Low-load automatic drain device suitable for inner cylinder of steam turbine and steam turbine

Abstract

The present invention provides a low-load automatic drain device suitable for the inner cylinder of a steam turbine and a steam turbine. The device includes a shell, a valve stem, a pressure difference spring, and a filter cover. The device can remain in an open state within a certain pressure difference range for draining the inner cylinder, and remain closed when the pressure difference is greater than a set value so that the steam in the inner cylinder no longer leaks into the inner and outer cylinder interlayer. Compared with the traditional inner cylinder cavity drain, which requires a drain pipe to pass through the outer cylinder and lead to the outside of the cylinder, it is also necessary to configure a drain valve and use a control system to control the opening and closing of the valve. The device has a simple structure, and the opening control of the drain is only related to the pressure in the inner cylinder cavity. It is easy to control and has a low cost. The present invention can well solve the problems of the traditional inner cylinder drain system complexity and high cost.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbines, and in particular to a low-load automatic drain device suitable for an inner cylinder of a steam turbine and a steam turbine. Background Art

[0002] The inner cylinder of a steam turbine is often arranged with extraction chambers and supplementary steam chambers with various parameter requirements. These annular chambers all have the problem of water accumulation at low points. When the unit is started and in the low-load operation stage, the accumulated water in this area needs to be removed in time, otherwise it will cause a large temperature difference between the upper and lower cylinders of the inner cylinder, causing uncoordinated deformation of the inner cylinder, causing the dynamic and static clearances in the flow area to deviate from the design value, thereby causing unit vibration problems.

[0003] In the prior art, the method for draining the inner cylinder is to arrange a drain pipe, pass the drain pipe through the outer cylinder to the outside of the cylinder, and configure a drain valve outside the cylinder, and control the opening and closing of the drain valve through the actuator of the drain valve.

[0004] However, the steam trap through the cylinder works in high-temperature and high-speed steam flow, and the expansion of the inner and outer cylinders is inconsistent, and the steam trap will occasionally rupture. In addition, the introduction of the steam trap not only increases the manufacturing cost of the steam turbine, but also makes the control system complicated. Summary of the invention

[0005] The purpose of the present invention is to provide a low-load automatic drain device suitable for the inner cylinder of a steam turbine and a steam turbine, so as to solve the problem of the complexity and high cost of the conventional inner cylinder drain in the current market, which requires the outer cylinder drain pipe to be passed through and the drain valve to be configured. The device has a simple structure and precise and appropriate functional design, which can not only greatly reduce the complexity of the inner cylinder drain system, but also greatly reduce the cost of the drain system.

[0006] In order to achieve the above objectives, the present invention is implemented by the following technical solutions:

[0007] A low-load automatic drain device suitable for an inner cylinder of a steam turbine, comprising:

[0008] A shell body is installed in a mounting hole at the lower part of the inner cylinder body, and a through drain hole is provided in the shell body, and the drain hole is a stepped hole;

[0009] A valve stem is sleeved in the drain hole of the housing, a first end of the valve stem contacts the pressure in the inner cylinder cavity, a second end of the valve stem contacts the pressure in the inner and outer cylinder interlayers, and a sealing portion extending radially is provided at the first end of the valve stem;

[0010] A pressure differential spring, which is sleeved on the outside of the valve stem and located in the large hole of the stepped hole, with one end abutting against the step of the stepped hole and the other end abutting against the sealing portion of the first end of the valve stem;

[0011] The pressure in the inner cylinder cavity and the pressure difference between the inner and outer cylinder interlayers act on the axial direction of the valve stem; when the pressure difference is lower than the maximum elastic force of the pressure difference spring, the first end of the valve stem moves away from the shell; when the pressure difference exceeds the maximum elastic force of the pressure difference spring, the first end of the valve stem contacts the shell, so that the sealing part contacts the sealing surface of the shell surface to form a seal, so as to block the hydrophobic hole.

[0012] Optionally, the elastic force of the pressure difference spring is adjustable.

[0013] Optionally, the housing and the valve stem are made of wear-resistant and high-temperature resistant materials.

[0014] Optionally, it also includes: a filter cover installed on the upper part of the shell body close to the inner side of the inner cylinder.

[0015] Optionally, an annular cutout matching the filter cover is provided on the upper portion of the shell, and the filter cover is installed in the annular cutout.

[0016] Optionally, the housing and the mounting hole of the inner cylinder body of the steam turbine are threadedly connected.

[0017] A steam turbine comprises an inner cylinder body, wherein a mounting hole is provided at the lower portion of the inner cylinder body, and a low-load automatic drain device suitable for the inner cylinder of the steam turbine as described above is installed in the mounting hole.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The complexity of the conventional inner cylinder drain system is simplified; the cost of the conventional inner cylinder drain system is reduced by more than 80%; and the on-site installation of the inner cylinder drain pipe is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are an embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0021] Figure 1 A cross-sectional view of a low-load automatic drain device applicable to an inner casing of a steam turbine provided by one embodiment of the present invention;

[0022] Figure 2 An exploded view of a low-load automatic drain device suitable for an inner casing of a steam turbine provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0023] The scheme proposed by the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the implementation method of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the accompanying drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the accompanying drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present invention.

[0024] An embodiment of the present invention provides a low-load automatic drain device suitable for the inner cylinder of a steam turbine, such as Figure 1 As shown, it includes a shell 1, a valve stem 2 and a pressure difference spring 3. In order to facilitate water drainage, a mounting hole 51 is usually provided at the lower part of the inner cylinder body 5 of the steam turbine for installing a water drainage device. In this embodiment, the shell 1 is installed in the mounting hole 51 at the lower part of the inner cylinder body 5, and a through water drainage hole 11 is provided in the shell 1, so that the accumulated water in the inner cylinder can be discharged from the water drainage hole 11 of the shell 1. The valve stem 2 is sleeved in the water drainage hole 11 of the shell 1, and the first end of the valve stem 2 contacts the pressure in the inner cylinder cavity, and the second end contacts the pressure between the inner and outer cylinders. The pressure difference spring 3 is sleeved on the outside of the valve stem 2, and abuts against the shell 1 and the first end of the valve stem 2.

[0025] The pressure inside the inner cylinder cavity and the pressure difference between the inner and outer cylinder interlayers act on the axial direction of the valve stem 2; when the pressure difference is lower than the maximum elastic force of the pressure difference spring 3, the first end of the valve stem 2 is away from the shell 1; when the pressure difference exceeds the maximum elastic force of the pressure difference spring 3, the first end of the valve stem 2 contacts the shell 1 and blocks the drain hole 11.

[0026] like Figure 1 and 2 As shown, the first end of the valve stem 2 is provided with a sealing portion 21 extending in the radial direction. When the pressure difference exceeds the maximum elastic force of the pressure difference spring 3, the sealing portion 21 contacts the sealing surface 13 on the surface of the housing 1 and forms a seal to block the drain hole 11. Furthermore, the pressure difference spring 3 abuts against the sealing portion 21. In order to make the structure of the drain device more compact, the drain hole 11 is designed as a stepped hole. The pressure difference spring 3 is located in the large hole of the stepped hole and one end abuts against the step of the stepped hole, and the other end abuts against the sealing portion of the first end of the valve stem 2.

[0027] The pressure difference at both ends of the valve stem 2 and the elastic force of the pressure difference spring 3 generate a combined force. The maximum elastic force of the pressure difference spring 3 can be considered as the design target value for opening / closing the drain device. When the pressure difference is lower than the design target value, the axial pressure of the valve stem 2 will offset the elastic force of the pressure difference spring 3, and the valve stem 2 is in the normally open position (that is, the first end of the valve stem 2 is away from the shell 1 to open the drain hole 11); when the pressure difference reaches the design target value, the valve stem 2 moves to the closed position (that is, the first end of the valve stem 2 contacts the shell 1 and blocks the drain hole 11), forming a sealed contact to block the inner cylinder steam from leaking into the inner and outer cylinder interlayer. When the steam turbine unit enters the medium and high load range, the drain device is normally closed because the pressure difference is higher than the design target value. When the steam turbine unit enters the low load area or the shutdown process, the drain device automatically opens and remains normally open because the pressure difference is lower than the design target value, and the condensate generated in the process is discharged into the inner and outer cylinder interlayer, and discharged out of the cylinder through the outer cylinder drain.

[0028] In this embodiment, the elastic force of the pressure difference spring 3 is adjustable to meet the use range of different pressure differences in different areas. According to the different use positions of the hydrophobic device, the elastic force of the pressure difference spring 3 is adjusted so that the device meets a specific closing pressure difference, so that the device is closed when the pressure difference is greater than the design target value and opened when it is less than the design target value.

[0029] The housing 1 and the valve stem 2 are made of wear-resistant and high-temperature resistant materials, thereby increasing the long-term sustainable normal operation of the device and avoiding the jamming of the hydrophobic device due to corrosion and wear of the parts themselves.

[0030] like Figure 1 and Figure 2 As shown, the hydrophobic device further includes: a filter cover 4, which is installed on the upper part of the housing 1 near the inner side of the inner cylinder. The setting of the filter cover 4 not only limits the range of movement of the valve stem 2 and the pressure difference spring 3, but also prevents large particles of impurities in the inner cylinder from entering the device, causing the device to become stuck and unable to work normally.

[0031] Specifically, the outer circumference of the upper part of the housing 1 is provided with an annular cutout 12 adapted to the filter cover 4, and the filter cover 4 is installed in the annular cutout 12. The annular cutout 12 is provided with an external thread, and the filter cover 4 is provided with an internal thread, and the two are connected by threads.

[0032] In order to facilitate disassembly and assembly, the housing 1 and the mounting hole 51 of the steam turbine inner cylinder body 5 are threadedly connected.

[0033] Based on the same inventive concept, the present invention also provides a steam turbine, comprising an inner cylinder body, wherein a mounting hole is provided at the lower portion of the inner cylinder body, and a low-load automatic drain device suitable for the inner cylinder of the steam turbine as described above is installed in the mounting hole. The steam turbine described in the present invention particularly refers to a steam turbine with supercritical and ultra-supercritical main steam parameters.

[0034] In summary, the automatic drain device provided by the present invention has a simple structure, a single function, and high working reliability, which greatly simplifies the complexity of the inner cylinder drain system and reduces the high cost of the conventional drain system.

[0035] 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 sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0036] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A low-load automatic drain device suitable for the inner cylinder of a steam turbine, characterized in that: include: A shell body is installed in a mounting hole at the lower part of the inner cylinder body, and a through drain hole is provided in the shell body, and the drain hole is a stepped hole; A valve stem is sleeved in the drain hole of the housing, a first end of the valve stem contacts the pressure in the inner cylinder cavity, a second end of the valve stem contacts the pressure in the inner and outer cylinder interlayers, and a sealing portion extending radially is provided at the first end of the valve stem; A pressure differential spring, which is sleeved on the outside of the valve stem and located in the large hole of the stepped hole, with one end abutting against the step of the stepped hole and the other end abutting against the sealing portion of the first end of the valve stem; The pressure in the inner cylinder cavity and the pressure difference between the inner and outer cylinder interlayers act on the axial direction of the valve stem; when the pressure difference is lower than the maximum elastic force of the pressure difference spring, the first end of the valve stem moves away from the shell; when the pressure difference exceeds the maximum elastic force of the pressure difference spring, the first end of the valve stem contacts the shell, so that the sealing part contacts the sealing surface of the shell surface to form a seal, so as to block the hydrophobic hole.

2. The low-load automatic drain device for the inner cylinder of a steam turbine as claimed in claim 1, characterized in that: The elastic force of the pressure difference spring is adjustable.

3. The low-load automatic drain device for the inner cylinder of a steam turbine as claimed in claim 1, characterized in that: The housing and the valve stem are made of wear-resistant and high-temperature resistant materials.

4. The low-load automatic drain device for the inner cylinder of a steam turbine as claimed in claim 1, characterized in that: Also includes: The filter screen cover is installed on the upper part of the shell body close to the inner side of the inner cylinder.

5. The low-load automatic drain device for the inner cylinder of a steam turbine as claimed in claim 1, characterized in that: An annular cutout matched with the filter cover is provided on the upper part of the shell, and the filter cover is installed in the annular cutout.

6. The low-load automatic drain device for the inner cylinder of a steam turbine as claimed in claim 1, characterized in that: The housing and the mounting hole of the inner cylinder body of the steam turbine are connected by threads.

7. A steam turbine, comprising an inner cylinder block, characterized in that: A mounting hole is provided at the lower portion of the inner cylinder body, and a low-load automatic drain device suitable for the inner cylinder of a steam turbine as claimed in any one of claims 1 to 6 is installed in the mounting hole.

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