Quantitative design method for pressure steel bifurcated pipe group

Abstract

The application discloses a kind of pressure steel bifurcated pipe group quantitative design method in the field of hydraulic engineering, comprising the following steps: first, according to the actual situation of engineering, the quantitative index of steel bifurcated pipe group is formulated, head loss and steel pipe total weight, then according to the actual situation of engineering, the preliminary design of steel bifurcated pipe group structure is completed, and the head loss of steel bifurcated pipe group is calculated and verified in turn using the formula of hydraulics, finite element fluid numerical calculation method and model test, finally, the structure stress analysis and weight calculation of steel bifurcated pipe group are carried out, and the index requirements are met by adjusting the structure design during the period.The application adopts the design idea of first formulating quantitative index, then optimizing structure according to quantitative index, according to the steps of first meeting head loss, then meeting structural strength, and then optimizing structure weight, and adjusts steel bifurcated pipe structure in combination with feedback mechanism, realizes the optimization design of head loss and steel pipe weight, improves the design efficiency and structural performance of steel bifurcated pipe group, and reduces engineering cost.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering, and in particular to a quantitative design method for pressure steel branch pipe groups. Background Technology

[0002] The design of pressure steel branch pipes in hydropower stations is a crucial and important part of the overall pressure pipeline design. The design of pressure steel pipes and branch pipes includes structural stress analysis and head loss analysis. Traditional branch pipe layouts are simple; the design typically determines the inlet and outlet diameters of the branch pipes based on empirical flow velocities, selects a certain branch angle, and then directly proceeds to structural design. There are no quantitative regulations regarding head loss, meaning the design of the branch pipes is solely structural. However, when there are many pressure steel branch pipes in a hydropower station, the head loss of the pressure steel pipes and branch pipes cannot be ignored. Therefore, the layout must consider meeting the requirements for both structural stress and head loss, necessitating a quantitative design of the branch pipe group. Ensuring optimal hydraulics, minimum head loss, best structural stress, and minimal steel consumption are two important performance indicators for pressure steel pipe design.

[0003] Generally, the head loss of a pressure steel branch pipe group is inversely proportional to its weight. The head loss is a function of the diameter D, the roughness n, and the branch pipe geometry S, i.e., H = n / D(S). In other words, the greater the roughness, the greater the head loss; the larger the pipe diameter, the smaller the head loss. Simultaneously, the branch pipe geometry S also implicitly functions as a function of the diameter. A good geometry allows for a smaller diameter, while a poor geometry requires an increased diameter, thus affecting the weight.

[0004] The weight T of the steel branch pipe group is directly proportional to its diameter D and wall thickness t, i.e., T = Dt. The head loss variable H and the weight variable T of the branch pipe group are given target values ​​at the initial design stage; therefore, their product K = H * T is a constant. When the final K value is larger than the given value, it indicates that H or T needs to be reduced, or both need adjustment. The entire pipeline design revolves around the variables H and T, which are inversely proportional. To reduce H, the pipe diameter D needs to be increased, and the weight T will also increase. To reduce T, the pipe's diameter D(S) needs to be reduced, or its shape S needs to be optimized, thus reducing the wall thickness and weight, but this will increase H. Currently, existing literature does not provide good guidance on how to balance these two indicators. Summary of the Invention

[0005] To overcome the aforementioned shortcomings of existing steel branch pipe designs based on general experience, the technical problem to be solved by this invention is to provide a quantitative design method for pressure steel branch pipe groups that can simultaneously take into account head loss and structural lightweighting.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A quantitative design method for pressure steel branch pipe groups includes the following steps:

[0008] Step 1: Develop quantitative indicators for the steel branch pipe group based on the actual project conditions, including the head loss H from the start to the end of the steel pipe and the total weight T of the steel pipe;

[0009] Step 2: Complete the preliminary design of the steel branch pipe group structure based on the actual project conditions;

[0010] Step 3: Calculate the head loss of the steel branch pipe group using hydraulic calculation formulas. If the calculated head loss is less than H, proceed to Step 4; otherwise, return to Step 2 to readjust the layout and structure of the steel branch pipe group.

[0011] Step 4: Calculate the head loss of the pressure steel pipe using the finite element fluid numerical calculation method. If the calculated head loss is less than H, proceed to step 5; otherwise, return to step 2 to readjust the arrangement and structure of the steel branch pipe group.

[0012] Step 5: Verify the head loss of the steel branch pipe group structure using model tests. If the test head loss is less than H, proceed to Step 6; otherwise, return to Step 2 to readjust the steel branch pipe group layout and structure.

[0013] Step 6: Perform structural stress analysis on the steel branch pipe group. If the requirements are met, calculate the total weight of the steel pipes based on the current pipe wall thickness. If the calculated weight is less than T, proceed to Step 7; otherwise, return to Step 2 to readjust the layout and structure of the steel branch pipe group. If the stress analysis does not meet the requirements, adjust the pipe wall thickness and re-analyze until the stress requirements are met.

[0014] Step 7: Manufacture and install the steel pipes, and measure the head loss on site after completion.

[0015] Furthermore, in step three, the focus is on calculating the local head loss at the branch section of the steel branch pipe.

[0016] Furthermore, in step four, the finite element fluid numerical calculation method is used to simulate the geometric abrupt changes, bifurcation angles, and local flow patterns of the actual turning points of the steel branch pipe group. The parameter ranges of the bifurcation angle, transition cone angle, and width of the reinforcing beam extending over the flow surface of each branch pipe are determined by comparing multiple schemes. Subsequently, the structure of the steel branch pipe group is adjusted within this parameter range.

[0017] Furthermore, in step five, a physical model is established based on the parameter range determined in step four. The model is 1:20 scaled to the actual engineering project, and the actual head loss is measured through hydraulic model tests.

[0018] Furthermore, in step six, if the structural stress analysis meets the requirements but the weight does not, the steel pipe wall thickness can be gradually reduced. If both the stress and weight requirements are met simultaneously during this process, then proceed to step seven; otherwise, return to step two to readjust the steel branch pipe group layout and structure.

[0019] The beneficial effects of this invention are: by first formulating quantitative indicators and then optimizing the structure based on these indicators, following the steps of first satisfying head loss, then structural strength, and finally optimizing structural weight, and combining these with a feedback mechanism to adjust the branch pipe layout and shape parameters, a solution that can simultaneously satisfy both head loss and steel pipe weight is obtained, thereby improving the design efficiency and structural performance of the steel branch pipe group and reducing engineering costs. Attached Figure Description

[0020] Figure 1 This is a flowchart of the design process of the present invention. Detailed Implementation

[0021] The invention will be further described below with reference to the accompanying drawings.

[0022] The present invention provides a quantitative design method for pressure steel branch pipe groups, comprising the following steps:

[0023] Step 1: Develop quantitative indicators for the steel branch pipe group based on the actual project conditions, including the head loss H from the start to the end of the steel pipe and the total weight T of the steel pipe;

[0024] Step 2: Complete the preliminary design of the steel branch pipe group layout and structure based on the actual project conditions;

[0025] Step 3: Calculate the head loss of the steel branch pipe group using hydraulic calculation formulas. If the calculated head loss is less than H, proceed to Step 4; otherwise, return to Step 2 to readjust the layout and structure of the steel branch pipe group.

[0026] Step 4: Calculate the head loss of the pressure steel pipe using the finite element fluid numerical calculation method. If the calculated head loss is less than H, proceed to step 5; otherwise, return to step 2 to readjust the arrangement and structure of the steel branch pipe group.

[0027] Step 5: Verify the head loss of the steel branch pipe group structure using model tests. If the test head loss is less than H, proceed to Step 6; otherwise, return to Step 2 to readjust the steel branch pipe group layout and structure.

[0028] Step 6: Perform structural stress analysis on the steel branch pipe group. If the requirements are met, calculate the total weight of the steel pipes based on the current pipe wall thickness. If the calculated weight is less than T, proceed to Step 7; otherwise, return to Step 2 to readjust the layout and structure of the steel branch pipe group. If the stress analysis does not meet the requirements, adjust the pipe wall thickness and re-analyze until the stress requirements are met.

[0029] Step 7: Manufacture and install the steel pipes, and measure the head loss on site after completion.

[0030] Because head loss directly affects the power generation performance of a power plant, it is considered first in the design. In the preliminary design stage of the steel branch pipe group, the maximum allowable head loss is calculated and determined based on the power plant's output requirements. This maximum head loss value is then used as a quantitative indicator for head loss control in the subsequent detailed design stage. Steps three, four, and five involve head loss analysis, focusing on calculating the local head loss at the branch pipe sections. Since local head loss at the branch pipe sections accounts for a major proportion of the overall head loss in the steel branch pipe group, controlling the branch pipe shape to minimize this head loss is crucial to meeting the limiting requirements. The mechanical calculations in step three are primarily for a rough assessment. When there are many branch pipes, local mechanical calculations become complex and may lack accuracy. Therefore, step four, finite element analysis, is necessary. The finite element method can fully simulate the geometrical abrupt changes, bifurcation angles, and actual flow patterns and head losses at the branch pipe bends. This method also allows for multi-scheme comparison and optimization. The key factors affecting head loss are identified, and sensitivity analysis is performed on these factors to determine suitable parameters for the steel branch pipe structure, including the range of parameters such as the bifurcation angle, transition cone angle, and the width of the reinforcing beam extending over the flow surface. The structure of the steel branch pipe group can then be adjusted within this parameter range. Step five primarily involves a practical verification of the theoretical analysis. A physical model is established based on the parameter range determined in step four. The scale of the physical model to the actual engineering project can be set at 1:20. Then, hydraulic model tests are conducted to measure the actual head loss, thereby verifying the correctness of the design's theoretical basis.

[0031] After meeting the head loss requirements, the mechanical analysis and weight calculation of the pressure steel pipes are then performed. During the preliminary design phase of the steel branch pipe group, the maximum allowable weight of the steel branch pipe group is calculated and determined based on the power station construction cost control and economic requirements. This maximum allowable weight will be used as a quantitative indicator for weight control in the subsequent detailed design phase. The mechanical analysis can actually be performed simultaneously in step four, using finite element analysis to determine the stress conditions of each part. Because the steel pipe wall thickness may be designed to be thinner or thicker in the initial preliminary design, in step six, if the structural stress analysis meets the requirements but the weight does not, the steel pipe wall thickness can be gradually reduced. During this process, if both the stress and weight requirements are met simultaneously, proceed to step seven; otherwise, return to step two to readjust the steel branch pipe group structure. If the stress analysis does not meet the requirements, the steel pipe wall thickness is gradually increased. If both the stress and weight requirements are met simultaneously, proceed to step seven; otherwise, return to step two to readjust the steel branch pipe group structure. The ultimate goal is to optimize the head loss and total weight of the steel pipe to be less than the head loss H and total weight T specified in step one, respectively.

[0032] The present invention will be further described below with reference to embodiments.

[0033] Taking a complex pressure steel branch pipe group as an example, the quantitative design method of pressure steel branch pipe group is described in detail:

[0034] The quantitative design method for steel branch pipe groups has two quantitative control indicators: the average head loss (H) of the three units from the starting point to the end point of the steel pipe does not exceed 2.893m, and the total weight (T) of the steel pipe from the starting point to the end point does not exceed 10017t.

[0035] The product of the constraint indices of the steel branch pipe group is HT = 2.893 * 10017 = 28979.181 (mt).

[0036] first step:

[0037] The layout design of the steel branch pipe group was carried out. When determining the initial head loss, empirical hydraulic calculation formulas were used to calculate the head loss of the complex branch pipe group. The calculation showed that the head loss of the pressure steel pipe was H = 2.775m, which met the limit of 2.894m. At this point, the structural strength design to determine the steel pipe thickness was not carried out, and further analysis of the head loss was required.

[0038] Step Two:

[0039] The head loss of the pressure steel pipe was calculated using the finite element fluid numerical calculation method. The head loss was calculated to be H = 2.416m, which also meets the limit requirements.

[0040] Step 3:

[0041] For the branch pipe layout and shape parameters (branching angle, transition cone angle, width of the overflow surface of the reinforcing beam, etc.) determined in the second step, a 1:20 overall physical model of the steel branch pipe group was established using the physical model test method. Through hydraulic model tests, the head loss of the branch pipe group was further determined. The head loss value of the branch pipe determined by this layout is H = 2.521m, which also meets the limit value requirements.

[0042] Step 4:

[0043] After completing the above three steps, a stress analysis of the steel branch pipe group structure is required to determine the thickness t of each part of the steel branch pipe group. Further calculations are then performed on the weight of the entire steel branch pipe group, ultimately yielding a weight of T = 8500t, which meets the requirement of 10017t. If the wall thickness of the steel branch pipe group is too large and the weight exceeds 10017t, the aforementioned three steps need to be repeated with adjustments and a redesign until both H and T meet the requirements.

[0044] Step 5:

[0045] When the power station is actually generating electricity, the head loss at the beginning and end of the pressure steel pipe is measured. If the head loss of the pressure steel pipe meets the limit of 2.894m, then the requirements are met. The measured head loss is 1.635m, which meets the design requirements.

Claims

1. A quantitative design method for pressure steel branch pipe groups, characterized in that, Includes the following steps: Step 1: Develop quantitative indicators for the steel branch pipe group based on the actual project conditions, including the head loss H from the start to the end of the steel pipe and the total weight T of the steel pipe; Step 2: Complete the preliminary design of the steel branch pipe group layout and structure based on the actual project conditions; Step 3: Calculate the head loss of the steel branch pipe group using hydraulic calculation formulas. If the calculated head loss is less than H, proceed to Step 4; otherwise, return to Step 2 to readjust the layout and structure of the steel branch pipe group. Step 4: Calculate the head loss of the pressure steel pipe using the finite element fluid numerical calculation method. If the calculated head loss is less than H, proceed to step 5; otherwise, return to step 2 to readjust the arrangement and structure of the steel branch pipe group. Step 5: Verify the head loss of the steel branch pipe group structure using model tests. If the test head loss is less than H, proceed to step 6; otherwise, return to step 2 to readjust the steel branch pipe group layout and structure. Step 6: Perform structural stress analysis on the steel branch pipe group. If the requirements are met, calculate the total weight of the steel pipes based on the current pipe wall thickness. If the calculated weight is less than T, proceed to Step 7; otherwise, return to Step 2 to readjust the layout and structure of the steel branch pipe group. If the stress analysis does not meet the requirements, adjust the pipe wall thickness and re-analyze until the stress requirements are met. Step 7: Manufacture and install the steel pipes, and measure the head loss on site after completion.

2. The quantitative design method for pressure steel branch pipe groups as described in claim 1, characterized in that: In step three, the focus is on calculating the local head loss at the branch section of the steel branch pipe.

3. The quantitative design method for pressure steel branch pipe groups as described in claim 1, characterized in that: In step four, the finite element fluid numerical calculation method is used to simulate the geometric abrupt changes, bifurcation angles, and local flow patterns of the steel branch pipe group. The parameter ranges of the bifurcation angle, transition cone angle, and width of the reinforcing beam extending over the flow surface of each branch pipe are determined by comparing multiple schemes. The structure of the steel branch pipe group is then adjusted within these parameter ranges.

4. The quantitative design method for pressure steel branch pipe groups as described in claim 3, characterized in that: In step five, a physical model is established based on the parameter range determined in step four. The model is 1:20 scaled to the actual engineering project. The actual head loss is measured through a hydraulic model test.

5. The quantitative design method for pressure steel branch pipe groups as described in claim 1, characterized in that: In step six, if the structural stress analysis meets the requirements but the weight does not, the steel pipe wall thickness can be gradually reduced. If both the stress and weight requirements are met during this process, proceed to step seven; otherwise, return to step two to readjust the steel branch pipe group structure.

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