Air system two-dimensional CFD calculation method and system based on porous medium model

Abstract

The application discloses a kind of based on porous medium model air system two-dimensional CFD calculation method and system, wherein, the method includes: two-dimensional CFD modeling and setting the initial loss coefficient of porous medium model;Two-dimensional CFD calculation is carried out and porous medium model hole parameter is extracted;Determine whether the porous medium model hole parameter is consistent with real parameter;If the porous medium model hole parameter is not consistent with real parameter, then adjust loss coefficient, and two-dimensional CFD calculation is carried out again and porous medium model hole parameter is extracted;If the porous medium model hole parameter is consistent with real parameter, then end calculation.The application is based on porous medium, by changing the parameter of porous medium and establishing the loss coefficient of model material conversion, to carry out two-dimensional CFD calculation, and the calculation result can be corrected multiple times, and calculation deviation can be controlled within predetermined range.

Description

Technical Field

[0001] The present invention belongs to the field of CFD calculation, and in particular relates to a two-dimensional CFD calculation method and system for an air system based on a porous medium model. Background Art

[0002] CFD (Computational Fluid Dynamics) is computational fluid dynamics. When performing two-dimensional CFD calculation analysis, the existing technical method uses the equal flow area conversion method to convert the circumferentially discontinuous air system throttle hole into a circumferentially continuous annular gap, thereby providing a structural basis for two-dimensional CFD calculation. Figure 1 As shown in the figure, 36 circumferentially discontinuous holes with a centerline height of 138 mm and a diameter of 1.80 mm are converted to circumferentially continuous annular gaps based on equal flow area, resulting in an annular gap width of 0.1057 mm. This drastic reduction in model scale is a catastrophic problem for meshing. The pressure, temperature, and flow rate values ​​calculated using existing methods for the air system throttle holes are severely distorted. Aircraft engine and gas turbine air systems contain numerous throttle holes. If these throttle holes are converted to equal flow area and then subjected to 2D CFD calculations, the flow parameters at each throttle hole location are inaccurate and the errors accumulate, affecting the calculation results of other upstream and downstream air system components and failing to meet the computational accuracy requirements of the air system network. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the present invention aims to solve the problem of severe distortion of the calculation results obtained by the existing two-dimensional CFD calculation method. To achieve the above-mentioned purpose, the present invention provides the following technical solutions:

[0004] A two-dimensional CFD calculation method for air systems based on a porous media model includes:

[0005] 2D CFD modeling and setting the initial loss coefficient of the porous media model;

[0006] Perform two-dimensional CFD calculations and extract pore parameters of porous media models;

[0007] Determine whether the pore parameters of the porous media model are consistent with the actual parameters;

[0008] If the pore parameters of the porous media model are inconsistent with the actual parameters, the loss coefficient is adjusted, and the 2D CFD calculation is repeated to extract the pore parameters of the porous media model;

[0009] If the pore parameters of the porous medium model are consistent with the actual parameters, the calculation ends.

[0010] Furthermore, when setting the initial loss coefficient of the porous medium model, the initial loss coefficient can be set arbitrarily.

[0011] Further, the two-dimensional CFD calculation comprises: calculating the mass flow of the orifice of the porous medium model according to the loss coefficient and the geometric parameters of the porous medium model; and calculating the real mass flow of the orifice according to the geometric parameters and the actual flow parameters of the orifice.

[0012] Further, the judging whether the orifice parameters of the porous medium model are consistent with the real parameters comprises: calculating the deviation of the mass flow of the orifice of the porous medium model and the real mass flow; and judging whether the deviation is within a predetermined range, if the deviation is within the predetermined range, the orifice parameters of the porous medium model are consistent with the real parameters, if the deviation is not within the predetermined range, the orifice parameters of the porous medium model are not consistent with the real parameters.

[0013] 5. The two-dimensional CFD calculation method of an air system based on a porous medium model according to claim 4, wherein the calculation formula of the deviation of the mass flow of the orifice of the porous medium model and the real mass flow is:

[0014]

[0015] wherein dev represents the deviation, m_2D represents the mass flow of the orifice of the porous medium model, and m_Real represents the real mass flow.

[0016] Further, the adjusting the loss coefficient comprises:

[0017] calculating a new loss coefficient according to the deviation of the mass flow of the orifice of the porous medium model and the real mass flow.

[0018] Further, the calculating the new loss coefficient comprises the following steps:

[0019] obtaining the loss coefficient used in the previous calculation;

[0020] obtaining the deviation obtained in the previous calculation;

[0021] calculating the new loss coefficient according to the loss coefficient and the deviation in the previous calculation.

[0022] Further, the calculation formula of the new loss coefficient is:

[0023] res i+1 =res i +α·dev i ·res i ;

[0024] wherein i is a positive integer, res1 is an initial loss coefficient, res i+1represents the loss coefficient after the i-th adjustment; alpha is a relaxation factor, used to adjust the amplitude of the change of the loss coefficient in the two iterations before and after; dev i represents the deviation calculated in the i-th time.

[0025] Further, the alpha can be any value in the interval (0, 1].

[0026] The application also provides a two-dimensional CFD calculation system of an air system based on a porous medium model, which adopts the two-dimensional CFD calculation method of the air system based on the porous medium model and comprises:

[0027] A modeling module is configured to perform two-dimensional CFD modeling.

[0028] A storage module is configured to store computer executable instructions, model material parameters, calculation formulas and calculation results.

[0029] A processor module is configured to run the computer executable instructions, call the model material parameters and perform calculation.

[0030] The technical effects and advantages of the application are as follows:

[0031] Based on the porous medium, the application changes the parameters of the porous medium and establishes a loss coefficient of model material conversion, so as to perform two-dimensional CFD calculation, and the calculation result can be corrected multiple times, and the calculation deviation can be controlled within a predetermined range.

[0032] Other features and advantages of the application will be described in the following specification, and some of them will become apparent from the specification, or will be understood by those skilled in the art through implementation of the application. The purposes and other advantages of the application can be achieved and obtained by the structures indicated in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 It is a schematic diagram of model conversion in two-dimensional CFD calculation of an air system throttle hole in the prior art.

[0034] Figure 2 It is a flowchart of the two-dimensional CFD calculation method of the air system based on the porous medium model. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, but not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0036] In addition, in the application, the terms "first", "second" and other similar words do not imply any order, quantity and importance, but are only used to distinguish different elements, and the terms "up", "down", "left", "right" and other similar words are only the positional relationship in the drawing.

[0037] In the two-dimensional CFD calculation analysis of the air system, the prior art method converts the circumferential discontinuous air system throttle hole into a circumferential continuous ring slit by equal flow area conversion, and the calculation result is seriously distorted, which cannot meet the calculation accuracy requirement of the air system network.

[0038] In the application, the two-dimensional CFD calculation is performed by changing the parameters of the porous medium model and establishing the loss coefficient of the model material conversion, and the calculation result can be corrected for multiple times, and the calculation deviation can be controlled within a predetermined range.

[0039] It should be noted that the porous medium is a solid material, which has a certain number of pores filled with gas, liquid or multiphase mixture. Fluid can flow in the pores, and both solid and fluid can act as heat conduction medium. The fluid mass flow and pressure drop in the porous medium model can be calculated by the loss coefficient, and the heat conduction temperature can be calculated after setting the heat conduction coefficient.

[0040] The following will be further described through specific embodiments.

[0041] The embodiment provides a two-dimensional CFD calculation method of an air system based on a porous medium model, comprising:

[0042] Two-dimensional CFD modeling and setting initial loss coefficient of the porous medium model;

[0043] Two-dimensional CFD calculation and extraction of porous medium model hole parameters;

[0044] Judging whether the porous medium model hole parameters are consistent with the real parameters;

[0045] If the porous medium model hole parameters are not consistent with the real parameters, adjusting the loss coefficient, and re-performing two-dimensional CFD calculation and extracting the porous medium model hole parameters;

[0046] If the porous medium model hole parameters are consistent with the real parameters, ending the calculation.

[0047] The embodiment adjusts the loss coefficient through multiple iterations after two-dimensional CFD modeling, so as to determine the appropriate loss coefficient. When the throttle hole of the workpiece is modeled by the method, the hole diameter is consistent with the real value, and the calculation result of the pressure, temperature and flow value and other parameters caused by the sharp reduction of the model size can be avoided.

[0048] Figure 2 A flow chart of a two-dimensional CFD calculation method of an air system based on a porous medium model according to the present application is shown. The following will be described in detail with reference to Figure 2

[0049] The two-dimensional CFD modeling is performed and the initial loss coefficient of the porous medium model is set;

[0050] In an embodiment of the present application, the throttle hole is H3, the physical domain of the throttle hole is Fluid (fluid) and the type is Porous Region (porous medium model) when modeling, and the diameter of the throttle hole is consistent with the real value. Refer to Figure 1 Figure 1 The actual aperture of the throttle hole of the workpiece is consistent with the aperture of the throttle hole in the two-dimensional CFD modeling. In addition, the initial loss coefficient value can be set at will or an approximate value can be set according to experience.

[0051] The two-dimensional CFD calculation is performed and the porous medium model hole parameters are extracted;

[0052] In an embodiment of the present application, the two-dimensional CFD calculation includes: calculating the throttle hole mass flow of the porous medium model according to the loss coefficient and the geometric parameters of the porous medium model, denoted as m_2D; extracting the flow parameters of the throttle hole, denoted as F; and extracting the geometric parameters of the throttle hole, denoted as G. Then the real mass flow of the throttle hole can be calculated, denoted as m_Real, m_Real=f(F,G).

[0053] It is judged whether the porous medium model hole parameters are consistent with the real parameters;

[0054] In an embodiment of the present application, the above judging method includes: calculating the deviation of the throttle hole mass flow of the porous medium model and the real mass flow; judging whether the deviation is within a predetermined range, if the deviation is within the predetermined range, the porous medium model hole parameters are consistent with the real parameters, and if the deviation is not within the predetermined range, the porous medium model hole parameters are not consistent with the real parameters.

[0055] The calculation formula for calculating the deviation of the throttle hole mass flow of the porous medium model and the real mass flow is:

[0056]

[0057] Wherein, dev represents the deviation, m_2D represents the throttle hole mass flow of the two-dimensional axisymmetric CFD calculation, and m_Real represents the real mass flow.

[0058] If the porous medium model hole parameters are not consistent with the real parameters, the loss coefficient is adjusted, and the two-dimensional CFD calculation is performed again and the porous medium model hole parameters are extracted; ​​

[0059] In one embodiment of the present application, the method for adjusting the loss coefficient comprises:

[0060] calculating a new loss coefficient according to the deviation of the mass flow of the throttle calculated by the two-dimensional CFD calculation and the real mass flow;

[0061] wherein the calculation formula for calculating the new loss coefficient is:

[0062] res i+1 = res i + a·dev i · res i ;

[0063] wherein i is a positive integer, res1 is the initial loss coefficient, res i+1 represents the loss coefficient after the i adjustment; a is a relaxation factor, a∈(0,1], used to adjust the amplitude of the change of the loss coefficient in the two iterations; dev i represents the deviation obtained by the i calculation.

[0064] In addition, it should be noted that the method for judging whether the pore parameter of the porous medium model is consistent with the real parameter is: comparing the deviation with the predetermined acceptable deviation value range, if the deviation belongs to the acceptable deviation value range, the pore parameter of the porous medium model is consistent with the real parameter, if the deviation does not belong to the acceptable deviation value range, the pore parameter of the porous medium model is not consistent with the real parameter, and the loss coefficient needs to be adjusted.

[0065] For example:

[0066] If the acceptable range of dev is ±5%, and devi=7%, the loss coefficient needs to be adjusted continuously;

[0067] If the acceptable range of dev is ±5%, and devi=3%, the loss coefficient does not need to be adjusted continuously.

[0068] In one embodiment of the present application, after the i+1 calculation, dev i+1 is close to the acceptable range, but does not belong to the acceptable range, then res i and res i are recalculated according to dev i+1 , and then the two-dimensional CFD calculation is performed again to obtain dev i+1 and judge whether it is within the acceptable range.

[0069] In addition, it is to be noted that the two-dimensional CFD calculation result of the air system calculated according to the present application is consistent with the true value. Compared with one-dimensional calculation of the air system, the two-dimensional calculation result of the air system calculated according to the present application has more abundant flow field information, and can be used for detailed design and optimization of the air system of the aero-engine and the gas turbine; compared with three-dimensional calculation of the air system, the two-dimensional calculation of the air system calculated according to the present application has low calculation cost, and can be used for air system calculation at the whole machine level. According to the present application, two-dimensional axisymmetric CFD calculation is performed on the aero-engine air system described above, and the flow deviation of the throttle hole in the air system is compared with the three-dimensional CFD calculation result, which is -0.72%, -2.79%, -2.73%, -0.64% and 2.87% respectively, and the deviation is within ±3%.

[0070] The above embodiment provides a two-dimensional CFD calculation method of an air system based on a porous medium model, and the present embodiment provides a two-dimensional CFD calculation system of an air system based on a porous medium model on the basis of the above embodiment. Since the principle of the calculation system has been specifically embodied in the above calculation method embodiment, the present calculation system embodiment is only briefly described.

[0071] A two-dimensional CFD calculation system of an air system based on a porous medium model comprises a modeling module for two-dimensional CFD modeling, a storage module for storing contents including computer executable instructions, model material parameters, calculation formulas and calculation results, and a processor module for running the computer executable instructions, calling the model material parameters and calculating.

[0072] In the present calculation system, two-dimensional calculation of the air system is used. Compared with one-dimensional calculation of the air system, the two-dimensional calculation result of the air system calculated according to the present calculation system has more abundant flow field information, and can be used for detailed design and optimization of the air system of the aero-engine and the gas turbine; compared with three-dimensional calculation of the air system, the two-dimensional calculation of the air system calculated according to the present calculation system has low calculation cost, and can be used for air system calculation at the whole machine level. Compared with the existing two-dimensional CFD calculation system, the calculation result of the two-dimensional calculation of the air system calculated according to the present calculation system is more accurate, and the calculation error can be strictly controlled within a predetermined range.

[0073] Finally, it should be noted that the above description is only the preferred embodiment of the present application and is not used to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions recorded in the foregoing embodiments or make equivalent replacements to some technical features, as long as they are within the spirit and principle of the present application. Any modification, equivalent replacement, improvement, etc. made within the scope of the present application should be included in the protection scope of the present application.

Claims

1. A two-dimensional CFD calculation method for air systems based on a porous media model, characterized in that: include: 2D CFD modeling and setting the initial loss coefficient of the porous media model; Perform two-dimensional CFD calculations and extract the pore parameters of the porous media model. The two-dimensional CFD calculations include: calculating the mass flow rate of the throttle hole of the porous media model based on the loss coefficient and the geometric parameters of the porous media model; calculating the true mass flow rate of the throttle hole based on the geometric parameters of the throttle hole and the actual flow parameters; Determine whether the pore parameters of the porous media model are consistent with the actual parameters; If the pore parameters of the porous media model are inconsistent with the actual parameters, the loss coefficient is adjusted, and the 2D CFD calculation is repeated to extract the pore parameters of the porous media model; If the pore parameters of the porous medium model are consistent with the actual parameters, the calculation ends.

2. The two-dimensional CFD calculation method for an air system based on a porous media model according to claim 1, characterized in that: When setting the initial loss coefficient of the porous medium model, the initial loss coefficient can be set arbitrarily.

3. A two-dimensional CFD calculation method for an air system based on a porous medium model according to any one of claims 1-2, characterized in that: Determining whether the pore parameters of the porous medium model are consistent with the actual parameters includes: calculating the deviation between the throttling hole mass flow rate of the porous medium model and the actual mass flow rate; determining whether the deviation is within a predetermined range, if the deviation is within the predetermined range, the pore parameters of the porous medium model are consistent with the actual parameters, and if the deviation is not within the predetermined range, the pore parameters of the porous medium model are inconsistent with the actual parameters.

4. The two-dimensional CFD calculation method for an air system based on a porous media model according to claim 3, characterized in that: The calculation formula for the deviation between the orifice mass flow rate of the porous media model and the true mass flow rate is: ； Where dev represents the deviation, m_2D represents the orifice mass flow rate of the porous media model, and m_Real represents the real mass flow rate.

5. The two-dimensional CFD calculation method for an air system based on a porous media model according to claim 3, characterized in that: Adjusted loss factors include: The new loss coefficient is calculated based on the deviation between the orifice mass flow rate calculated from the porous media model and the actual mass flow rate.

6. The two-dimensional CFD calculation method for an air system based on a porous media model according to claim 5, characterized in that: Calculating the new loss coefficient involves the following steps: Get the loss coefficient used in the previous calculation; Get the deviation obtained in the previous calculation; Calculate the new loss coefficient based on the loss coefficient and deviation calculated in the previous step.

7. The two-dimensional CFD calculation method for an air system based on a porous media model according to claim 5, characterized in that: The calculation formula for the new loss coefficient is: ； Among them, i is a positive integer, res1 is the initial loss coefficient, res i+1 represents the loss coefficient after the i-th adjustment; is the relaxation factor, which is used to adjust the amplitude of the loss coefficient change between the two iterations; dev i represents the deviation obtained by the i-th calculation.

8. The two-dimensional CFD calculation method for an air system based on a porous media model according to claim 7, characterized in that: described Can be an interval Any value within .

9. A two-dimensional CFD calculation system for air systems based on a porous media model, characterized in that: A two-dimensional CFD calculation method for an air system based on a porous medium model according to any one of claims 1 to 8 is adopted, and includes: Modeling module, used for two-dimensional CFD modeling; A storage module, storing contents including: computer executable instructions, model material parameters, calculation formulas, and calculation results; The processor module is used to run the computer executable instructions, call model material parameters, and perform calculations.

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