A ramjet engine numerical simulation method, device, equipment and storage medium

Abstract

This application discloses a ramjet numerical simulation method, apparatus, device, and storage medium, relating to the field of aerodynamics. The method comprises: determining a dimensionless temperature corresponding to a gas component in an initial flow field; determining a molecular viscosity collision integral function of the gas component based on the dimensionless temperature by fitting a polynomial fraction; determining a viscosity coefficient of the gas component based on the molecular viscosity collision integral function; and generating a ramjet computational grid based on the viscosity coefficient to perform numerical simulation operations on the ramjet. In this way, during the numerical simulation of the ramjet, the present application uses a polynomial fraction to fit the viscosity collision integral function, effectively shortening the calculation time of the gas viscosity coefficient while maintaining computational accuracy that meets user requirements. Furthermore, the method can adapt to the temperature and component requirements of the ramjet combustion flow field, thereby improving the efficiency of the ramjet numerical simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of aerodynamics, and in particular to a ramjet numerical simulation method, device, equipment and storage medium. Background Art

[0002] The purpose of numerical simulation of ramjet engines is to provide data for engine performance evaluation and structural design. In the numerical simulation of ramjet engines, the viscosity coefficient of gas components is required in multiple steps. The commonly used methods for calculating the viscosity coefficient of gas are as follows: (1) Based on the molecular dynamics method, the Lennard-Jones model is used to simulate the interaction force between molecules. This method can simulate the transport coefficient of gas and liquid. The maximum temperature is generally 5000K (Kelvin). (2) Using the Chapman-Enskog theory, the viscosity coefficient of the component is calculated by solving the Boltzmann equation (a thermodynamic equation). Since the full Chapman-Enskog (a mathematical method) is computationally expensive, the Chapman-Enskog approximate formula is usually used. This method is mainly used to calculate the transport coefficient of high-temperature dissociated gas, with a maximum temperature of up to 30,000K. These methods are highly complex and have limited adaptability to ramjet engine scenarios; the combustion flow field of a ramjet engine has many gas components and the temperature is fixed within 5000K.

[0003] It can be seen that how to optimize the numerical simulation of ramjet engines is a problem that needs to be solved in this field. Summary of the Invention

[0004] In view of this, the present invention aims to provide a ramjet numerical simulation method, apparatus, device, and storage medium. During the ramjet numerical simulation process, a polynomial fraction is used to fit the viscous collision integral function, effectively shortening the calculation time of the gas viscosity coefficient while maintaining the calculation accuracy to meet the actual use requirements. Furthermore, the method can adapt to the temperature and composition requirements of the ramjet combustion flow field, thereby improving the efficiency of the ramjet numerical simulation. The specific scheme is as follows:

[0005] In a first aspect, the present application provides a ramjet engine numerical simulation method, comprising:

[0006] Determine the dimensionless temperature corresponding to the gas components of the initial flow field;

[0007] Determining the molecular viscosity collision integral function of the gas component by polynomial fraction fitting based on the dimensionless temperature;

[0008] determining the viscosity coefficient of the gas component according to the molecular viscosity collision integral function;

[0009] A computational grid of a ramjet engine is generated based on the viscosity coefficient to perform a numerical simulation operation on the ramjet engine.

[0010] Optionally, determining the dimensionless temperature corresponding to the gas components of the initial flow field includes:

[0011] Performing a data query operation on a preset gas component transport coefficient database according to the gas component of the initial flow field to obtain a potential well depth corresponding to the gas component;

[0012] The dimensionless temperature of the gas component at each spatial position is determined based on the potential well depth and the simulated temperature of the initial flow field corresponding to each spatial position.

[0013] Optionally, determining the viscosity coefficient of the gas component according to the molecular viscosity collision integral function includes:

[0014] The viscosity coefficient of the gas component is determined according to the gas molecular weight, collision diameter and the molecular viscosity collision integral function corresponding to the gas component.

[0015] Optionally, when the initial flow field is a multi-component mixed gas, determining the viscosity coefficients of the gas components according to the molecular viscosity collision integral function includes:

[0016] The viscosity coefficient of the mixed gas corresponding to the initial flow field is determined according to the viscosity coefficient, molecular weight and mole fraction corresponding to each gas component in the initial flow field, so as to perform a numerical simulation operation on the ramjet engine using the viscosity coefficient of the mixed gas.

[0017] Optionally, generating a computational grid of the ramjet engine based on the viscosity coefficient includes:

[0018] generating a flow field grid of the ramjet engine corresponding to the initial flow field;

[0019] Based on the viscosity coefficient, the flow field grid is encrypted along the wall normal of the flow field grid to obtain a calculation grid corresponding to the ramjet engine.

[0020] Optionally, the performing a numerical simulation operation on the ramjet engine includes:

[0021] The viscosity coefficient is used to perform calculation processing on the viscous fluid motion differential equation to perform a data simulation operation on the ramjet engine.

[0022] Optionally, the process of performing the numerical simulation operation further includes:

[0023] The viscous fluid motion differential equation is calculated and processed in an iterative manner until a preset iteration condition is met; the preset iteration condition is that a residual convergence condition is reached in a steady calculation, or a set end time is reached in an unsteady calculation.

[0024] In a second aspect, the present application provides a ramjet engine numerical simulation device, comprising:

[0025] A dimensionless temperature determination module, used to determine the dimensionless temperature corresponding to the gas components of the initial flow field;

[0026] A polynomial fitting module, configured to determine the molecular viscosity collision integral function of the gas component by polynomial fraction fitting based on the dimensionless temperature;

[0027] a viscosity coefficient determination module, configured to determine the viscosity coefficient of the gas component according to the molecular viscosity collision integral function;

[0028] The numerical simulation module is used to generate a computational grid corresponding to the ramjet engine based on the viscosity coefficient, so as to perform a numerical simulation operation on the ramjet engine.

[0029] In a third aspect, the present application provides an electronic device, comprising:

[0030] Memory, used to store computer programs;

[0031] A processor is used to execute the computer program to implement the ramjet engine numerical simulation method as described above.

[0032] In a fourth aspect, the present application provides a computer-readable storage medium for storing a computer program, wherein the computer program, when executed by a processor, implements the ramjet engine numerical simulation method as described above.

[0033] As can be seen, in this application, the dimensionless temperature corresponding to the gas components of the initial flow field is first determined; then, based on the dimensionless temperature, the molecular viscosity collision integral function of the gas components is determined by polynomial fraction fitting; then, the viscosity coefficient of the gas components is determined based on the molecular viscosity collision integral function; and then, based on the viscosity coefficient, a computational grid for the ramjet engine is generated to perform numerical simulation operations on the ramjet engine. In this way, during the numerical simulation of the ramjet engine, the present application uses polynomial fractions to fit the viscosity collision integral function, which can effectively shorten the calculation time of the gas viscosity coefficient while maintaining the calculation accuracy that meets the application requirements; furthermore, it can adapt to the temperature requirements and component requirements of the ramjet engine's combustion flow field, thereby improving the efficiency of the ramjet engine numerical simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0035] Figure 1 This is a flow chart of a ramjet engine numerical simulation method disclosed in this application;

[0036] Figure 2 A viscosity coefficient calculation flow chart disclosed in this application;

[0037] Figure 3 This is a schematic diagram of a ramjet engine numerical simulation module disclosed in this application;

[0038] Figure 4 This is a schematic diagram of the change of the viscosity coefficient of nitrogen N2 with temperature disclosed in this application;

[0039] Figure 5 This is a schematic diagram of the change of air viscosity coefficient with temperature disclosed in this application;

[0040] Figure 6 This is a schematic diagram of the change of viscosity coefficient of methane CH4 with temperature disclosed in this application;

[0041] Figure 7 This is a schematic diagram of the change of viscosity coefficient of ethylene C2H4 with temperature disclosed in this application;

[0042] Figure 8 A decane C disclosed in this application 10 H 22 Schematic diagram of viscosity coefficient changing with temperature;

[0043] Figure 9 This is a schematic diagram of the change of the viscosity coefficient of carbon dioxide CO2 with temperature disclosed in this application;

[0044] Figure 10 This is a schematic diagram of the geometric dimensions of a ramjet combustion chamber model disclosed in this application;

[0045] Figure 11 A schematic diagram comparing the calculated and tested pressure distributions of a combustion chamber wall centerline disclosed in this application;

[0046] Figure 12 A schematic diagram of the relationship between a gas viscosity coefficient calculation method disclosed in this application and the calculation time of the ramjet flow field;

[0047] Figure 13A combustion chamber wall friction line distribution diagram disclosed in this application;

[0048] Figure 14 This is a schematic structural diagram of a ramjet numerical simulation device disclosed in this application;

[0049] Figure 15 This is a structural diagram of an electronic device disclosed in this application. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0051] It's understandable that the viscosity coefficient plays a crucial role in the numerical simulation of ramjet engines, encompassing the mesh generation phase, the solution of the governing equations, and the post-processing phase. Furthermore, analyzing the distribution of friction lines on the wall reveals the flow separation zone, providing data support for fuel ignition and structural design of the ramjet engine. The wall friction lines require solving for friction components in three directions, as well as calculating the wall viscosity coefficient. In the numerical simulation of ramjet engines, the calculation of the viscosity coefficient of multi-component gases is characterized by the presence of numerous gas components. Besides pure air's nitrogen and oxygen, there are also components primarily composed of hydrocarbon fuels, such as methane, ethylene, and aviation kerosene. Aviation kerosene, in particular, is a mixture containing multiple molecular structures, including decane and benzene. The viscosity coefficient is not only temperature-dependent, but also depends on the molar ratio of the various components. The combustion flow field temperature of a ramjet engine generally does not exceed 5000K. Furthermore, the present application adopts a polynomial fraction to fit the viscous collision integral function, which can effectively shorten the calculation time of the viscosity coefficient of the gas components, ensure the calculation accuracy, and improve the effect of the ramjet numerical simulation.

[0052] See also Figure 1 As shown, an embodiment of the present invention discloses a ramjet engine numerical simulation method, comprising:

[0053] Step S11: Determine the dimensionless temperature corresponding to the gas components of the initial flow field.

[0054] In this application, the initial flow field of the ramjet engine contains multiple gas components, such as nitrogen, oxygen, and fuel gas. To calculate the viscosity coefficient of the gas components, it is first necessary to determine the dimensionless temperature of each gas component. The dimensionless temperature calculation process needs to be combined with the pre-set simulation temperature (given temperature) and the potential well depth of each gas component.

[0055] In a specific embodiment, determining the dimensionless temperature corresponding to the gas components of the initial flow field may include: performing a data query operation on a preset gas component transport coefficient database based on the gas components of the initial flow field to obtain the potential well depth corresponding to the gas component; and determining the dimensionless temperature corresponding to the gas component based on the potential well depth and the preset simulation temperature corresponding to the ramjet engine. Specifically, the potential well depth corresponding to each gas component of the initial flow field may be found by querying a preset gas component transport coefficient database; for example, a pre-set public transport coefficient database may be used to query the potential well depth of the relevant gas component. Thereafter, the dimensionless temperature of the relevant gas component may be calculated based on the preset simulation temperature and the queried potential well depth: , where T is the temperature in K; ε / k is the potential well depth of the component in K; is the dimensionless temperature of the gas component.

[0056] Step S12: Based on the dimensionless temperature, determine the molecular viscosity collision integral function of the gas component by polynomial fraction fitting.

[0057] In this application, after obtaining the dimensionless temperature corresponding to the gas component through the above steps, the molecular viscosity collision integral function of each gas component can be calculated using the fitted polynomial fraction. Specifically, the molecular viscosity collision integral function is calculated using the polynomial fraction as shown in the following formula (1): ;

[0058] in, is the molecular viscous collision integral function.

[0059] Step S13: determining the viscosity coefficient of the gas component according to the molecular viscosity collision integral function.

[0060] Furthermore, after obtaining the molecular viscosity collision integral function of the gas component, the viscosity coefficient corresponding to the gas component can be further calculated; in a specific embodiment, determining the viscosity coefficient of the gas component based on the molecular viscosity collision integral function can include: determining the viscosity coefficient of the gas component based on the gas molecular weight, collision diameter and molecular viscosity collision integral function corresponding to the gas component. Specifically, calculating the viscosity coefficient requires combining the gas molecular weight, collision diameter and corresponding molecular viscosity collision integral function of the gas component; calculating the viscosity coefficient of the i-th gas component When , the formula (2) used is as follows:

[0061] ;

[0062] in, The unit is Pa.s, and W is the molecular weight of the gas. is the Lennard-Jones collision diameter in (1 =10 -10 Lennard-Jones collision diameter This can be queried from public gas databases.

[0063] Furthermore, in a specific embodiment, when the initial flow field is a multi-component gas mixture, determining the viscosity coefficients of the gas components based on the molecular viscosity collision integral function may include determining the viscosity coefficient of the mixed gas corresponding to the initial flow field based on the viscosity coefficient, molecular weight, and mole fraction corresponding to each gas component in the initial flow field, so as to utilize the viscosity coefficient of the mixed gas to perform numerical simulation operations on the ramjet engine. Specifically, in the case of a multi-component gas mixture, after obtaining the viscosity coefficient of each individual gas component, the viscosity coefficient μ of the multi-component gas mixture may be calculated based on the Wilke's law of mixing formula. It will be understood that the process of determining the mixed viscosity coefficient corresponding to the multi-component gas mixture involves information such as the number of components, the viscosity coefficient, molecular weight, and mole fraction corresponding to each gas component.

[0064] In a specific embodiment, the viscosity coefficient of the multi-component mixed gas is calculated according to the mixing law formula The process involves formula (3) and formula (4) as follows:

[0065] ;

[0066] ;

[0067] Where ns is the number of components, i and j are the viscosity coefficients of the i-th component and the j-th component respectively, and the unit of viscosity coefficient is Pa.s (Pascal-seconds); W i and W j are the molecular weights of the i-th component and the j-th component, both in g / mol (molar mass); X i and X j are the mole fractions of the i-th component and the j-th component, respectively.

[0068] In another specific embodiment, before performing a numerical simulation operation on the ramjet engine, the method may further include: generating a flow field grid corresponding to the initial flow field of the ramjet engine; and encrypting the flow field grid along the wall normal of the flow field grid based on the viscosity coefficient to obtain a computational grid corresponding to the ramjet engine. It is understandable that in order to simulate the turbulent boundary layer of the ramjet engine, it is necessary to encrypt the grid along the wall normal to ensure that the dimensionless normal height (the dimensionless distance from the grid to the wall) Y of the first layer of grid is + <5. Y + The calculation of requires the wall viscosity coefficient, which is calculated as follows:

[0069] ;

[0070] Here Y is the wall normal distance (the distance from the grid to the wall); ρ is the density; U τ is the friction velocity. μ w is the viscosity coefficient. At the same time, the ratio of the heights of two adjacent layers of grids in the normal direction of the wall (i.e., the grid growth rate) is between 1.1 and 1.3.

[0071] It is understood that in a specific embodiment, Figure 2 As shown in the figure, the calculation process of gas viscosity coefficient specifically includes: querying the potential well depth and collision diameter corresponding to the gas component in the public gas component transport coefficient database. If the corresponding data is found, the dimensionless temperature can be continued. , and then the collision integral function of the gas components is calculated based on the dimensionless temperature, and the molecular viscosity coefficient of the gas components is further calculated; further, if the gas is a multi-component mixed gas, the molecular viscosity coefficient of the mixture can be calculated according to the mixing law.

[0072] In another specific embodiment, for a typical inflow condition of a supersonic ramjet engine: air with an inflow temperature of 300K. The air composition is composed of 79% nitrogen and 21% oxygen by mole fraction, and the viscosity coefficient of the inflow gas is calculated. Step 1: Calculate the dimensionless temperature of each component The Lennard-Jones potential well depths of nitrogen N2 and oxygen O2 are 97.53K and 107.4K respectively in the public gas component transport coefficient database. Therefore, the dimensionless temperature of nitrogen N2 and oxygen O2 at 300K is 3.076 and 2.793 respectively; Step 2: Calculate the molecular viscosity collision integral function Ω of each component using the polynomial fraction in the above embodiment μ (See formula ), we can get the molecular viscosity collision integral function of N2 and O2 at 300K to be 1.03 and 1.06 respectively; Step 3: Calculate the viscosity coefficient of the i-th gas component by combining the gas molecular weight and collision diameter (see formula ), the viscosity coefficients of N2 and O2 can be obtained and Step 4: Calculate the viscosity coefficient of the multi-component gas mixture by combining the mixing law formula (see formula and ). Input the mole fraction of N2 X1=0.79 and the mole fraction of O2 X2=0.21, the viscosity coefficients of N2 and O2 and , the molecular weights of N2 and O2 are W1=28g / mol and W2=32g / mol, and according to the corresponding mixing law calculation formula, the viscosity coefficient of the mixed gas (i.e. air) is .

[0073] Step S14: generating a computational grid of the ramjet engine based on the viscosity coefficient to perform a numerical simulation operation on the ramjet engine.

[0074] In this application, the viscosity coefficients of the gas components can be quickly obtained through the above steps, and the relevant viscosity coefficients can be applied to the numerical simulation process of the ramjet engine, specifically involving the parameter solution of the grid model, to perform performance analysis of the ramjet engine and provide relevant data support for fuel ignition and structural design.

[0075] In a specific embodiment, the process of performing numerical simulation operations on a ramjet engine may include: using viscosity coefficients to calculate and process the differential equations of viscous fluid motion to perform data simulation operations on the ramjet engine. Specifically, the numerical simulation of the ramjet engine involves control equations, gas models, chemical reaction mechanisms, and turbulence models. The control equations can be set as multi-component viscous NS equations, the gas model can be set as chemical non-equilibrium gas, and the corresponding chemical reaction mechanism can be determined based on the fuel. The turbulence model uses two-equation eddy viscosity SST or Turbulence model; based on the viscosity coefficient obtained in the above steps, the corresponding viscous fluid motion differential equation is calculated and solved, and relevant data simulation operations are performed.

[0076] In another specific embodiment, the numerical simulation process may further include iteratively calculating the differential equations for viscous fluid motion until a preset iteration condition is met; the preset iteration condition is when the residual convergence condition is reached in a steady-state calculation, or when a set end time is reached in an unsteady-state calculation. Specifically, during the process of solving the governing equation, the numerical simulation process may be performed iteratively according to the preset iteration condition. It will be understood that during the iterative calculation process, the viscosity coefficient corresponding to the intermediate flow field is calculated and updated in real time to provide data for solving the differential equations for viscous fluid motion. Furthermore, in steady-state calculations, the iterations are terminated until the residual converges; in unsteady calculations, the calculations need to be completed until a given time. The relevant calculation results can then be post-processed to calculate the drag or thrust of the ramjet engine and analyze the simulation results to evaluate the engine's performance and structural design.

[0077] It can be seen that in the numerical simulation process of the ramjet engine, the present application uses a polynomial fraction to fit the viscous collision integral function, which can effectively shorten the calculation time of the gas viscosity coefficient and maintain the calculation accuracy to meet the use requirements; and can adapt to the temperature requirements and component requirements of the combustion flow field of the ramjet engine, which can improve the efficiency of the numerical simulation of the ramjet engine.

[0078] like Figure 3 As shown, the embodiment of the present application discloses a ramjet engine numerical simulation method, which involves a gas viscosity coefficient calculation module, a grid generation module, a control equation solution module, and a post-processing module. The gas viscosity coefficient calculation module provides relevant data for grid generation, control equation solution, and post-processing, and is used for performing ramjet engine simulation calculations. Specifically, the method includes:

[0079] In this embodiment, based on the steps in the above embodiment, the multi-component gas viscosity coefficient can be calculated using the gas viscosity coefficient calculation module; the grid generation module can call the gas viscosity coefficient calculation module to obtain the wall viscosity coefficient and calculate Y + = 1, the first-layer mesh height ∆Y is increased in the wall normal direction to ensure that the first-layer mesh height reaches ∆Y. The Governing Equation Solver module performs calculations for pre-set multi-component Navier-Stokes equations. The Gas Viscosity Calculator module is called at each step of the calculation to obtain the viscosity coefficient of the spatial mesh. The Post-Processing Calculator module can be used to calculate the drag or thrust of the ramjet engine. The friction calculation requires the Gas Viscosity Calculator module to obtain the viscosity coefficient of the wall mesh.

[0080] Furthermore, the viscosity coefficient calculation process in the technical solution of this application can effectively shorten the calculation time compared with other commonly used viscosity coefficient calculation methods (Neufeld, Blottner, Gupta, Capitelli, and McBride). Specifically, when making a comparison, it can simulate the calculation time of the viscosity coefficient of a flow field with 5 million grid cells using conventional computational fluid dynamics software. As can be seen from Table 1 below, for the calculation of the viscosity coefficient of a single-component gas, the calculation time of the other five methods is 3.4 to 13.4 times that of this solution. As can be seen from Table 2, for the calculation of the viscosity coefficient of a two-component gas, although the calculation time of Wilke's law of mixing is increased, the calculation time of the other five methods is still 1.2 to 2.2 times that of this solution.

[0081] Table 1

[0082]

[0083] The multiple is the ratio of the computation time to the computation time of this solution.

[0084] Table 2

[0085]

[0086] Among them, air is composed of 79% nitrogen and 21% oxygen in molar fraction.

[0087] Furthermore, the viscosity coefficient calculation process in the technical solution of the present application also ensures calculation accuracy compared with other commonly used viscosity coefficient calculation methods; other commonly used viscosity coefficient calculation methods include: Neufeld, Blottner, Gupta, Capitelli, and McBride. Specifically, when making a comparison, the test data used covers the following temperature ranges: air and N2 are 300K~4000K, methane and ethylene cover 300~1000K, and CO2 and decane cover up to 2000K. Its overall algorithm design supports seamless calculation of gas viscosity coefficients from 300K~5000K, and the uncovered part is due to reference data limitations. For the viscosity coefficient of single-component N2, from Figure 4 As can be seen from Table 3, the maximum deviation of this method compared to other methods is 7.45%. For the viscosity coefficient of air, air can be regarded as a molar ratio of 79% nitrogen N2 and 21% oxygen O2. Since the Sutherland formula is accurate for calculating the viscosity coefficient of pure air within 2000K, the air viscosity coefficient calculated by the Sutherland formula is also added here. Figure 5As can be seen from Table 4, the maximum deviation of this method compared to other methods is 5.15%. Compared with the Sutherland formula, the maximum error of the calculation results of this method is only 4.36%. As for the viscosity coefficient of hydrocarbon fuels (such as methane, ethylene and decane), Capitelli, Blottner and Gupta did not provide corresponding data, so there is no data from these methods in the following comparison. The reason for choosing decane here is that it is one of the main components of aviation kerosene. In addition, since Carl L. Yoss gave the data on the viscosity coefficient of methane, ethylene and decane, Figures 6 to 8 The data of Carl L. Yoss were added as references, using Matheson as the representation. Figure 6 From Table 5, we can see that the maximum deviation of the methane viscosity coefficient calculated by this scheme is 3.3% compared with other methods; from Table 6 and Figure 7 It can be seen that the maximum deviation of the ethylene viscosity coefficient calculated by this scheme is 4.57% compared with other methods; from Table 8 and Figure 7 It can be seen that the maximum deviation of the decane viscosity coefficient calculated by this method is 4.9% compared with other methods. For the viscosity coefficient of CO2, data within 2000K can be obtained from the website of relevant research institutes, as shown in Table 8 and Figure 9 In the table, NIST and a certain research institute are used to represent the data of the website. Figure 9 As can be seen, the maximum deviation of the CO2 viscosity coefficient calculated by this scheme compared to other methods is 1.74%. The Lennard-Jones potential well depth and collision diameter used in this scheme's component calculations are shown in Table 9. In summary, the viscosity coefficients calculated by this scheme for N2, air, methane, ethylene, decane, and CO2 are all within 7.45% of those calculated by other methods, with the errors for methane, ethylene, and decane being less than 5%. This demonstrates that this scheme's accuracy in calculating the viscosity coefficients of gas components is roughly comparable to that of other methods, ensuring accuracy while reducing calculation time.

[0088] Table 3

[0089]

[0090] Among them, single-component N2 will undergo a dissociation reaction at 4000K, so only the data with a temperature of 300K to 4000K are compared; the deviation calculation method is: (value obtained by a certain calculation method - value obtained by this scheme) / value obtained by a certain calculation method.

[0091] Table 4

[0092]

[0093] Oxygen O2 will undergo a dissociation reaction at 2000K, so only the data at temperatures of 300K to 2000K are compared.

[0094] Table 5

[0095]

[0096] Among them, Matheson only has data on methane at temperatures between 300K and 900K.

[0097] Table 6

[0098]

[0099] Table 7

[0100]

[0101] Table 8

[0102]

[0103] Table 9

[0104]

[0105] It can be seen that in the technical solution of the present application, the multi-component gas viscosity calculation can be applied to the numerical simulation of ramjet engines at temperatures of 300~5000K, and the gas components include ethylene, methane, decane and CO2; compared with other commonly used viscosity coefficient calculation methods, this solution can use polynomial fractions to fit the viscosity collision integral function during the numerical simulation of ramjet engines, which can shorten the calculation time while ensuring the calculation accuracy, and is suitable for the viscosity coefficient calculation of multi-component gases in the combustion flow field of ramjet engines, which can improve the efficiency of ramjet engine numerical simulation.

[0106] like Figure 10 The figure shows the dimensions of a 2D combustion chamber model of a ramjet engine. The model is 500 mm long and 100 mm wide. The inflow conditions are shown in Table 10. In the grid generation module, the computational grid can be generated using NNW-GridStar (a grid generation software used to generate the grids required for computational fluid dynamics analysis). The total number of grids is 1.344 million. The gas viscosity coefficient calculation module in this solution is used to obtain the wall viscosity coefficient distribution. In order to ensure the Y of the first layer of wall grid is + Equal to 1 (see formula ), the first layer of mesh spacing in the wall normal direction needs to be controlled within 0.003mm, so the mesh spacing in the wall normal direction is increased by 0.003mm. The wall normal mesh growth rate is 1.3.

[0107] Table 10

[0108]

[0109] Furthermore, the pressure distribution on the center line of the wall under the model is calculated. According to the control equation solving module, it is verified that the calculation can use three-component gas (O2, N2 and H2O), without fuel, and without considering chemical reactions. The control equation of the calculation is the steady-state multi-component NS equation, the time advancement method adopts the LU-SGS (an implicit algorithm for solving discrete linear equations) method, and the inviscid flux adopts the AUSMPW+ format. The turbulence model adopts the BSL turbulence model, the wall adopts the no-slip non-catalytic adiabatic wall model, the combustion chamber inlet is the supersonic inlet boundary, and the outlet is the supersonic outflow boundary. The calculation convergence criterion is that the L2 modulus of the flow field density residual is reduced by 4 orders of magnitude compared to the initial error. The number of calculation convergence steps is 10,000 steps. The gas viscosity coefficient is calculated using the method of this scheme. From Figure 11 It can be seen that the wall centerline pressure distribution obtained by numerical calculation is consistent with the experimental value, with a maximum error of 10%. This illustrates the reliability of the gas viscosity coefficient calculation method used in this scheme for predicting the ramjet flow field. Correspondingly, the impact of this scheme and Neufeld's gas viscosity coefficient calculation method on the ramjet flow field calculation time can be specifically as follows: The calculation is carried out in a self-built 112-core computing cluster. MPI is used to achieve 24-core parallel computing; in order to speed up the calculation, the parallel computing program uses three-level optimization compilation. From Figure 12 It can be seen that when the number of iteration steps is 10,000, the calculation time of the gas viscosity coefficient calculation method using this solution is 2716 seconds, while the calculation time of the gas viscosity coefficient calculation method using Neufeld is 2798 seconds. This can save about 3% of the time. Furthermore, in the post-processing solution module, it can be obtained that the resistance of the ramjet engine is 193.8N, of which the friction resistance accounts for 70N (Newton). The calculation of friction resistance calls the gas viscosity coefficient calculation module. In addition, from Figure 13 The distribution of friction lines on the combustion chamber wall calculated using this scheme also shows the presence of two flow separation zones. The right flow separation zone can serve as a flame stabilizer by extending the fuel residence time. The left flow separation zone has a pressure of 1.5 atm before and 3.4 atm after. Due to the large pressure gradient, it needs to be considered in the structural design.

[0110] It can be seen that in the process of ramjet numerical simulation, this scheme uses polynomial fractions to fit the viscous collision integral function, which can not only effectively shorten the calculation time of the gas viscosity coefficient, but also maintain the same calculation accuracy, thereby improving the computational efficiency of ramjet numerical simulation.

[0111] like Figure 14As shown, the embodiment of the present application discloses a ramjet numerical simulation device, comprising:

[0112] The dimensionless temperature determination module 11 is used to determine the dimensionless temperature corresponding to the gas components of the initial flow field;

[0113] A polynomial fitting module 12 is configured to determine the molecular viscosity collision integral function of the gas component by polynomial fraction fitting based on the dimensionless temperature;

[0114] a viscosity coefficient determination module 13, configured to determine the viscosity coefficient of the gas component according to the molecular viscosity collision integral function;

[0115] The numerical simulation module 14 is configured to generate a computational grid of the ramjet engine based on the viscosity coefficient, so as to perform a numerical simulation operation on the ramjet engine.

[0116] It can be seen that in the numerical simulation process of the ramjet engine, the present application uses a polynomial fraction to fit the viscous collision integral function, which can effectively shorten the calculation time of the gas viscosity coefficient and maintain the calculation accuracy to meet the use requirements; and can adapt to the temperature and component requirements of the combustion flow field of the ramjet engine, which can improve the effect of the numerical simulation of the ramjet engine.

[0117] In a specific embodiment, the dimensionless temperature determination module 11 may include:

[0118] A query unit, configured to perform a data query operation on a preset gas component transport coefficient database according to the gas component of the initial flow field, so as to obtain a potential well depth corresponding to the gas component;

[0119] The dimensionless temperature determination unit is used to determine the dimensionless temperature of the gas component at each spatial position based on the potential well depth and the simulation temperature of each spatial position corresponding to the initial flow field.

[0120] In a specific embodiment, the viscosity coefficient determination module 13 may include:

[0121] The first viscosity coefficient determining unit is configured to determine the viscosity coefficient of the gas component according to the gas molecular weight, collision diameter, and the molecular viscosity collision integral function corresponding to the gas component.

[0122] In another specific embodiment, the viscosity coefficient determination module 13 may include:

[0123] The second viscosity coefficient determination unit is used to determine the viscosity coefficient of the mixed gas corresponding to the initial flow field based on the viscosity coefficient, molecular weight and mole fraction corresponding to each gas component in the initial flow field, so as to perform a numerical simulation operation on the ramjet engine using the viscosity coefficient of the mixed gas.

[0124] In a specific embodiment, the device may further include:

[0125] A network generation module, used for generating a flow field grid of the ramjet engine corresponding to the initial flow field;

[0126] A grid encryption module is used to encrypt the flow field grid along the wall normal of the flow field grid based on the viscosity coefficient to obtain a calculation grid corresponding to the ramjet engine.

[0127] In a specific embodiment, the numerical simulation module 14 may include:

[0128] The first processing unit is used to calculate and process the viscous fluid motion differential equation using the viscosity coefficient to perform a data simulation operation on the ramjet engine.

[0129] In a specific embodiment, the device may further include:

[0130] The second processing unit is used to calculate and process the viscous fluid motion differential equation in an iterative manner until a preset iteration condition is met; the preset iteration condition is to reach a residual convergence condition in a steady calculation, or to reach a set end time in an unsteady calculation.

[0131] Furthermore, the embodiment of the present application also discloses an electronic device, Figure 15 This is a structural diagram of an electronic device 20 according to an exemplary embodiment. The content in the diagram should not be considered as any limitation to the scope of application of the present application.

[0132] Figure 15 This is a schematic diagram of the structure of an electronic device 20 provided in an embodiment of the present application. The electronic device 20 may specifically include: at least one processor 21, at least one memory 22, a power supply 23, a communication interface 24, an input / output interface 25, and a communication bus 26. The memory 22 is used to store a computer program, which is loaded and executed by the processor 21 to implement the relevant steps of the ramjet engine numerical simulation method disclosed in any of the aforementioned embodiments. Furthermore, the electronic device 20 in this embodiment may specifically be an electronic computer.

[0133] In this embodiment, the power supply 23 is used to provide operating voltage for each hardware device on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and the external device. The communication protocol it follows is any communication protocol that can be applied to the technical solution of this application and is not specifically limited here; the input and output interface 25 is used to obtain external input data or output data to the outside world. Its specific interface type can be selected according to specific application needs and is not specifically limited here.

[0134] In addition, the memory 22, as a carrier for resource storage, can be a read-only memory, random access memory, disk or CD, etc. The resources stored thereon can include an operating system 221, a computer program 222, etc., and the storage method can be temporary storage or permanent storage.

[0135] The operating system 221 is used to manage and control the hardware devices on the electronic device 20 and the computer program 222. The operating system 221 can be Windows Server, NetWare, Unix, Linux, etc. In addition to including a computer program capable of performing the ramjet engine numerical simulation method performed by the electronic device 20 as disclosed in any of the aforementioned embodiments, the computer program 222 can further include computer programs capable of performing other specific tasks.

[0136] Furthermore, this application discloses a computer-readable storage medium for storing a computer program. When executed by a processor, the computer program implements the aforementioned ramjet engine numerical simulation method. The specific steps of this method can be found in the corresponding content disclosed in the aforementioned embodiments and will not be further elaborated here.

[0137] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from the other embodiments. Reference can be made to the descriptions of the identical or similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and the relevant parts can be referred to the descriptions of the methods.

[0138] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0139] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in random access memory (RAM), internal memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0140] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or device comprising the element.

[0141] The above is a detailed introduction to the technical solution provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. At the same time, for those skilled in the art, according to the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A ramjet numerical simulation method, characterized in that: include: Determine the dimensionless temperature corresponding to the gas components of the initial flow field; Determining the molecular viscosity collision integral function of the gas component by polynomial fraction fitting based on the dimensionless temperature; determining the viscosity coefficient of the gas component according to the molecular viscosity collision integral function; generating a computational grid of a ramjet engine based on the viscosity coefficient to perform a numerical simulation operation on the ramjet engine; Wherein, the molecular viscosity collision integral function includes: ； is the molecular viscosity collision integral function, is the dimensionless temperature; Wherein, the viscosity coefficient includes: ； is the viscosity coefficient of the i-th gas component, W is the molecular weight of the i-th gas component, T is the temperature, is the collision diameter.

2. The ramjet engine numerical simulation method according to claim 1, characterized in that: The determining of the dimensionless temperature corresponding to the gas components of the initial flow field includes: Performing a data query operation on a preset gas component transport coefficient database according to the gas component of the initial flow field to obtain a potential well depth corresponding to the gas component; The dimensionless temperature of the gas component at each spatial position is determined based on the potential well depth and the simulated temperature of the initial flow field corresponding to each spatial position.

3. The ramjet engine numerical simulation method according to claim 1, characterized in that: Determining the viscosity coefficient of the gas component according to the molecular viscosity collision integral function includes: The viscosity coefficient of the gas component is determined according to the gas molecular weight, collision diameter and the molecular viscosity collision integral function corresponding to the gas component.

4. The ramjet engine numerical simulation method according to claim 1, characterized in that: When the initial flow field is a multi-component mixed gas, determining the viscosity coefficients of the gas components according to the molecular viscosity collision integral function includes: The viscosity coefficient of the mixed gas corresponding to the initial flow field is determined according to the viscosity coefficient, molecular weight and mole fraction corresponding to each gas component in the initial flow field, so as to perform a numerical simulation operation on the ramjet engine using the viscosity coefficient of the mixed gas.

5. The ramjet engine numerical simulation method according to claim 1, characterized in that: Generating a computational grid of the ramjet engine based on the viscosity coefficient includes: generating a flow field grid of the ramjet engine corresponding to the initial flow field; Based on the viscosity coefficient, the flow field grid is encrypted along the wall normal of the flow field grid to obtain a calculation grid corresponding to the ramjet engine.

6. The ramjet engine numerical simulation method according to any one of claims 1 to 5, characterized in that: The performing of a numerical simulation operation on the ramjet engine includes: The viscosity coefficient is used to perform calculation processing on the viscous fluid motion differential equation to perform a data simulation operation on the ramjet engine.

7. The ramjet engine numerical simulation method according to claim 6, characterized in that: The process of performing the numerical simulation operation also includes: The viscous fluid motion differential equation is calculated and processed in an iterative manner until a preset iteration condition is met; the preset iteration condition is that a residual convergence condition is reached in a steady calculation, or a set end time is reached in an unsteady calculation.

8. A ramjet numerical simulation device, characterized in that: include: A dimensionless temperature determination module, used to determine the dimensionless temperature corresponding to the gas components of the initial flow field; A polynomial fitting module, configured to determine the molecular viscosity collision integral function of the gas component by polynomial fraction fitting based on the dimensionless temperature; a viscosity coefficient determination module, configured to determine the viscosity coefficient of the gas component according to the molecular viscosity collision integral function; a numerical simulation module, configured to generate a computational grid corresponding to the ramjet engine based on the viscosity coefficient, so as to perform a numerical simulation operation on the ramjet engine; Wherein, the molecular viscosity collision integral function includes: ； is the molecular viscosity collision integral function, is the dimensionless temperature; Wherein, the viscosity coefficient includes: ； is the viscosity coefficient of the i-th gas component, W is the molecular weight of the i-th gas component, T is the temperature, is the collision diameter.

9. An electronic device, characterized in that: include: Memory, used to store computer programs; A processor, configured to execute the computer program to implement the ramjet engine numerical simulation method according to any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that Used to store a computer program, which, when executed by a processor, implements the ramjet engine numerical simulation method according to any one of claims 1 to 7.

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