Width measuring device for rhombic root crown of steam turbine blade and use method

Abstract

The invention discloses a width measuring device for a rhombic root crown of a turbine blade. The width measuring device comprises a device body and a dial indicator. An opening is formed in one transverse side of the device body, and a cavity for placing a rhombic blade crown or a rhombic blade root of the turbine blade is formed in the device body; the cavity comprises an upper inner side face and a lower inner side face which are vertically opposite and arranged in parallel, and the lower inner side face is a datum plane parallel to the horizontal plane. The datum plane is tightly attached to the plane of the blade steam inlet side or the blade steam outlet side of the turbine blade. The upper side of the upper end of the device body is detachably connected with a dial indicator corresponding to the reference surface; a gauge rod of the dial gauge vertically passes through the upper inner side surface, extends into the cavity, and abuts against a blade steam outlet side or a blade steam inlet side plane which is far away from one side of the reference surface. The device has the advantages of being simple in structure, wide in application range, high in measurement precision, high in measurement efficiency and very easy to operate.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbine blade measurement, and specifically relates to a device and method for measuring the width of a diamond root crown of a steam turbine blade. Background Art

[0002] As Figure 1 shown, the moving and stationary blades of a reaction steam turbine unit usually adopt a "diamond" root crown design structure. Specifically, the diamond root crown of the steam turbine blade 1 includes a diamond leaf crown 11 and a diamond leaf root 12; the steam inlet side of the blade of the diamond root crown includes a leaf crown steam inlet side 111 and a leaf root steam inlet side 121. The steam outlet side of the blade of the diamond root crown includes a leaf crown steam outlet side 112 and a leaf root steam outlet side 122; the plane of the leaf crown steam inlet side 111 is parallel to the plane of the leaf crown steam outlet side 112; the plane of the leaf root steam inlet side 121 is parallel to the plane of the leaf root steam outlet side 122.

[0003] During use, the processing accuracy requirements for the diamond root crown of the steam turbine blade 1 are very high, especially for the processing accuracy of the width dimensions of the steam inlet and outlet sides of the leaf root, and the tolerance requirement range is 0.03 mm (as Figure 2 shown); the processing accuracy of this position dimension will directly affect the assembly quality of the blade (mainly the assembly clearance), which is a key control index in the blade processing process and must be precisely controlled.

[0004] For such a high-precision leaf root width dimension, the following three detection methods are usually adopted: One is the coordinate measuring machine (CMM), but the CMM has low detection efficiency and high detection cost, and for CMM detection, each blade must be removed from the machine tool and then transported to the detection location. In this case, there is a problem: when the removed blade fails the CMM detection and needs to be repaired, it has to be re-clamped and positioned on the machine tool again. At this time, due to the influence of repeated positioning errors caused by secondary clamping. This not only makes the detection process not real-time, but also is not conducive to ensuring the processing accuracy of the blade.

[0005] The second detection method is on-line detection, but this detection method must be equipped with the necessary software and hardware for on-line detection for each processing machine tool, and the investment cost is relatively high.

[0006] The third method is to use a flat head micrometer 2 for measurement, but it is often affected by the large diamond angle of the blade, and the end points of the planes of the steam inlet and outlet sides of the leaf root are "dislocated" and the blade interferes with the measuring tool and cannot be measured (as Figure 3 shown).

[0007] Combined with the structure and processing and assembly requirements of reaction-type blades, the present invention invented a device and method for real-time measuring the width of the diamond root crown of steam turbine blade 1. This measuring tool can be used for steam turbine blades 1 with diamond root crowns, and has the advantages of low cost, high measuring accuracy, high measuring efficiency, and very simple operation. Summary of the Invention

[0008] The purpose of the present invention is to provide a device and method for measuring the width of the diamond root crown of steam turbine blades, which has low cost, high measuring accuracy, high measuring efficiency, and very simple operation, aiming at the deficiencies of the prior art.

[0009] The technical purpose of the present invention is achieved through the following technical solutions: A device for measuring the width of the diamond root crown of a steam turbine blade, comprising a device body and a dial indicator; One side of the device body is open horizontally, and is provided with a cavity for placing the diamond leaf crown or diamond leaf root of the steam turbine blade; the cavity includes an upper inner side and a lower inner side that are relatively and parallelly arranged up and down, and the lower inner side is a reference surface parallel to the horizontal plane; the reference surface is in close contact with the plane of the steam inlet side or steam outlet side of the blade of the steam turbine blade; a dial indicator is detachably connected to the upper side of the upper end of the device body; the stem of the dial indicator vertically passes through the upper inner side and extends into the cavity, and abuts against the plane of the steam outlet side or steam inlet side of the blade on the side away from the reference surface.

[0010] Preferably, the device body includes an upper side section, a lower side section, and a connecting section; the upper side section and the lower side section are arranged in parallel, and a dial indicator is detachably connected to the upper side of the upper side section; the upper side surface of the lower side section is the lower inner side surface of the cavity; the horizontal length of the lower side section is greater than the horizontal length of the plane of the steam inlet side or steam outlet side of the blade; one end of the upper side section and the lower side section in the same direction are respectively connected to the upper end and the lower end of the connecting section; the lower side section, the connecting section, and the upper side section together enclose a cavity for placing the diamond leaf crown or diamond leaf root of the steam turbine blade.

[0011] Preferably, the connecting section is inclined, the included angle between the lower side section and the connecting section is an obtuse angle, and the included angle between the upper side section and the connecting section is an acute angle.

[0012] Preferably, the inclination angle of the connecting section is the same as the inclination angle of the inclined surface of the diamond leaf crown or diamond leaf root of the steam turbine blade.

[0013] Preferably, a plurality of vertical through holes penetrating the upper and lower ends of the upper side section are provided at intervals in the horizontal direction of the upper side section corresponding to the lower side section, and the diameter of the vertical through holes is slightly larger than the diameter of the stem of the dial indicator; the stem and the vertical through holes are in clearance fit; a locking device for locking the stem is provided on the front / rear side of the upper side section.

[0014] Preferably, the locking device is a locking bolt, and threaded holes communicating with the vertical through holes and mating with the locking bolt are provided corresponding to the front / rear sides of the upper side section; the length of the screw rod of the locking bolt is greater than the depth of the threaded hole.

[0015] The usage method of the width measuring device for the diamond root crown of the steam turbine blade described above includes the following steps: Step 1, perform pre-treatment on the surface of the steam turbine blade to be measured. Step 2, calibrate the dial indicator through the measuring device and the standard block gauge. The size X of the standard block gauge should be consistent with the theoretical width of the diamond root crown of the steam turbine blade to be measured. Step 3, when measuring the width of the blade inlet and outlet sides of the diamond root crown with the measuring device, based on the measuring device calibrated in Step 2, make the plane of the blade inlet side or the blade outlet side of the diamond root crown close to the reference plane of the measuring device, make the lower end of the dial indicator rod abut against the plane of the blade outlet side or the blade inlet side away from the reference plane, and then observe the reading of the dial indicator pointer. Step 4, when the reading of the dial indicator pointer is Y, the width dimension of the measured blade can be calculated as (X ± Y) mm.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The measuring device of the present invention has a simple structure and is easy to operate; by providing a cavity for accommodating the diamond root crown of the steam turbine blade in the device body of the measuring device, when measuring, the problem that the blade interferes with the measuring device and causes unable to measure will not occur; the present invention has the advantages of low cost, high measuring accuracy, high measuring efficiency and very simple operation.

[0017] 2. The usage method of the present invention has fewer measuring steps and can be completed by a single person holding it; it has the advantages of simple operation, high measuring accuracy and high measuring efficiency. Description of the Drawings

[0018] Figure 1 is a schematic structural diagram of a prior steam turbine blade with a diamond root crown; Figure 2 is Figure 1 the leaf root width tolerance schematic diagram of Figure 3 is a schematic diagram when measuring the diamond root crown of a steam turbine blade with a flat head micrometer; Figure 4 is a schematic structural diagram of the present invention; Figure 5 is Figure 4 the reference diagram of the usage state of Reference numerals: 1 - steam turbine blade; 11 - diamond-shaped blade crown; 111 - steam inlet side of the blade crown; 112 - steam outlet side of the blade crown; 12 - diamond-shaped blade root; 121 - steam inlet side of the blade root; 122 - steam outlet side of the blade root; 2 - flat micrometer; 3 - device body; 31 - lower side section; 311 - reference plane; 32 - upper side section; 321 - lower side surface of the upper side section; 322 - vertical through hole; 323 - threaded hole; 33 - connecting section; 331 - inclined surface of the connecting section; 4 - dial indicator; 41 - dial head; 42 - dial rod; 5 - locking bolt. Detailed implementation manners

[0019] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0021] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, the terms "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0022] Such as Figure 1 — Figure 5As shown in the figure, a width measuring device for the diamond root crown of a steam turbine blade includes a device body 3 and a dial indicator 4; one side of the device body 3 is open horizontally and is provided with a cavity for placing the diamond leaf crown 11 or the diamond leaf root 12 of the steam turbine blade 1; the cavity includes an upper inner side surface and a lower inner side surface that are arranged opposite and parallel to each other, and the lower inner side surface is a reference surface 311 parallel to the horizontal plane; the reference surface 311 is closely attached and positioned with the plane of the steam inlet side or the steam outlet side of the steam turbine blade 1; a dial indicator 4 is detachably connected to the upper side of the upper end of the device body 3 corresponding to the reference surface 311; the stem 42 of the dial indicator 4 vertically passes through the upper inner side surface and extends into the cavity, and abuts against the plane of the steam outlet side or the steam inlet side of the blade on the side away from the reference surface 311. In actual use, the cavity of the device body 3 can accommodate the diamond leaf root 12 or the diamond root crown 11 of the steam turbine blade 1, the reference surface 311 of the device body 3 is closely attached to the plane of the steam inlet side or the steam outlet side of the blade, the stem 42 of the dial indicator 4 vertically passes through the upper inner side surface and extends into the cavity, and abuts against the plane of the steam outlet side or the steam inlet side of the blade on the side away from the reference surface 311. Observe the reading of the pointer of the dial indicator 4 and calculate the width dimension of the measured blade. The single-piece measurement time ≤ 2 minutes, and the detection efficiency is increased by 5 times compared with the coordinate measuring machine. By providing a cavity for accommodating the diamond root crown of the steam turbine blade 1, the measuring device will not have the problem that the blade interferes with the measuring device and causes inability to measure during measurement; at the same time, the measuring device has a simple structure, and has the advantages of low cost, high measurement accuracy, high measurement efficiency and very simple operation.

[0023] As Figure 1 , Figure 3 , Figure 5 shown in the figure, the diamond root crown of the steam turbine blade 1 includes a diamond leaf crown 11 and a diamond leaf root 12; the steam inlet side of the diamond root crown includes a crown steam inlet side 111 and a root steam inlet side 121. The steam outlet side of the diamond root crown includes a crown steam outlet side 112 and a root steam outlet side 122; the plane of the crown steam inlet side 111 is parallel to the plane of the crown steam outlet side 112; the plane of the root steam inlet side 121 is parallel to the plane of the root steam outlet side 122.

[0024] As Figure 4 , Figure 5As shown, the device body 3 includes an upper side section 32, a lower side section 31, and a connecting section 33; the upper side section 32 and the lower side section 31 are arranged in parallel, and a dial indicator 4 is detachably connected to the upper side of the upper side section 32; the upper side surface of the lower side section 31 is the lower inner side surface of the cavity; the transverse length of the lower side section 31 is greater than the transverse length of the plane on the steam inlet side or the steam outlet side of the blade; one end of the upper side section 32 and the lower side section 31 in the same direction are respectively connected to the upper end and the lower end of the connecting section 33; the lower side section 31, the connecting section 33, and the upper side section 32 together enclose a cavity for the diamond-shaped crown 11 or the diamond-shaped root 12 of the steam turbine blade 1 to be placed. In specific implementation, the upper side section 32, the lower side section 31, and the connecting section 33 are generally strip-shaped plate structures. The dial indicator 4 includes a gauge head 41 and a gauge rod 42 connected to each other. The device body 3 is a horizontally arranged "U" - shaped structure, and the lower side section 31, the connecting section 33, and the upper side section 32 together enclose a cavity for the diamond-shaped crown 11 or the diamond-shaped root 12 of the steam turbine blade 1 to be placed. Among them, the dial indicator 4 is detachably connected to the upper side of the upper side section 32.

[0025] The upper side surface of the lower side section 31 is the lower inner side surface of the cavity, that is, the upper side surface of the lower side section 31 is the reference surface 311, and the upper side surface of the lower side section 31 is in close contact and positioned with the lower plane on the steam inlet side or the steam outlet side of the steam turbine blade 1. As Figure 4 shown, the transverse length of the lower side section 31 is greater than the transverse length of the plane on the steam inlet side or the steam outlet side of the blade. When using the measuring device for measurement, the lower plane on the steam inlet side or the steam outlet side of the blade with the diamond root crown to be measured is horizontally arranged transversely on the lower side section 31, so that the lower plane on the steam inlet side or the steam outlet side of the blade will not be suspended, ensuring quick positioning during measurement, ensuring measurement accuracy, and at the same time being applicable to the diamond root crowns of steam turbine blades 1 of different sizes. Adopting this technical measure has the advantages of simple structure, wide application range, high measurement accuracy, high measurement efficiency, and very simple operation.

[0026] One end of the upper side section 32 and the lower side section 31 in the same direction are respectively connected to the upper end and the lower end of the connecting section 33. In specific implementation, the right end of the upper side section 32 and the right end of the lower side section 31 are respectively connected to the upper end and the lower end of the connecting section 33; or the left end of the upper side section 32 and the left end of the lower side section 31 are respectively connected to the upper end and the lower end of the connecting section 33. In this embodiment, the widths of the upper side section 32 and the lower side section 31 are quite the same, the transverse length of the upper side section 32 is greater than the transverse length of the lower side section 31; the right end of the upper side section 32 and the right end of the lower side section 31 are respectively connected to the upper end and the lower end of the connecting section 33; the left ends of the upper side section 32 and the lower side section 31 are flush.

[0027] In this embodiment, the connecting section 33 is inclined, the angle between the lower section 31 and the connecting section 33 is an obtuse angle, and the angle between the upper section 32 and the connecting section 33 is an acute angle. Among them, the connecting section 33 is inclined, so that the cavity of the device body 3 forms a V-shaped avoidance groove, and when the device body 3 is measuring, there will be no problem that the blade interferes with the measuring device and causes the measurement to be impossible. In actual use, the connecting section 33 can also be an arc or other structures.

[0028] As Figure 5 shown, the inclination angle of the connecting section 33 is the same as the inclination angle of the inclined surface of the diamond-shaped blade crown 11 or the diamond-shaped blade root 12 of the steam turbine blade 1. In actual use, the inclination angle of the connecting section inclined surface 331 on the side of the connecting section facing the cavity opening is the same as the inclination angle of the inclined surface of the diamond-shaped blade crown 11 or the diamond-shaped blade root 12. The connecting section inclined surface 331 on the side of the connecting section facing the cavity opening can be used as an inclined direction reference surface 311, which can assist in positioning; adopting this technical measure has the advantages of high measurement accuracy, high measurement efficiency and very simple operation.

[0029] As Figure 4 、 Figure 5 shown, in the transverse direction of the upper section 32, a plurality of vertical through holes 322 penetrating the upper and lower ends of the upper section 32 are provided corresponding to the spacing of the lower section 31. The diameter of the vertical through holes 322 is slightly larger than the diameter of the stem 42 of the dial indicator 4; there is a clearance fit between the stem 42 and the vertical through holes 322; a locking device for locking the stem 42 is provided on the front / rear side of the upper section 32. In this embodiment, Figure 5 the side where the locking bolt 5 is provided is the front side of the upper section 32.

[0030] The transverse direction of the upper section 32 is the length direction of the upper section 32; the upper section 32 and the lower section 31 are arranged in parallel, and the upper side surface (reference surface 311) of the lower section 31 is arranged in parallel with the upper and lower side surfaces of the upper section 32; the lower side surface 321 of the upper section is the upper inner side surface of the cavity; the axis of the vertical through holes 322 penetrating the upper and lower ends of the upper section 32 opened on the upper section 32 is perpendicular to the upper and lower side surfaces of the upper section 32 and the reference surface 311; the stem 42 arranged in clearance fit in the vertical through holes 322 is also perpendicular to the upper and lower side surfaces of the upper section 32 and the reference surface 311. When measuring, the stem 42 passes through the vertical through holes 322 and abuts against the steam outlet side or the steam inlet side plane of the blade far from the reference surface 311; that is, the contact head or probe at the bottom end of the stem 42 abuts against the steam outlet side or the steam inlet side plane of the blade far from the reference surface 311. By providing a plurality of vertical through holes 322, the measuring device can adjust the position of the dial indicator 4 as needed, so as to be applicable to measuring the diamond roots of steam turbine blades 1 of different models. Adopting this technical measure has the advantages of simple structure, wide application range, high measurement accuracy, high measurement efficiency and very simple operation.

[0031] As shown Figure 5 in the figure, taking the measurement of the inlet / outlet steam side width of the diamond-shaped blade root 12 as an example; the reference plane 311 of the cavity of the measuring device is closely attached to the plane of the outlet steam side 122 of the blade root of the diamond-shaped blade root 12, and the plane of the inlet steam side 121 of the blade root is in contact with the bottom end of the dial rod 42; then observe the pointer reading of the dial gauge 4 and calculate the width dimension of the inlet / outlet steam side of the measured diamond-shaped blade root 12. In actual use, when the reference plane 311 is closely attached to the plane of the inlet steam side 121 of the diamond-shaped blade root 12, the plane of the outlet steam side 122 is in contact with the bottom end of the dial rod 42. When measuring the inlet / outlet steam side width of the diamond-shaped blade crown 11, adjust the dial rod 42 of the dial gauge 4 so that the bottom end of the dial rod 42 is in contact with the inlet steam side 111 or the outlet steam side 112 of the blade crown, and other steps can refer to the steps of measuring the inlet / outlet steam side width of the diamond-shaped blade root 12.

[0032] A locking device for locking the dial rod 42 is provided on the front / rear side of the upper side section 32. In specific implementation, since the measuring device will be used to measure the diamond root crowns of steam turbine blades 1 of different models, the dial gauge 4 needs to be disassembled and reinstalled into the adapted vertical through hole 322. At the same time, when measuring, the up and down position of the dial rod 42 in the cavity also needs to be adjusted. By setting the locking device, the dial gauge 4 can be detachably connected to the upper side section 32, and at the same time, the up and down position of the dial rod 42 can be adjusted according to requirements.

[0033] In this embodiment, the locking device is a locking bolt 5, and threaded holes 323 communicating with the vertical through hole 322 and cooperating with the locking bolt 5 are provided on the front / rear side of the upper side section 32 corresponding to the vertical through hole 322; the screw length of the locking bolt 5 is greater than the depth of the threaded hole 323. When in use, by tightening or loosening the locking bolt 5, the end of the screw away from the bolt head is in contact with or separated from the outer surface of the dial rod 42, so that the dial gauge 4 can be detachably installed on the upper side section 32, and at the same time, the up and down position of the dial rod 42 in the cavity can be adjusted. Adopting this technical measure has the advantages of simple structure, wide application range and very simple operation.

[0034] A method for using a width measuring device for the diamond root crown of a steam turbine blade includes the following steps: Step 1, perform blade surface pretreatment on the steam turbine blade 1 to be measured; By performing blade surface pretreatment on the steam turbine blade 1 to be measured, the interference of burrs and foreign objects on the measurement is eliminated, and the accuracy of the measurement reference plane 311 is ensured.

[0035] Mainly aiming at the edges of the steam inlet and outlet sides of the blade crown and the steam inlet and outlet sides of the blade root of the diamond root crown, focus on removing the metal burrs, oxide scales and oil stains remaining after machining. Use a fine file (grain size ≥ 800 mesh) or a nylon grinding wheel to grind the burrs; use an ultrasonic cleaning machine (neutral cleaning agent) to remove the oil stains; wipe the surface with a lint-free cloth to avoid fiber residue. Acceptance criteria: No visible burrs can be seen by visual inspection; no scratching feeling when gently touching the edge with fingertips; the surface roughness of the measurement area ≤ Ra 1.6μm, etc.

[0036] Step 2, calibrate the dial indicator 4 with a measuring device and a standard gauge block; the size X of the standard gauge block should be consistent with the theoretical width of the diamond root crown of the measured steam turbine blade 1.

[0037] In specific implementation, assume that the theoretical size of the width of the measured diamond root crown is X. Match the size X with the standard gauge block and calibrate it with this measuring device. Adjust the pointer of the dial indicator 4 until the pointer reading on the dial indicates an appropriate position (generally, the pointer reading is at the 0 position).

[0038] Step 3, when measuring the width of the steam inlet and outlet sides of the blade of the diamond root crown (diamond blade crown 11 or diamond blade root 12) with the measuring device, on the basis of the measuring device calibrated in Step 2, make the plane of the steam inlet side or the steam outlet side of the blade of the diamond root crown closely adhere to the reference plane 311 of the measuring device, and make the lower end of the measuring rod 42 of the dial indicator 4 abut against the plane of the steam outlet side or the steam inlet side of the blade on the side far from the reference plane 311, and then observe the pointer reading of the dial indicator 4.

[0039] Step 4, when the pointer reading of the dial indicator 4 is Y, the width dimension of the measured blade can be calculated as (X + / - Y) mm.

[0040] Adopting this technical measure, the measurement steps are few, and a single person can complete the measurement by hand; it has the advantages of simple operation, high measurement accuracy and high measurement efficiency.

[0041] The technical solutions provided by the embodiments of the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principles and implementation manners of the embodiments of the present invention. The descriptions of the above embodiments are only applicable to help understand the principles of the embodiments of the present invention; at the same time, for those of ordinary skill in the art, according to the embodiments of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A device for measuring the width of a rhombus root crown of a steam turbine blade, characterized in that: Including the device body and the dial indicator; One side of the device body is open laterally and is provided with a cavity for placing the rhombus-shaped blade crown or rhombus-shaped blade root of the steam turbine blade; The cavity comprises an upper inner side surface and a lower inner side surface which are arranged opposite to each other and in parallel, and the lower inner side surface is a reference surface parallel to the horizontal plane; The reference surface is in close contact with the plane of the steam inlet side or the steam outlet side of the steam turbine blade; a dial indicator is detachably connected to the upper side of the upper end of the device body corresponding to the reference surface; The dial indicator rod vertically passes through the upper inner side surface and extends into the cavity, and abuts against the steam outlet side or steam inlet side plane of the blade away from the reference plane.

2. The device for measuring the width of the rhombus root cap of a steam turbine blade according to claim 1, characterized in that: The device body comprises an upper section, a lower section and a connecting section; The upper section is arranged in parallel with the lower section, and a dial indicator is detachably connected to the upper side of the upper section; The upper side surface of the lower side segment is the lower inner side surface of the cavity; The transverse length of the lower side section is greater than the transverse length of the plane of the steam inlet side of the blade or the steam outlet side of the blade; One end of the upper side section and the lower side section in the same direction are connected to the upper end and the lower end of the connecting section respectively; The lower section, the connecting section and the upper section together enclose a cavity for the rhombus-shaped blade crown or the rhombus-shaped blade root of the steam turbine blade to be placed in.

3. The device for measuring the width of the rhombus root cap of a steam turbine blade according to claim 2, characterized in that: The connecting section is inclined, the angle between the lower section and the connecting section is an obtuse angle, and the angle between the upper section and the connecting section is an acute angle.

4. The device for measuring the width of the rhombus root cap of a steam turbine blade according to claim 3, characterized in that: The inclination angle of the connecting section is the same as the inclination angle of the rhombus-shaped blade crown or rhombus-shaped blade root inclined surface of the steam turbine blade.

5. The device for measuring the width of the rhombus root cap of a steam turbine blade according to claim 2 or 3, characterized in that: The upper section is provided with a plurality of vertical through holes penetrating the upper and lower ends of the upper section at intervals corresponding to the lower section in the lateral direction, the diameter of the vertical through holes being slightly larger than the diameter of the dial gauge rod; the clearance between the dial gauge rod and the vertical through holes is matched; The front / rear side of the upper side section is provided with a locking device for locking the meter rod.

6. The device for measuring the width of the rhombus root cap of a steam turbine blade according to claim 5, characterized in that: The locking device is a locking bolt, and the vertical through hole corresponding to the front / rear side of the upper section is provided with a threaded hole connected to the vertical through hole and matched with the locking bolt; the screw length of the locking bolt is greater than the depth of the threaded hole.

7. The method for using the device for measuring the width of a rhombus root cap of a steam turbine blade according to any one of claims 1 to 6, characterized in that: The steps include: Step 1, performing blade surface pretreatment on the steam turbine blade to be tested; Step 2, calibrate the dial indicator by using a measuring device and a standard block gauge, and the size X of the standard block gauge must be consistent with the theoretical width of the rhombus root crown of the measured turbine blade; Step 3, when measuring the width of the blade steam inlet and outlet sides of the rhombus root crown with a measuring device, on the basis of the measuring device calibrated in step 2, the plane of the blade steam inlet side or the blade steam outlet side of the rhombus root crown is made to be close to the reference plane of the measuring device, the lower end of the dial indicator rod is made to abut against the plane of the blade steam outlet side or the blade steam inlet side away from the reference plane, and then the pointer reading of the dial indicator is observed; Step 4: The dial indicator pointer reading is Y, and the width of the measured blade can be calculated to be (X + / - Y) mm.

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