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CN-121980707-A - Design method for movable trash rack bars

CN121980707ACN 121980707 ACN121980707 ACN 121980707ACN-121980707-A

Abstract

The invention discloses a design method, in particular a design method for movable trash rack bars, and belongs to the technical field of hydraulic metal structure design processes. The design method for the movable trash rack grid bar can remarkably reduce design calculation workload and fully consider the overall comprehensive performance of the grid bar. The design method comprises a grid frame, the design method firstly takes an upper main beam and a lower main beam of the grid frame as two simple supporting points, preliminarily determines the length l 1 of each cantilever end of the grid strip positioned outside each main beam supporting simple supporting point according to the following calculation, The length L 0 of the simple branch ends of the grid bars positioned at the inner sides of the two simple fulcra is determined by the following calculation, and finally the total length L of each grid bar is determined, When the total length L of the grid bar exceeds 3300mm, correction is also required according to the following calculation formula, . The design method of the application can realize the rapid distribution of the lengths of the sections of the trash rack bars taking the simple supporting point as the supporting center.

Inventors

  • TU JIANWEI
  • Chen zujia
  • YU DAN

Assignees

  • 中国电建集团成都勘测设计研究院有限公司

Dates

Publication Date
20260505
Application Date
20260129

Claims (10)

  1. 1. The design method for the movable trash rack grid bar comprises a grid frame and is characterized in that the design method firstly takes an upper main beam (1) and a lower main beam (1) of the grid frame as two simple supporting points, preliminarily determines the length l 1 of each cantilever end of the grid bar (2) positioned outside each main beam supporting simple supporting point according to the following calculation, , The length L 0 of the simple branch ends of the bars located inside the two simple fulcra is then determined according to the following calculation formula, and finally the total length L of each bar is determined, , When the total length L of the grid bar exceeds 3300mm, correction is also required according to the following calculation formula, , L in each calculation formula is the length of the grid bar in mm, L 1 in each calculation formula is the length of the single-side cantilever end in mm, and L 0 in each calculation formula is the simply supported distance between two simply supported points of the grid bar in mm.
  2. 2. The method for designing movable trash rack bars according to claim 1, wherein the height of the grid frame is maximized based on the height of the aperture of the trash hole and the width limited by transportation conditions, and is not more than 3800mm, and the length L of the single grid bar (2) is adapted to the height of the grid frame.
  3. 3. The method for designing movable trash rack bars according to claim 1 or 2, wherein the length l 1 of the cantilever end is obtained by mathematical modeling and calculation based on the cantilever end stability factor k 1 and the simply supported end stability system k 2 being equal or close and not less than 2, K 1 is obtained as follows, , K 2 is obtained as follows, , In the two formulas, q is the uniformly distributed load intensity born by a single grid (2), E is the elastic modulus of the material, G is the shear modulus of the material, I y is the moment of inertia of the grid to the y axis, I d is the torsional moment of inertia of the end face of the grid, and the units are all the units specified by national standards.
  4. 4. The method for designing a movable trash rack bar according to claim 3, wherein the process of mathematically modeling and deriving the cantilever end length l 1 is as follows, let k 1 = k 2 be Can be obtained Then L=l 0 +2l 1 is substituted into the former formula to obtain 。
  5. 5. The method for designing a movable trash rack bar according to claim 4, further comprising designing a bar connection system including at least a simple support end connection system (3) and a cantilever end connection system (4), and re-combining the simple support end length l 0 according to a predetermined vibration characteristic requirement Or (b) A simple support end connection system (3) is provided, and at least one cantilever end connection system (4) is provided in accordance with the specified vibration characteristic requirements in combination with the cantilever end length at a distance corresponding to the support distance of the simple support end.
  6. 6. The method for designing movable trash rack bars according to claim 5, wherein the distance l 2 between two adjacent simple support end connecting systems (3) is 450-600 mm, and the cantilever end connecting system (4) is adaptively adjusted according to the running condition of the trash cleaning grab when the cantilever end connecting system is determined according to the specified vibration characteristic requirement and the length of the cantilever end.
  7. 7. The method of claim 6, wherein the length of the grating bars and the arrangement positions of the grating bar connection system are determined, at least the intensity calculation and the vibration calculation are performed according to the specification, and the cross-sectional shape and the cross-sectional size of the grating bars (2) are selected according to the processing conditions, the manufacturing difficulty, the manufacturing cost and the maintenance convenience of the grating bars.
  8. 8. The method for designing a movable trash rack bar according to claim 7, wherein the cross section of the bar (2) is rectangular, double-round-head or fish belly streamline, the cross section of the bar (2) comprises the width of the bar cross section and the height of the bar cross section, and the cross section of the simple support end connection system (3) and the cantilever end connection system (4) is matched with the cross section of the bar.
  9. 9. The design method for the movable trash rack grid bar according to claim 8, wherein the cross section width of the grid bar (2) is 10-20mm, the cross section height of the grid bar (2) is 100-300mm, and the two free ends of the grid bar (2) are further provided with stable supporting angle steel (5).
  10. 10. The method for designing the movable trash rack grid bar according to claim 9, wherein the method further comprises the step of determining the connection mode of the grid bar (2) and a support connection system, the support connection system comprises a main beam (1), a simple support end connection system (3), a cantilever end connection system (4) and stable support angle steel (5), the grid bar is connected with the main beam in a welding mode or in a bolt mode, and the grid bar is connected with the simple support end connection system (3), the cantilever end connection system (4) and the stable support angle steel (5) in a welding mode.

Description

Design method for movable trash rack bars Technical Field The invention relates to a design method, in particular to a design method for movable trash rack bars, and belongs to the technical field of hydraulic metal structure design processes. Background The trash rack is important to protect the hydroelectric generating set and maintain the safe operation of the hydropower station. According to whether the trash rack can be overhauled by the hole, the trash rack is divided into a fixed trash rack and a movable trash rack. The fixed trash rack has simple structure and low cost, but is difficult to overhaul, and is more applied to small-sized hydropower stations in foreign countries. The movable trash rack has a complex structure and slightly high manufacturing cost, but is convenient to operate and maintain, reduces the later operation and maintenance time, and is widely used at home and abroad. The movable trash rack can be roughly divided into a rack frame structure and a rack row structure according to the structure. The grating frame structure is a supporting main body of the trash rack, bears the water pressure of the trash rack and transmits the pressure to the hydraulic model structure, and other structures except the main beam are arranged inside the grating groove and are not directly impacted by water flow, so that the situation that the grating frame structure is damaged rarely occurs in engineering practice. The grating structure mainly comprises a trash rack grating strip and a connecting system thereof, mainly bears the task of intercepting dirt, bears the direct impact of water flow, and sometimes damages the grating strip due to the reasons of dirt impact, vibration damage and the like in engineering practice. Because the trash rack is designed according to the water pressure difference, compared with a gate, the integral stress of the trash rack is relatively small, the structural strength of the grid frame structure is generally more abundant, and the design of the trash rack is mainly concentrated on the design of the grid structure, namely the design of the grid and the connection system thereof. In addition, the weight of the grating bars of the trash rack is high in proportion to the weight of the whole trash rack, the design of the grating bars is directly related to the safety of the trash rack, the engineering cost of the trash rack is directly influenced, and the repair period of the damaged grating bars is directly related to the power generation benefit of the power station in the operation process of the power station. The design of the grating bars mainly focuses on grating pitch, grating structural strength, grating stability and grating vibration characteristics, wherein the grating pitch is directly selected according to the requirements of a water turbine, and the grating structural strength of the grating designed according to water pressure difference is generally high, so the design of the grating bars is mainly focused on the design of stability and grating vibration characteristics, how to improve the overall stability and vibration resistance of the grating bars is important to the design of the grating bars, and is also the focus of the research of the grating bars. In order to reduce the water blocking area and reduce the grating flow velocity of the trash rack, the movable trash rack generally adopts a double-girder structure, and single-section grating blades are made higher as much as possible under the condition of meeting transportation so as to reduce the number of girders in the flow cross section and reduce the flow blocking area. The grating bars of the trash rack are supported on the double main beams, and according to practical experience, the arrangement of the double cantilever ends is more economical and reasonable, so that the design of the trash rack is the consensus, but the specific proportion of the length of the cantilever ends is adopted, so that the overall stability of the grating bars of the trash rack is more reasonable, and the length of the cantilever ends of the grating bars is corrected by taking the vibration characteristics of the grating bars into consideration, so that an instructive formula is lacked. The existing design method of the grating bars of the trash rack is to carry out trial-and-error analysis based on design experience, design the grating bars of the trash rack according to experience, then check stability and vibration characteristics of the grating bars of the trash rack according to standard requirements, and adjust technical parameters of the grating bars to check again until the standard requirements are met if the check requirements are not met. The traditional design method of the grating bars of the trash rack is simple and effective, a repeated checking process can exist for many times, the design workload can be increased, the optimal design of the grating bars is not considered, the existing repeated checking