Low-temperature turbine with standing vortex drainage device

Abstract

The low-temperature turbine comprises the standing vortex drainage device, the standing vortex drainage device comprises at least one bent tooth assembly and at least one drainage channel, each bent tooth assembly comprises lower bent teeth and upper bent teeth, the lower bent teeth and the upper bent teeth are arranged at intervals in the R direction, the lower bent teeth are arranged on the wheel back of an impeller, and the upper bent teeth are arranged on an inner casing; the lower bent teeth limit a first groove, the upper bent teeth limit a second groove, and the opening directions of the first groove and the second groove are opposite; each drainage channel is at least partially arranged on the back of the impeller, and the first groove is communicated with the turbine outlet through the drainage channels. According to the low-temperature turbine with the trapped vortex drainage device, bidirectional leakage flow in the wheel back cavity can be effectively restrained, fluctuation of a floating temperature zone of the air bearing is weakened, and the aerodynamic efficiency of the low-temperature turbine and the operation stability of a low-temperature system are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of cryogenic technology, and more particularly to a cryogenic turbine with a vortex retainer flow guide. Background Art

[0002] With the development of cryogenic science, large cryogenic systems in the liquid helium temperature range have received increasing attention and are widely used in frontier fields such as nuclear fusion, high-energy physics, and superconducting systems. The core component of a cryogenic system is a cryogenic turbine expander (hereinafter referred to as a cryogenic turbine), and its performance is related to the economy and feasibility of the entire cryogenic system.

[0003] As Figure 1 shown, the existing cryogenic turbine includes an impeller 10 (usually a centripetal type), an outer casing 20, nozzle stator blades 30, an inner casing 40, an air-bearing 50, a main shaft 60, and fasteners 70 (such as screws). There is a tip clearance between the top of the impeller 10 and the outer casing 20, and there is a rotor-stator transition cavity between the outlet annulus of the nozzle stator blades 30 and the inlet annulus of the rotor blades 11 of the impeller 10. A backspace cavity 80 is formed between the back of the impeller 10 and the inner casing 40, an axial clearance is formed between the main shaft 60 and the inner casing 40, and a pressure stabilizing groove cavity exists between the inner casing 40 and the air-bearing 50. The tip clearance, the rotor-stator transition cavity, the backspace cavity 80, the axial clearance, and the pressure stabilizing groove cavity are interconnected to form a leakage flow path. When the cryogenic turbine is operating, the flow path of the cryogenic gas medium is to enter the cryogenic turbine from the turbine inlet 110, and then after passing through the nozzle stator blades 30, it is divided into a main flow and a leakage flow. The main flow accounts for most of the cryogenic gas medium, and after passing through the rotor blades 11, it leaves from the turbine outlet 120. The leakage flow accounts for a small part and is transmitted in the leakage flow path. The leakage flow passes through the main shaft clearance labyrinth 61 downstream of the backspace cavity 80 and enters the pressure stabilizing groove cavity. The leakage flow in the pressure stabilizing groove cavity will cause operation hazards and failures of the air-bearing 50, and will also significantly reduce the efficiency of the cryogenic turbine. Therefore, adopting appropriate technical means to control the leakage flow of the cryogenic turbine is an important way to improve the efficiency of the cryogenic turbine and enhance the stability of the cryogenic system.

[0004] Currently, the main means of controlling the leakage flow applied to cryogenic turbines are: As Figure 2As shown in the figure, by opening an air flow channel 40a inside the inner casing 40, one end of the air flow channel 40a extends to communicate with the outside, and the other end extends to the main shaft labyrinth seal 61. Through the air flow channel 40a, normal temperature air flow is introduced from the outside to the main shaft labyrinth seal 61 to form an inflatable seal. However, this method requires an external differential pressure valve to regulate the inflation pressure to meet the sealing of the leakage flow under different rotational speed conditions. If the inflation pressure is too low, the inflation sealing effect is poor; on the contrary, if the inflation pressure is too high, it will break through the wheel back cavity and enter the mainstream area, affecting the low temperature effect. Therefore, it is difficult to regulate the opening of the valve, especially during the on-site implementation of the last-stage turbine, and the sealing effect of this means is not good. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-temperature turbine with a vortex retainer to effectively control the bidirectional leakage of low-temperature gas medium in the leakage flow path, thereby improving the working efficiency and enhancing the operation stability.

[0006] Based on the above purpose, the present invention provides a low-temperature turbine with a vortex retainer, including an impeller, an outer casing, nozzle stator blades, an inner casing, an aerostatic bearing and a main shaft. There is a tip clearance between the top of the impeller and the outer casing, a rotor-stator handover cavity between the outlet annulus of the nozzle stator blades and the inlet annulus of the rotor blades of the impeller, a wheel back cavity is formed between the wheel back of the impeller and the inner casing, an axial clearance is formed between the main shaft and the inner casing, and a pressure stabilizing groove cavity exists between the inner casing and the aerostatic bearing. The tip clearance, the rotor-stator handover cavity, the wheel back cavity, the axial clearance and the pressure stabilizing groove cavity communicate with each other to form a leakage flow path. The low-temperature turbine is characterized in that it further includes a vortex retainer, and the vortex retainer includes at least one curved tooth assembly and at least one drainage channel. Each curved tooth assembly includes a lower curved tooth and an upper curved tooth. The lower curved tooth and the upper curved tooth are arranged at intervals along the R direction. The lower curved tooth is arranged on the wheel back of the impeller, and the upper curved tooth is arranged on the inner casing; the lower curved tooth defines a first groove, the upper curved tooth defines a second groove, and the opening directions of the first groove and the second groove are opposite; each drainage channel is at least partially arranged on the wheel back of the impeller, and the first groove communicates with the turbine outlet through the drainage channel.

[0007] Further, the lower curved tooth and the wheel back of the impeller are integrally formed, and the upper curved tooth and the inner casing are integrally formed.

[0008] Further, the projected profile of the lower curved tooth includes a first inner ring and a first outer ring. The first inner ring is an arc tangent to the wheel back of the impeller; the first outer ring is formed by offsetting the first inner ring by a first preset distance along the R direction, and both ends of the first outer ring and the first inner ring are connected by two first line segments extending in the R direction to form a closed projected profile.

[0009] Further, the diameter of the first inner ring is 1 / 2 to 3 / 4 of the Z-direction width of the wheel back cavity; the first preset distance is 1 / 5 to 1 / 8 of the diameter of the first inner ring.

[0010] Further, the projected profile of the upper curved tooth includes a second inner ring and a second outer ring. The second inner ring is an arc tangent to the inner casing; the second outer ring is formed by offsetting the second inner ring by a second preset distance in the R direction. The two ends of the second outer ring and the second inner ring are connected by two second line segments extending in the R direction to form a closed projected profile.

[0011] Further, the diameter of the second inner ring is 1 / 2 to 3 / 4 of the Z-direction width of the wheel back cavity; the second preset distance is 1 / 5 to 1 / 8 of the diameter of the second inner ring.

[0012] Further, the drainage channel includes an outlet and at least one inlet. The inlets correspond to the curved tooth assemblies one by one. Each inlet communicates with the first groove of the lower curved tooth of the corresponding curved tooth assembly, and the outlet communicates with the turbine outlet.

[0013] Further, each inlet is located below the center of the first inner ring of the projected profile of the lower curved tooth of the corresponding curved tooth assembly, and the R-direction distance between the inlet and the center of the first inner ring does not exceed 1 / 4 of the diameter of the first inner ring.

[0014] Further, it further includes a fastener for fixing the impeller to the main shaft. The drainage channel includes a first part and a second part. The first part is provided on the wheel back of the impeller, the second part is provided on the fastener, the outlet of the drainage channel is provided on the second part, and the inlet of the drainage channel is provided on the first part.

[0015] Further, there are multiple drainage channels, which are evenly arranged in the circumferential direction.

[0016] For the cryogenic turbine with a vortex drainage device of the present invention, by arranging a vortex drainage device in the wheel back cavity, the bidirectional leakage flow in the wheel back cavity can be effectively suppressed, and the stable leakage flow vortex is drained to the turbine outlet, further weakening the fluctuation of the floating temperature zone of the aerostatic bearing, and significantly improving the aerodynamic efficiency of the cryogenic turbine with a vortex drainage device and the operation stability of the cryogenic system. Description of the Drawings

[0017] Figure 1 It is a partial cross-sectional view of an existing cryogenic turbine without an air flow channel;

[0018] Figure 2Partial cross-sectional view of an existing low-temperature turbine with an air flow channel set;

[0019] Figure 3 Partial cross-sectional view of a low-temperature turbine with a vortex retaining flow deflector according to an embodiment of the present invention;

[0020] Figure 4 Schematic diagram of the principle of suppressing leakage flow of the vortex retaining flow deflector according to an embodiment of the present invention;

[0021] Figure 5 Schematic diagram of the principle of suppressing reverse leakage flow of the vortex retaining flow deflector according to an embodiment of the present invention. Detailed implementation manners

[0022] The following combines the accompanying drawings to give a preferred embodiment of the present invention and describes it in detail.

[0023] As Figure 3 shown, an embodiment of the present invention provides a low-temperature turbine with a vortex retaining flow deflector. On the basis of the existing low-temperature turbine, a vortex retaining flow deflector is added. The vortex retaining flow deflector is arranged in the back-wheel cavity 80 and is used to control the bidirectional leakage of the low-temperature gas working medium in the leakage flow channel. The vortex retaining flow deflector includes at least one curved tooth assembly and at least one flow deflector channel 13. Each curved tooth assembly includes a lower curved tooth 12 and an upper curved tooth 41. The lower curved tooth 12 and the upper curved tooth 41 are arranged at intervals along the extending direction of the back-wheel cavity 80 (i.e., the R direction). The lower curved tooth 12 is arranged on the back of the impeller 10, and the upper curved tooth 41 is arranged on the inner casing 40, that is, the lower curved tooth 12 and the upper curved tooth 41 are staggered; the lower curved tooth 12 defines a first groove 12a, and the upper curved tooth 41 defines a second groove 41a. The opening directions of the first groove 12a and the second groove 41a are opposite, so that the first groove 12a and the second groove 41a face each other (i.e., face to face). For example, the opening of the first groove 12a faces upward, and the opening of the second groove 41a faces downward; at least part of the flow deflector channel 13 is arranged on the back of the impeller 10. The first groove 12a is communicated with the flow deflector channel 13, and the flow deflector channel 13 is communicated with the turbine outlet 120. The flow deflector channel 13 is used to communicate the first groove 12a with the turbine outlet 120, so that the leakage flow in the back-wheel cavity 80 can be guided to the turbine outlet 120, avoiding the leakage flow from entering the pressure stabilizing tank cavity and causing operation hazards and failures of the air floating bearing 50.

[0024] In some embodiments, the lower curved tooth 12 can be integrally formed with the back of the impeller 10, and the upper curved tooth 41 can be integrally formed with the inner casing 40.

[0025] In some embodiments, the number of the bent tooth assemblies can be set according to the actual situation. Specifically, the number of the bent tooth assemblies is related to the extension length of the wheel back cavity. The longer the extension length of the wheel back cavity is, the more the number of the bent tooth assemblies is; the shorter the extension length of the wheel back cavity is, the fewer the number of the bent tooth assemblies is. Exemplarily, the number of the bent tooth assemblies is two.

[0026] In some embodiments, the projected profiles of the upper bent tooth 41 and the lower bent tooth 12 in the ZR plane are both crescent-shaped, and the concave surfaces of the crescent shapes are used to define the first groove or the second groove. Specifically, the projected profile of the lower bent tooth 12 includes a first inner ring 12b and a first outer ring 12c. The first inner ring 12b is an arc (preferably a semi-circle) tangent to the wheel back of the impeller 10, and the diameter of the first inner ring 12b is 1 / 2 to 3 / 4 of the Z-direction width of the wheel back cavity 80; the first outer ring 12c is formed by offsetting the first inner ring 12b by a first preset distance in the R direction (for example, it can be 1 / 5 to 1 / 8 of the diameter of the first inner ring 12b). Therefore, the length and diameter of the first outer ring 12c are the same as those of the first inner ring 12b. The two ends of the first outer ring 12c and the first inner ring 12b are connected by two first line segments extending in the R direction, so that the first outer ring 12c, the first inner ring 12b and the two first line segments form a closed profile, which is the projected profile of the lower bent tooth 12. The projected profile of the upper bent tooth 41 includes a second inner ring 41b and a second outer ring 42c. The second inner ring 41b is an arc (preferably a semi-circle) tangent to the inner casing 40, and the diameter of the second inner ring 41b is 1 / 2 to 3 / 4 of the Z-direction width of the wheel back cavity 80; the second outer ring 41c is formed by offsetting the second inner ring 41b by a second preset distance in the R direction (for example, it can be 1 / 5 to 1 / 8 of the diameter of the second inner ring 41b). Therefore, the length and diameter of the second outer ring 41c are the same as those of the second inner ring 41b. The two ends of the second outer ring 41c and the second inner ring 41b are connected by two second line segments extending in the R direction, so that the second outer ring 41c, the second inner ring 41b and the two second line segments form a closed profile, which is the projected profile of the upper bent tooth 41.

[0027] The drainage channel 13 includes an outlet 132 and at least one inlet 131. Each inlet 131 corresponds to each bent tooth assembly one by one. Each inlet 131 communicates with the first groove 12a of the lower bent tooth 12 of the corresponding bent tooth assembly, and the outlet 132 communicates with the turbine outlet 120. Each inlet 131 is located below the center of the first inner ring 12b of the projected profile of the lower bent tooth 12 of the corresponding bent tooth assembly, and the R-direction distance between the inlet 131 and the center of the first inner ring 12b does not exceed 1 / 4 of the diameter of the first inner ring 12b.

[0028] In some embodiments, the fastener 70 is used to fix the impeller 10 to the main shaft 60; the drainage channel 13 may include a first part and a second part. The first part is disposed on the back of the impeller 10, and the second part is disposed on the fastener 70. The outlet 132 of the drainage channel 13 is disposed on the second part, and the inlet 131 of the drainage channel 13 is disposed on the first part. That is, the drainage channel 13 penetrates through the back of the impeller 10 and the fastener 70, and the leakage flow reaches the turbine outlet 120 after passing through the back of the impeller 10 and the fastener 70 in sequence. The first part and the second part are in communication with each other and have the same diameter, and the diameter is preferably less than 1 / 4 of the diameter of the fastener 70.

[0029] In some embodiments, there are multiple drainage channels 13, which are evenly arranged in the circumferential direction.

[0030] The parameter indexes of the vortex retention drainage device include: the inner ring envelope angle θ1 of the downward-bent tooth 12 (i.e., the size of the central angle corresponding to the first inner ring 12b), the first inner ring radius R1, the inner ring envelope angle θ2 of the upward-bent tooth 41 (i.e., the size of the central angle corresponding to the second inner ring 41b), the second inner ring radius R2, the R-direction spacing W1 between two adjacent downward-bent teeth 12 of two adjacent bent tooth assemblies, the R-direction spacing W2 between two adjacent upward-bent teeth 41 of two adjacent bent tooth assemblies, the spacing L between two adjacent bent tooth assemblies, the diameter D of the drainage channel 13, and the number of bent tooth assemblies. The specific values of these parameter indexes can be determined according to the cryogenic turbine structure and the actual design and operating condition parameters.

[0031] As Figure 4 shown, the principle of the vortex retention drainage device of the embodiment of the present invention for suppressing the leakage flow is as follows:

[0032] When the cryogenic turbine is operating normally, the cryogenic gas working medium is divided into the mainstream and the leakage flow during the process from the nozzle stator blade 30 to the rotor blade 11. The mainstream flows out from the turbine outlet 120 after passing through the rotor blade 11, and the leakage flow enters the back cavity 80 after passing through the stator-rotor interface cavity and flows downward in the back cavity 80. Therefore, the leakage flow will first reach the convex surface of the upward-bent tooth 41 of the bent tooth assembly of the vortex retention drainage device. Under the guidance of the upward-bent tooth 41, a part of it enters the first groove 12a of the downward-bent tooth 12 to form a leakage flow vortex retention, and the other part flows to the upward-bent tooth 41 of the next bent tooth assembly and repeats the above process. Thus, after passing through multiple bent tooth assemblies, a stable vortex group can be formed and retained. The leakage flow vortex retention in the first groove 12a is discharged from the turbine outlet 120 through the drainage channel 13, thereby significantly suppressing the leakage flow from entering the axial clearance and the pressure stabilizing cavity. The outlet 132 of the drainage channel 13 can be located downstream of the mainstream, so that the flow mixing effect is low and the influence on the working efficiency of the cryogenic turbine is weak.

[0033] As Figure 5 shown, the principle of the vortex retention drainage device of the embodiment of the present invention for suppressing the leakage reverse flow is as follows:

[0034] When the cryogenic system is in an abnormal operating condition, the cryogenic turbine will experience short-term shutdown or restart. At this time, the leakage flow in the back of the wheel cavity 80 will be sucked back by the mainstream jet, generating a leakage reverse flow. At this time, the leakage reverse flow from the axial clearance will first pass through the convex surface of the lower bent tooth 12, and after being guided by it, enter the second groove 41a of the upper bent tooth 41, and then enter the next bent tooth assembly after being guided by the concave surface of the upper bent tooth 41. Thus, after passing through multiple bent tooth assemblies, an effective flow resistance can be formed to inhibit the leakage flow from being sucked into the mainstream channel. Since the reverse leakage flow rate is relatively low, there is no need to set a drainage channel similar to that at the lower bent tooth 12 at the upper bent tooth 41.

[0035] It should be noted that the vortex retention flow guide of the embodiment of the present invention can be used not only for the expansion end of the cryogenic turbine, but also for the braking end of the cryogenic turbine. Therefore, cryogenic turbines provided with a vortex retention flow guide at the expansion end and / or the braking end all fall within the protection scope of the present invention.

[0036] The cryogenic turbine with a vortex retention flow guide according to the embodiment of the present invention can effectively inhibit the bidirectional leakage flow in the back of the wheel cavity 80 by arranging a vortex retention flow guide in the back of the wheel cavity 80. The stable leakage flow vortex is guided to the turbine outlet 120, further weakening the fluctuation of the floating temperature zone of the aerostatic bearing, and significantly improving the aerodynamic efficiency of the cryogenic turbine and the operation stability of the cryogenic system.

[0037] In the present invention, the Z direction is the axial direction of the main shaft 60, and the R direction is the radial direction of the main shaft 60.

[0038] It should be understood that the directional terms such as up, down, left, and right used in the present invention are all descriptive terms set for clearly describing the relative position relationship between components, and do not constitute any limitation on the actual use, installation, or operation direction of the present invention. These directional descriptions are only used to help understand the content of the present invention, and the direction in the actual product may vary according to specific circumstances, including but not limited to installation methods, usage habits, or design requirements, etc.

[0039] The ordinal numbers such as "first" and "second" used in the present invention are not used to indicate the order, priority, or importance of objects, but are only for the convenience of description and distinction of multiple similar or related objects. The use of these ordinal numbers does not constitute any limitation on the order, priority, or function of any object in the actual application of the present invention. In actual applications, these objects may appear in any order according to specific circumstances, or have equal status and functions.

[0040] The above are only the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Various changes can be made to the above embodiments of the present invention. That is, all simple, equivalent changes and modifications made in accordance with the claims and the content of the specification of the present invention application fall within the scope of protection of the claims of the present invention patent. Those not described in detail in the present invention are all conventional technical contents.

Claims

1. A low-temperature turbine with a trapped vortex inducer, comprising an impeller, an outer casing, nozzle stator blades, an inner casing, an air bearing and a main shaft, wherein there is a blade tip clearance between the top of the impeller and the outer casing, there is a rotor-static interface cavity between the outlet annular surface of the nozzle stator blades and the inlet annular surface of the rotor blades of the impeller, a wheel back cavity is formed between the wheel back of the impeller and the inner casing, an inter-axial clearance is formed between the main shaft and the inner casing, a pressure stabilizing groove cavity is present between the inner casing and the air bearing, the blade tip clearance, the rotor-static interface cavity, the wheel back cavity, the inter-axial clearance and the pressure stabilizing groove cavity are interconnected to form a leakage flow channel, and the invention is characterized in that: The low-temperature turbine also includes a trapped vortex inducer, which includes at least one curved tooth assembly and at least one drainage channel, each curved tooth assembly includes a lower curved tooth and an upper curved tooth, the lower curved tooth and the upper curved tooth are arranged at intervals along the R direction, the lower curved tooth is arranged on the wheel back of the impeller, and the upper curved tooth is arranged on the inner casing; the lower curved tooth defines a first groove, and the upper curved tooth defines a second groove, and the opening directions of the first groove and the second groove are opposite; each of the drainage channels is at least partially arranged on the wheel back of the impeller, and the first groove is connected to the turbine outlet through the drainage channel.

2. The low-temperature turbine with a trapped vortex inducer according to claim 1, characterized in that: The lower curved teeth are formed as one piece with the wheel back of the impeller, and the upper curved teeth are formed as one piece with the inner casing.

3. The low-temperature turbine with a trapped vortex inducer according to claim 1, characterized in that: The projection profile of the lower curved tooth includes a first inner ring and a first outer ring, the first inner ring is an arc tangent to the back of the impeller; the first outer ring is formed by offsetting the first inner ring along the R direction by a first preset distance, and the two ends of the first outer ring and the first inner ring are connected by two first line segments extending in the R direction to form a closed projection profile.

4. The low-temperature turbine with a trapped vortex inducer according to claim 3, characterized in that: The diameter of the first inner ring is 1 / 2 to 3 / 4 of the Z-direction width of the wheel back cavity; the first preset distance is 1 / 5 to 1 / 8 of the diameter of the first inner ring.

5. The low temperature turbine with a trapped vortex inducer according to claim 1, characterized in that: The projection contour of the upper curved tooth includes a second inner ring and a second outer ring, the second inner ring is an arc tangent to the inner casing; the second outer ring is formed by offsetting the second inner ring along the R direction by a second preset distance, and the two ends of the second outer ring and the second inner ring are connected by two second line segments extending in the R direction to form a closed projection contour.

6. The low-temperature turbine with a trapped vortex inducer according to claim 5, characterized in that: The diameter of the second inner ring is 1 / 2 to 3 / 4 of the Z-direction width of the wheel back cavity; the second preset distance is 1 / 5 to 1 / 8 of the diameter of the second inner ring.

7. The low-temperature turbine with a trapped vortex inducer according to claim 3, characterized in that: The diversion channel includes an outlet and at least one inlet, the inlets correspond to the bent tooth assemblies one by one, each of the inlets is connected to the first groove of the lower bent tooth of the corresponding bent tooth assembly, and the outlet is connected to the turbine outlet.

8. The low-temperature turbine with a trapped vortex inducer according to claim 7, characterized in that: Each of the inlets is located below the center of the first inner ring of the projection profile of the lower curved tooth of the corresponding curved tooth assembly, and the R-direction distance between the inlet and the center of the first inner ring does not exceed 1 / 4 of the diameter of the first inner ring.

9. The low-temperature turbine with a trapped vortex inducer according to claim 7, characterized in that: It also includes a fastener, which is used to fix the impeller to the main shaft; the drainage channel includes a first part and a second part, the first part is arranged on the wheel back of the impeller, the second part is arranged on the fastener, the outlet of the drainage channel is arranged at the second part, and the inlet of the drainage channel is arranged at the first part.

10. The low temperature turbine with a trapped vortex inducer according to claim 1, characterized in that: There are multiple drainage channels, which are evenly arranged along the circumferential direction.

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