A welding method for turbine spiral casing

Abstract

This application relates to the field of turbine installation technology and discloses a method for welding turbine spiral casings, including the following steps: 1) First, calculate the dimension L of the intersection between the cross section of each spiral casing and the inclined plate. an α an l an and A an ;2) Calculate the dimension L of each inclined plate. bn α bn l bn and A bn 2) Cut the inclined plates according to the dimensions of the intersection between each volute cross section and the inclined plate and the dimensions of each inclined plate; 3) Make welding bevels on the inclined plates to extend the welding points between the seat ring and the volute outward; 4) Weld the inclined plates onto the seat ring in sequence on site, and then weld the volute onto the inclined plates. This increases the welding space, facilitates welding, weld defect elimination, and flaw detection, and avoids vibration and noise during unit operation, which would affect power generation efficiency.

Description

Technical Field

[0001] This invention relates to the field of water turbine installation technology, specifically a method for welding the spiral casing of a water turbine. Background Technology

[0002] The turbine casing is one of the important components of a hydro-generator set. The casing is made up of multiple circular pipe sections welded together. Its main function is not only to make the water flow form a certain circulation in front of the guide mechanism, but also to make the water flow evenly into the guide mechanism along the entire circumference. In addition, the casing must also withstand a large internal water pressure.

[0003] Chinese document CN105537787B discloses a welding method for a turbine spiral casing. The method involves adjusting and positioning the positioning section of the turbine spiral casing, and performing locating welding on the circumferential seams of the spiral casing sub-sections. One or both sides of the positioning section are welded to the circumferential seams of adjacent spiral casing sub-sections. Then, the circumferential seams of the adjacent spiral casing sub-sections are welded to the next spiral casing sub-section. Next, the upper and lower butterfly edges of the positioning section are welded, or simultaneously, the circumferential seams of the next spiral casing sub-section and the next spiral casing sub-section are welded. Then, the upper and lower butterfly edges of the next spiral casing sub-section are welded, or simultaneously, the circumferential seams of the next spiral casing sub-section and another spiral casing sub-section are welded, and so on, welding the remaining spiral casing sub-sections. Finally, a fitting section is welded to the gap that appears after the spiral casing sub-sections on both sides are gradually welded towards the center.

[0004] Currently, inclined plate structures are first installed on the bearing ring of large water turbines. The multiple circular pipe sections of the spiral casing are all connected to the inclined plates. The length of the inclined plates is taken as equal as possible or gradually changes with the cross-sectional area of ​​the spiral casing. During the installation process, the on-site welding personnel make appropriate adjustments according to the welding process of the workpieces cut from the factory, which is within the specification range.

[0005] The existing technology has the following shortcomings: because the spiral casing of large and low-head turbines is relatively large and cannot meet the transportation requirements, it is necessary to produce, process and pre-assemble each section of the spiral casing in the factory and then weld it on site. However, due to the limited space and conditions on site, it is inconvenient to operate, which may result in welding defects in the spiral casing, affecting the welding quality. As a result, vibration and noise will be generated during the operation of the unit, which in turn affects the power generation efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a method for welding the spiral casing of a water turbine, so as to solve the problems that welding the spiral casing is inconvenient, and that vibration and noise will be generated during use, thereby affecting the power generation efficiency.

[0007] To achieve the above objectives, the present invention provides a method for welding the spiral casing of a hydraulic turbine, characterized by comprising the following steps:

[0008] 1) First, calculate the dimension L at the intersection of each volute section and the inclined plate. an α anl an and A an L an α is the length of the first inclined plate; an The angle of the first inclined plane; l an The first contact distance; A an Let n be the center distance of the first volute, and n be a positive integer.

[0009] 2) Calculate the dimension L of each inclined plate. bn α bn l bn and A bn L bn α is the length of the second inclined plate; bn The angle of the second inclined plate; l bn The second contact distance; A bn The distance between the centers of the second volute is n, where n is a positive integer.

[0010] 3) Cut the inclined plates according to the dimensions of the intersection between each volute cross section and the inclined plate, and the dimensions of each inclined plate;

[0011] 4) The inclined plate has a welding bevel, which extends the welding point between the seat ring and the volute outward;

[0012] 5) On site, the inclined plate is welded onto the seat ring in sequence, and then the volute is welded onto the inclined plate.

[0013] Furthermore, in step 1, the calculation method for the intersection dimensions of each volute cross section and the inclined plate is as follows:

[0014] ε an =arcsin((H+h) an ) / r an );

[0015] γ an =arcsin(H / r an );

[0016] δ an =ε an -γ an ;

[0017] L an =2×r an ×sin(δ an / 2);

[0018] α an =(180°-δ) an ) / 2-γ an ;

[0019] l an =R a +L an ×cosαan ;

[0020] A an =l an +r an ×cosα an ;

[0021] ε an - First included angle α; H - Height of the seat ring, h an - Height of the first inclined plate; r an - Radius of the first volute section; γ an -Second included angle a; δ an - Third included angle a; R a - Distance between the intersection points of the first inclined plate, where n is a positive integer.

[0022] Furthermore, in step 2, the calculation method for the dimensions of each inclined plate is as follows: the height h of the second inclined plate. bn Take the adjacent h an Half of the sum, the radius r of the second volute cross section bn Take two adjacent r an Half of the sum;

[0023] ε bn =arcsin((H+h) bn ) / r bn );

[0024] γ bn =arcsin(H / r bn );

[0025] δ bn =ε bn -γ bn ;

[0026] L bn =2×r bn ×sin(δ bn / 2);

[0027] α bn =(180°-δ) bn ) / 2-γ bn ;

[0028] l bn =R b +L bn ×cosα bn ;

[0029] A bn =l bn +r bn cosα bn ;

[0030] εbn - First included angle b; H - Height of seat ring, h bn - Height of the second inclined plate; r bn - Radius of the second volute section; γ bn -Second included angle b; δ bn -Third included angle b; R b - Distance between the intersection points of the second inclined plate, where n is a positive integer.

[0031] Furthermore, in step 3, the upper inclined plate of the volute is cut with an external slit, and the inclined plate is cut horizontally after welding.

[0032] Furthermore, in step 3, the lower inclined plate of the volute is internally cut, and the inclined plate is cut vertically after welding.

[0033] To protect the root of the volute from being washed away by the water flow, guide plates are welded onto the seat ring and inclined plate in step 4.

[0034] The beneficial effects of this invention are as follows: An inclined plate structure is installed on the bearing ring of a large water turbine. First, the inclined plate is welded to the bearing ring, and then the volute is welded to the inclined plate. During this process, it is necessary to determine the parameters of the intersection between the volute cross section and the inclined plate, as well as the parameters of the inclined plate itself. The value of L needs to be calculated. an α an l an A an L bn α bn l bn and A bn This ensures that each inclined plate is properly welded to the volute, minimizing the difference in arc between the inclined plate and the circular pipe section, making it smooth and preventing vibration and noise during volute operation, thereby improving power generation efficiency. The length and welding angle of each inclined plate are calculated for material cutting. In addition, welding bevels are opened according to the on-site welding method, extending the welding point between the seat ring and the volute outward, increasing the welding space, and facilitating welding, weld defect elimination, and flaw detection. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the volute and inclined plate in Embodiment 1;

[0036] Figure 2 for Figure 1 A schematic diagram of the arrangement of the volute cross section and the inclined plate cross section;

[0037] Figure 3 for Figure 2 A schematic diagram of the partial layout structure;

[0038] Figure 4 The structural calculation diagram shows the intersection dimensions of the volute cross section and the inclined plate;

[0039] Figure 5Structural calculation diagram showing the intersection dimensions of each inclined plate;

[0040] Figure 6 This is a schematic diagram of the upper inclined plate bevel structure;

[0041] Figure 7 This is a schematic diagram of the structure of the downward-sloping plate bevel.

[0042] Reference numerals in the attached diagram: 1. Seat ring; 2. Volute; 3. Inclined plate; 4. Cross-section of volute; 5. Cross-section of inclined plate; 6. Guide plate; 7. Upper inclined plate; 8. Lower inclined plate. Detailed Implementation

[0043] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. However, the present invention is not limited to these embodiments. Any improvements made to the present invention without departing from the principle of the present invention also fall within the protection scope of the claims of the present invention.

[0044] θ° - volute cross-sectional angle; L an - Length of the first inclined plate; r an - Radius of the first volute section; A an - First volute center distance; l an -First contact distance; R a - Distance between the intersection points of the first inclined plate; h an - Height of the first inclined plate; α an - First inclined plane angle; ε an -First included angle a; γ an -Second included angle a; δ an - The third included angle α; The volute is composed of multiple multi-section circular tube segments spliced ​​together. The parameters of each volute are different, and each is represented by adding n after the symbol, and then using positive integers (1, 2, 3, 4, 5, 6...).

[0045] H - Seater ring height (distance from the upper or lower plane of the seat ring to the center of the guide vane), r an - Radius of the first volute section, R a - Distance between the intersection points of the first inclined plate and h an -The height of the first inclined plate is known;

[0046] β° - Inclined section angle; L bn - Length of the second inclined plate; r bn - Radius of the second volute section; A bn -Second volute center distance; l bn -Second contact distance; R b - Distance between the intersection points of the second inclined plate; h bn - Height of the second inclined plate; α bn -Second inclined plane angle; ε bn -First included angle b; γ bn -Second included angle b; δbn - The third included angle b; multiple circular pipe sections are connected to multiple inclined plates, each with different parameters, each represented by a positive integer (1, 2, 3, 4, 5, 6...) after the symbol;

[0047] H - Seater ring height (distance from the upper or lower plane of the seat ring to the center of the guide vane), r bn - Radius of the second volute section, R b - Distance between the intersection points of the second inclined plate, h bn - Height of the second inclined plate and L bn - The lengths of the second inclined plane are all known.

[0048] Example 1

[0049] like Figure 1-3 As shown, a method for welding the spiral casing of a water turbine includes the following steps:

[0050] Step 1: Calculation of the intersection dimensions of the volute section 4 and the inclined plate 3 (unit: mm)

[0051] Given: Height of the seat ring H = 465; Number of volute cross sections 24 = 360° / 15°; Distance from the intersection of the first inclined plate R a =2000;

[0052] ① First section of volute 2: θ°=0° Height of the first inclined plate h a1 =350, radius r of the first volute section a1 =1765;

[0053] Then: ε a1 =arcsin((H+h) a1 ) / r a1 ) = 27.5°

[0054] γ a1 =arcsin(H / r a1 ) = 15.28°

[0055] δ a1 =ε a1 -γ a1 =12.22°

[0056] L a1 =2×r a1 ×sin(δ a1 / 2)=375.73

[0057] α a1 =(180°-δ) a1 ) / 2-γ a1 =68.61°

[0058] l a1 =Ra +L a1 ×cosα a1 =2137.1

[0059] A a1 =l a1 +r a1 ×cosα a1 =3702.6

[0060] ②The second section of the volute 2: θ°=15°h a2 =340,r a2 =1716, calculated

[0061] ε a 2=arcsin((H+h a2 ) / r a2 ) = 27.98°

[0062] γ a2 =arcsin(H / r a2 ) = 15.72°

[0063] δ a2 =ε a 2-γ a2 =12.26°

[0064] L a2 =2×r a2 ×sin(δ a2 / 2)=366.31

[0065] α a2 =(180°-δ) a2 ) / 2-γ a2 =68.15°

[0066] l a2 =R a +L a2 ×cosα a2 =2136.3

[0067] A a2 =l a2 +r a2 ×cosα a21 =3651.8

[0068] ③ The third section of the volute 2: θ°=30°, h a3 =330,r a3 =1666, then substitute them into the formula to calculate;

[0069] Step 2: Calculate the dimensions of the inclined plate 3 (unit: mm).

[0070] Given: Height of the seat ring H = 465; Number of volute cross sections 24 = 360° / 15°; Distance of the intersection point of the second inclined plate R b =2000;

[0071] ①The first section of inclined plate 3: The calculated dimensions of the intersection between the volute section 4 and inclined plate 3 are consistent;

[0072] ② The second section of inclined plate 3: β° = 22.5° (the angle of the inclined plate section of the volute is staggered by two volute section angles); the height of the second inclined plate in the second section is taken from the attached... Figure 2 Chinese h a2 with h a3 Half of the sum, i.e., h b2 =(h a2 +h a3 ) / 2=335; The radius of the second volute section of the second cross-section is taken as half of the sum of the radii of the two adjacent second volute sections, i.e., r b2 =(r a2 +r a3 ) / 2 = 1691;

[0073] Then ε b2 =arcsin((H+h) b2 ) / r b2 ) = 28.24°

[0074] γ b2 =arcsin(H / r b2 ) = 15.96°

[0075] δ b2 =ε b2 -γ b2 =12.28°

[0076] L b2 =2×r b2 ×sin(δ b2 / 2)=361.56

[0077] α b2 =(180°-δ) b2 ) / 2-γ b2 =67.9°

[0078] l b2 =R b +L b2 ×cosα b2 =2136.0

[0079] A b2 =L b2 +r b2 cosα b21 =3625.8

[0080] ③ Third section of the inclined plate: β°=30°, hb3=315, r b3 =(r a4 +r a5 ) / 2 = 1591, then substitute them into the formula to calculate;

[0081] Step 3, place each L an α an l an A an L bn α bn l bn and A bn Input into the CNC machine tool, and cut the inclined plate 3 according to the size of the intersection of each volute section 4 and the inclined plate 3 and the size of each inclined plate;

[0082] Step 4: The inclined plate 3 includes an upper inclined plate 7 and a lower inclined plate 8. The upper inclined plate 7 has an external cut and is cut horizontally after welding. The lower inclined plate 8 has an internal cut and is cut vertically after welding.

[0083] Step 5: First, weld the inclined plate 3 onto the seat ring 1, and then weld the volute 2 onto the inclined plate 3;

[0084] Step 6: Weld guide plates 6 to the positions of seat ring 1 and inclined plate 3 to protect the root of volute 2 from being washed by water flow, make the flow channel smoother, and prevent turbulence from causing unit vibration.

[0085] Appendix Figure 1 In the process, the inclined plate section 5 is numbered I, II, III, IV, V, VI, VII, VIII, IX, X and XI, and the volute section 4 is numbered 1, 2, 3, 4, 5, 6, 7, 8, 9, 10... In order to avoid the appearance of a "cross" weld when welding the volute 2 and the inclined plate 3, the inclined plate section 5 is numbered exactly two positions away from the volute section 4.

Claims

1. A method of welding a spiral case of a hydraulic turbine, characterized in that, The method comprises the following steps: 1) First, calculate the size L of intersection of each volute section with the inclined plate an , α an , l an and A an , L an is the first inclined plate length; α an is the first inclined plate angle; l an is the first joint distance; A an is the first volute center distance, and n is a positive integer; the calculation method of the size of intersection of each volute section with the inclined plate is: ε an = arcsin ((H + h an ) / r an ) ; gamma an = arcsin(H / r an ) ; δ an =ε an -γ an ​ L an = 2 x r an x sin(δ an / 2); a an = (180° - δ an ) / 2 - γ an ​ l an = R a + L an x cos a an ; A an =l an +r an ×cosα an ; ε an - first included angle a; H - seat ring height, h an - first vane height; r an - first volute section radius; γ an - second included angle a; δ an - third included angle a; R a - first vane intersection distance, n is a positive integer; 2) Recalculate the size of each piece of the inclined plate L bn , α bn , l bn and A bn , L bn is the second inclined plate length; α bn is the second inclined plate angle; l bn is the second joint distance; A bn is the second volute center distance, n is a positive integer; the size of each piece of the inclined plate is calculated as follows: the inclined plate height h bn is half the sum of adjacent h an , the volute cross section radius r bn is half the sum of adjacent 2 r an ; ε bn =arcsin ((H+h bn ) / r bn ) ; gamma bn = arcsin(H / r bn ) ; δ bn =ε bn -γ bn ​ L bn =2×r bn ×sin(δ bn / 2) ; a bn = (180° - δ bn ) / 2 - γ bn ; l bn = R b + L bn × cos α bn ; A bn =l bn +r bn cosα bn ; epsilon bn - first included angle; b - seat ring height, h bn - second slanted plate height; r bn - second volute section radius; gamma bn - second included angle; b bn - third included angle; b b - second slanted plate intersection distance, n is a positive integer 3) according to the size of each volute section intersecting with the inclined plate and the size of each inclined plate, the inclined plate is cut; 4) the inclined plate is provided with a welding bevel, so that the welding point of the seat ring and the volute is extended outward; 5) the inclined plate is sequentially welded on the seat ring, and then the volute is welded on the inclined plate.

2. The method of welding a spiral case for a hydraulic turbine according to claim 1, characterized in that: In step 3, the upper inclined plate of the volute adopts an outer profile, and the inclined plate is cut into horizontal after being welded.

3. The method of welding a spiral case for a hydraulic turbine according to claim 2, characterized in that: In step 3, the lower inclined plate of the volute adopts an inner profile, and the inclined plate is cut into vertical after being welded.

4. The method of welding a spiral case for a hydraulic turbine according to claim 3, characterized in that: In step 4, the upper guide plate is welded at the position of the seat ring and the inclined plate.

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