A leakage-proof structure and a centripetal turbine

Abstract

This invention belongs to the field of radial turbines, specifically relating to a leakage prevention structure and a radial turbine. One leakage prevention structure includes a first inlet pipe, a first outlet pipe, and a second outlet pipe; the outlet of the first inlet pipe is connected to the inlet of the first outlet pipe and the inlet of the second outlet pipe, respectively; the leakage prevention structure is installed at the tip of the moving blade, allowing pressure-side fluid to enter the first inlet pipe, fluid ejected from the first outlet pipe to act within the gap, and fluid ejected from the second outlet pipe to act on the suction side. The leakage prevention structure of this invention can introduce pressure-side fluid into the gap and suction side, thereby reducing blade load; on the other hand, the fluid flowing into the gap significantly increases the leakage flow resistance, reducing the leakage flow rate; the fluid flowing into the suction side impacts the leakage vortex, weakening the leakage vortex intensity and further reducing the leakage flow rate; thus, it has the effect of weakening the leakage vortex intensity, reducing losses, and improving turbine efficiency.

Description

Technical Field

[0001] This invention belongs to the field of centripetal turbines, specifically relating to a leakage prevention structure and a centripetal turbine. Background Technology

[0002] A radial turbine is a compact power unit characterized by radial flow. To avoid friction between the blades and the casing of the radial turbine, there is a gap between the blade tip and the casing, which will result in gap leakage. Therefore, it is necessary to improve the gap leakage problem of the radial turbine.

[0003] Chinese Patent CN101699037B discloses a method for suppressing tip leakage flow to improve the efficiency of an impeller and a reverse vortex generator thereof. The method for suppressing tip leakage flow is characterized by ejecting airflow in the opposite direction of the leakage flow to form a reverse vortex flow, thereby suppressing tip airflow leakage. The airflow has an outflow angle of 30° to 70°.

[0004] Although this solution suppresses leakage by using a reverse eddy current generator, leakage is still a problem.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the present invention provides a leakage prevention structure and a radial turbine. The leakage prevention structure of the present invention can introduce pressure-side fluid into the gap and suction side, which on the one hand reduces the blade load; on the other hand, the fluid flowing into the gap significantly increases the leakage flow resistance and reduces the leakage flow rate; the fluid flowing into the suction side impacts the leakage vortex, weakens the leakage vortex intensity, and further reduces the leakage flow rate; thus, it has the effect of weakening the leakage vortex intensity, reducing losses, and improving turbine efficiency.

[0007] This invention includes the following technical solutions:

[0008] The present invention provides a first aspect of a leakage prevention structure, including a first air inlet pipe, a first air outlet pipe, and a second air outlet pipe; the outlet of the first air inlet pipe is connected to the inlet of the first air outlet pipe and the inlet of the second air outlet pipe respectively; the leakage prevention structure is used to be installed at the tip of the moving blade, so that the fluid on the pressure side enters the first air inlet pipe, the fluid ejected from the first air outlet pipe acts within the gap, and the fluid ejected from the second air outlet pipe acts on the suction side.

[0009] Furthermore, the inlet end of the first air intake pipe is provided with a beveled surface.

[0010] Furthermore, the outlet end of the second vent pipe is provided with a beveled surface.

[0011] Furthermore, the diameter D1 of the first intake pipe is greater than the diameter D3 of the first outlet pipe 20; and the diameter D1 of the first intake pipe is greater than the diameter D2 of the second outlet pipe.

[0012] A second aspect of the present invention provides a centripetal turbine, including a casing, a rotor, and a leakage prevention structure as described above, wherein the rotor is disposed within the casing, and the tips of the rotor blades are provided with a plurality of the leakage prevention structures.

[0013] Furthermore, the anti-leakage structure is arranged at 40%-95% of the meridional chord region of the moving blade.

[0014] Furthermore, the angle between the first intake pipe and the middle arc is ≤30°.

[0015] Furthermore, the angle between the second air outlet pipe and the middle arc is , and the value range of is 30°-90°.

[0016] Furthermore, the first intake pipe is located on the suction side, the first intake pipe is located in the gap between the moving blade and the casing, and the second intake pipe is located on the pressure side.

[0017] Furthermore, the distance between the air inlet of the first air inlet pipe and the plane where the blade tip is located is H1, where H1≤15h; and h is the clearance height between the moving blade and the casing.

[0018] Furthermore, the distance between the outlet of the second exhaust pipe and the plane where the blade tip is located is H2, 4h≤H2≤9h; where h is the clearance height between the moving blade and the casing.

[0019] Furthermore, the distance between the outlet of the first exhaust pipe and the pressure surface is W1, where 0.5h ≤ W1 ≤ 1.5h; and h is the clearance height between the moving blade and the casing.

[0020] By adopting the above technical solution, the present invention has the following advantages:

[0021] 1. The anti-leakage structure of the present invention can introduce the pressure-side fluid into the gap and the suction side, which on the one hand reduces the blade load; on the other hand, the fluid flowing into the gap significantly increases the leakage flow resistance and reduces the leakage flow rate; the fluid flowing into the suction side impacts the leakage vortex, weakens the leakage vortex intensity, and further reduces the leakage flow rate; it has the effect of weakening the leakage vortex intensity, reducing losses, and improving turbine efficiency.

[0022] 2. The anti-leakage structure of the present invention is applicable to centripetal turbines with large expansion ratios and high speeds.

[0023] 3. This invention controls leakage loss from both leakage flow and leakage vortex aspects. The design has a large degree of freedom and is highly adaptable to the geometry and operating conditions of centripetal turbines with large expansion ratios.

[0024] 4. The anti-leakage structure of the present invention is simple and easy to manufacture.

[0025] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention can be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a leakage prevention structure in an embodiment of the present invention. Figure 1 ;

[0028] Figure 2 This is a schematic diagram of a leakage prevention structure in an embodiment of the present invention. Figure 2 ;

[0029] Figure 3 This is a schematic diagram of the structure of a centripetal turbine in an embodiment of the present invention;

[0030] Figure 4 This is a schematic diagram showing the angle between the anti-leakage structure and the middle arc line in an embodiment of the present invention;

[0031] Figure 5 This is a schematic diagram of the structure of the large expansion centripetal turbine in an embodiment of the present invention;

[0032] In the figure, 10-first intake pipe, 20-first exhaust pipe, 30-second exhaust pipe, 40-moving blade, 1-guide vane, 2-gap, 3-blade tip, 4-casing, 6-gap, 7-back of the wheel, 8-back cavity of the wheel, 9-back sealing flow, 10-hub. Detailed Implementation

[0033] The following description provides many different embodiments or examples for implementing various features of the invention. The elements and arrangements described in the specific examples below are only for concise expression of the invention and are merely examples, not intended to limit the invention.

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The structure of a centripetal turbine is as follows Figure 5 As shown, the centripetal turbine mainly includes guide vanes 1, gaps 2, blade tips 3, casing 4, moving blades 40, gaps 6, back of the impeller 7, back cavity of the impeller 8, back sealing flow 9, and hub 10. Multiple guide vanes 1 and moving blades 40 are evenly distributed circumferentially to form the stator and rotor; their number, geometry, and structural dimensions are determined by design parameters. The working fluid enters through the inlet of guide vane 1, is accelerated and has its flow direction changed by the guide vane 1, and then enters through the inlet of moving blade 40, driving the moving blade 40 to rotate and do work. While the airflow does work within the impeller, its flow direction also changes. In addition to the mainstream fluid, there are two additional fluids inside the impeller: the back sealing flow 9 and the blade tip leakage flow. The back sealing flow 9 passes through the back of the impeller 7 and the back cavity of the impeller 8, and enters the blade tip 3 through the back gap 6. The blade tip leakage flow flows from the pressure side to the suction side of the blade through the blade tip gap 2, and then enters the mainstream flow channel, mixing with the mainstream. The losses caused by leakage flow are mainly affected by the pressure difference between the blade tip pressure surface and the suction surface and the scraping flow generated by the relative motion between the blade tip and the casing 4. The loss mechanisms of the two are not the same.

[0036] Experiments revealed that in the axial clearance section of the radial impeller inlet, the clearance flow is primarily driven by scraping flow, which to some extent suppresses the tip clearance leakage flow driven by the circumferential pressure difference between the suction and pressure surfaces. However, in the radial clearance section at the impeller outlet, as the impeller radius decreases, the influence of scraping flow gradually diminishes, and leakage flow becomes dominant. The leakage flow losses caused by the clearance are mainly divided into two parts: 1) the presence of leakage flow reduces the mainstream flow rate, resulting in reduced work output; 2) the leakage flow mixes with the mainstream flow, forming leakage vortices and causing mixing losses. Approximately one-third of the flow losses in a turbine are caused by tip clearance leakage flow. Therefore, to effectively control the leakage flow and significantly improve turbine efficiency, it is necessary to control both the leakage flow and leakage vortices.

[0037] This embodiment provides a leakage prevention structure, such as Figure 1 , Figure 2As shown, it includes a first air inlet pipe 10, a first air outlet pipe 20, and a second air outlet pipe 30; the outlet of the first air inlet pipe 10 is connected to the inlet of the first air outlet pipe 20 and the inlet of the second air outlet pipe 30, respectively; the anti-leakage structure is used to be installed at the tip of the moving blade 40, so that the fluid on the pressure side enters the first air inlet pipe 10, the fluid ejected from the first air outlet pipe 20 acts in the gap, and the fluid ejected from the second air outlet pipe 30 acts on the suction side.

[0038] In some embodiments, such as Figure 1 As shown, the inlet end of the first air intake pipe 10 is provided with a beveled surface.

[0039] In some embodiments, such as Figure 1 As shown, the outlet end of the second air outlet pipe 30 is provided with a beveled surface.

[0040] In some embodiments, such as Figure 2 As shown, the diameter D1 of the first intake pipe 10 is larger than the diameter D3 of the first outlet pipe 20; the diameter D1 of the first intake pipe 10 is larger than the diameter D2 of the second outlet pipe 30. This ensures sufficient intake volume, significantly increasing the flow resistance of the leakage flow and reducing the leakage flow rate; the fluid flowing into the suction side impacts the leakage vortex, weakening the leakage vortex intensity; thereby further reducing the leakage flow rate.

[0041] In some embodiments, the diameter D3 of the first outlet pipe 20 is ≥ 0.3 mm. Limiting the pipe diameter allows the fluid to flow faster within the pipe, which helps to improve the suppression effect and ensures that the outlet has sufficient air volume to impact the leakage vortex.

[0042] This embodiment also provides a centripetal turbine, such as Figure 3 As shown, it includes a casing, a rotor, and the aforementioned anti-leakage structure. The rotor is disposed inside the casing, and the blade tips of the rotor's moving blades 40 are provided with multiple anti-leakage structures.

[0043] In some embodiments, the anti-leakage structure is arranged at 40%-95% of the meridional chord region of the moving blade 40. The vortex structure formed by leakage in a high-expansion-ratio radial turbine mainly consists of leakage vortices and scraping vortices. The scraping ratio is relatively large at the blade leading edge, where leakage is primarily affected by scraping, and changes in tip load have a relatively small impact on leakage. As the flow direction increases, changes in tip load have a greater impact on leakage, at which point the load plays a dominant role, the leakage vortex gradually increases, and aerodynamic losses increase. Therefore, arranging this structure at the mid-to-trail edge (40%-95% of the meridional chord region) can reduce tip load and improve leakage flow suppression. Furthermore, the leakage vortex changes along the chord length by first increasing, then decreasing, and then increasing again. Near the 40% region of the meridional chord, the size and intensity of the leakage vortex are smaller, making it easier to suppress.

[0044] In some embodiments, such as Figure 4 As shown, the angle between the first intake pipe 10 and the middle arc is... , ≤30°. This has the advantage of avoiding significant mixing losses at the tail end.

[0045] In some embodiments, such as Figure 4 As shown, the angle between the second exhaust pipe 30 and the central arc is... , The value range is 30°-90°. The limitation on its value helps to reduce its mixing loss with the mainstream; it also allows the airflow ejected from the second outlet pipe 30 to act more effectively on the leakage vortex.

[0046] In some embodiments, the first intake pipe 10 is located on the suction side, the first intake pipe 10 is located in the gap between the moving blade 40 and the casing, and the second intake pipe is located on the pressure side.

[0047] In some embodiments, the distance between the air inlet of the first air inlet pipe 10 and the plane where the blade tip is located is H1, where H1 ≤ 15h; and h is the clearance height between the moving blade 40 and the casing. This design enhances the anti-leakage structure and reduces the load on the moving blade 40.

[0048] In some embodiments, the distance between the outlet of the second exhaust pipe 30 and the plane containing the blade tip is H2, where 4h ≤ H2 ≤ 9h; and h is the clearance height between the moving blade 40 and the casing. This design enhances the leakage prevention structure and weakens leakage vortices.

[0049] In some embodiments, the distance between the outlet of the first exhaust pipe 20 and the pressure surface is W1, where 0.5h ≤ W1 ≤ 1.5h; and h is the clearance height between the moving blade 40 and the casing. This ensures that the outlet of the first exhaust pipe 20 is within the separation bubble, further improving the suppression of leakage flow.

[0050] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0051] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A centripetal turbine, characterized in that, It includes a casing, a rotor, and a leak-proof structure. The rotor is disposed inside the casing, and the tips of the rotor blades (40) are provided with multiple leak-proof structures. The anti-leakage structure includes a first air inlet pipe (10), a first air outlet pipe (20), and a second air outlet pipe (30); the outlet of the first air inlet pipe (10) is connected to the inlet of the first air outlet pipe (20) and the inlet of the second air outlet pipe (30), respectively; the anti-leakage structure is used to be installed at the tip of the moving blade (40) so that the fluid on the pressure side enters the first air inlet pipe (10), the fluid ejected from the first air outlet pipe (20) acts in the gap, and the fluid ejected from the second air outlet pipe (30) acts on the suction side; The inlet end of the first air intake pipe (10) is provided with a beveled surface; The outlet end of the second air outlet pipe (30) is provided with a beveled surface; The diameter D1 of the first air inlet pipe (10) is greater than the diameter D3 of the first air outlet pipe (20); and the diameter D1 of the first air inlet pipe (10) is greater than the diameter D2 of the second air outlet pipe (30).

2. A centripetal turbine according to claim 1, characterized in that, The anti-leakage structure is arranged at 40%-95% of the meridional chord region of the moving blade (40).

3. A centripetal turbine according to claim 2, characterized in that, The angle between the first intake pipe (10) and the middle arc line is , ≤30°.

4. A centripetal turbine according to claim 3, characterized in that, The angle between the second exhaust pipe (30) and the middle arc is , The value range is 30°-90°.

5. A centripetal turbine according to claim 4, characterized in that, The distance between the air inlet of the first air inlet pipe (10) and the plane where the blade tip is located is H1, where H1≤15h; where h is the clearance height between the moving blade (40) and the casing.

6. A centripetal turbine according to claim 4, characterized in that, The distance between the outlet of the second exhaust pipe (30) and the plane where the blade tip is located is H2, 4h≤H2≤9h; where h is the clearance height between the moving blade (40) and the casing.

7. A centripetal turbine according to claim 4, characterized in that, The distance between the outlet of the first exhaust pipe (20) and the pressure surface is W1, 0.5h≤W1≤1.5h; where h is the clearance height between the moving blade (40) and the casing.

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