A machining method for a reverse T-shaped blade root groove of a steam turbine rotor

Abstract

The application discloses a processing method for a turbine rotor inverted T-shaped blade root groove, and relates to a processing method for a rotor blade root groove. The application is used to solve the problem that the profile of the blade root groove has an elliptical track, and the blade root groove is inconvenient to program, thereby causing low processing efficiency of the blade root groove. The application is simple, convenient, efficient and practical. An elliptical arc segment is changed into a plurality of circular arc segments which are connected in sequence by using a pellipse instruction in AutoCAD software, programming is performed on the plurality of circular arc segments by using a circular arc interpolation instruction, different tools are matched, and turning processing of the blade root groove is realized on a numerical control horizontal lathe. After the method is used, the processing error of the blade root groove is within 0.03 mm, the quality requirement of the blade root groove processing is met, and the processing method has been widely applied to production practice. The application belongs to the technical field of turbine rotor processing.

Description

Technical Field

[0001] This invention relates to a method for machining rotor blade root grooves, specifically a method for machining inverted T-shaped blade root grooves of a steam turbine rotor, belonging to the field of steam turbine rotor machining technology. Background Technology

[0002] The profile of conventional turbine rotor blade root slots is generally an inverted T-shaped structure formed by connecting circular arcs and straight lines, and is usually machined on a CNC lathe using a right-angle (90-degree) bent cutting tool. In recent years, due to the large thermal stress generated on the rotor by high-power turbines under high temperature and high pressure during startup and operation, a new inverted T-shaped blade root slot composed of elliptical, circular arc, and straight line connections has been designed to relieve this stress.

[0003] However, this structure presents a new challenge for the turning of the blade root groove: ordinary CNC instructions cannot directly process elliptical trajectories, and manual programming requires the use of macro programs on the CNC system. This programming method requires a high level of skill from the programmer. Furthermore, adjusting the macro program after the dimensions of the blade root groove change is time-consuming and laborious, especially for internal cavity surfaces like the blade root groove, where adjusting program variables becomes even more cumbersome and complex, resulting in low machining efficiency for the blade root groove.

[0004] In summary, how to propose a processing method to address the aforementioned technical problems has become a pressing issue for those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of the prior art, this invention provides a method for machining inverted T-shaped blade root grooves on a steam turbine rotor.

[0006] The technical solution of the present invention is: a method for processing an inverted T-shaped blade root groove of a steam turbine rotor, including the profile of the blade root groove, which includes a contact surface, a first stress relief groove, a second stress relief groove and a third stress relief groove connected in sequence.

[0007] The first stress relief groove is composed of a circular arc segment with radius R1 and a circular arc segment with radius R2 that are tangent to each other.

[0008] The third stress relief groove is composed of two tangent arc segments with a radius of R3 and a radius of R4.

[0009] The second stress relief groove includes a first elliptical arc segment with major axis a and minor axis b, a second elliptical arc segment with major axis c and minor axis d, and a third elliptical arc segment with major axis e and minor axis f.

[0010] Specifically, the method is carried out in the following steps:

[0011] Step 1: Draw the profile of the blade root groove using AutoCAD software;

[0012] Step 2: Before drawing the first, second, and third elliptical arc segments, enter the pellipse command in AutoCAD and press Enter. AutoCAD will then display the current value of Pellipse.

[0013] Step 3: Change the current value of Pellipse to "1";

[0014] Step 4: Draw the first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment. The drawn first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment are all transformed into several sequentially connected circular arc segments.

[0015] Step 5: Manually program the completed profile and input the program into the CNC system of the CNC machine tool to process the blade root groove.

[0016] Furthermore, a left-hand offset tool is used when machining the first stress relief groove, the first elliptical arc segment, and the second elliptical arc segment.

[0017] Furthermore, a right-hand offset tool is used when machining the third stress relief groove and the third elliptical arc segment.

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

[0019] 1. This invention is simple and convenient to operate, and is a highly efficient and practical machining method: by using the pellipse command in AutoCAD software to transform an elliptical arc segment into several sequentially connected circular arc segments, the circular interpolation command can be used to program several circular arc segments. With different cutting tools, the turning of the blade root groove can be realized on a CNC lathe. After adopting this method, the machining error of the blade root groove is within 0.03mm, which meets the quality requirements of blade root groove machining. This machining method has been widely used in production practice. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the leaf root groove profile of the present invention;

[0021] Figure 2 This is a first schematic diagram of the present invention when machining the blade root groove by turning;

[0022] Figure 3 This is a second schematic diagram of the present invention when machining the blade root groove;

[0023] Figure 4 This is a third schematic diagram of the present invention when machining the blade root groove;

[0024] Figure 5 This is the fourth schematic diagram of the present invention when machining the blade root groove;

[0025] Figure 6 This is the fifth schematic diagram of the present invention when machining the blade root groove;

[0026] Figure 7 This is the sixth schematic diagram of the present invention when machining the blade root groove;

[0027] Figure 8 This is the seventh schematic diagram of the present invention when machining the blade root groove;

[0028] In the figure: 1. First stress relief groove; 2. Second stress relief groove; 3. Third stress relief groove; 4. Contact surface. Detailed Implementation

[0029] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments.

[0030] Specific implementation method one: Combining Figure 1 This embodiment describes a method for machining an inverted T-shaped blade root groove of a steam turbine rotor, which includes a profile of the blade root groove, comprising a contact surface 4, a first stress relief groove 1, a second stress relief groove 2, and a third stress relief groove 3 connected in sequence.

[0031] The first stress relief groove 1 is composed of a circular arc segment with radius R1 and a circular arc segment with radius R2 that are tangent to each other.

[0032] The third stress relief groove 3 is composed of a circular arc segment with radius R3 and a circular arc segment with radius R4 that are tangent to each other.

[0033] The second stress relief groove 2 includes a first elliptical arc segment with major axis a and minor axis b, a second elliptical arc segment with major axis c and minor axis d, and a third elliptical arc segment with major axis e and minor axis f.

[0034] Specifically, the method is carried out in the following steps:

[0035] Step 1: Draw the profile of the blade root groove using AutoCAD software;

[0036] Step 2: Before drawing the first, second, and third elliptical arc segments, enter the pellipse command (pellipse: creates a real ellipse object / creates an ellipse composed of polylines) in AutoCAD software and press Enter. AutoCAD software will then display the current value of Pellipse. By default, the current value of Pellipse is 0. At this time, the drawn ellipse is a complete, closed elliptical curve.

[0037] Step 3: Change the current value of Pellipse to "1";

[0038] Step 4: Draw the first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment. The drawn first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment are all transformed into several sequentially connected circular arc segments. That is, the first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment are all transformed into elliptical arc segments fitted by multiple circular arc segments. Thus, several circular arc segments can be programmed using circular arc interpolation instructions.

[0039] Step 5: Manually program the completed profile and input the program into the CNC system of the CNC machine tool to process the blade root groove.

[0040] Furthermore, the two endpoints of the first elliptical arc segment are tangent to the first stress relief groove 1 and the second elliptical arc segment, respectively. The second elliptical arc segment is connected to the third elliptical arc segment by a straight line, and the third elliptical arc segment is connected to the third stress relief groove 3 by a straight line.

[0041] Furthermore, a left-hand offset tool is used when machining the first stress relief groove 1, the first elliptical arc segment, and the second elliptical arc segment.

[0042] Furthermore, a right-hand offset tool is used when machining the third stress relief groove 3 and the third elliptical arc segment.

[0043] Furthermore, the CNC system in step five is the Siemens 840D CNC system.

[0044] Example

[0045] Combination Figures 1 to 8 This embodiment is described as follows:

[0046] In the specific processing, based on the structural characteristics of the blade root groove profile, the processing can be carried out in sections, specifically in the following order:

[0047] First cut: Machining the second elliptical arc segment

[0048] like Figure 2 As shown, the first left-hand cutting tool is selected. The thick solid line in the figure represents the machining cutting trajectory, and the dashed line represents the tool entry and exit trajectory.

[0049] Second cut: Machining the first elliptical arc segment

[0050] like Figure 3 As shown, the second left-hand cutting tool is selected. The thick solid line in the figure is the machining cutting trajectory, and the dashed line is the tool entry and exit trajectory.

[0051] Third cut: Machining the first elliptical arc segment

[0052] like Figure 4As shown, the third left-hand cutting tool is selected. The thick solid line in the figure represents the machining cutting trajectory, and the dashed line represents the tool entry and exit trajectory.

[0053] Cut 4: Machining the first elliptical arc segment, the circular arc segment with radius R2, and the contact surface 4.

[0054] like Figure 5 As shown, the fourth left-hand cutting tool is selected. The thick solid line in the figure is the machining cutting trajectory, and the dashed line is the tool entry and exit trajectory.

[0055] Cut 5: Machining the arc segment with radius R1.

[0056] like Figure 6 As shown, the fifth left-hand cutting tool is selected. The thick solid line in the figure is the machining cutting trajectory, and the dashed line is the tool entry and exit trajectory.

[0057] Cut 6: Machining the third elliptical arc segment, the circular arc segment with radius R4, and the contact surface 4.

[0058] like Figure 7 As shown, the first right-hand cutting tool is selected. The thick solid line in the figure represents the machining cutting trajectory, and the dashed line represents the tool entry and exit trajectory.

[0059] Cut 7: Machining an arc segment with a radius of R3.

[0060] like Figure 8 As shown, the second right-hand cutting tool is selected. The thick solid line in the figure is the machining cutting trajectory, and the dashed line is the tool entry and exit trajectory.

[0061] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. Any simple modifications, equivalent changes and alterations made by those skilled in the art to the above embodiments without departing from the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for machining an inverted T-shaped blade root groove of a steam turbine rotor, including the profile of the blade root groove; The profile includes a contact surface (4), a first stress relief groove (1), a second stress relief groove (2), and a third stress relief groove (3) connected in sequence; The first stress relief groove (1) is composed of a circular arc segment with radius R1 and a circular arc segment with radius R2 that are tangent to each other; The third stress relief groove (3) is composed of a circular arc segment with radius R3 and a circular arc segment with radius R4 that are tangent to each other; The second stress relief groove (2) includes a first elliptical arc segment with a major axis of a and a minor axis of b, a second elliptical arc segment with a major axis of c and a minor axis of d, and a third elliptical arc segment with a major axis of e and a minor axis of f; Its features are: This method is specifically carried out in the following steps: Step 1: Draw the profile of the blade root groove using AutoCAD software; Step 2: Before drawing the first, second, and third elliptical arc segments, enter the pellipse command in AutoCAD and press Enter. AutoCAD will then display the current value of Pellipse. Step 3: Change the current value of Pellipse to "1"; Step 4: Draw the first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment. The drawn first elliptical arc segment, the second elliptical arc segment, and the third elliptical arc segment are all transformed into several sequentially connected circular arc segments. Step 5: Manually program the completed profile and input the program into the CNC system of the CNC machine tool to process the blade root groove.

2. The method for machining the inverted T-shaped blade root groove of a steam turbine rotor according to claim 1, characterized in that: The two ends of the first elliptical arc segment are tangent to the first stress relief groove (1) and the second elliptical arc segment respectively. The second elliptical arc segment is connected to the third elliptical arc segment by a straight line, and the third elliptical arc segment is connected to the third stress relief groove (3) by a straight line.

3. The method for machining the inverted T-shaped blade root groove of a steam turbine rotor according to claim 2, characterized in that: The left-hand cutting tool is used when machining the first stress relief groove (1), the first elliptical arc segment and the second elliptical arc segment.

4. The method for machining the inverted T-shaped blade root groove of a steam turbine rotor according to claim 3, characterized in that: The right-hand side cutter is used when machining the third stress relief groove (3) and the third elliptical arc segment.

5. The method for machining the inverted T-shaped blade root groove of a steam turbine rotor according to claim 4, characterized in that: The CNC system in step five is the Siemens 840D CNC system.

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