A CFD-based Flow Field Optimization Method and Structure for Glue Ball Recovery Net

Abstract

The present invention relates to a method and structure for optimizing the flow field of a rubber ball collecting net based on CFD. The method includes: Step 1: Collect on-site data to obtain parameters of the circulating water outlet pipeline, flow field, collecting net, and guide plate; Step 2: Construct a geometric model of the computational domain according to the size and structural parameters and divide the grid; Step 3: Set the computational boundary conditions and perform parameter calculations according to the model; Step 4: Extract the calculation results and output parameters such as flow velocity, pressure, and velocity in each region; Step 5: Export the results to obtain the influence law of each boundary condition on the flow field; Step 6: Determine the optimal structural and dimensional parameters in combination with actual situations such as process and budget. The present invention greatly shortens the improved design cycle, reduces the design cost and experimental cost, and effectively improves the problem of rubber ball accumulation on the collecting net plate without modifying the structure of the collecting net.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation, and particularly relates to a method and structure for optimizing the flow field of a rubber ball collecting net based on CFD. Background Art

[0002] The society has higher and higher requirements for the thermal power industry. The pressure of energy conservation and emission reduction faced by the thermal power industry is still huge. How to improve the thermal efficiency of thermal power units and the requirements of economy have become increasingly urgent. Obviously, energy conservation and consumption reduction are the themes of the future development of the thermal power industry. The cleanliness of the condenser tube wall will directly affect the back pressure of the steam turbine and the upper and lower terminal differences of the condenser. According to relevant thermal tests, when the vacuum degree of the small steam turbine condenser rises by 1 kPa, the steam consumption rate of the unit will decrease by 1.5 - 2.5%, thus ensuring the safe and stable operation of the whole unit and smoothly taking load. Improving the cleanliness of the condenser tube bundle of the unit is crucial for energy conservation, emission reduction, and the safe and stable operation of the unit in thermal power plants, and the economic benefits brought are also very significant.

[0003] In order to maintain the cleanliness of the condenser tube bundle, each thermal power plant generally uses a rubber ball cleaning system to maintain the cleanliness of the condenser (the domestic design cleaning coefficient is 0.80 - 0.85). The automatic rubber ball cleaning of the condenser sponge is to squeeze the sponge rubber ball larger than the inner diameter of the condenser tube into the condenser tube by the action of water flow, scrub the condenser tube, maintain the cleanliness of the inner wall of the condenser tube, ensure that the designed heat transfer efficiency of the condenser does not decrease, and thus maintain the terminal difference of the condenser and the back pressure of the steam turbine; at the same time, avoid the corrosion of the inner wall of the condenser tube, improve the operating conditions, and extend the service life of the unit. However, due to various reasons, the input rate and collection rate of many rubber ball cleaning systems are in an unsatisfactory state, affecting the rubber ball collection rate. The insufficient output of the rubber ball pump or the dead zone of the condenser will have a certain impact on the collection rate. When the pressure difference of the collecting net or the diversion device does not meet the requirements, problems such as ball accumulation on the net plate of the collecting net or blockage of the collecting pipeline will occur.

[0004] In view of the above situation, many relevant units have studied and improved the rubber ball cleaning system, achieving normal operation and significant economic benefits. The vacuum of the unit is maintained at a relatively high level. The improved rubber ball cleaning system has brought obvious economic benefits to the unit with more power generation, higher efficiency, and lower consumption. The existing technologies all add a diversion device on the original structure or completely change the overall structure of the collecting net. Based on qualitative empirical analysis or theoretical analysis, without quantitative data support, while achieving some effects, there are also two problems: one is that due to the large structural changes, it is necessary to change the overall structure or install a new diversion device, so it is time-consuming and laborious; the other is that due to the lack of rigorous data support, when changes occur in various aspects such as the inlet flow rate, pressure, and other external environments, it is impossible to flexibly adjust the device to the optimal operating state, and after running for a period of time, it will gradually deviate from the optimal operating condition. Summary of the Invention

[0005] The object of the present invention is to provide a CFD-based flow field optimization method and structure for a rubber ball collecting net, so as to solve the above technical problems.

[0006] The present invention provides a CFD-based flow field optimization method for a rubber ball collecting net, comprising the following steps:

[0007] Step 1: Collect on-site data to obtain parameters of the circulating water outlet pipeline, flow field, collecting net and guide vane at the condenser outlet;

[0008] Step 2: Construct a geometric model of the computational domain according to the size and structural parameters and divide the grid;

[0009] Step 3: Set the computational boundary conditions and perform parameter calculations according to the model;

[0010] Step 4: Extract the calculation results and output the flow velocity and pressure parameters of each region;

[0011] Step 5: Export the results to obtain the influence law of each boundary condition on the flow field;

[0012] Step 6: Combine the actual situations of the process and budget to determine the optimal structure and size parameters.

[0013] Further, the specific content of Step 2 includes:

[0014] Establish a structural model using SolidWorks software;

[0015] Generate a fluid domain based on the structural model and perform fluid grid division using ICEM.

[0016] Further, the structural model successively includes a circulating water outlet pipeline, a guide vane, a rubber ball collecting net and a ball collecting pipeline from top to bottom.

[0017] Further, the specific steps of fluid grid division in Step 2 are: Cut the fluid domain into blocks of different sizes, and perform targeted grid division on each block respectively.

[0018] Further, the grid shape is a tetrahedron.

[0019] Further, Step 3 includes:

[0020] Establish a computational model in CFX;

[0021] Obtain a rational calculation model: Calculate based on the measured values of the circulating water pressure at the outlet of the condenser, the pressures before and after the ball collecting net, and in the ball collecting pipeline. After the calculation is completed, extract the calculated values of the velocity and pressure at several points in the geometric model, and compare the calculated values of the velocity and pressure with the measured values to verify the rationality of the calculation model. If the difference between the calculated value and the measured value is within ±15%, the calculation model is reasonable; if the calculation model is unreasonable, steps 1 and 2 need to be repeated until a reasonable calculation model is obtained.

[0022] Furthermore, in step 3, the parameter values include the shape, angle, and installation position of the deflector, the angle and length of the net plate, and the circulating water flow velocity.

[0023] Furthermore, the parameters output in step 4 include the average velocity and the local velocity distribution above the ball collecting net plate and in the ball collecting pipeline.

[0024] The present invention also provides a flow field structure of a ball collecting net for rubber balls, which is obtained by the above-mentioned flow field optimization method of a ball collecting net for rubber balls based on CFD.

[0025] Furthermore, the ball collecting net for rubber balls is parallel to the deflector, and the range of the included angle between the two and the vertical direction is ≤20°. The deflector is locally arranged, with a length of 300 mm, a width of 100 mm, and a thickness of 10 mm above the ball collecting pipeline.

[0026] By means of the above solution, through the flow field optimization method and structure of the ball collecting net for rubber balls based on CFD, the improvement design cycle is greatly shortened, the design cost and experimental cost are reduced, and on the basis of not changing the structure of the ball collecting net, the problem of ball accumulation on the ball collecting net plate is effectively improved.

[0027] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it in accordance with the content of the description, the following describes the preferred embodiments of the present invention in detail. Brief Description of the Drawings

[0028] Figure 1 is a flowchart of the flow field optimization method of the ball collecting net for rubber balls based on CFD of the present invention;

[0029] Figure 2 is the flow field structure of the ball collecting net for rubber balls in an embodiment of the present invention.

[0030] Reference Numerals in the Drawings:

[0031] 1 - Circulating water pipeline at the outlet of the condenser; 2 - Ball collecting net for rubber balls; 3 - Shaft; 4 - Deflector; 5 - Ball collecting pipeline; 6 - Horizontal baffle. Detailed Embodiments

[0032] The following will further describe in detail the specific implementation manners of the present invention in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0033] Refer Figure 1 As shown, in this embodiment, CFD is the abbreviation of Computational Fluid Dynamics. Starting from the calculation method, it uses the fast computing power of the computer to obtain an approximate solution of the fluid control equation. The general structure of the CFD software consists of three parts: pre-processing, solver, and post-processing. The three major modules of pre-processing, solver, and post-processing.

[0034] This embodiment provides a method for optimizing the flow field of a rubber ball collecting net based on CFD technology. The specific steps are as follows:

[0035] Step 1: Collect on-site data to obtain the parameters of the circulating water outlet pipeline, flow field, ball collecting net, and guide vane.

[0036] Step 2: Construct a geometric model of the computational domain according to the size and structure parameters and divide the grid.

[0037] Step 3: Set the calculation boundary conditions and perform parameter calculations according to the model.

[0038] Step 4: Extract the calculation results and output parameters such as the flow velocity and pressure in each region.

[0039] Step 5: Export the results to obtain the influence law of each boundary condition on the flow field.

[0040] Step 6: Combine the actual situations such as the process and budget to determine the optimal structure and size parameters.

[0041] Step S2 specifically includes the following steps:

[0042] Step 2.1: Use SolidWorks software to establish a structure model. In other embodiments, other modeling software such as CAD, 3DMAX, sketchup, etc. can also be used for modeling.

[0043] Step 2.2: Generate a fluid domain based on the structure model and use ICEM for fluid mesh division. In other embodiments, other software such as Gambit, CFD, CFX, etc. can also be used for division.

[0044] The structure model sequentially includes a circulating water outlet pipe, a guide vane, a rubber ball collecting net, and a ball collecting pipeline from top to bottom.

[0045] In Step 2.2, the specific steps for fluid mesh division are as follows: Divide the fluid domain into blocks of different sizes, and perform targeted mesh division on each block.

[0046] The grid shape is a tetrahedron or a hexahedron.

[0047] Step 3 includes:

[0048] Step 3.1: Establish a calculation model in CFX. In other embodiments, other software such as Fluent, STAR-CCM, comsol, OpenFOAM, Phoenics, etc. can also be used for calculation and analysis;

[0049] Refer to Figure 2 , in this embodiment, the structure model successively includes a condenser outlet circulating water pipe 1, a guide vane 4, a rubber ball collecting net 2, a collecting pipe 5 and a horizontal baffle 6 from top to bottom. In the original collecting net structure, the guide vane 4 is arc-shaped downward, at an angle of 45° with the vertical direction, 4 mm wide, and is integrally arranged at the corresponding pipe wall above the collecting net. Based on the improved method for the flow field of the collecting net guide, the structure parameter of the guide vane in the embodiment of the present invention is obtained. The rubber ball collecting net and the guide vane are parallel, and the range of the angle between the two and the vertical direction is ≤ 20°. The guide vane is locally arranged above the collecting pipe. The local maximum speed of the collecting pipe can be increased by 15 - 25%, and the local minimum speed can be increased by 10 - 15%. The uniformity of the flow field above the collecting net is increased by 20% - 30%. Through comprehensive evaluation, the best parameter values under actual working conditions are obtained: the guide vane is locally arranged in length above the collecting pipe, with a length of 300 mm, a width of 100 mm, and a thickness of 10 mm, and the effect is better. At this parameter value, the local maximum speed of the collecting pipe is increased by 24.4%, the local minimum speed is increased by 12.5%, and the uniformity of the flow field above the collecting net is increased by 27.1%, greatly improving the guiding effect on the flow field of the collecting net.

[0050] Step 3.2: Obtain a reasonable calculation model: Calculate according to the measured values of the pressure at the outlet of the circulating water, before and after the collecting net, and in the collecting pipe. After the calculation is completed, extract the calculated values of the velocity and pressure at several points in the geometric model, and compare the calculated values of the velocity and pressure with the measured values to verify the rationality of the calculation model. If the difference between the calculated value and the measured value is within ±15%, the calculation model is reasonable; if the calculation model is unreasonable, steps 1 and 2 need to be repeated until a reasonable calculation model is obtained.

[0051] In step 3, the parameter values include the shape, angle and installation position of the guide vane, the angle and length of the net plate, and the circulating water flow velocity.

[0052] The parameters output in step 4 include: the average velocity and the local velocity distribution above the collecting net plate and in the collecting pipe.

[0053] Through the CFD-based flow field optimization method and structure of the rubber ball collecting net, the improvement design cycle is greatly shortened, the design cost and experimental cost are reduced, and on the basis of not changing the structure of the collecting net, the problem of ball accumulation on the collecting net plate is effectively improved.

[0054] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A CFD-based method for optimizing the flow field of a rubber ball collecting net, characterized in that, it includes the following steps: Step 1: Collect on-site data to obtain the parameters of the circulating water pipeline, flow field, collecting net and guide vane at the outlet of the condenser; Step 2: Construct a geometric model of the computational domain and divide the grid according to the size and structural parameters, including: Use SolidWorks software to establish a structural model, and the structural model successively includes a circulating water outlet pipe, a guide vane, a rubber ball collecting net and a ball collecting pipeline from top to bottom; Generate a fluid domain based on the structural model and use ICEM to perform fluid grid division. The fluid domain is cut into blocks of different sizes, and targeted grid division is performed on each block respectively; the grid shape is tetrahedron; Step 3: Set the calculation boundary conditions and perform parameter calculations according to the model, including: Establish a calculation model in CFX; Obtain a reasonable calculation model: Calculate according to the measured values of the circulating water pressure at the outlet of the condenser, the pressures before and after the collecting net and in the ball collecting pipeline. After the calculation is completed, extract the calculated values of the velocity and pressure at several points in the geometric model, and compare the calculated values of the velocity and pressure with the measured values to verify the rationality of the calculation model. If the difference between the calculated value and the measured value is within ±15%, the calculation model is reasonable; if the calculation model is unreasonable, steps 1 and 2 need to be repeated until a reasonable calculation model is obtained; the parameter values include the shape, angle and installation position of the guide vane, the angle and length of the net plate, and the circulating water flow velocity; Step 4: Extract the calculation results and output the flow velocity and pressure parameters of each region. The output parameters include the average velocity and local velocity distribution above the collecting net plate and at the ball collecting pipeline; Step 5: Export the results to obtain the influence law of each boundary condition on the flow field; Step 6: Combine the actual situation of the process and budget to determine the optimal structure and size parameters, including: The rubber ball collecting net is parallel to the guide vane, and the range of the included angle between the two and the vertical direction ≤ 20°. The guide vane is locally arranged, with a length of 300 mm, a width of 100 mm and a thickness of 10 mm above the ball collecting pipeline.

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