Research On Hydraulic Characteristics Of Energy Dissipator In Three Stage Variable Aperture Orifice Plate

As a new type of internal energy dissipator,orifice plate energy dissipation device has been widely used in water conservancy projects due to its simple structure,high energy dissipation efficiency,and convenient handling.Based on the traditional three-stage orifice plate energy dissipation device,this paper constructs a variable aperture orifice plate energy dissipation device.Using the method of combining physical model test and numerical simulation,it systematically analyzes and studies the pressure difference between adjacent sections,the pressure drop ratio at the core location,the pressure distribution along the path,the cavitation number,the flow velocity distribution,the flow capacity of the pipeline,and the energy dissipation efficiency under different torsion angles,area contraction ratios,and Reynolds numbers of the orifice plate,And summarize the relevant laws.（1）The orifice plate combination section is the core position of the entire test pipe section.The physical model test results show that when the torsion angle and Reynolds number of the orifice plate remain unchanged,the smaller the area shrinkage ratio,the greater the pressure reduction ratio of the orifice plate combination section,and the smaller the minimum cavitation number after the orifice plate combination section;When the torsion angle and area contraction ratio of the orifice plate remain unchanged,the greater the Reynolds number,the greater the pressure drop ratio of the orifice plate combination section,and the smaller the minimum cavitation number after the orifice plate combination section;When the area contraction ratio and Reynolds number remain constant,the greater the torsion angle,the greater the pressure drop ratio of the orifice plate combination section,and the smaller the minimum cavitation number after the orifice plate combination section;The pressure distribution and cavitation number distribution along the path of each scheme are basically the same;Each scheme has a positive cavitation number before the orifice plate assembly section,and the cavitation number reaches the minimum value at a distance of 1m from the 1#pressure measuring section.The cavitation resistance is the weakest,and the possibility of cavitation is the greatest.（2）According to the analysis of the flow velocity distribution of each scheme,the law of velocity vector distribution along the route is basically the same for all schemes,The flow velocity of water near the center of the pipe axis before the orifice plate assembly section is larger,while the flow velocity near the pipe wall is smaller.After the orifice plate assembly section,the flow velocity rises sharply,forming two strong jets at the YZ section,and then tends to stabilize.Moreover,the presence of orifice plate assembly sections has a significant impact on the magnitude and direction of the axial,tangential,and radial velocities of water flow in the pipeline.（3）According to the analysis of pipeline flow capacity and energy dissipation efficiency of each scheme,When the area contraction ratio remains unchanged,under the same Reynolds number for the same group of schemes,the flow capacity of the pipeline decreases with the increase of the torsion angle,and the rate of reduction increases with the increase of the torsion angle,while the energy dissipation efficiency increases with the increase of the torsion angle;Under the same torsion angle for the same group of schemes,the flow capacity of the pipeline does not significantly change with the increase of Reynolds number,while the energy dissipation efficiency increases with the increase of Reynolds number.When the Reynolds number remains constant,the flow capacity of a pipe at the same torsion angle increases with the increase of the area contraction ratio,while the energy dissipation efficiency significantly decreases with the increase of the area contraction ratio.The smaller the area contraction ratio,the more easily the energy dissipation efficiency of the pipe changes with the increase of the torsion angle.（4）Based on the comprehensive analysis of the flow capacity and energy dissipation efficiency of pipelines in various schemes,The change in energy dissipation efficiency and the change in flow capacity present an opposite trend,and an increase in pipeline energy dissipation efficiency will inevitably lead to a decrease in flow capacity.In order to balance the contradiction between flow capacity and energy dissipation efficiency,it is recommended to select a combination of orifice plates of the energy dissipation device with a torsion angle of 6°and an area contraction ratio of ξ ₂=0.341.This combination method can provide theoretical basis and reference for long-distance pressurized pipeline water transportation projects.