CN114687817A - Central body, exhaust diffuser, gas turbine and combined cycle power plant - Google Patents
Central body, exhaust diffuser, gas turbine and combined cycle power plant Download PDFInfo
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- 238000009792 diffusion process Methods 0.000 claims description 26
- 230000008859 change Effects 0.000 claims description 9
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- 230000007423 decrease Effects 0.000 claims description 3
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- 239000007789 gas Substances 0.000 description 46
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- 238000013461 design Methods 0.000 description 4
- 238000009434 installation Methods 0.000 description 3
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- 239000002918 waste heat Substances 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
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- 239000003546 flue gas Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/30—Exhaust heads, chambers, or the like
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/16—Arrangement of bearings; Supporting or mounting bearings in casings
- F01D25/162—Bearing supports
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
- F01D25/28—Supporting or mounting arrangements, e.g. for turbine casing
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Abstract
The present application provides a centerbody, and an exhaust diffuser, a gas turbine, and a combined cycle power plant utilizing the centerbody. The central body comprises a first structural body and a second structural body, the first structural body extends in a straight and preset length along the flowing direction of the airflow, and a plurality of support plate structures used for being connected with the exhaust diffuser are mounted on the first structural body; the second structural body is smoothly connected with the outer contour of the extending tail end of the first structural body, the outer contour of the axial section of the second structural body smoothly expands and then smoothly contracts along the airflow flowing direction, and the area of the axial section of the tail end of the second structural body extending along the airflow flowing direction is zero. The gas backflow effect of the exhaust diffuser can be effectively weakened, and therefore exhaust loss is reduced.
Description
Technical Field
The present application relates to the field of gas turbine technology, and more particularly, to a centerbody, and exhaust diffusers, gas turbines, and combined cycle power plants utilizing the same.
Background
The gas turbine is one of the main equipments of the combined cycle power plant, and its safe and stable operation plays a decisive role in the whole power plant. The turbine exhaust diffuser in the gas turbine can effectively recover and convert kinetic energy into static pressure, so that the static pressure of an exhaust system is improved, the static pressure at the outlet of the turbine can be reduced, the work of the turbine is increased, and the efficiency of a unit is improved. Thus, exhaust diffusers are important components of gas turbines.
For a combined cycle unit, exhaust gas of the last stage of a gas turbine enters a waste heat boiler, and water is converted into superheated steam meeting parameters after convective heat transfer and enters a steam turbine to do work. The spiral flue gas with high temperature discharged by the gas turbine is expanded and depressurized, and is guided to be turbulent flow gas with a certain rule to enter an inlet flue of the waste heat boiler, so that thermal deformation caused by thermal stress concentration is avoided, and the operation safety of the waste heat boiler is improved. Thus, the performance of the exhaust diffuser also affects the gas turbine performance to a greater extent.
In order to improve the performance of the exhaust diffuser, the structure of the exhaust diffuser is designed and optimized in various ways, including the improvement of design optimization of the profile lines of inlet support columns, the tail structure of a bearing seat, the profile lines of a flow passage, the flow passing rule, the pneumatic excitation and the like, and the total pressure loss generated in the exhaust diffuser is expected to be reduced and the pressure recovery performance of the exhaust diffuser is expected to be improved by the means. In which, many companies and institutions at home and abroad improve the structure of the bearing seat (central body) and other parts. Some runner molded lines are changed into continuous bending, so that the flow of air flow at an inlet is influenced, and the exhaust loss is reduced; some guide elements are added at the tail part of the bearing seat to change the through-flow rule and further reduce the exhaust loss. Although the structures can improve the performance of the exhaust diffuser in principle, the backflow effect of the reduced airflow is not very obvious, and the exhaust loss is still serious, so that the pressure recovery performance of the exhaust diffuser is influenced, and the performance of a combustion engine and the efficiency of a unit are further influenced.
Therefore, how to design an exhaust diffuser capable of effectively reducing the gas backflow effect and reducing the exhaust loss becomes a hot spot of research in the industry.
Disclosure of Invention
An object of an embodiment of the present invention is to provide a center body for an exhaust diffuser, which has the advantages of a weak air flow backflow effect and low exhaust loss compared to the existing exhaust diffuser.
It is a second object of an embodiment of the present application to provide an exhaust diffuser that uses the center body described above.
It is a further object of an embodiment of the present application to provide a gas turbine using the above exhaust diffuser.
It is a fourth object of embodiments of the present application to provide a combined cycle power plant using the gas turbine described above.
In a first aspect, there is provided a centerbody for an exhaust diffuser comprising: the first structure body extends in a preset length straightly along the flowing direction of the airflow, and a plurality of support plate structures used for being connected with the exhaust diffuser are installed on the first structure body; and the second structural body is smoothly connected with the outer contour of the extending tail end of the first structural body, the outer contour of the axial section of the second structural body smoothly expands along the airflow flowing direction and then smoothly contracts, and the area of the tail axial section of the second structural body extending along the airflow flowing direction is zero.
In one embodiment, the second structure is a symmetrical rotating structure.
In an implementation scheme, the second structural body is an ellipsoid body comprising a part of left half shaft and a whole right half shaft, the structure of the ellipsoid body positioned on the part of the left half shaft is a first sub ellipsoid body, and the structure of the ellipsoid body positioned on the whole right half shaft is a second sub ellipsoid body; the first ellipsoid corresponds to the expanded part of the outer contour of the axial section of the second structural body, and the second ellipsoid corresponds to the contracted part of the outer contour of the axial section of the second structural body.
In an implementation scheme, the slope of the outer contour line of the second structural body located at the upper half part of the coordinate system of the ellipsoid decreases from a positive value to zero along the airflow direction and then turns to a negative value.
In one embodiment, the change in slope of the outer contour of the upper half of the first ellipsoid along the direction of flow of the gas stream is 0.29 to 0 and the change in slope of the outer contour of the upper half of the second ellipsoid along the direction of flow of the gas stream is 0 to ∞.
In one embodiment, the second structure has a generatrix equation of
Wherein a is the half-long axial length, b is the half-short axial length, the radius of the hub at the junction of the first structural body and the second structural body is r, and the device is arranged
Setting a to be more than or equal to b and the threshold value of the bus equation to be
In one embodiment, the first structure and the second structure are detachably connected.
According to a second aspect of the present application, there is also provided an exhaust diffuser comprising: the central body in the above technical scheme; and an outer shell, arranged at the periphery of the central body and coaxial with the central body, the outer shell being provided with an annular wall surface for forming with the central body 10 a flow passage for guiding the diffusion fluid.
In one practical scheme, the shell comprises a bearing seat section, a first diffusion section and a second diffusion section which are connected in sequence; the bearing seat section is connected with the support plate structure of the central body and is used for supporting and positioning the central body; the first diffusion section is used for connecting the bearing seat section and the second diffusion section and is in a gradually expanding shape along the airflow flowing direction; the second diffusion section is in a gradually-expanding shape along the airflow flowing direction, the gradually-expanding inclination angle is larger than that of the first diffusion section, and the tail end of the second diffusion section is used for being connected with an external component.
In an implementation scheme, the horizontal length ratio of the bearing seat section to the first diffusion section to the second diffusion section is 1 (2-3) to (7-8).
In an implementation scheme, the bearing seat section 31 comprises at least one gradually-expanding section, each gradually-expanding section is gradually expanded along the airflow flowing direction, the inclination angle between the outer contour line of the first diffusion section and the central axis of the exhaust diffuser is 3 degrees to 5 degrees, and the inclination angle between the outer contour line of the second diffusion section and the central axis of the exhaust diffuser is 5 degrees to 8 degrees.
In an implementable scheme, the number of the support plate structures is 3-6, the support plate structures are wing-shaped, the support plate structures are obliquely arranged between the central body and the shell and are distributed in a circumferential array around the center of the first structural body.
According to a third aspect of the present application, there is also provided a gas turbine comprising the exhaust diffuser of the above-described aspect.
According to a fourth aspect of the present application, there is also provided a combined cycle power plant comprising the gas turbine of the above technical solution.
Benefits of the centerbody for an exhaust diffuser in the present application:
1. the central body is provided with a first structural body and a second structural body, the outer contour of the axial section of the second structural body is smoothly expanded and then smoothly contracted along the airflow flowing direction, so that the flow channel cannot be suddenly expanded and is influenced by the outer contour of the second structural body, the flow channel is smoothly contracted and then smoothly expanded, the airflow backflow area at the tail part of the second structural body is greatly reduced, the backflow effect of the airflow is weakened as much as possible, and the exhaust loss is reduced.
2. The axial cross-sectional area of the tail end of the second structure body extending along the airflow flowing direction is zero, the design can control the gas backflow effect at an extremely low level, the airflow backflow effect caused by structural influence can be eliminated, and the exhaust loss is reduced to the maximum extent.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
FIG. 1 is a schematic diagram of an exhaust diffuser with a center body mounted thereto according to an embodiment of the present application;
FIG. 2 is a cross-sectional view of an exhaust diffuser with a center body installed in accordance with an embodiment of the present application;
FIG. 3 is a diagram illustrating a generatrix square equation of an outer contour line of a second structure according to an embodiment of the present application;
FIG. 4 is a meridional flow simulation of the exhaust diffuser of FIG. 1;
FIG. 5 is a meridional flow simulation of an exhaust diffuser of the prior art;
FIG. 6 is a schematic diagram of a prior art exhaust diffuser.
In the figure: 10. a central body; 11. a first structure body; 12. a second structural body; 121. a first sub-ellipsoid; 122. a second sub-ellipsoid; 20. a support plate structure; 30. a housing; 31. a bearing block section; 32. a first diffusion section; 33. a second diffusion section; 40. a central shaft; 50. and (4) an oil pipe.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In order to improve the performance of the exhaust diffuser, various designs and optimizations have been performed on the structure of the exhaust diffuser, including optimization of the profile line of the inlet strut structure, the structure of the bearing seat tail, the line of the flow passage, the flow-through law, the aerodynamic excitation, and so on, and it is desired to reduce the total pressure loss generated in the exhaust diffuser and improve the pressure recovery performance thereof by these measures. The inventor of the present application has found that one of the main causes of the total pressure loss of the exhaust diffuser is the exhaust loss, the main cause of the exhaust loss is the strong air flow backflow effect of the exhaust diffuser, and the air flow backflow effect is mainly caused by the tail end structure of the central body of the exhaust diffuser. Therefore, in order to reduce the backflow effect of the gas flow, reduce the exhaust loss, and further reduce the total pressure loss, the structure of the exhaust diffuser, especially the structure of the center body, needs to be optimized and designed.
According to a first aspect of the present application, there is first provided a centerbody for use on an exhaust diffuser. Fig. 1 is a schematic structural view of an exhaust diffuser with a center body mounted thereto according to an embodiment of the present application, and fig. 2 is a sectional view of an exhaust diffuser with a center body mounted thereto according to an embodiment of the present application. Referring to fig. 1 and 2, the central body 10 includes a first structural body 11 and a second structural body 12.
The first structure body 11 is extended straight by a predetermined length in the direction in which the air flow flows, and a plurality of strut structures 20 for connection with the exhaust diffuser are mounted on the first structure body 11. The second structure body 12 is smoothly connected with the outer contour of the extending end of the first structure body 11, the outer contour of the axial section of the second structure body 12 smoothly expands and then smoothly contracts along the airflow flowing direction, and the axial section area of the extending end of the second structure body 12 along the airflow flowing direction is zero.
In the solution of the embodiment of the present application, it can be seen that the second structural body 12 of the present application is very different from the end cap structure of the prior art, compared with the prior art shown in fig. 6. The first structure 11 and the strut structure 20 cooperate with the exhaust diffuser to direct the flow of air into and then through the second structure 12 of the center body 10. The outer contour of the axial cross section of the second structural body 12 of the central body 10 is smoothly expanded and then smoothly contracted along the airflow flowing direction, so that the flow passage is not suddenly expanded but is influenced by the outer contour of the second structural body 12, and the flow passage is smoothly contracted and then smoothly expanded, so that the airflow backflow area at the tail part of the second structural body 12 is greatly reduced, the backflow effect of the airflow is weakened as much as possible, and the exhaust loss is reduced. In addition, the axial cross-sectional area of the tail end of the second structural body 12 extending in the airflow direction is zero, and after the airflow reaches the axial cross-sectional area, the airflow smoothly converges to the center of the tail end structure along the wall surface, and then continues to develop downstream, and no serious airflow backflow effect occurs.
It should be noted that the first structural body 11 and the second structural body 12 may be provided as a solid structure or a shell structure, and the structure of the solid structure or the shell structure has no great influence on the functions thereof, but in the case of considering the installation and positioning effects on other structures and reducing the weight as much as possible, the first structural body 11 and the second structural body 12 may be provided as a shell structure, and the thickness of the shell is determined according to the properties of the adopted materials.
In one embodiment, referring to fig. 2, second structure 12 is a symmetric rotational structure. The first structure 11 is a straight cylindrical structure, so the second structure 12 is a symmetrical rotating structure, and the opening of the second structure 12 and the hub of the first structure 11 must be engaged with each other to avoid the direct contact between the bearing in the hub and the high temperature gas, thereby protecting the bearing. In addition, the symmetrical rotating structure is low in processing difficulty, cost control is facilitated, and subsequent batch production is facilitated.
In one embodiment, referring to FIG. 2, the second structural body 12 is an ellipsoid including a portion of the left half axis and an entirety of the right half axis, the structure of the ellipsoid at the portion of the left half axis is a first sub-ellipsoid 121, and the structure of the ellipsoid at the entirety of the right half axis is a second sub-ellipsoid 122; the first ellipsoid splitter 121 corresponds to the expanded part of the outer contour of the axial section of the second structural body 12, and the second ellipsoid splitter 122 corresponds to the contracted part of the outer contour of the axial section of the second structural body 12. The ellipsoid is a rotational symmetric structure, the processing difficulty is low, the cost can be effectively reduced, and the outline shape of the ellipsoid changes smoothly, so that the ellipsoid is favorable for guiding airflow. It should be noted that, when describing the left half axis and the right half axis of the ellipsoid, the three-dimensional coordinate center is at the geometric center of the ellipsoid, the major axis of the ellipsoid is the y axis, the minor axis of the ellipsoid is the x axis, and the z axis is perpendicular to the coordinate plane formed by the x axis and the y axis. The ellipsoidal structure of the second structure body 12 is matched with the casing of the exhaust diffuser to form an airflow channel, so that the airflow channel passing through the first ellipsoid 121 can be smoothly contracted and smoothly expanded, namely, the axial sectional area of the airflow channel formed by the second structure body 12 and the casing of the exhaust diffuser is smoothly contracted and then smoothly expanded, so that the airflow passing through the second structure body 12 is accelerated for a short time and then developed to the downstream, the backflow effect generated by the exhaust gas at the turbine end due to the sudden expansion of the flow channel can be obviously weakened, the exhaust loss at the turbine end is reduced, the pressure recovery capability of the exhaust section is improved, and the turbine efficiency is improved.
In one embodiment, referring to FIG. 2, the slope of the outer contour of the structure of the second structure 12 in the upper half of the coordinate system of the ellipsoid decreases from a positive value to zero and then to a negative value in the direction of airflow. In particular, the above-mentioned slope is described with respect to the upper half of the cross-section in fig. 2. The slope of the outline profile of the upper half of the second structure 12 is positive and negative, so that the axial cross-sectional area of the flow channel at the rear of the support plate structure 20 of the exhaust diffuser is contracted and then expanded, and a nozzle-type flow channel is formed together, and the axial cross-sectional area changes continuously, so that the airflow does not expand suddenly when flowing. Specifically, the gas is compressed and accelerated when passing through the positive slope portion, and is released when passing through the negative slope portion.
In one embodiment, referring to FIG. 2, the change in slope of the outer contour of the upper half of the first sub-ellipsoid 121 along the direction of flow of the gas stream is 0.29 to 0 and the change in slope of the outer contour of the upper half of the second sub-ellipsoid 122 along the direction of flow of the gas stream is 0 to- ∞. When the slope change of the first ellipsoid 121 is between 0.29 and 0, the flow channel at the first ellipsoid 121 has substantially no backflow zone, thereby reducing exhaust loss; when the slope of the first ellipsoid 121 is greater than 0.29, a backflow region may occur in the flow channel of the first ellipsoid 121, thereby blocking the flow of exhaust gas through the section and increasing the exhaust loss. When the slope change of the second ellipsoid component 122 is between 0 and ∞, the tail end of the second ellipsoid component 122 has substantially no recirculation zone, and no sharp corner exists, so that the recirculation effect can be controlled to a low level; conversely, when the slope of the second ellipsoid component 122 is not varied from 0 to ∞ the back-flow region is generally present at the end of the second ellipsoid component 122, and there may be a sharp corner at the end of the second ellipsoid component 122, which may cause the back-flow effect of the gas flow at the tail end of the second ellipsoid component 122, resulting in exhaust losses.
Fig. 3 is a diagram illustrating a bus bar equation of an outer contour line of a second structural body according to an embodiment of the present application. In one embodiment, referring to FIGS. 2 and 3, the generatrix equation for the second structure 12 is defined as
Wherein a is a half-long axial length, b is a half-short axial length, and the radius of the hub at the junction of the first structural body 11 and the second structural body 12 is r
Setting a to be more than or equal to b and the threshold value of the bus equation to be
In one embodiment, first structure 11 and second structure 12 are removably connected. The second structure 12 will inevitably bear more airflow impact due to the structural feature that its outer profile is expanded and then contracted, and the long-term airflow impact will erode the surface of the second structure 12, thereby accelerating the wear of the second structure 12. Therefore, the detachable installation mode of the first structural body 11 and the second structural body 12 is adopted, so that only the second structural body 12 can be replaced and maintained in the later period without replacing other structural parts, the maintenance difficulty and cost are reduced, the maintenance efficiency is improved, and the later period maintainability is better.
Fig. 4 is a meridian flow simulation diagram of the exhaust diffuser shown in fig. 1, and fig. 5 is a meridian flow simulation diagram of an exhaust diffuser in the prior art. Comparing the simulation diagrams of fig. 4 and fig. 5, it is obvious that the air flow backflow area is substantially disappeared by using the technical solution of the embodiment of the present application.
To validate and analyze the fluid details and physical parameters of the centerbody 10, the present application utilizes numerical simulation methods for calculation, evaluation and analysis. The formula required by calculation is as follows:
1. total pressure loss coefficient ω:
wherein p is01-p02Is the total pressure difference, p, between the inlet and the outlet of the exhaust diffuser01-p1Is the kinetic energy of the exhaust diffuser inlet.
2. Static pressure recovery coefficient Cp：
Wherein p is2-p1Is the static pressure difference, p, between the outlet and inlet of the exhaust diffuser01-p1The total pressure and static pressure difference, namely the kinetic energy of the inlet of the exhaust diffuser are obtained.
By using the above formula to perform a series of analysis and calculation, it is found that the backflow effect of the gas loss generated by the sudden expansion of the flow passage at the tail of the original center body 10 structure basically disappears, the total pressure loss of the exhaust diffuser is obviously reduced by about 10%, the static pressure recovery coefficient is improved by about 15%, the turbine efficiency is further improved by about 0.1%, and a relatively considerable benefit is obtained.
According to a second aspect of the present application, there is also provided an exhaust diffuser, see fig. 1 and 2, comprising a central body 10 as in the previous embodiment and an outer casing 30, the outer casing 30 being arranged at the periphery of the central body 10 and coaxially to the central body 10 and being provided with an annular wall surface for forming with the central body 10 a flow passage for guiding the diffusing fluid. The outer shell 30 serves to position and support the hub 10 by the brace arrangement 20. The casing 30 serves to suppress the separation of the wall surface of the air flow and reduce the loss of the air flow.
In one embodiment, referring to fig. 1, the housing 30 includes a bearing seat section 31, a first diffuser section 32, and a second diffuser section 33 connected in series; the bearing block section 31 is connected to the strut arrangement 20 of the central body 10 for supporting and positioning the central body 10; the first diffuser section 32 is used for connecting the bearing seat section 31 and the second diffuser section 33, and is divergent along the airflow direction. The second diffuser section 33 is divergent along the airflow flowing direction, the divergent inclined angle is larger than that of the first diffuser section 32, and the tail end of the second diffuser section 33 is used for connecting with an external component. The three sections of the shell 30 are installed in a modularized mode, and each part can be independently disassembled, installed and replaced, so that the maintenance cost is low, and the maintainability in the later period is good.
It should be noted that the bearing block section 31 and the center body 10 are connected behind the last stage blade of the gas turbine, and play a role in supporting and positioning the central rotor of the gas turbine; the second diffuser section 33 is important for connecting the exhaust diffuser with the outside (atmosphere or preheating boiler); while the first diffuser section 32 is the transition between the bearing seat section 31 and the second diffuser section 33, there is a necessity for its presence.
In one embodiment, referring to FIG. 1, the bearing seat section 31, the first diffuser section 32 and the second diffuser section 33 have a horizontal length ratio of 1 (2-3) to (7-8). In order to inhibit wall surface separation of the airflow, the length proportion of the bearing seat section 31, the first diffusion section 32 and the second diffusion section 33 is set and the inclination angle of each section is correlated, and according to the characteristics of the airflow pressure, the airflow speed and the like, the shorter lengths of the bearing seat section 31, the first diffusion section 32 and the second diffusion section 33 are obtained through calculation and simulation verification, and the airflow loss can be reduced as far as possible. In the technical scheme of the embodiment of the application, the optimal length ratio is 1:2.45:7.36, the separation of the airflow along the wall surface can be well inhibited, the exhaust loss is reduced, and the high pressure recovery capability is further obtained, but the optimal value is also set relatively in consideration of the fact that the length ratio setting needs to take into consideration many factors such as air pressure, flow speed, structure, exhaust characteristics and the like.
In one embodiment, referring to fig. 1, the bearing seat section 31 includes at least one divergent section, each divergent section is divergent in the flow direction of the air flow, specifically, the angle between the outer contour line of each divergent section of the bearing seat section 31 and the central axis 40 of the exhaust diffuser is 5 degrees to 8 degrees, the angle between the outer contour line of the first diffuser section 32 and the central axis 40 of the exhaust diffuser is 3 degrees to 5 degrees, and the angle between the outer contour line of the second diffuser section 33 and the central axis 40 of the exhaust diffuser is 5 degrees to 8 degrees. The inclination angle range can restrain the flow separation of the air flow along the wall surface at each section to a certain degree, and the flow loss of the exhaust gas is reduced. In the technical solution of the embodiment of the present application, the inclination angle between the outer contour line of the bearing seat section 31 and the central axis 40 of the exhaust diffuser is optimally 6.64 degrees, the inclination angle between the outer contour line of the first diffuser section 32 and the central axis 40 of the exhaust diffuser is optimally 4.07 degrees, and the inclination angle between the outer contour line of the second diffuser section 33 and the central axis 40 of the exhaust diffuser is optimally 6.25 degrees.
The bearing seat section 31 may also be divided into two parts in the direction of the central axis 40 and set with different inclination angles, and the first diffuser section 32 and the second diffuser section 33 may also be divided into multiple parts in the direction of the central axis 40 and set with different inclination angles, thereby further subdividing the housing 30 into more parts, allowing the housing 30 to have more various angular variations, and thus allowing the effect of suppressing the separation of the air flow along the wall surface to be better.
It should be noted that each section of the housing 30 is provided with a different angle of inclination, which is determined primarily by the structure and exhaust characteristics of each section. The bearing seat is connected behind the last-stage blade of the gas turbine, the exhaust gas speed is high, the structure of the bearing seat section 31 is complex, the bearing seat section 31 is provided with the support plate structure 20, the hub and the like, the exhaust gas flowing through the bearing seat section is influenced inevitably, the exhaust gas loss of the exhaust gas at the section is increased, particularly the flow separation along the wall surface is increased, therefore, the inclination angle of the wall surface of the bearing seat section 31 must be adjusted according to the exhaust gas speed and the complex flowing condition, the flow separation along the wall surface is reduced to the greatest extent under a proper inclination angle, and the exhaust gas loss is reduced. The second diffuser 33 (external diffuser, named in fig. 6) is connected to the outside (the atmosphere or the exhaust heat boiler), and the exhaust gas velocity passing through this section is greatly reduced compared to the bearing seat section 31, and in order to suppress the flow separation of this section along the wall surface, it is necessary to adjust the inclination angle according to the exhaust gas velocity of this section and the influence of the outside, and to reduce the flow separation along the wall surface as much as possible at a relatively suitable inclination angle. The first diffuser section 32 (conical diffuser section, named in fig. 6) is a transition part between the bearing seat section 31 and the second diffuser section 33, and in order to suppress the flow separation along the wall surface of the section, the flow separation along the wall surface needs to be reduced by setting an inclination angle according to the exhaust gas velocity.
In one embodiment, referring to fig. 1, the number of strut structures 20 is 3 to 6, the strut structures 20 are airfoil-shaped, and the strut structures 20 are obliquely installed between the central body 10 and the outer shell 30 and circumferentially arrayed around the center of the first structural body 11. The function of the brace arrangement 20 is to provide better secure support and accurate positioning of the outer shell 30 relative to the hub 10. In the technical scheme of the embodiment of the application, the number of the support columns is set to be 5, the structure is that the wing profile mainly rectifies the airflow at the last stage outlet of the turbine, and the installation inclination angle is mainly used for matching the rotating airflow at the outlet of the turbine to reduce the flow loss of the airflow. In aerodynamics, an airfoil is generally understood to be a two-dimensional wing, i.e. an infinite-span wing with a constant cross-sectional shape. Here with airfoil profile application to the stay plate structure 20 on, the main function is for improving the air current flow performance, reduces the effect of blockking to the air current, according to the air current condition, the stay plate structure 20 includes but not limited to symmetrical airfoil profile, biconvex airfoil profile, plano-convex airfoil profile, unsmooth airfoil profile, S-shaped airfoil profile etc..
In one embodiment, referring to fig. 1, the exhaust diffuser further comprises an oil pipe 50, the oil pipe 50 being disposed between the outer shell 30 and the center body 10. The oil line 50 is used to supply oil to lubricate the bearings mounted on the hub 10 and to cool them down, thereby ensuring that the bearings work properly.
It should be further noted that, the central body 10 is a part of an exhaust diffuser, when the exhaust diffuser is in operation, airflow flows into an annular flow channel formed by the outer casing 30 and the central body 10, and passes through the wing-shaped support plate structure 20, and then reaches the second structural body 12, at this time, the airflow is affected by the structure of the second structural body 12 and the reducing structure of the outer casing 30, the outer contour of the axial section of the flow channel is smoothly contracted and then smoothly expanded, so that the air passing through the diffuser is accelerated for a short time and then develops downstream, thereby greatly weakening the backflow effect generated by the exhaust gas at the turbine end due to the sudden expansion of the flow channel, reducing the exhaust loss at the turbine end, improving the pressure recovery capability of the exhaust section, and thus improving the turbine efficiency.
According to a third aspect of the present application, there is provided a gas turbine comprising the exhaust diffuser of the above embodiment. The turbine efficiency of the gas turbine adopting the exhaust diffuser can be improved better.
According to a fourth aspect of the present application, there is provided a combined cycle power plant comprising the gas turbine of the above embodiment. The combined cycle power plant using the above gas turbine also has an improved overall efficiency of the combined cycle power plant due to the improved centerbody of the exhaust diffuser.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (14)
1. A centerbody (10) for an exhaust diffuser, comprising:
a first structural body (11) extending straightly in a direction of flow of the air flow by a predetermined length, the first structural body (11) having a plurality of strut structures (20) mounted thereon for connection with the exhaust diffuser;
and the second structural body (12) is smoothly connected with the outer contour of the extending tail end of the first structural body (11), the outer contour of the axial section of the second structural body (12) smoothly expands and then smoothly contracts along the airflow flowing direction, and the axial section area of the tail end of the second structural body (12) extending along the airflow flowing direction is zero.
2. The centerbody of claim 1 wherein the second structural body (12) is a symmetrical rotating structure.
3. A central body as claimed in claim 2, characterized in that the second structural body (12) is an ellipsoid comprising a part of the left half axis and the whole of the right half axis, the structure of the ellipsoid in the part of the left half axis being a first ellipsoid component (121), the structure of the ellipsoid in the whole of the right half axis being a second ellipsoid component (122); the first ellipsoid splitter (121) corresponds to an expanded part of the outer contour of the axial section of the second structural body (12), and the second ellipsoid splitter (122) corresponds to a contracted part of the outer contour of the axial section of the second structural body (12).
4. A central body according to claim 3, characterized in that the slope of the outer contour of the structure of the second structure (12) in the upper half of the coordinate system of the ellipsoid decreases from a positive value to zero in the direction of the flow of the gas stream and then to a negative value.
5. The central body as claimed in claim 4, characterized in that the change in the slope of the outer contour of the upper half of the first ellipsoid segment (121) in the direction of the flow of the gas stream is 0.29 to 0 and the change in the slope of the outer contour of the upper half of the second ellipsoid segment (122) in the direction of the flow of the gas stream is 0 to- ∞.
6. Central body according to any of claims 3-5, characterized in that the generatrix equation of the second structural body (12) is
Wherein a is a half-long axial length, b is a half-short axial length, the radius of a hub at the junction of the first structural body (11) and the second structural body (12) is r, and the structure is provided
Setting a to be more than or equal to b and the threshold value of the bus equation to be
7. Central body according to claim 1, characterized in that the first structural body (11) and the second structural body (12) are detachably connected.
8. An exhaust diffuser, comprising:
-a central body (10) according to any one of claims 1 to 7; and
the outer shell (30) is arranged on the periphery of the central body (10) and is coaxial with the central body (10), and the outer shell (30) is provided with an annular wall surface and is used for forming a flow passage for guiding diffusion fluid with the central body (10).
9. The exhaust diffuser of claim 8, wherein the casing (30) comprises a bearing block section (31), a first diffuser section (32) and a second diffuser section (33) connected in series;
said bearing block section (31) being connected to said strut structure (20) of said central body (10) for supporting and positioning said central body (10);
the first diffusion section (32) is used for connecting the bearing seat section (31) and the second diffusion section (33) and is in a gradually expanding shape along the airflow flowing direction;
the second diffusion section (33) is divergent along the airflow flowing direction, the divergent inclination angle is larger than that of the first diffusion section (32), and the tail end of the second diffusion section (33) is used for being connected with an external component.
10. The exhaust diffuser of claim 9 wherein the bearing block section (31), the first diffuser section (32) and the second diffuser section (33) have a horizontal length ratio of 1 (2-3): 7-8.
11. The exhaust diffuser of claim 9, wherein the bearing seat section (31) comprises at least one diverging section, each diverging section being diverging in the direction of flow of the gas stream;
the inclination angle between the outer contour line of the first diffusion section (32) and the central axis (40) of the exhaust diffuser is 3-5 degrees, and the inclination angle between the outer contour line of the second diffusion section (33) and the central axis (40) of the exhaust diffuser is 5-8 degrees.
12. The exhaust diffuser of claim 8 wherein said strut structures (20) are 3-6 in number, said strut structures (20) are airfoil shaped, and said strut structures (20) are obliquely mounted between said center body (10) and said outer casing (30) in a circumferential array about the center of said first body (11).
13. A gas turbine comprising an exhaust diffuser according to any one of claims 8 to 11.
14. A combined cycle power plant comprising the gas turbine of claim 13.
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| US20110056179A1 (en) * | 2009-06-02 | 2011-03-10 | John Orosa | Turbine exhaust diffuser with region of reduced flow area and outer boundary gas flow |
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