smoothly transferred from the heat exchange plate to the air, further enhancing the heat exchange effect.

[0007] Further, the welding portions are continuously welded from the air inlet side to the air outlet side.

[0008] After the above technical scheme is adopted, the wave-shaped welding portions formed by continuous welding can make the connection between the two thin plates more close and firm. Compared with intermittent welding, it can better withstand the pressure generated by the air flowing in the air cavity and external forces such as vibration that the plate-type air preheater may be subjected to during operation.

[0009] Further, the welding portions are discontinuously welded from the air inlet side to the air outlet side.

[0010] After the above technical scheme is adopted, the discontinuous welding is not a continuous connection between the two thin plates, and the welding stress generated during the welding process is relatively small compared with continuous welding. When the air flows through these discontinuous welding portions, local turbulent flow and disturbance are formed. This local disturbance can break the relatively stable laminar flow state that the air may form in the air cavity, thereby promoting the heat transfer from the heat exchange plate to the air, and to a certain extent, improving the heat exchange efficiency.

[0011] Further, the region between the two thin plates located between the two adjacent welding portions up and down is a first air flow cavity, and the region between the two thin plates located between the two adjacent welding portions left and right is a second air flow cavity, and the first air flow cavity and the second air flow cavity are connected to each other.

[0012] The mutually-communicating flow air cavities can guide air to be more evenly distributed in the entire heat exchange plate region.

[0013] Further, the left and right adjacent two first flow air cavities are staggered.

[0014] The staggered arrangement can avoid the air from flowing to a certain place in the adjacent region, and under the conventional arrangement, the air tends to flow along certain fixed paths, resulting in excessive air flow in some regions and insufficient air flow in other regions.

[0015] Further, the welding portion includes at least a first welding line and a second welding line, the first welding line is close to the air inlet side, the second welding line is close to the air outlet side, and the vertical spacing between adjacent two first welding lines is smaller than the vertical spacing between adjacent two second welding lines.

[0016] As the air flows from the air inlet side to the air outlet side, the vertical spacing between adjacent two second welding lines gradually increases. This change allows the air to gradually obtain a wider flow space during the flow process, which meets the physical characteristics of the air requiring a larger flow space due to factors such as temperature rise and volume expansion during heat exchange. Moreover, the air speed at the air inlet side is relatively high, and therefore the first welding line with smaller spacing can increase the strength of the heat exchange plate.

[0017] Further, the welding portion includes at least a first welding line and a second welding line, the width of a single wave segment of the first welding line and a single wave segment of the second welding line in the left-right direction is different.

[0018] The first welding line and the second welding line have different wave segment widths, and when the air encounters welding lines with different widths, the flow direction and speed of the air will change constantly due to the differences in resistance and guiding force. The wider wave segment can cause the air to change direction relatively gently but over a larger range, and the narrower wave segment can cause the air to change direction more sharply and locally. In this way, the convection path of the air in the cavity is greatly enriched, increasing the opportunity for cold air to fully contact the heat exchange plate, allowing different temperature air to mix more fully in the cavity and exchange heat, thereby effectively improving the heat exchange efficiency.

[0019] Further, the welding part at least includes a first welding line and a second welding line, and a height difference between a wave crest and a wave trough of the first welding line is different from a height difference between a wave crest and a wave trough of the second welding line.

[0020] By using the foregoing technical solution, the height difference between the wave crest and the wave trough of the first welding line and the second welding line is different, so that the shape of the welding part is more complex. When the air flows through the air cavity, the complex shape can generate more diversified air disturbance. The air disturbances caused by the welding lines with different height differences cooperate with each other in space and intensity, and further destroy the air boundary layer. Because the height difference between the wave crest and the wave trough of the first welding line and the second welding line is different, the air disturbances and convection effects generated by the welding lines at different positions in the air cavity are different. This can make the air more uniformly distributed in the entire air cavity, and avoid the situation that local air flow is not smooth or heat exchange is insufficient.

[0021] Further, the single welding part is composed of the first welding line and the second welding line, or the welding part is the first welding line, or the welding part is the second welding line.

[0022] By using the foregoing technical solution, when the single welding part can be composed of the first welding line and the second welding line, the differences (if there are these difference characteristics) between the two in the height difference between the wave crest and the wave trough, the width in the left and right directions of a single wave band, etc. can be used to generate more fine and diversified air disturbance effects on the air flow in the air cavity. For example, the first welding line can mainly change the air flow direction on a larger scale to form macroscopic air disturbance, and the second welding line can generate more fine local air disturbance on a relatively small scale. The combination of the two can make the air boundary layer be more completely destroyed, and the convection path of the air in the cavity be more complex and sufficient, greatly improving the heat transfer efficiency and making the heat exchange effect better.

[0023] When the welding part is only the first welding line, in some working conditions, such as the air flow is relatively stable and moderate, and the requirement for heat exchange uniformity is not extremely high, the wavy structure of the first welding line itself can still generate a certain degree of air disturbance, break part of the air boundary layer, and promote the air to form convection, so as to realize relatively stable and effective heat exchange. Although the air disturbance effect may not be as rich as the combination of the two welding lines, it is sufficient to meet the basic heat exchange demand of such specific working conditions, and may have certain performance stability advantages due to the relatively simple structure.

[0024] Similarly, when the welding part is only the second welding line, in some specific working conditions such as special space layout of the air cavity, precise air flow regulation for local areas is needed to achieve efficient heat exchange, the second welding line itself can generate targeted air disturbance and guiding effect on the air flow in the specific area by virtue of its own characteristics (such as unique wave crest and wave trough morphology, wave band width, etc.), realize local efficient heat exchange, and further play a beneficial complementary role on the overall heat exchange effect.

[0025] Further, water drop-shaped flow disturbing members are arranged between the two welding portions.

[0026] By the above technical solution, the water drop-shaped flow disturbing members can generate more concentrated and strong flow disturbing effect in the specific area between the two welding portions. In some local positions of the air cavity, the flow disturbing effect generated by the welding portions may be relatively weak. The water drop-shaped flow disturbing members can make up for this deficiency. The water drop-shaped flow disturbing members can strengthen the contact and heat exchange between the air and the heat exchange plate in these local positions, so as to ensure that the air cavity can achieve efficient heat exchange in each local position, thereby improving the heat exchange uniformity of the entire heat exchange plate. BRIEF DESCRIPTION OF DRAWINGS

[0027] The application will be further described below in conjunction with the accompanying drawings:

[0028] Figure 1 FIG. 1 is a schematic view of a continuous welding portion of a heat exchange plate according to the application;

[0029] Figure 2 FIG. 2 is a schematic view of a discontinuous welding portion of a heat exchange plate according to the application;

[0030] Figure 3 FIG. 3 is a schematic view of another embodiment of a discontinuous welding portion of a heat exchange plate according to the application.

[0031] BRIEF DESCRIPTION OF DRAWINGS: 1, heat exchange plate; 2, welding portion; 21, first welding line; 22, second welding line; 3, air cavity; 31, air inlet side; 32, air outlet side; 33, first air flow cavity; 34, second air flow cavity; 4, flow disturbing member. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described clearly and completely below in conjunction with the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments of the application.

[0033] The terms "first," "second," and so on (if any) in the specification and claims of this application are used to distinguish similar objects, not to describe a specific order or precedence. Even if "second" is used before a technical feature to distinguish it, it does not necessarily imply the presence of "first." It should be understood that in this application, "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. It should be understood that in this application, "plurality" refers to two or more. "And / or" is merely a description of an association between related objects, indicating that three relationships can exist. For example, "X and / or Y" can mean: X exists alone, X and Y exist simultaneously, or Y exists alone. The character " / " generally indicates that the related objects are in an "or" relationship. "Including X, Y, and Z" means that all three of X, Y, and Z are included. "Including X, Y, or Z" means that one of X, Y, and Z is included. "Including X, Y, and / or Z" means that any one, any two, or any three of X, Y, and Z are included.

[0034] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined or replaced with each other according to actual conditions, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0035] Example 1:

[0036] like Figure 1 As shown, the present application provides a heat exchange plate 1 for a plate air preheater and a plate air preheater, wherein the heat exchange plate 1 is formed by welding two thin plates arranged in front and behind through multiple linear welding parts 2, and the unwelded parts of the two thin plates are away from each other to form an air cavity 3 for flowing air, and the left side of the air cavity 3 is the air inlet side 31, and the right side is the air outlet side 32, and the linear welding part 2 is in a wavy shape that undulates up and down.

[0037] After adopting the above technical solution, the present application has the following advantages: since during the heat exchange process, air will form a boundary layer near the surface of the heat exchange plate 1, and the air flow rate in the boundary layer is low, it will hinder the transfer of heat. The wavy welding part 2 of this solution will first form a turbulent protrusion in the air cavity, which can produce a turbulent effect on the air in the air cavity 3, making the flow path of the air in the air cavity 3 complicated, which makes the air produce a convection effect, and significantly increases the chance of contact between the colder air inside the air cavity 3 and the heat exchange plate 1. Secondly, it can form a wavy channel in the original air cavity 3, and the turbulence generated by the wavy channel can effectively destroy this boundary layer, so that the heat conduction between the air and the heat exchange plate 1 is no longer restricted by the boundary layer, and the heat can be transferred more smoothly from the heat exchange plate 1 to the air, further enhancing the heat exchange effect.

[0038] Further, the welding part 2 is continuously welded from the air inlet side 31 to the air outlet side 32.

[0039] With the foregoing technical solution, the wave-shaped welding part 2 formed by continuous welding can make the connection between the two thin plates more compact and firm. Compared with intermittent welding, it can better withstand the pressure generated by the air flowing in the air cavity 3 and the external force such as vibration that the plate-type air preheater may be subjected to during operation.

[0040] Further, the welding part 2 includes at least a first welding line 21 and a second welding line 22, and the width of a single wave segment of the first welding line 21 and the width of a single wave segment of the second welding line 22 are different in the left-right direction.

[0041] With the foregoing technical solution, the wave segment widths of the first welding line 21 and the second welding line 22 are different. When the air encounters welding lines of different widths, the flow direction and speed will change constantly due to the difference in resistance and guiding force. The wider wave segment may cause the air to turn relatively gently but over a larger range, while the narrower wave segment may cause the air to form more drastic and localized changes in flow direction. In this way, the convection path of the air in the cavity is greatly enriched, increasing the opportunity for cold air to fully contact the heat exchange plates 1, allowing different temperature air to mix more fully and exchange heat in the cavity, thereby effectively improving heat exchange efficiency.

[0042] For example Figure 3 In the embodiment, the width values of B1 and B2 are different.

[0043] Further, the welding part 2 includes at least a first welding line 21 and a second welding line 22, and the height difference between the wave peaks and wave troughs of the first welding line 21 and the height difference between the wave peaks and wave troughs of the second welding line 22 are different.

[0044] With the foregoing technical solution, the height differences between the wave peaks and wave troughs of the first welding line 21 and the second welding line 22 make the shape of the welding part 2 more complex. When the air flows through the air cavity 3, this complex shape produces more diverse turbulence. The turbulence caused by welding lines of different height differences cooperate with each other in space and intensity, further disrupting the air boundary layer. Because the height differences between the wave peaks and wave troughs of the first welding line 21 and the second welding line 22 are different, the turbulence and convection effects they produce at different positions in the air cavity 3 are different. This can make the air distribution more uniform throughout the air cavity 3, avoiding situations where air flow is not smooth or heat exchange is insufficient in some areas.

[0045] For example Figure 3 In the embodiment, the height values of H1 and H2 are different.

[0046] Further, water droplet-shaped turbulence elements 4 are arranged between the two welding parts 2.

[0047] By adopting the above-mentioned technical solution, the water drop-shaped spoiler 4 can be a spoiler rod horizontally mounted in the flue gas channel, and the cross-sectional shape of the spoiler rod is water drop-shaped. When the large and small ends of the water drop are at different angles relative to the flow direction of the flue gas, different strong spoiler effects can be generated in the specific area between the two welding parts 2. In some local positions of the air cavity 3, the spoiler generated by the welding part 2 may be relatively weak. The presence of the water drop-shaped spoiler 4 can just make up for this deficiency. It can enhance the contact and heat exchange between the air and the heat exchange plate 1 in these local areas, ensuring that efficient heat exchange can be achieved in all parts of the air cavity 3, thereby improving the heat exchange uniformity of the entire heat exchange plate 1.

[0048] Example 2:

[0049] like Figure 2 and Figure 3 As shown, the difference from Example 1 is that the welding portion 2 is formed by intermittent welding from the air inlet side 31 to the air outlet side 32.

[0050] With the aforementioned technical solution, intermittent welding does not continuously connect the two thin plates. Compared to continuous welding, the welding stress generated during the welding process is relatively small. In addition, when air flows through these intermittent welds 2, it will form local turbulence and disturbance. This local disturbance can disrupt the relatively stable laminar flow state that may have formed in the air cavity 3, thereby promoting heat transfer from the heat exchange plate 1 to the air, and to a certain extent improving heat exchange efficiency.

[0051] Furthermore, the area between the two upper and lower adjacent welding parts between the two thin plates is the first air flow cavity 33, and the area between the left and right adjacent welding parts between the two thin plates is the second air flow cavity 34. The first air flow cavity 33 and the second air flow cavity 34 are connected to each other.

[0052] Using the aforementioned technical solution, the interconnected airflow cavities can guide air to be more evenly distributed throughout the entire area of ​​the heat exchange plate 1. In some cases, if only a single type of airflow cavity is used, air may be excessively concentrated in a local area or flow may be blocked. However, the interconnected structure allows air to flexibly adjust its flow path between the two airflow cavities based on factors such as pressure differential, thereby achieving a more reasonable and uniform air flow distribution within the heat exchange plate 1, ensuring that all parts of the heat exchange plate 1 are in full contact with the air for heat exchange.

[0053] Furthermore, the two first air flow cavities 33 adjacent to each other on the left and right are arranged in a staggered manner.

[0054] The staggered arrangement can avoid the situation that air flows to a certain place in the adjacent area. In the conventional arrangement, air may tend to flow along certain fixed paths, resulting in excessive air flow in some areas and insufficient air flow in other areas. The staggered arrangement changes the layout of the air flow cavity to guide the air to be more evenly distributed in the entire heat exchange plate 1, so that each part of the heat exchange plate 1 can have a more appropriate air flow to contact and exchange heat, ensuring the uniformity of air flow during heat exchange.

[0055] Specifically, the staggered arrangement refers to that the first air flow cavity 33 on the left side and the first air flow cavity 33 on the right side are staggered in the up-down direction, so that the welding portion 2 on the left side corresponds to the first air flow cavity 33 on the right side, and the welding portion 2 on the right side corresponds to the first air flow cavity 33 on the left side.

[0056] Further, the welding portion 2 includes at least a first welding line 21 and a second welding line 22. The first welding line 21 is close to the air inlet side 31, and the second welding line 22 is close to the air outlet side 32. As shown in Figure 2 The distance between the adjacent two first welding lines 21 in the up-down direction is less than the distance between the adjacent two second welding lines 22 in the up-down direction.

[0057] With the foregoing technical solution, as the air flows from the air inlet side 31 to the air outlet side 32, the distance between the adjacent two second welding lines 22 in the up-down direction gradually increases. This change allows the air to gradually obtain a wider flow space during the flow process, which is consistent with the physical characteristics of air that requires a larger flow space due to factors such as temperature rise and volume expansion during heat exchange. In addition, the air speed at the air inlet side 31 is relatively high, so the first welding line 21 with smaller spacing can increase the strength of the heat exchange plate 1.

[0058] It can be understood that, since the first welding line 21 has a smaller spacing than the second welding line 22, in some embodiments, the number of first welding lines 21 is greater than the number of second welding lines 22.

[0059] Embodiment 3:

[0060] On the basis of Embodiment 1 and Embodiment 2, a single welding portion 2 is composed of a first welding line 21 and a second welding line 22.

[0061] With the foregoing technical solutions, when the single welding portion 2 can be composed of the first welding line 21 and the second welding line 22, the differences (if there are such difference characteristics) in the height difference between the wave peaks and wave troughs, the width in the left and right directions of a single wave band, etc. of the two can be used to produce more fine and diversified disturbance effects on the air flow in the air cavity 3. For example, the first welding line 21 can mainly change the air flow direction on a larger scale to form macroscopic disturbance, and the second welding line 22 can produce more fine local disturbance on a relatively smaller scale. The combination of the two can make the air boundary layer be more thoroughly destroyed, the convection path of the air in the cavity be more complex and sufficient, greatly improve the heat transfer efficiency, and make the heat exchange effect reach a better state.

[0062] Embodiment 4:

[0063] On the basis of Embodiment 1 and Embodiment 2, the welding portion 2 is the first welding line 21.

[0064] With the foregoing technical solutions, when the welding portion 2 is only the first welding line 21, in some working conditions, such as the air flow is relatively stable and moderate, and the requirement for heat exchange uniformity is not extremely high, the wavy structure of the first welding line 21 can still produce a certain degree of disturbance, break part of the air boundary layer, promote the air to form convection, and realize relatively stable and effective heat exchange. Although the disturbance effect may not be as rich as that of the combination of the two welding lines, it is sufficient to meet the basic heat exchange demand of such specific working conditions, and at the same time, it can have certain performance stability advantages due to the relatively simple structure.

[0065] Embodiment 4:

[0066] On the basis of Embodiment 1 and Embodiment 2, the welding portion 2 is the second welding line 22.

[0067] With the foregoing technical solutions, similarly, when the welding portion 2 is only the second welding line 22, in some specific working conditions such as the special spatial layout of the air cavity 3, the need to accurately regulate the air flow in a local area to realize efficient heat exchange, the second welding line 22 can produce targeted disturbance and guidance on the air flow in the specific area by virtue of its own characteristics (such as the unique wave peak and wave trough morphology, wave band width, etc.), realize local efficient heat exchange, and thus play a beneficial complementary role on the overall heat exchange effect.

[0068] In addition to the preferred embodiments described above, the present application also has other embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without making creative efforts fall within the scope of the present application.

Claims

1. A heat exchange plate, characterized in that: The heat exchange plate is formed by welding two thin plates arranged in front and behind through multiple linear welding parts. The unwelded parts of the two thin plates are away from each other to form an air cavity for flowing air. The left side of the air cavity is the air inlet side, and the right side is the air outlet side. The linear welding parts are wavy and undulate.

2. A heat exchange plate according to claim 1, characterized in that: The welding portion is formed by continuous welding from the air inlet side to the air outlet side.

3. The heat exchange plate according to claim 1, characterized in that: The welding portion is formed by intermittent welding from the air inlet side to the air outlet side.

4. The heat exchange plate according to claim 3, characterized in that: The area between the two upper and lower adjacent welding parts between the two thin plates is the first air flow cavity, and the area between the left and right adjacent welding parts between the two thin plates is the second air flow cavity. The first air flow cavity and the second air flow cavity are connected to each other.

5. The heat exchange plate according to claim 4, characterized in that: The two first air flow cavities adjacent to each other on the left and right are arranged alternately.

6. The heat exchange plate according to claim 3, characterized in that: The welding portion includes at least a first welding line and a second welding line, wherein the first welding line is close to the air inlet side, and the second welding line is close to the air outlet side, and the vertical distance between two adjacent first welding lines is smaller than the vertical distance between two adjacent second welding lines.

7. The heat exchange plate according to claim 1, characterized in that: The welding portion includes at least a first welding line and a second welding line, and a single wave segment of the first welding line and a single wave segment of the second welding line have different widths in the left-right direction.

8. The heat exchange plate according to claim 1, characterized in that: The welding portion includes at least a first welding line and a second welding line, and the height difference between the crest and trough of the first welding line is different from the height difference between the crest and trough of the second welding line.

9. A heat exchange plate according to any one of claims 7 and 8, characterized in that: The single welding portion is composed of a first welding line and a second welding line, or the welding portion is the first welding line, or the welding portion is the second welding line.

10. The heat exchange plate according to claim 1, characterized in that: A water drop-shaped spoiler is also provided between the two welding portions.

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