CN111414687A - Simulation method for flow channel of throwing system of green fodder harvester - Google Patents
Simulation method for flow channel of throwing system of green fodder harvester Download PDFInfo
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Abstract
The invention provides a simulation method for a flow channel of a throwing system of a ensilage harvester, which comprises the following steps of carrying out three-dimensional modeling on components of the throwing system of the ensilage harvester, carrying out Boolean operation on a model, carrying out multi-face mixed grid division on the obtained calculation model, outputting the multi-face mixed grid division into a grid type for CFD calculation, calculating the output grid through a finite volume algorithm, obtaining the numerical value of the grid, and carrying out post-processing on the calculated numerical value to obtain a corresponding data curve and a cloud picture. The invention can save a large amount of test time, reduce test material consumption and personnel cost; and guiding a designer to carry out optimization design on the material throwing system model through a calculation result until the design requirement is met.
Description
Technical Field
The invention belongs to the technical field of agricultural machinery, and relates to a simulation method for a flow channel of a throwing system of a green feed harvester.
Background
With the rapid increase in the market demand for high-quality meat products and dairy products, the demand for high-quality feeds, represented by silage, is being driven. However, the requirement of the industry on the degree of mechanization is high, and the ensilage harvester is seriously dependent on foreign import, so that the production cost is high, and the healthy development of the industry is not facilitated. By carrying out simulation on a key functional component of the green feed harvester, namely a material throwing system flow passage, the problem is found in the design stage, the product quality and the production efficiency are improved, the cost is saved for producers and users, and the value is created.
At present, the design and improvement of the flow passage of the throwing system of the green fodder harvester mainly pass through a test method. A large number of tests are required, data representing main parameters of the flow channel are collected by matching with various sensors for analysis, the design of the flow channel is improved, a new round of prototype is manufactured, and the tests are repeated again. The method is long in time consumption, a lot of crops, fuel, materials and personnel are consumed in the test period, the data acquisition and processing workload is large, and the complexity is high; the flow characteristic of the interior of the flow channel is difficult to capture by a simple test method, and data cannot be visually acquired on the abrasion degree of the interior material to the inner wall of the throwing cylinder, the material flow track and the curvature matching degree of the throwing cylinder; in addition, each test prototype has long manufacturing period, high cost and great research and development pressure of enterprises. Therefore, the simulation method for the flow channel of the throwing system of the green fodder harvester by adopting the limited volume method has great application value and positive significance for the research and development of the green fodder harvester.
Disclosure of Invention
The invention aims to provide a simulation method for a flow channel of a throwing system of a green feed harvester, aiming at solving the problems in the prior art.
Therefore, the invention adopts the following technical scheme:
a simulation method for a flow channel of a throwing system of a ensilage harvester comprises the following steps:
(1) performing three-dimensional modeling on components of the throwing system of the ensilage harvester;
(2) deleting geometric parameters irrelevant to the flow channel characteristics in the model, performing Boolean operation on the deleted model to obtain a calculation model of an internal flow channel fluid calculation domain, and removing external redundant geometric characteristics of the calculation model;
(3) carrying out multi-face mixed grid division on the calculation model, and outputting the divided grids as grid types for CFD calculation;
(4) setting boundary conditions for the output grids;
(5) selecting a fluid dynamics model;
(6) substituting the flow model into a grid, calculating by a finite volume algorithm, and obtaining a numerical value of the flow model;
(7) and processing the calculated numerical value to obtain a corresponding data curve and a cloud picture, and comparing to judge whether the calculated numerical value meets the design requirement.
Further, the computational model is divided into a structured grid and an unstructured grid by adopting an FVM discrete system in the step (3), the quality of the structured grid and the unstructured grid is adjusted and assembled, and the structured grid and the unstructured grid are combined into a full-flow-channel computational grid according to nodes.
Further, the setting of the boundary conditions in the step (4) includes the types of the inlet and the outlet of the flow passage, the inlet speed, the outlet pressure, and the rotating speed and the rotating direction of the rotating component.
Further, the flow model in the step (5) is a steady turbulent flow.
Further, the step (6) adopts the SIMP L EC algorithm to solve the pressure-velocity coupling, and the relaxation factor is adjusted to obtain a faster convergence speed.
The invention has the beneficial effects that:
(1) compared with the traditional design and improvement method of the throwing system of the green feed harvester, the method adopts a finite volume method, and is matched with a CFD calculation means in the design stage, so that a large amount of test time, test material consumption and personnel cost can be saved, and the number of trial-production wheels of a prototype can be greatly reduced; by adopting the method, the flowing state of the medium in the flow channel of the throwing system can be more intuitively reflected;
(2) the method adopts a mixed grid division method to carry out a grid division strategy on the calculation domain of the flow channel of the green feed harvester throwing system, and compared with the method which only adopts a structured grid or an unstructured grid, the method not only utilizes the characteristic that the unstructured grid has good adaptability to a complex curved surface, but also has the characteristics of good quality of the structured grid and small division quantity, and improves the iterative calculation efficiency by using the minimum grid quantity on the premise of ensuring the grid quality of the flow channel calculation domain of the green feed harvester throwing system;
(3) under the limited volume environment, the calculation domain of the flow channel of the green feed harvester throwing system is discretized, a multi-reference-system dynamic and static coupling model is matched, a turbulence calculation model and an SIMP L EC algorithm are selected, and a convergent calculation result can be rapidly obtained under the condition of good grid quality.
Drawings
FIG. 1 is a flow chart of the present invention.
Detailed Description
As shown in fig. 1, the implementation of a simulation method for a flow channel of a throwing system of a green fodder harvester includes the following steps:
(1) the method is characterized in that a solid structure of a throwing system component of the green fodder harvester is modeled in a three-dimensional mode (wherein the main components of the throwing system comprise a chopping device, a throwing shovel and a throwing cylinder), and the calculated object is a runner of the throwing system, so that in order to reduce the workload of designers, the structure part which does not participate in forming the runner of the throwing system can be modeled accurately, and the part forming the runner is modeled accurately according to actual design parameters and structure sizes, and the aim of providing an accurate calculation model for subsequent flow field calculation is achieved.
(2) Geometric parameters irrelevant to flow channel characteristics in the model calculation part are deleted, Boolean calculation is carried out on the deleted material throwing system by utilizing a SolidWorks2019 three-dimensional modeling method to obtain a calculation model of a fluid calculation domain of an internal flow channel, the internal flow channel is extracted to carry out a full flow channel calculation domain, redundant entities are cut off, and the entity cutting-off boundary is controlled by the outer boundaries of a cavity of a chopping device and a cavity of an accelerator to obtain an internal flow field.
(3) Carrying out polyhedral mesh division on a computational domain of an internal flow channel of a green fodder harvester throwing system by using a mesh division method, specifically, dividing the computational domain into a structured mesh and an unstructured mesh, firstly discretizing the computational domain, outputting the mesh type suitable for computational fluid mechanics, adopting a mixed mesh technology (tetrahedral mesh and hexahedral mesh), and carrying out mesh division on a flow field with a complicated boundary by using the characteristic that the unstructured mesh has strong adaptability to a geometric body, so as to conveniently cover the complicated computational domain; the structured grid is utilized to carry out discretization on a calculation area with a simple geometric structure by using a difference value calculation method, so that a smooth grid which is very close to an actual model is obtained, the number of the grids is reduced on the premise of ensuring the adaptability of the grid to the calculation area, the expenditure of computer resources in numerical calculation is reduced, and the calculation time is shortened; after the division is finished, grid quality adjustment (modification and fairing) is carried out in processing software, grid assembly is carried out, the unstructured grid computing domain and the structured grid computing domain are combined into a full-flow-channel computing grid according to nodes, and the grid type suitable for CFD computing is output.
(4) And setting boundary conditions of the output grids, wherein the setting of the boundary conditions comprises the types of inlets and outlets of the flow channels, the inlet speed, the outlet pressure, the rotating speed and the rotating direction of the rotating component.
(5) And selecting a fluid dynamic model, wherein the fluid dynamic model is selected to be constant turbulent flow according to the fluid flow characteristics of the internal flow channel, the temperature in the flow field is equal, and the gravity action is ignored.
(6) And introducing the fluid dynamics model and the grid into a SolidWorks software Flow Simulation module, simultaneously calculating and solving, setting a turbulence mode in the process, and adjusting a relaxation factor by adopting a pressure-velocity coupling method so as to obtain a faster convergence speed. In the solution calculation, since the boundary of the calculation domain fluid includes both a stationary part and a rotating part, a Multiple Reference Frame (MRF) is selected.
(7) And obtaining a calculation result through calculation, and obtaining a cloud picture and a data curve of a corresponding physical field such as pressure, speed and the like by utilizing a Flow Simulation post-processing function, wherein the result is used for guiding a designer to carry out optimization design on the material throwing system model until the design requirement is met.
Claims (5)
1. A simulation method for a flow channel of a throwing system of a ensilage harvester is characterized by comprising the following steps:
(1) performing three-dimensional modeling on components of the throwing system of the ensilage harvester;
(2) deleting geometric parameters irrelevant to the flow channel characteristics in the model, performing Boolean operation on the deleted model to obtain a calculation model of an internal flow channel fluid calculation domain, and removing external redundant geometric characteristics of the calculation model;
(3) carrying out multi-face mixed grid division on the calculation model, and outputting the divided grids as grid types for CFD calculation;
(4) setting boundary conditions for the output grids;
(5) selecting a fluid dynamics model;
(6) substituting the flow model into a grid, calculating by a finite volume algorithm, and obtaining a numerical value of the flow model;
(7) and processing the calculated numerical value to obtain a corresponding data curve and a cloud picture, and comparing to judge whether the calculated numerical value meets the design requirement.
2. The method for simulating the flow channel of the throwing system of the ensilage harvester according to claim 1, wherein in the step (3), the computational model is divided into a structured grid and an unstructured grid by using an FVM discrete system, and the structured grid and the unstructured grid are subjected to quality adjustment and assembly to form the full-flow-channel computational grid according to the node combination.
3. The method for simulating the flow channel of the throwing system of the ensilage harvester according to claim 1, wherein the setting of the boundary conditions in the step (4) comprises the inlet and outlet types of the flow channel, the inlet speed, the outlet pressure, the rotating speed and the rotating direction of the rotating component.
4. The method for simulating the flow channel of the throwing system of the ensilage harvester according to the claim 1, wherein the flow model in the step (5) is a steady turbulent flow.
5. The method for simulating the flow channel of the throwing system of the ensilage harvester according to claim 1, wherein the step (6) adopts a SIMP L EC algorithm to solve the pressure-velocity coupling, and the relaxation factor is adjusted to obtain a faster convergence rate.
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