Steam flow rectifying device behind regulating stage of steam turbine

Abstract

The invention discloses a steam flow rectifying device behind a regulating stage of a steam turbine, and belongs to the technical field of steam turbines. The structure comprises a regulating stage for regulating the steam inlet condition of high-pressure steam according to the load requirement; the pressure stage is positioned behind the regulating stage and is used for further expanding the high-pressure steam to do work; the transition section is located between the adjusting stage and the pressure stage and used for leading high-pressure steam guided out by the adjusting stage into the pressure stage, a first set of rib plates and / or a second set of rib plates are / is arranged in the transition section, the first set of rib plates is located at a first preset position of a high-pressure steam outlet section of the adjusting stage, and the second set of rib plates is located at a second preset position of a high-pressure steam outlet section of the adjusting stage. The first set of rib plates is located at a first preset position in the transition section and used for conducting preliminary rectification on transverse steam flow in the transition section after the adjusting stage, and the second set of rib plates is located at a second preset position in the radial channel of the transition section and used for conducting carding on the radial steam flow in the transition section. The steam flow circumferential distribution and the steam flow angle of the regulating stage outlet are changed, the boundary condition of the pressure stage inlet is improved, and the efficiency of the steam turbine is improved.

Description

Technical Field

[0001] The present application relates to the technical field of steam turbines, and in particular to a steam flow rectifying device after a steam turbine regulating stage. Background Art

[0002] As the installed capacity of renewable energy power generation increases year by year, the peak load regulation of power grid becomes more and more severe, forcing the basic energy power system dominated by coal-fired power to fully participate in the deep peak load regulation of power grid, which will lead to frequent changes in the load of steam turbine units.

[0003] The operating condition change of the steam turbine is achieved by adjusting the steam inlet amount by adjusting the opening of the regulating valve. Therefore, there is a very large deviation between the main operating parameters of the steam turbine and the design parameters. That is, when the steam turbine unit is operating under variable operating conditions, the partial steam inlet degree of the regulating stage changes, which in turn causes the circumferential unevenness of the steam flow after the regulating stage to increase and the absolute steam flow angle to deviate from the axial direction. This is the main reason for the reduction in the efficiency of the steam turbine under variable operating conditions. Summary of the invention

[0004] In view of the problem of reduced efficiency of steam turbines under variable operating conditions in the prior art, the present application mainly provides a steam flow rectification device after the regulating stage of a steam turbine.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted in the present application is: a steam flow straightening device after the regulating stage of a steam turbine, which includes: a regulating stage, which adjusts the steam intake of high-pressure steam according to load requirements; a pressure stage, which is located after the regulating stage, and the high-pressure steam further expands to do work, thereby realizing the conversion from thermal energy to mechanical energy; a transition section, which is located between the regulating stage and the pressure stage, and is used to introduce the high-pressure steam exported from the regulating stage into the pressure stage, wherein a first group of ribs and / or a second group of ribs are provided in the transition section, the first group of ribs being located at a first predetermined position of the high-pressure steam outlet section of the regulating stage, and being used to perform preliminary straightening of the transverse steam flow in the transition section after the regulating stage, and the second group of ribs being located at a second predetermined position in the radial channel of the transition section, and being used to comb the radial steam flow in the transition section.

[0006] Optionally, the steam flow straightening device after the turbine regulating stage also includes: a high-pressure inner cylinder, which is a circular hollow structure for separating and guiding high-pressure steam, and the regulating stage, pressure stage and transition section are all located in the hollow interior of the high-pressure inner cylinder.

[0007] Optionally, the first group of ribs includes a first predetermined number of first ribs uniformly distributed in N circumferential directions, and the second group of ribs includes a second predetermined number of second ribs uniformly distributed in N circumferential directions, wherein N is not less than 10 and N is an integer.

[0008] Optionally, the first group of ribs and the second group of ribs are components that penetrate the entire cross-section of the transition section channel or components that occupy a partial area of ​​the cross-section of the transition section channel.

[0009] Optionally, the width of the first group of ribs is 10 to 60 mm, and the width of the second group of ribs is 10 to 80 mm.

[0010] Optionally, the cross-section of the ribs of the first group of ribs and the second group of ribs is rectangular or airfoil-shaped, and the airfoil is a uniform-section airfoil structure or a variable-section airfoil structure.

[0011] Optionally, the geometric steam inlet angle of the airfoil structure ranges from 60° to 90°.

[0012] Optionally, the first group of ribs and the second group of ribs are fixed to the inner surface of the high-pressure inner cylinder.

[0013] Optionally, the installation angles of the first group of rib plates and the second group of rib plates in the axial direction of the high-pressure inner cylinder are determined according to the steam flow conditions of the high-pressure steam.

[0014] Optionally, the height H1 of the first group of ribs is greater than half the channel height Hc, and the corresponding rib width W1 is 1 to 3 times the rib height H1; the height H2 of the second group of ribs is greater than half the channel height Hs, and the corresponding rib width W2 is 1 to 3 times the rib height H2.

[0015] The present application solves the problem that the circumferential steam flow of a variable operating condition steam turbine using nozzle regulation is uneven under some operating conditions, and the absolute steam outlet angle after the regulation stage significantly deviates from the axial direction, thereby solving the problem that the pressure stage working efficiency of the variable operating condition steam turbine using nozzle regulation decreases. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 is a cross-sectional view of a steam flow straightening device of the present application equipped with two sets of rib plates;

[0018] Figure 2 It is a schematic diagram of a steam flow straightening device equipped with two sets of rib plates in the present application;

[0019] Figure 3 It is a schematic diagram of a rib plate profile of the steam flow straightening device of the present application;

[0020] Figure 4 It is a Mach number distribution diagram in the pressure stage channel of the steam flow straightening device after adding the turbine regulating stage before and after the rib plate;

[0021] [Explanation of the accompanying drawings] 1- regulating stage static blades; 2- regulating stage moving blades; 3- pressure stage first stage static blades; 4- pressure stage first stage moving blades; 5- high-pressure inner cylinder; 6- first group of ribs; 7- second group of ribs.

[0022] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0023] The preferred embodiments of the present application are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present application can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present application.

[0024] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "include..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0025] With the increasing installed capacity of new energy power generation year by year, the peak load regulation of the power grid has become more and more severe, forcing the basic energy power system dominated by coal-fired power to fully participate in the deep peak load regulation of the power grid, which will lead to frequent changes in the load of the steam turbine unit. The operating condition change of the steam turbine is achieved by adjusting the steam inlet volume by adjusting the opening of the regulating valve. Therefore, there is a very large deviation between the main operating parameters of the steam turbine and the design parameters. When the opening of the regulating valve decreases, the partial steam inlet of the regulating stage decreases, which significantly increases the partial steam inlet loss of the regulating stage. At the same time, the circumferential unevenness of the steam flow after the regulating stage increases, which will deteriorate the inlet flow conditions of the subsequent pressure stage, and the efficiency of the pressure stage will be greatly reduced. At this time, the absolute outlet steam flow angle of the steam flow after the regulating stage increases, which significantly increases the positive angle of attack of the subsequent pressure stage, further reducing the efficiency of the pressure stage; when the opening of the regulating valve increases, the partial steam inlet of the regulating stage increases, and the absolute outlet steam flow angle of the steam flow after the regulating stage decreases, which significantly increases the negative angle of attack of the subsequent pressure stage, resulting in a decrease in the efficiency of the pressure stage, and will cause some pressure stage channels to be blocked, reducing the actual flow capacity. It can be seen from this that when the steam turbine unit is operating under variable operating conditions, the change in the steam inlet degree of the regulating stage, which in turn causes an increase in the circumferential unevenness of the steam flow after the regulating stage and the deviation of the absolute steam flow angle from the axial direction, is the main reason for the reduction in the variable operating condition efficiency of the steam turbine.

[0026] In response to the above-mentioned problems, the present application arranges circumferential ribs after the regulating stage of the steam turbine, so that when the operating conditions of the steam turbine change, the steam flow ribs after the regulating stage are rectified, thereby reducing the problem of uneven circumferential steam flow in the steam pipe after the regulating stage, and at the same time reducing the deviation of the absolute steam outlet angle of the steam flow from the axial direction, significantly improving the flow boundary conditions at the inlet of the subsequent pressure stage, thereby improving the efficiency of the pressure stage under variable operating conditions, and further ensuring that the steam turbine unit has a higher operating efficiency within a wider load range.

[0027] Figure 1 It is a cross-sectional view of the steam flow straightening device of the present application which is equipped with two sets of rib plates.

[0028] like Figure 1 The steam flow straightening device shown includes: a regulating stage, which adjusts the steam intake of high-pressure steam according to load requirements; a pressure stage, which is located after the regulating stage, and the high-pressure steam further expands to do work, thereby realizing the conversion from thermal energy to mechanical energy; a transition section, which is located between the regulating stage and the pressure stage, and is used to introduce the high-pressure steam exported from the regulating stage into the pressure stage, wherein a first group of rib plates and / or a second group of rib plates are provided in the transition section, the first group of rib plates being located at a first predetermined position of the high-pressure steam outlet section of the regulating stage, and being used to perform preliminary straightening of the transverse steam flow in the transition section after the regulating stage, and the second group of rib plates being located at a second predetermined position in the radial channel of the transition section, and being used to comb the radial steam flow in the transition section.

[0029] Specifically, the conventional transition channels between the regulating stage and the pressure stage are all smooth-walled. When the steam turbine operates near the design operating conditions, the absolute steam flow angle at the outlet of the regulating stage moving blades is large, and the steam flow attack angle at the inlet of the rear pressure stage stationary blades is small, so the loss of the pressure stage caused by the attack angle is small; but because of the existence of partial steam inlet, the circumferential direction of the steam flow behind the regulating stage moving blades is extremely uneven, which causes the circumferential direction of the pressure stage inlet to be uneven, resulting in very small flow rate in some pressure stage channels and low overall efficiency; when the steam turbine operates under variable operating conditions, the absolute steam flow angle at the outlet of the regulating stage moving blades quickly deviates from the axial direction, causing the loss of the pressure stage caused by the attack angle to increase rapidly, and the efficiency to drop significantly; at the same time, when operating under partial variable operating conditions, the partial steam inlet gradually decreases, and the circumferential unevenness of the steam flow behind the regulating stage moving blades further increases, which further deteriorates the boundary conditions at the inlet of the turbine pressure stage and continues to decrease the efficiency. In order to solve the problem of reduced unit efficiency caused by deterioration of flow in the transition section between the regulating stage and the pressure stage when the conventional steam turbine is under variable operating conditions, the present application proposes a method such as Figure 1 Steam flow rectification device.

[0030] like Figure 1 The steam flow straightening device shown also includes regulating stage stationary blades, regulating stage moving blades, pressure stage first stage stationary blades, pressure stage first stage moving blades and high pressure inner cylinder. The steam flow is preliminarily processed by the regulating stage stationary blades and regulating stage moving blades, reaches the regulating stage outlet section, and then passes through the first group of ribs to preliminarily straighten the steam flow after the regulating stage. The rectified steam flow continues to flow in the transition section and reaches the second group of ribs located in the radial channel of the transition section. The second group of ribs combs the radial steam flow in the steam flow in the transition section, and then the steam flow flows to the longitudinal section of the transition section, and flows through the pressure stage first stage stationary blades and the pressure stage first stage moving blades, and flows out of the steam flow straightening device. Among them, the first group of ribs 6 is installed in the straight section near the regulating stage moving blade outlet, and the second group of ribs 7 is installed in the radial channel of the transition section. Both groups of ribs are installed on the inner wall surface of the high pressure inner cylinder 5.

[0031] The ribs are divided into two groups, and are mainly arranged at the steam flow turning section near the outlet section of the regulating stage and the transition section. According to the variable operating performance of the steam turbine unit, that is, the change of the absolute steam outlet angle of the regulating stage, a certain group of ribs or a combination of two groups of ribs is selected for use, and by adjusting the geometric parameters, position, angle, etc. of each group of ribs, the change of the steam flow direction and the combing of the steam flow can be achieved. The present application solves the problem that the circumferential steam flow of a variable operating condition steam turbine using nozzle regulation is uneven under some operating conditions, and the absolute steam outlet angle after the regulating stage significantly deviates from the axial direction, resulting in a significant decrease in the working efficiency of the pressure stage. It changes the circumferential distribution of the regulating stage outlet steam flow and the steam flow angle, improves the inlet boundary conditions of the pressure stage, and improves the efficiency and output of the steam turbine.

[0032] In actual application, at least one set of rib plates is used to comb the steam flow. Any set of rib plates can be used alone, or two sets of rib plates can be used at the same time to comb the steam flow. That is, only one set of rib plates or two sets of rib plates can achieve the effect of combing the steam flow in this application, thereby changing the circumferential uniform distribution of the steam flow and the steam flow angle at the outlet of the regulating stage, improving the boundary conditions of the pressure stage inlet, and improving the efficiency and output of the turbine.

[0033] The device has the following beneficial effects: when the steam turbine is operated under the condition of small partial steam inlet, because only part of the arc segment is inlet, the circumferential distribution of the steam flow after the regulating stage is extremely uneven. By adding the rectifying ribs, the steam flow increases the circumferential mixing under the disturbance of the ribs, which greatly reduces the circumferential unevenness of the steam flow and significantly improves the inlet boundary conditions of the subsequent pressure stage. When the steam turbine is operated under variable conditions, that is, under non-design point conditions, the absolute outlet steam flow angle of the regulating stage moving blade will obviously deviate from the axial direction, causing a large positive or negative angle of attack at the inlet of the subsequent pressure stage, so the pressure stage will experience a decrease in efficiency or flow blockage. After the steam flow is combed by the rectifying ribs, the steam flow basically eliminates the change in angle of attack caused by different operating conditions before entering the pressure stage stator, further improving the inlet boundary conditions of the pressure stage. After adding the rectifier ribs, the enthalpy drop distribution between the regulating stage and the subsequent pressure stage will change due to the pressure change in the transition section after the regulating stage. The enthalpy drop of the pressure stage will also be closer to the design point under variable operating conditions, that is, the high-efficiency operation of the design point can be maintained under variable operating conditions.

[0034] In a specific embodiment of the present application, the first group of ribs and the second group of ribs are arranged in the transition section between the regulating stage and the pressure stage. The first group of ribs is arranged near the outlet of the regulating stage, and is suitable for preliminary combing of the steam flow at the outlet of the regulating stage, reducing the circumferential non-uniformity of the steam flow, and reducing the deviation of the steam flow angle from the axial direction; the rectifying rib group in the transition section, i.e., the second group of ribs, is used for combing the radial steam flow in the transition section, and also reduces the circumferential non-uniformity of the steam flow, and reduces the deviation of the steam flow angle from the axial direction. Among them, the ribs of the first group of ribs and the second group of ribs can pass through the entire steam inlet channel or occupy part of the steam inlet channel, that is, the specific size of the ribs can be appropriately adjusted according to user needs. Preferably, the width of the first group of ribs is 10 to 60 mm, and the width of the second group of ribs is 10 to 80 mm. The height H1 of the first group of ribs is greater than half of the channel height Hc, and the corresponding rib width W1 is 1 to 3 times the rib height H1. The height H2 of the second group of ribs is greater than half of the channel height Hs, and the corresponding rib width W2 is 1 to 3 times the rib height H2. The first group of ribs has a first predetermined number of first ribs evenly distributed in N circumferential directions, and the second group of ribs has a second predetermined number of second ribs evenly distributed in N circumferential directions, 10≤N≤40, and N is an integer.

[0035] Furthermore, the first set of rib plates and the second set of rib plates are installed on the inner surface of the hollow surface of the high-pressure inner cylinder.

[0036] Specifically, when casting the high-pressure inner cylinder, the first group of ribs and the second group of ribs are cast at the same time, that is, the first group of ribs and the second group of ribs are formed integrally with the high-pressure inner cylinder, or, a mounting groove is cast in the high-pressure inner cylinder, and a tenon structure is added to the ends of the first group of ribs and the second group of ribs, and the connection between the first group of ribs, the second group of ribs and the high-pressure inner cylinder is achieved through the connection of the mounting groove and the tenon structure.

[0037] The above-mentioned first rib plate group close to the regulating stage is installed on the inner wall surface of the high-pressure inner cylinder and is separated from the outlet of the regulating stage moving blades by a certain distance; the second rib plate group used for rectification in the transition section is also installed on the inner wall surface of the high-pressure inner cylinder, and is located in the radial channel of the transition section and should not be arranged in the horizontal section in front of the stationary blades of the subsequent pressure stage.

[0038] Furthermore, the angles of the first and second ribs in the axial direction of the high-pressure inner cylinder are determined according to the steam flow conditions. That is, the user can set the angles of the first and second ribs in the axial direction according to the steam flow direction in the channel, etc., and the specific parameter settings are not limited in this application.

[0039] In a specific embodiment of the present application, Figure 2 is a schematic diagram of a steam flow straightening device with two sets of rib plates installed in the present application, and Figure 3 It is a schematic diagram of a rib plate type line of the steam flow straightening device of the present application, such as Figure 2 and Figure 3 As shown, the cross-section of the ribs of the first group of ribs and the second group of ribs is a rectangular structure or an airfoil structure, and when the cross-section of the ribs of the first group of ribs and the second group of ribs is an airfoil structure, the airfoil structure can be selected as a uniform cross-section airfoil structure or a variable cross-section airfoil structure. Preferably, the geometric steam inlet angle of the airfoil structure ranges from 60° to 90°.

[0040] Specifically, refer to Figure 2 and Figure 3 , setting the rib profile to an airfoil will effectively reduce the flow loss along the way, and the leading edge radius of the airfoil is large, which can effectively reduce the separation area of ​​the steam flow when the steam flow angle changes dramatically under variable working conditions. When the rib profile is an airfoil, the airfoil should be installed along the steam flow direction, that is, the leading edge of the first group of airfoils is close to the outlet of the regulating stage moving blades, and the leading edge of the second group of airfoils is far away from the inlet of the pressure stage stationary blades.

[0041] refer to Figure 2According to the changes in the partial steam inlet degree, and on the premise of taking into account multiple working conditions as much as possible, a certain number of rib plates are selected circumferentially for each group of rib plates, and they are arranged with equal or unequal spacing; the circumferential phase angles of the two groups of rib plates are not necessarily the same, they can overlap, or be arranged circumferentially with a certain phase angle staggered, which will be conducive to the two groups of rib plates to play a rectifying role on the steam flow, making the steam flow more uniform circumferentially.

[0042] Figure 4 This is the Mach number distribution diagram in the pressure stage channel of the steam flow straightening device before and after the rib plate is added. Figure 4 As shown in the figure, through numerical simulation experiments, the effect of the rib plate under multiple working conditions is verified. When the partial steam inlet degree is 0.4, the pressure stage flow condition is significantly improved after the rib plate is added, so that the pressure stage efficiency can be increased by about 20%, and the regulating stage and pressure stage specific work are increased by about 2%; under the working conditions close to the design point and the steam inlet is close to the full circle steam inlet, the pressure stage efficiency and specific work changes are within 0.5%.

[0043] Figure 1-2 The schematic diagrams of the structure of the rectifier device after the regulating stage of a variable working condition steam turbine according to the embodiment of the present invention are shown respectively. In particular, Figure 1-2 The rectifier device after the regulating stage of a variable-operating-condition steam turbine is only illustrative, and is used to help those skilled in the art understand the technical content of the present invention, but does not mean that the implementation of the present invention is limited to this. According to actual needs, the profile, relative position, angle and number of the two sets of ribs can be adaptively adjusted.

[0044] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0045] The above description is only an embodiment of the present application and does not limit the patent scope of the present application. Any equivalent structural transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A steam flow rectifying device after a steam turbine regulating stage, characterized in that: include: The regulating stage adjusts the steam inlet of high-pressure steam according to the load requirements; The pressure stage is located after the regulating stage, and the high-pressure steam further expands to do work, realizing the conversion from thermal energy to mechanical energy; A transition section, which is located between the regulating stage and the pressure stage, and is used to introduce the high-pressure steam discharged from the regulating stage into the pressure stage, wherein a first group of ribs and / or a second group of ribs are provided in the transition section, the first group of ribs being located at a first predetermined position of the high-pressure steam outlet section of the regulating stage, and being used to perform preliminary rectification of the transverse steam flow in the transition section after the regulating stage, and the second group of ribs being located at a second predetermined position in the radial channel of the transition section, and being used to comb the radial steam flow in the transition section.

2. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 1, characterized in that: Also includes: The high-pressure inner cylinder is a circular hollow structure, which is used to separate and guide the high-pressure steam, and the regulating stage, the pressure stage and the transition section are all located in the hollow interior of the high-pressure inner cylinder.

3. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 1, characterized in that: The first group of ribs includes a first predetermined number of first ribs uniformly distributed in N circumferential directions, and the second group of ribs includes a second predetermined number of second ribs uniformly distributed in N circumferential directions, wherein N is not less than 10 and is an integer.

4. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 1, characterized in that: The first group of ribs and the second group of ribs are components that penetrate the entire cross-section of the transition section channel or occupy a partial area of ​​the cross-section of the transition section channel.

5. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 1, characterized in that: The width of the first group of ribs is 10-60 mm, and the width of the second group of ribs is 10-80 mm.

6. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 1, characterized in that: The cross-sections of the ribs of the first group of ribs and the second group of ribs are rectangular or airfoil-shaped, and the airfoil is a uniform-section airfoil structure or a variable-section airfoil structure.

7. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 7, characterized in that: The geometric steam inlet angle of the airfoil structure has a value range of 60° to 90°.

8. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 2, characterized in that: The first group of ribs and the second group of ribs are fixed on the inner surface of the high-pressure inner cylinder.

9. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 8, characterized in that: The installation angles of the first group of rib plates and the second group of rib plates in the axial direction of the high-pressure inner cylinder are determined according to the steam flow conditions of the high-pressure steam.

10. The steam flow rectifying device after the regulating stage of the steam turbine according to claim 1, characterized in that: The height H1 of the first group of ribs is greater than half of the channel height Hc, and the corresponding rib width W1 is 1 to 3 times the rib height H1; the height H2 of the second group of ribs is greater than half of the channel height Hs, and the corresponding rib width W2 is 1 to 3 times the rib height H2.

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