A nozzle structure for throttling steam turbine

Abstract

The present invention provides a nozzle structure for a throttling steam turbine, comprising an inner ring and an outer ring, wherein the outer ring is interference-sleeved on the outer ring of the inner ring, and the inner ring and the outer ring are both connected to the steam chamber by fixing screws, and the outer ring surface of the inner ring has a plurality of equally distributed stationary blades, and a nozzle flow channel is formed between two adjacent stationary blades, and the nozzle flow channel connects the steam chamber and an external impeller so that the steam in the steam chamber flows out through the nozzle flow channel to drive the impeller to rotate, and the diameter of each stationary blade gradually decreases from one end facing the steam chamber to the other end facing the impeller; the present invention has the advantage of meeting the requirement of compact unit structure, and at the same time, through reasonable blade design, the unit can operate stably under the conditions of large enthalpy drop and a wide range of steam parameter changes.

Description

Technical Field

[0001] The invention relates to the field of steam turbines, and more particularly to a nozzle structure for a throttling regulating steam turbine. Background Art

[0002] The steam distribution methods of steam turbines are mainly divided into nozzle regulation and throttling regulation. For steam turbines using nozzle regulation, the new steam in the steam chamber needs to pass through several regulating steam valves that open and close in sequence after passing through the main steam valve to reach the turbine regulating stage. Each regulating steam valve controls a group of regulating stage nozzles. This steam distribution method requires a relatively complex and large regulating mechanism. Throttling regulation is that all steam passes through one or several regulating valves that open and close at the same time and then flows to the first-stage nozzle. No regulating stage is required, the structure is simple, the manufacturing cost is low, and when the steam parameter variation range is large, throttling regulation is more conducive to flow design. It is generally used in small units or units that bear basic loads. Such units basically require simple and compact structure, reliable operation, and on this basis, the lowest possible heat consumption rate and steam consumption rate.

[0003] The nozzle structure design currently used in throttling steam turbines has defects, making it difficult to meet the requirements of good adaptability to large enthalpy drops and drastic fluctuations in steam parameters, and the steam flow rate also fails to meet the specified requirements. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a nozzle structure for a throttling steam turbine, which meets the requirements of a compact unit structure and, through reasonable blade design, enables the unit to operate stably under large enthalpy drop and a wide range of steam parameter changes.

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

[0006] A nozzle structure for a throttling steam turbine comprises an inner ring and an outer ring, wherein the outer ring is interference-sleeved on the outer ring of the inner ring, and both the inner ring and the outer ring are connected to a steam chamber via fixing screws, and the outer ring surface of the inner ring has a plurality of evenly distributed stationary blades, and a nozzle flow channel is formed between two adjacent stationary blades, wherein the nozzle flow channel connects the steam chamber with an external impeller so that the steam in the steam chamber flows out through the nozzle flow channel to drive the impeller to rotate, and the diameter of one end of each stationary blade facing the steam chamber is larger than the diameter of the other end facing the impeller.

[0007] Furthermore, the stationary blade includes a head portion facing the steam chamber side and a tail portion facing the impeller side, and the outer edge of the head portion is sequentially formed by the first arc segment L FG , the second arc segment L GH , the third arc segment L HI And the fourth arc L IJ The outer edge of the tail portion is composed of the first straight line segment LAB , the second straight line segment L CD And the fifth arc L BC Connected to form the fifth arc segment L BC With the first straight line segment L AB and the second straight line segment L CD The second arc segment L GH The radius R1 and the fourth arc segment L IJ The radius R2 is equal to the first arc segment L FG The radius R3 is greater than the second arc segment L GH The radius R1, the second arc segment L GH The radius R1 is greater than the fifth arc segment L BC The radius R4.

[0008] Further, one side of the connection between the head and the tail is a pressure surface, and the other side is a suction surface, the pressure surface faces the head of the adjacent stationary blade, the suction surface faces the tail of the adjacent stationary blade, and the edge of the pressure surface includes a sixth arc segment L JA , the sixth arc segment L JA One end of the fourth arc segment L IJ The other end is connected to the first straight line segment L AB The edge of the suction surface includes a third straight line segment L EF and the seventh arc segment L DE , the sixth arc segment L JA With the seventh arc L DE Bend towards each other.

[0009] Furthermore, the nozzle flow channel includes a steam inlet end and a steam outlet end, and the steam outlet end is provided with a fifth arc segment L connected to two adjacent static sheets. BC The outlet airflow angle ε of the nozzle flow channel is in the range of 15° to 25°. The outlet airflow angle ε is the angle between the steam flow direction to the steam outlet end and the steam outlet edge. The first straight line segment L AB The value range of the angle β with the steam outlet edge is the same as the value range of the outlet airflow angle ε. The second straight line segment L CD The value range of the angle α with the steam outlet edge is β-6° to β-3°, the value range of the installation angle δ of the stationary blade is 30° to 40°, and the installation angle δ of the stationary blade is the fourth arc segment L IJ and the fifth arc segment L BC The angle between the tangent line and the steam outlet edge.

[0010] Furthermore, the second straight line segment L CD With the first straight line segment L AB The ratio is 1:1.3, the second arc segment L GH The radius R1, the fourth arc segment LIJ The radius R2, the first arc segment L FG The radius R3 and the five arc segments L BC The ratio of the radius R4 is 1:1:0.6:18.

[0011] Furthermore, a metal spiral wound gasket is provided between the inner ring and the steam chamber and between the outer ring and the steam chamber.

[0012] Furthermore, both the inner ring and the outer ring are provided with annular grooves for matching with fixing screws, and the fixing screws and the annular grooves are welded by welding wires.

[0013] The beneficial effects of the present invention are as follows: a plurality of equally distributed stationary blades are provided on the outer ring surface of the inner ring, and a nozzle flow channel is formed between every two adjacent stationary blades, so that the steam flow rate is higher. The shape of the stationary blades is set so that the nozzle flow channel has a pressure surface and a suction surface, so that no obvious vortex is generated when the steam flows, the shedding rate of the blade head is reduced, and the problems such as pressure pulsation at the leading edge of the blade are effectively solved, and the steam has good adaptability to large enthalpy drops and drastic fluctuations in steam parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the nozzle structure and assembly in the present invention;

[0015] Figure 2 yes Figure 1 A partial right view of

[0016] Figure 3 It is a structural diagram of the inner ring in the present invention;

[0017] Figure 4 It is the static blade line diagram;

[0018] Figure 5 is the nozzle blade end wall streamline diagram;

[0019] Figure 6 It is the Mach number distribution diagram of the nozzle blade.

[0020] Figure numerals: 1. inner ring; 2. outer ring; 3. steam chamber; 4. fixing screw; 5. stationary blade; 51. head; 52. tail; 6. nozzle flow channel; 7. impeller; 8. pressure surface; 9. suction surface; 10. steam inlet end; 11. steam outlet end; 12. steam outlet edge; 13. metal wound gasket; 14. welding wire. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. The same parts are represented by the same reference numerals. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "bottom surface" and "top surface", "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0022] Since the nozzle structure design currently used in the throttling regulating steam turbine has defects, it is difficult to meet the requirements of large enthalpy drop and violent fluctuation of steam parameters, and the steam flow rate cannot meet the specified requirements; therefore, the present invention designs such a nozzle structure for throttling regulating steam turbine, such as Figure 1 As shown, it includes an inner ring 1 and an outer ring 2, the outer ring 2 is sleeved on the outer ring of the inner ring 1, and the inner ring 1 and the outer ring 2 are connected to the steam chamber 3 by fixing screws 4. Compared with the existing inner ring 1 and the outer ring 2 are directly welded to the steam chamber 3, the connection method by fixing screws 4 is simpler, such as Figure 3 As shown, the outer ring surface of the inner ring 1 has a plurality of equally distributed stationary blades 5, and a nozzle flow channel 6 is formed between two adjacent stationary blades 5. The nozzle flow channel 6 connects the steam chamber 3 and the external impeller 7, so that the steam in the steam chamber 3 flows out through the nozzle flow channel 6 to drive the impeller 7 to rotate. The diameter of the end of each stationary blade 5 facing the steam chamber 3 is larger than the diameter of the end facing the impeller 7, that is, the radius of the leading edge and the trailing edge of the stationary blade 5 are greatly different, the head 51 is very large, and the tail 52 is very small, and the shape is similar to a "tadpole". The beneficial effect is that the outer ring surface of the inner ring 1 has a plurality of equally distributed stationary blades 5, and a nozzle flow channel 6 is formed between every two adjacent stationary blades 5, so that the steam flow rate is higher. The shape of the stationary blade 5 is set so that the nozzle flow channel 6 has a pressure surface 8 and a suction surface 9, so that no obvious vortex is generated when the steam flows, the shedding rate of the blade head 51 is reduced, and the problems such as pressure pulsation at the leading edge of the blade are effectively solved, and it has good adaptability to large enthalpy drop and drastic fluctuations in steam parameters.

[0023] like Figure 4 As shown, the stationary blade 5 includes a head portion 51 facing the steam chamber 3 and a tail portion 52 facing the impeller 7. The outer edge of the head portion 51 is composed of a first arc segment, a second arc segment, a third arc segment and a fourth arc segment in sequence, and the outer edge of the tail portion 52 is composed of a first straight line segment, a second straight line segment and a fifth arc segment in sequence. The fifth arc segment is tangent to both the first straight line segment and the second straight line segment. The radius R1 of the second arc segment is equal to the radius R2 of the fourth arc segment. The radius R3 of the first arc segment is greater than the radius R1 of the second arc segment. The radius R1 of the second arc segment is greater than the radius R4 of the fifth arc segment.

[0024] like Figure 4As shown, one side of the connection between the head 51 and the tail 52 is a pressure surface 8, and the other side is a suction surface 9. The pressure surface 8 faces the head 51 of the adjacent stationary blade 5, and the suction surface 9 faces the tail 52 of the adjacent stationary blade 5. The edge of the pressure surface 8 includes a sixth arc segment, one end of the sixth arc segment is connected to the fourth arc segment, and the other end is connected to the first straight line segment. The edge of the suction surface 9 includes a third straight line segment and a seventh arc segment connected to each other. The sixth arc segment and the seventh arc segment are bent toward each other, and the first arc segment, the second arc segment, the third arc segment, the fourth arc segment, the sixth arc segment, the first straight line segment, the fifth arc segment, the second straight line segment, the seventh arc segment and the third straight line segment are sequentially connected to form the outer edge of a stationary blade 5, which is shaped like a "tadpole".

[0025] like Figure 4 As shown, the nozzle flow channel 6 includes a steam inlet end 10 and a steam outlet end 11, the steam inlet end is provided with a steam inlet edge tangent to the fourth arc segment of the two adjacent stationary blades 5, and the steam outlet end 11 is provided with a steam outlet edge 12 tangent to the fifth arc segment of the two adjacent stationary blades (that is, the steam inlet edge and the steam outlet edge 12 can be obtained from the top view of the inner ring 1), the outlet airflow angle ε of the nozzle flow channel 6 ranges from 15° to 25°, the outlet airflow angle ε is the angle between the direction of steam flowing to the steam outlet end 11 and the steam outlet edge 12, the angle β between the first straight line segment and the steam outlet edge 12 has the same value range as the outlet airflow angle ε, the angle α between the second straight line segment and the steam outlet edge 12 ranges from β-6° to β-3°, the installation angle δ of the stationary blade 5 ranges from 30° to 40°, and the installation angle δ of the stationary blade 5 is the angle between the tangent line of the fourth arc segment and the fifth arc segment and the steam outlet edge 12.

[0026] like Figure 4 As shown, the ratio of the second straight line segment to the first straight line segment is 1:1.3, and the ratio of the radius R1 of the second arc segment, the radius R2 of the fourth arc segment, the radius R3 of the first arc segment, and the radius R4 of the fifth arc segment are 1:1:0.6:18.

[0027] The above are the shape and size designs of the stationary blade 5, as well as the design of the installation position of the stationary blade 5. Through the arrangement of the stationary blade 5 of the present invention, the steam flow has no obvious vortex, the problem of flow separation at the leading edge of the blade is reduced, and the problem of pressure pulsation at the leading edge of the blade is effectively solved. It has good adaptability to large enthalpy drop and drastic fluctuations of steam parameters. For details, please refer to Figure 5 The end wall streamline diagram of the middle nozzle blade is used as the basis, and the setting of this kind of stationary blade 5 can make the maximum Mach number of the nozzle outlet reach 2.477. For details, please refer to Figure 6 Mach number distribution diagram of the mid-nozzle blade profile.

[0028] In order to improve the airtightness between the nozzle and the steam chamber 3, as Figure 1As shown, a metal wound gasket 13 is provided between the inner ring 1 and the steam chamber 3 and between the outer ring 2 and the steam chamber 3, and a concentric circle waterline is processed at the contact position I between the nozzle and the metal wound gasket to ensure a good seal between the steam chamber 3 and the nozzle.

[0029] To ensure the reliability of nozzle assembly, Figure 2 As shown, an annular groove for matching the fixing screw 4 is provided on the inner ring 1 and the outer ring 2, and the fixing screw 4 and the annular groove are welded by welding wire 14 (the high-strength steel welding wire 14 is used to lock the fixing screw 4).

[0030] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A nozzle structure for a throttling steam turbine, characterized in that: The invention comprises an inner ring (1) and an outer ring (2), wherein the outer ring (2) is interference-fitted on the outer ring of the inner ring (1), and the inner ring (1) and the outer ring (2) are connected to the steam chamber (3) via fixing screws (4). The outer ring surface of the inner ring (1) has a plurality of evenly distributed stationary blades (5), and a nozzle flow channel (6) is formed between two adjacent stationary blades (5). The nozzle flow channel (6) connects the steam chamber (3) and an external impeller (7), so that the steam in the steam chamber (3) flows out through the nozzle flow channel (6) to drive the impeller (7) to rotate. The diameter of one end of each stationary blade (5) facing the steam chamber (3) is larger than the diameter of the other end facing the impeller (7); The stationary blade (5) comprises a head portion (51) facing the steam chamber (3) and a tail portion (52) facing the impeller (7), the outer edge of the head portion (51) being sequentially connected by a first arc segment, a second arc segment, a third arc segment and a fourth arc segment, the outer edge of the tail portion (52) being sequentially connected by a first straight line segment, a second straight line segment and a fifth arc segment, the fifth arc segment being tangent to both the first straight line segment and the second straight line segment, the radius R1 of the second arc segment being equal to the radius R2 of the fourth arc segment, the radius R3 of the first arc segment being greater than the radius R1 of the second arc segment, and the radius R1 of the second arc segment being greater than the radius R4 of the fifth arc segment; One side surface of the connection between the head portion (51) and the tail portion (52) is a pressure surface (8), and the other side surface is a suction surface (9), the pressure surface (8) faces the head portion (51) of the adjacent stationary blade (5), and the suction surface (9) faces the tail portion (52) of the adjacent stationary blade (5), the edge of the pressure surface (8) includes a sixth arc segment, one end of the sixth arc segment is connected to the fourth arc segment, and the other end is connected to the first straight line segment, the edge of the suction surface (9) includes a third straight line segment and a seventh arc segment connected to each other, and the sixth arc segment and the seventh arc segment are bent toward each other; The nozzle flow channel (6) comprises a steam inlet end (10) and a steam outlet end (11), the steam outlet end (11) is provided with a steam outlet edge (12) tangent to the fifth arc segments of two adjacent stationary blades, the outlet airflow angle ε of the nozzle flow channel (6) has a value range of 15° to 25°, the outlet airflow angle ε is the angle between the direction of steam flowing toward the steam outlet end (11) and the steam outlet edge (12), the value range of the angle β between the first straight line segment and the steam outlet edge (12) is the same as the value range of the outlet airflow angle ε, the value range of the angle α between the second straight line segment and the steam outlet edge (12) is β-6° to β-3°, the value range of the installation angle δ of the stationary blade (5) is 30° to 40°, the installation angle δ of the stationary blade (5) is the angle between the tangent line of the fourth arc segment and the fifth arc segment and the steam outlet edge (12); A metal wound gasket (13) is provided between the inner ring (1) and the steam chamber (3) and between the outer ring (2) and the steam chamber (3).

2. The nozzle structure for a throttling steam turbine according to claim 1, characterized in that: The ratio of the second straight line segment to the first straight line segment is 1:1.3, and the ratio of the radius R1 of the second arc segment, the radius R2 of the fourth arc segment, the radius R3 of the first arc segment, and the radius R4 of the fifth arc segment is 1:1:0.6:

18.

3. The nozzle structure for a throttling steam turbine according to claim 1, characterized in that: The inner ring (1) and the outer ring (2) are both provided with an annular groove for matching with a fixing screw (4), and the fixing screw (4) and the annular groove are welded by a welding wire (14).

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