A model preprocessing method for a turbomachine

Abstract

The application relates to the technical field of three-dimensional model simulation processing, and discloses a model preprocessing method for a turbomachine, which comprises the following steps: obtaining a three-dimensional model of a turbomachine structure, and simplifying the three-dimensional model; extracting a turbomachine fluid domain, and dividing the turbomachine fluid domain into a plurality of dynamic domains and a plurality of static domains; respectively dividing different area grids according to the divided dynamic domains and static domains, and ensuring that the quality of the shared surface grids is consistent; combining all the area grids to form complete grid of the fluid area; and setting corresponding boundary conditions and an interaction surface according to the divided dynamic domains and static domains. The turbomachine model preprocessing method has the beneficial effect that: by means of the method for setting a plurality of rotating domains, the rotating conditions of the multistage turbomachine can be simulated more realistically, so that the simulation problem of the multistage rotating turbomachine is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of three-dimensional model simulation processing, in particular to a model preprocessing method for a turbomachine. BACKGROUND

[0002] Computational fluid dynamics (CFD) is a product of the combination of modern fluid mechanics, numerical mathematics and computer science, and is a cross science with strong vitality. It is to approximate the integral and differential terms in the control equations of fluid mechanics as discrete algebraic forms, so that they become algebraic equations, and then the discrete algebraic equations are solved by computer to obtain numerical solutions at discrete time or space points.

[0003] At present, CFD has been widely used in the design and optimization process of turbomachines. The numerical values required for the simulation of fluid flow in turbomachines are calculated to determine whether the design of turbomachines meets the engineering requirements. However, the current simulation of turbomachines is limited to the turbomachine itself, and most simulations place the mechanical structure in an open space and use an open flow field as the boundary condition for simulation, that is, the simulation of the structure of the turbomachine itself, without considering the boundary conditions under actual working conditions. However, in general, turbomachines will have a protective shell, and some turbomachines may have multiple levels of structure. The changes in the flow field caused by these protective devices and multiple levels of structure will affect the inlet and outlet pressures, velocities and ranges of the structure, thereby changing the boundary conditions. Therefore, ignoring the external structure and only considering the turbomachine itself will result in inaccurate boundary condition settings, which deviates greatly from the actual situation, and the calculation results will also have large errors.

[0004] With the increasing number of types of turbomachines and their increasingly wide range of uses, two-stage rotation and even multi-stage rotation structures are also emerging. Therefore, for multi-stage turbomachine structures, a method is needed that can consider the overall mechanical structure including the turbomachine structure, so that the boundary conditions of the simulation calculation are closer to the actual situation, and the data obtained are more accurate. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a model preprocessing method for a turbomachine, which can more realistically simulate the rotation of a multi-stage turbomachine by setting a multi-stage rotation domain, thereby solving the simulation problem of a multi-stage rotating turbomachine.

[0006] To achieve the above object, the present application provides the following technical scheme:

[0007] A model preprocessing method for a turbomachine, comprising the following steps:

[0008] Step 1: obtain a three-dimensional model of the impeller mechanical structure, and simplify the three-dimensional model;

[0009] Step 2: extract the impeller mechanical fluid domain, and divide the impeller mechanical fluid domain into a plurality of dynamic domains and a plurality of static domains;

[0010] Step 3: according to the dynamic domain and the static domain divided in the step 2, respectively divide different area grids, and ensure that the grid quality of the common surface of different areas is consistent;

[0011] Step 4: combine all the area grids, and the area grids are all common nodes, to form a complete grid of the fluid area;

[0012] Step 5: set the corresponding boundary conditions according to the dynamic domain and the static domain divided in the step 2, and set the interaction surface for data exchange.

[0013] Further, since the small features have little effect on the simulation results, the small features in the impeller structure are simplified, the simplification of the three-dimensional model in the step 1 is the simplification of the small features in the impeller structure, and the small features include round corners, holes and matching devices; the simplification includes replacing the round corners with right angles, filling the holes and deleting the matching devices.

[0014] Further, the method of obtaining the three-dimensional model of the impeller mechanical structure includes that a client provides, an inventor models himself or scans the three-dimensional model of the impeller mechanical structure through a three-dimensional scanning device.

[0015] Further, the step 2 includes the following steps:

[0016] Step 21: according to the structural characteristics and actual use of the three-dimensional model of the impeller, the impeller is preliminarily divided into a plurality of dynamic domains and a plurality of static domains; for example, according to the whole impeller from outside to inside or from inside to outside, for example, according to the working order of the rotating mechanism of the impeller, the impeller is preliminarily divided into a plurality of dynamic domains and a plurality of static domains, the plurality of dynamic domains has at least two dynamic domains, and the plurality of static domains has at least two static domains, for example, the impeller is preliminarily divided into a first dynamic domain, a second dynamic domain, a first static domain and a second static domain.

[0017] Step 22: combining the plurality of dynamic domains and the plurality of static domains preliminarily divided, using a pre-processing software to extract the impeller mechanical fluid domain, and finally determining that the impeller mechanical fluid domain is divided into a plurality of dynamic domains and a plurality of static domains. The method of extracting the impeller mechanical fluid domain is to extract according to the inlet or the outlet. Generally, the division of the dynamic domain and the static domain in the preliminary division of the impeller into a plurality of dynamic domains and a plurality of static domains is consistent with the final determination of the division of the impeller fluid domain into a plurality of dynamic domains and a plurality of static domains.

[0018] Further, the step 21 further comprises defining the size of the dynamic region and the static region, so as to determine the boundary condition range in the subsequent fluid simulation calculation.

[0019] Further, the specific method of defining the size of the dynamic region and the static region is that the size of the static region is referenced to the size of the shell, and the size of the dynamic region is determined according to the rotating radius of the impeller, and in general cases, the radius and width of the dynamic region are set to be slightly larger than the mechanical rotating radius of the impeller and the width from the front surface to the rear surface.

[0020] Further, the method for finally determining the division of the fluid region of the impeller machine into a plurality of dynamic regions and a plurality of static regions in the step 22 is to divide the flow region, the model surfaces and the auxiliary lines into a plurality of dynamic regions and a plurality of static regions, to generate an interaction surface between different flow regions for data interaction, and to appropriately stretch the flow region volume when the gap between different regions is small and is not conducive to mesh division.

[0021] Further, the specific method of the step 3 is that the mesh of different regions is divided according to the dynamic region and the static region divided in the step 2; in order to ensure the consistency of the mesh quality of the shared surface of different regions, different mesh division sizes are set according to the different region calculation requirements and accuracies, for example, since the dynamic region has more and complex calculations and has high accuracy requirements, and the static region has no speed and has low accuracy requirements, the mesh of the dynamic region is divided to be higher in density than the mesh of the static region.

[0022] Further, the shared surface in the step 3 is an imprint surface cut by software, and the imprint surface is a surface or a line or a point that overlaps between the flow regions, between the flow regions and the entity, and between the auxiliary lines and the flow regions.

[0023] Further, the model preprocessing method is suitable for multi-stage impeller machines, and the multi-stage impeller machines include a shot blasting machine, a water pump and a compressed air blower.

[0024] Compared with the prior art, the model preprocessing method for the impeller machine has the following beneficial effects:

[0025] (1) The preprocessing method of the present application can not only separate the fluid region of the multi-stage impeller machine assembly for preprocessing and reasonably allocate the mesh density, but also obtain more accurate values by combining the method of dividing the whole fluid region of the original model into a plurality of dynamic regions and a plurality of static regions and then performing mesh division without changing the boundary conditions of the model.

[0026] (2) The preprocessing method of the present application separates the dynamic region and the static region, increases the mesh density of the key calculation region, reduces the mesh density of the region with low influence degree, and reduces the calculation amount according to the different calculation requirement accuracies and different mesh division degrees.

[0027] (3) The pre-processing method of the application is aimed at a two-stage or multi-stage impeller mechanical structure, is divided into multiple dynamic domains and static domains, boundary conditions are considered from the perspective of actual work, data transmission is completed between the regions using an interaction surface, and the calculation result is closer to the actual situation. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flow chart of the model pre-processing method of the application is shown in the figure.

[0029] Figure 2 The three-dimensional model of the impeller machine in the embodiment of the application is shown in the figure.

[0030] Figure 3 The fluid region of the impeller machine in the embodiment of the application is shown in the figure.

[0031] Figure 4 The dynamic domain and static domain segmentation of the impeller machine in the embodiment of the application is shown in the figure; wherein, (4a) is a first static domain schematic diagram, (4b) is a first-stage dynamic domain schematic diagram, (4c) is a second static domain schematic diagram, and (4d) is a two-stage dynamic domain schematic diagram.

[0032] Figure 5 The grid division of the dynamic domain and static domain of the impeller machine in the embodiment of the application is shown in the figure; wherein, (5a) is a grid division schematic diagram of the first static domain, (5b) is a grid division schematic diagram of the first-stage dynamic domain, (5c) is a grid division schematic diagram of the second static domain, and (5d) is a grid division schematic diagram of the two-stage dynamic domain.

[0033] Figure 6 The grid combination of each region in the embodiment of the application is shown in the figure.

[0034] Figure 7 The noise spectrum diagram in the noise simulation calculation in the embodiment of the application is shown in the figure.

[0035] The meanings of the reference signs in the figure are as follows: 1-first-stage shell; 2-second-stage shell; 3-first-stage rotation; 4-second-stage rotation; 5-first static domain; 6-second static domain; 7-first-stage dynamic domain; and 8-two-stage dynamic domain. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0037] The application is not limited by the relative positioning of parts and steps, numerical expressions, and numerical values set forth in these embodiments unless otherwise specifically stated. It is to be understood that the dimensions of the various parts shown in the drawings are not necessarily to scale, for the sake of convenience in description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail, but should be considered part of the specification, where appropriate. In all examples shown and discussed herein, any specific value should be interpreted as merely an example, and not as a limitation. Thus, other examples of the exemplary embodiments can also include different values. It should be noted that like reference numerals and letters refer to like items in the following drawings, and thus, once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

[0038] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus cannot be understood as limiting the scope of protection of the present application.

[0039] As shown in Figure 2 In one specific embodiment of the present embodiment, the impeller mechanism in the present application includes two rotating mechanisms and a shell, the two rotating mechanisms are divided into a first rotating mechanism and a second rotating mechanism from the outside to the inside, the shell is divided into a first shell and a second shell from the outside to the inside, the first rotating mechanism is arranged on the first shell, the second rotating mechanism is arranged on the second shell, and the first shell and the second shell are both stationary relative to the two rotating mechanisms. In order to obtain more prepared values in subsequent fluid simulation work and subsequent structural optimization design, the model preprocessing method of the present application considers the change of boundary conditions caused by the shell protection and possible multi-stage structure in the impeller mechanism, that is, the boundary conditions under the actual working conditions of the impeller mechanism, and the data transmission between regions is completed using the interaction surface, and the calculation result is closer to the actual situation.

[0040] It should be noted that the model preprocessing method of the second rotating mechanism and the second rotating mechanism is the same.

[0041] A model preprocessing method for an impeller mechanism, comprising the following steps:

[0042] Step 1: obtaining a three-dimensional model of the impeller mechanism structure, and simplifying the three-dimensional model;

[0043] The fine features have little influence on the simulation results, so the simplification of the three-dimensional model is to simplify the fine features in the impeller structure, including fillets, holes and matching devices. The simplification includes replacing the fillets with right angles, filling the holes and deleting the matching devices.

[0044] Generally, the three-dimensional model of the turbomachinery mechanism is obtained by a client providing, an inventor modeling himself or by a three-dimensional scanning device.

[0045] Step 2: Extract the turbomachinery fluid domain, and divide the turbomachinery fluid domain into multiple dynamic domains and multiple static domains.

[0046] Step 21: According to the structural characteristics and actual use of the three-dimensional model of the turbomachinery, predict the division of the turbomachinery into multiple dynamic domains and multiple static domains. For example, according to the whole turbomachinery from outside to inside or from inside to outside, for example, according to the working order of the rotating mechanism of the turbomachinery, preliminarily divide the turbomachinery into multiple dynamic domains and multiple static domains. The multiple dynamic domains have at least two dynamic domains, and the multiple static domains have at least two static domains, such as Figure 3 and Figure 4 As shown in the drawings, the turbomachinery is preliminarily divided into a first dynamic domain and a second dynamic domain according to a first rotation and a second rotation in the structure of the turbomachinery, and is divided into a first static domain and a second static domain according to a first shell and a second shell in the structure of the turbomachinery.

[0047] In addition, step 21 also includes defining the size of the dynamic domain and the static domain, so as to determine the range of the boundary condition in the subsequent fluid simulation calculation. The size of the static domain is referenced by the shell size, and the size of the dynamic domain is determined according to the impeller radius. In general, the radius and width of the dynamic domain size are set to be slightly larger than the rotating radius of the turbomachinery and the width from the front surface to the back surface.

[0048] Step 22: Combine the multiple dynamic domains and multiple static domains predicted to divide the turbomachinery, and finally determine the division of the turbomachinery fluid domain into multiple dynamic domains and multiple static domains by using the pre-processing software according to the extraction of the turbomachinery fluid domain.

[0049] Preferably, the method for extracting the turbomachinery fluid domain is to extract according to the inlet or outlet.

[0050] Generally, the preliminary division of the turbomachinery into multiple dynamic domains and multiple static domains is basically consistent with the division of the dynamic domains and the static domains in the final determination of the division of the turbomachinery fluid domain into multiple dynamic domains and multiple static domains.

[0051] The method for finally determining the division of the impeller mechanical fluid domain into a plurality of dynamic domains and a plurality of static domains in step 22 is to divide the flow domain, the model surface and the auxiliary line into a plurality of dynamic domains and a plurality of static domains, and generate an interaction surface between different flow domains for data interaction, and appropriately stretch the flow domain volume when the gap between different regions is small and is not conducive to mesh division.

[0052] Step 3: According to the dynamic domain and the static domain divided in step 2, the grid of different regions is divided respectively; in order to ensure the grid quality of the shared surface of different regions is consistent, different grid division sizes are set according to the region calculation requirements and different accuracies, for example, because the dynamic domain has more calculations and is complex, and the accuracy requirement is high, while the static domain has no speed and the accuracy requirement is low, so the grid division of the dynamic domain is higher than that of the static domain.

[0053] The shared surface in step 3 is the embossed surface cut by the software, and the embossed surface is the surface or line or point overlapping between the flow domain and the flow domain, the flow domain and the entity, and the auxiliary line and the flow domain.

[0054] Step 4: Combine all the region grids, and the region grids are all shared nodes to form a complete fluid region grid;

[0055] Step 5: Set the corresponding boundary conditions according to the dynamic domain and the static domain divided in step 2, and set the interaction surface for data exchange.

[0056] By the model preprocessing method of the application, the fluid grid shown in Figure 5 can be obtained. Figure 5 a represents the first static domain grid division result, 5b represents the first dynamic domain grid division result, 5c represents the second static domain grid division result, and 5d represents the second dynamic domain grid division result.

[0057] Combine all the dynamic and static region grids, and the region grids are all shared nodes to form a complete fluid region, as shown in Figure 6 The result of the application finally obtains Figure 6 such a combination of region grids, which can be seen from Figure 6 that the flow field changes caused by the protective shell and the secondary structure of the impeller mechanical structure, and the first static domain is no longer an open flow domain, but the size and shape are limited by the first shell and the first dynamic domain, and the second static domain is limited in size and shape by the second shell and the second dynamic domain, which is closer to the actual situation than the simple open field flow field.

[0058] In one specific embodiment of the embodiment, the accuracy of the preprocessing method of the application is verified by taking noise calculation as an example, Figure 2The average value of the noise of the middle impeller mechanical field test is 97.18dB, the noise spectrum simulated by the flow field simulation noise after the model pre-processing method of the application is processed is as shown in Figure 7 The read noise value is 99.16dB, and the relative error is only about 2%, which can verify the accuracy of the fluid model constructed by the model pre-processing method of the application, so the fluid simulation of the application for the secondary impeller machine is accurate and reliable.

[0059] In one specific embodiment of the present embodiment, the model pre-processing method of the application is suitable for multi-stage impeller machines, and the multi-stage impeller machines include shot blasting machines, water pumps and compressed air blowers.

[0060] It should be noted that in the present application, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0061] Although the embodiments of the application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.

Claims

1. A model preprocessing method for turbomachinery, characterized in that, Includes the following steps: Step 1: Obtain a three-dimensional model of the impeller mechanical structure and simplify the three-dimensional model; Step 2: Extract the impeller mechanical fluid domain and divide it into multiple dynamic domains and multiple static domains; Step 3: Based on the dynamic and static domains defined in Step 2, divide the mesh into different regions to ensure that the mesh quality of the common surfaces in different regions is consistent. Step 4: Combine all the region meshes to form a complete mesh for the fluid region; Step 5: Set the corresponding boundary conditions and interaction surfaces according to the dynamic and static domains divided in Step 2; In step 1, the simplification of the 3D model involves simplifying the small features in the impeller structure, including fillets, holes, and mating devices. The simplification process includes replacing fillets with right angles, filling holes, and deleting mating devices. The specific method of step 3 is as follows: based on the dynamic domain and static domain divided in step 2, different regional grids are divided respectively. In order to ensure that the grid quality of the common surface of different regions is consistent, different grid division sizes are set according to the different regional calculation requirements and accuracy. Step 2 includes the following steps: Step 21: Based on the structural characteristics and actual applications of the three-dimensional model of the turbomachinery, it is expected that the turbomachinery will be divided into multiple dynamic domains and multiple static domains; It also includes defining the dimensions of the dynamic and static domains; the static domain dimensions are referenced to the casing dimensions, while the dynamic domain dimensions are determined based on the impeller's rotation radius. Step 22: Combining the multiple dynamic and multiple static domains that are expected to be divided into the turbomachinery, the preprocessing software is used to extract the fluid domains of the turbomachinery and finally determine the division of the turbomachinery fluid domains into multiple dynamic and multiple static domains.

2. The model preprocessing method for turbomachinery according to claim 1, characterized in that: In step 22, the final method for dividing the turbomachinery fluid domain into multiple dynamic domains and multiple static domains is to use the fluid domain, model surfaces, and auxiliary lines to divide it into multiple dynamic domains and multiple static domains.

3. The model preprocessing method for turbomachinery according to claim 1, characterized in that: The common surface in step 3 is an imprinted surface cut by software, which is an overlapping surface between watersheds, between watersheds and entities, and between auxiliary lines and watersheds.

4. The model preprocessing method for turbomachinery according to claim 1, characterized in that: The model preprocessing method is applicable to multi-stage impeller machinery, including shot blasting machines, water pumps, and compressed air fans.

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