A method for reducing the stress at the root of the bucket of an impulse water turbine

Abstract

The present invention belongs to the technical field of hydraulic turbines, and particularly relates to a method for reducing the stress at the root of the bucket of an impulse hydraulic turbine. The technical solution is as follows: A method for reducing the stress at the root of the bucket of an impulse hydraulic turbine includes the following steps: forming the integral bucket by rounding the connection between the front and back surfaces of the root of the bucket; establishing a calculation model of the bucket, and applying boundary conditions and loads; extracting the stress distribution nephogram at the root of the bucket according to the calculation results; regularly cutting off the high-stress area at the root of the bucket by using three-dimensional modeling software according to the stress distribution nephogram at the root of the bucket; making the surfaces at the root of the bucket smooth and have a smooth transition to form a new three-dimensional model of the bucket with a lower stress level. The present invention provides a method for reducing the stress at the root of the bucket of an impulse hydraulic turbine, which can effectively reduce the stress level at the root of the bucket, and has the advantages of simple operation, strong versatility, and shortening the development cycle of the bucket.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydraulic turbines, and particularly relates to a method for reducing the stress at the root of the bucket of an impulse hydraulic turbine. Background Art

[0002] The bucket is one of the core components of an impulse hydraulic turbine, and has a complex structure and drastic changes in the curved surface. During the operation of the unit, the bucket bears huge alternating loads and is extremely prone to crack or even bucket breakage accidents. The high-stress area formed at the root of the bucket is one of the main reasons for such accidents. Therefore, measures must be taken to strictly control the static stress and dynamic stress levels in the high-stress area of the bucket.

[0003] At present, in view of the main factors affecting the stress level at the root of the bucket, the structure is optimized step by step to reduce the stress at the root of the bucket. Establish a finite element model of the impulse bucket; apply boundary conditions and loads; perform finite element solution and provide stress results; adjust the parameters affecting the root stress multiple times; determine the optimal structure plan.

[0004] The invention patent application No. CN201510056014.X discloses a method for optimizing the root structure of the water dividing edge of the bucket of an impulse hydraulic turbine. A calculation model of the bucket is established by using finite element analysis software, and boundary conditions and loads are applied. The curvature uniformity, depth and thickness of the root of the water dividing edge of the bucket are adjusted step by step and multiple times. The stress calculation results of the root of the water dividing edge of each plan are calculated and extracted, and the structure with the lowest stress level is determined as the optimal plan for the root structure of the water dividing edge of the bucket. The advantages of this method are as follows: in view of the main influencing factors of the stress level at the root of the water dividing edge of the bucket, the curvature uniformity, depth and thickness are optimized step by step for the structure. The optimal structure plan is determined by comparing the stress level calculation results. This optimization method can effectively reduce the stress level in the high-stress area of the bucket, significantly improve the strength safety factor and fatigue life of the bucket, and is of great significance for ensuring the safe and stable operation of the unit.

[0005] The advantages of the existing method for reducing the stress at the root of the bucket are that it can reduce the stress level in the high-stress area of the bucket, and the disadvantages are that the operation is complex, the universality is poor, and the R & D cycle of the bucket is greatly prolonged. Summary of the Invention

[0006] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a method for reducing the stress at the root of the bucket of an impulse hydraulic turbine, which can effectively reduce the stress level at the root of the bucket, and is simple to operate, has strong universality, and shortens the development cycle of the bucket.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for reducing the stress at the root of the bucket of an impulse hydraulic turbine, comprising the following steps:

[0009] Connect the front and back surfaces of the bucket root by means of rounding to form the overall bucket;

[0010] Establish a bucket calculation model and apply boundary conditions and loads;

[0011] Extract the stress distribution nephogram of the bucket root according to the calculation results;

[0012] According to the stress distribution nephogram of the bucket root, regularly cut the high-stress area of the bucket root using 3D modeling software;

[0013] Make the surfaces of the bucket root smooth and have a smooth transition to form a new 3D model of the bucket with a lower stress level.

[0014] In the present invention, first, the front and back surfaces of the bucket root are connected by means of variable-radius rounding to form the overall bucket. Then, a bucket calculation model is established using commercial software, boundary conditions and loads are applied, and the stress distribution nephogram of the bucket root is extracted. Next, according to the stress distribution nephogram of the bucket root, the high-stress area of the bucket root is regularly cut using 3D modeling software. Finally, by means of edge rounding or bridging surfaces, the surfaces of the bucket root are made smooth and have a smooth transition to form a new 3D model of the bucket with a lower stress level.

[0015] The present invention can effectively reduce the stress level of the bucket root, and has simple operation and strong versatility, and can be applied to impulse units of various capacities and various water heads; it greatly shortens the R & D and design cycle of the bucket.

[0016] As a preferred embodiment of the present invention, when connecting the front and back surfaces of the bucket root to form the overall bucket, the variable-radius rounding method is adopted.

[0017] As a preferred embodiment of the present invention, when establishing the bucket calculation model, a commercial software is used to establish the bucket calculation model and apply boundary conditions and loads.

[0018] As a preferred embodiment of the present invention, when making the surfaces of the bucket root smooth and have a smooth transition, the edge rounding method is used.

[0019] As a preferred embodiment of the present invention, when making the surfaces of the bucket root smooth and have a smooth transition, the bridging surface method is used.

[0020] As a preferred embodiment of the present invention, the following steps are further included:

[0021] Machine the bucket according to the finally generated 3D model of the bucket.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. The present invention can effectively reduce the stress level of the bucket root.

[0024] 2. The operation of the present invention is simple and has strong versatility, and it can be applied to impulse turbines with various capacities and various water heads;

[0025] 3. The present invention greatly shortens the R & D and design cycle of the water bucket. Description of the Drawings

[0026] Figure 1 is the flowchart of the method of the present invention;

[0027] Figure 2 is the flowchart of the existing method for reducing the stress at the root of the water bucket;

[0028] Figure 3 is a schematic diagram of the water bucket and its root established by the variable - radius rounding method;

[0029] Figure 4 is a schematic diagram of the water bucket and its root after regular cutting;

[0030] Figure 5 is a schematic diagram of the water bucket and its root after fairing. Detailed Embodiments

[0031] 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. Generally, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the 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. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0033] As Figure 1 shown, the method for reducing the stress at the root of the water bucket of the impulse turbine in this embodiment includes the following steps:

[0034] Connect the front and back surfaces of the root of the water bucket by rounding to form the overall water bucket;

[0035] Establish a calculation model of the water bucket and apply boundary conditions and loads;

[0036] Extract the stress distribution nephogram at the root of the water bucket according to the calculation results;

[0037] According to the stress distribution nephogram of the bucket root, the high-stress area at the bucket root is regularly cut using 3D modeling software;

[0038] Make the surfaces at the bucket root smooth and have a smooth transition to form a new 3D model of the bucket with a lower stress level;

[0039] Machine the bucket according to the finally generated 3D model of the bucket.

[0040] First, the present invention forms the whole bucket by connecting the front and back surfaces of the bucket root in a variable-radius fillet manner. Then, a calculation model of the bucket is established using commercial software, boundary conditions and loads are applied, and the stress distribution nephogram of the bucket root is extracted. Next, according to the stress distribution nephogram of the bucket root, the high-stress area at the bucket root is regularly cut using 3D modeling software. Finally, by means of edge filleting or bridging surfaces, the surfaces at the bucket root are made smooth and have a smooth transition to form a new 3D model of the bucket with a lower stress level.

[0041] The present invention can effectively reduce the stress level at the bucket root, and has simple operation and strong versatility, and can be applied to impulse turbines of various capacities and various water heads; it greatly shortens the R & D and design cycle of the bucket.

[0042] Among them, when connecting the front and back surfaces of the bucket root to form the whole bucket, a variable-radius fillet manner is adopted.

[0043] When establishing the calculation model of the bucket, a calculation model of the bucket is established using commercial software, and boundary conditions and loads are applied.

[0044] When making the surfaces at the bucket root smooth and have a smooth transition, it is achieved by means of edge filleting or bridging surfaces.

[0045] In summary, the specific working process of the present invention is as follows:

[0046] S1: Connect the front and back surfaces of the bucket root to form the whole bucket by adopting a variable-radius fillet manner (see Figure 3 );

[0047] S2: Establish a calculation model of the bucket using commercial software, and apply boundary conditions and loads;

[0048] S3: Extract the stress distribution nephogram of the bucket root according to the calculation results;

[0049] S4: According to the stress distribution nephogram of the bucket root, regularly cut the high-stress area at the bucket root using 3D modeling software (see Figure 4 );

[0050] S5: Smooth and roundly transition between each surface at the root of the water bucket by means of edge rounding or bridging the surface, forming a new three-dimensional model of the water bucket with a lower stress level.

[0051] The present invention is not limited to the above optional embodiments. Any person can obtain other various forms of products under the inspiration of the present invention. However, no matter what changes are made in its shape or structure, as long as the technical solutions fall within the scope defined by the claims of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for reducing the stress at the root of the bucket of an impulse water turbine, characterized in that: It includes the following steps: Connect the front and back sides of the bucket root by means of rounding to form the overall bucket; Establish a bucket calculation model and apply boundary conditions and loads; Extract the stress distribution nephogram of the bucket root according to the calculation results; Cut off the high-stress area of the bucket root using 3D modeling software according to the stress distribution nephogram of the bucket root; Make the surfaces of the bucket root smooth and have a smooth transition to form a new 3D model of the bucket with a lower stress level; When connecting the front and back sides of the bucket root to form the overall bucket, adopt the variable radius rounding method; When making the surfaces of the bucket root smooth and have a smooth transition, use the edge rounding or bridging surface method.

2. A method for reducing the stress at the root of the bucket of an impulse turbine according to claim 1, characterized in that: When establishing the bucket calculation model, use commercial software to establish the bucket calculation model and apply boundary conditions and loads.

3. A method for reducing the stress at the root of the bucket of an impulse water turbine according to claim 1 or 2, characterized in that: It also includes the following steps: Machine the bucket according to the finally generated 3D model of the bucket.

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