Numerical simulation method, device and equipment for ramjet and storage medium

Abstract

The invention discloses a ramjet numerical simulation method, device and equipment and a storage medium, and relates to the technical field of aerodynamics, and the method comprises the steps: determining a dimensionless temperature corresponding to a gas component of an initial flow field; based on the dimensionless temperature, determining a molecular viscosity collision integral function of the gas component in a polynomial fraction fitting mode; determining the viscosity coefficient of the gas component according to the molecular viscosity collision integral function; and generating a computational grid of the ramjet based on the viscosity coefficient so as to perform numerical simulation operation on the ramjet. Therefore, in the numerical simulation process of the ramjet, the polynomial fraction is adopted to fit the viscosity collision integral function, the calculation time of the gas viscosity coefficient can be effectively shortened, and the calculation precision is kept to meet the use requirement; in addition, the method can adapt to the combustion flow field temperature requirement and the component requirement of the ramjet engine, and the numerical simulation efficiency of the ramjet engine can be improved.

Description

Technical Field

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

[0002] The purpose of the numerical simulation of a ramjet engine is to provide data for the performance evaluation and structural design of the engine. In the numerical simulation of a ramjet engine, the viscosity coefficient of gas components is required in multiple steps; and the current common methods for gas viscosity coefficient specifically involve: (1) According to the molecular dynamics method, the Lennard-Jones model is used to simulate the intermolecular interaction force. This method can simulate the transport coefficients of gases and liquids. The highest temperature is generally 5000K (Kelvin, the temperature unit). (2) Using the Chapman-Enskog theory, the viscosity coefficient of components is calculated by solving the Boltzmann equation. Since the complete Chapman-Enskog calculation is relatively large, the Chapman-Enskog approximation formula is usually adopted. This method is mainly used for the calculation of the transport coefficients of high-temperature dissociating gases, and the highest temperature can reach 30,000K. These methods have the problems of high complexity and limited adaptability to the ramjet engine scenario; the gas components in the combustion flow field of the ramjet engine are numerous, and the temperature is fixed within 5000K.

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

[0004] In view of this, the purpose of the present invention is to provide a numerical simulation method, device, equipment and storage medium for a ramjet engine. During the numerical simulation process of the ramjet engine, a polynomial fraction is used 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 usage requirements; and it can adapt to the temperature requirements and component requirements of the combustion flow field of the ramjet engine, and can improve the efficiency of the numerical simulation of the ramjet engine. The specific scheme is as follows:

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

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

[0007] Based on the dimensionless temperature, determine the molecular viscous collision integral function of the gas components by means of polynomial fraction fitting;

[0008] Determine the viscosity coefficient of the gas components according to the molecular viscous collision integral function;

[0009] Generate a computational grid for a ramjet engine based on the viscosity coefficient to perform numerical simulation operations on the ramjet engine.

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

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

[0012] Based on the potential well depth and the simulation temperature at each spatial position corresponding to the initial flow field, determine the dimensionless temperature of the gas components at each spatial position.

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

[0014] Determine the viscosity coefficient of the gas components according to the gas molecular weight, collision diameter corresponding to the gas components, and the molecular viscosity collision integral function.

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

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

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

[0018] Generate a flow field grid for the ramjet engine corresponding to the initial flow field;

[0019] Based on the viscosity coefficient, perform encryption processing on the flow field grid along the wall normal direction of the flow field grid to obtain the computational grid corresponding to the ramjet engine.

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

[0021] Perform computational processing on the differential equation of viscous fluid motion using the viscosity coefficient to perform data simulation operations on the ramjet engine.

[0022] Optionally, during the process of performing numerical simulation operations, it further includes:

[0023] The differential equation of the viscous fluid motion is calculated iteratively until the preset iteration condition is met; the preset iteration condition is to reach the residual convergence condition under steady-state calculation or to reach the set end time under unsteady calculation.

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

[0025] A dimensionless temperature determination module for determining the dimensionless temperature corresponding to the gas components of the initial flow field;

[0026] A polynomial fitting module for determining the molecular viscosity collision integral function of the gas components by means of polynomial fractional fitting based on the dimensionless temperature;

[0027] A viscosity coefficient determination module for determining the viscosity coefficient of the gas components according to the molecular viscosity collision integral function;

[0028] A numerical simulation module for generating a computational grid corresponding to the ramjet engine based on the viscosity coefficient to perform numerical simulation operations on the ramjet engine.

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

[0030] A memory for storing a computer program;

[0031] A processor for executing 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, and when the computer program is executed by a processor, the ramjet engine numerical simulation method as described above is implemented.

[0033] Thus, in the present application, first, the dimensionless temperature corresponding to the gas components of the initial flow field is determined; then, based on the dimensionless temperature, the molecular viscosity collision integral function of the gas components is determined by means of polynomial fractional fitting; then, the viscosity coefficient of the gas components is determined according to the molecular viscosity collision integral function; and then, a computational grid of the ramjet engine is generated based on the viscosity coefficient to perform numerical simulation operations on the ramjet engine. In this way, in the numerical simulation process of the ramjet engine, the present application uses a polynomial fraction to fit the viscosity collision integral function, which can effectively shorten the calculation time of the gas viscosity coefficient and maintain the calculation accuracy to meet the usage requirements; moreover, it can adapt to the combustion flow field temperature requirements and component requirements of the ramjet engine, and can improve the efficiency of the ramjet engine numerical simulation. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the provided drawings.

[0035] Figure 1 Flowchart of a numerical simulation method for a ramjet engine disclosed in the present application;

[0036] Figure 2 Flowchart of a calculation method for viscosity coefficient disclosed in the present application;

[0037] Figure 3 Schematic diagram of a numerical simulation module for a ramjet engine disclosed in the present application;

[0038] Figure 4 Schematic diagram showing the variation of the viscosity coefficient of nitrogen N2 with temperature disclosed in the present application;

[0039] Figure 5 Schematic diagram showing the variation of the viscosity coefficient of air Air with temperature disclosed in the present application;

[0040] Figure 6 Schematic diagram showing the variation of the viscosity coefficient of methane CH4 with temperature disclosed in the present application;

[0041] Figure 7 Schematic diagram showing the variation of the viscosity coefficient of ethylene C2H4 with temperature disclosed in the present application;

[0042] Figure 8 Schematic diagram showing the variation of the viscosity coefficient of decane C 10 H 22 with temperature disclosed in the present application;

[0043] Figure 9 Schematic diagram showing the variation of the viscosity coefficient of carbon dioxide CO2 with temperature disclosed in the present application;

[0044] Figure 10 Schematic diagram of the geometric dimensions of a ramjet engine combustion chamber model disclosed in the present application;

[0045] Figure 11 Schematic diagram comparing the pressure distributions of the calculation and test of the centerline of the combustion chamber wall disclosed in the present application;

[0046] Figure 12 Schematic diagram showing the relationship between the calculation method of the gas viscosity coefficient and the change of the calculation time of the ramjet engine flow field disclosed in the present application;

[0047] Figure 13A distribution diagram of the friction force lines on the combustion chamber wall disclosed in the present application;

[0048] Figure 14 A schematic structural diagram of a numerical simulation device for a ramjet engine disclosed in the present application;

[0049] Figure 15 A structural diagram of an electronic device disclosed in the present application. Specific embodiments

[0050] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0051] It can be understood that in the numerical simulation of a ramjet engine, the viscosity coefficient plays an important role, involving the grid generation stage, the control equation solving stage, and the post-processing stage; in addition, the flow separation region can be obtained by analyzing the distribution of the friction force lines on the wall surface, providing data support for the fuel ignition and structural design of the ramjet engine. The friction force lines on the wall surface need to solve the friction force components in three directions and also need to calculate the wall surface viscosity coefficient. In the numerical simulation of a ramjet engine, the calculation characteristics of the viscosity coefficient of multi-component gases are as follows: there are many gas components. In addition to nitrogen and oxygen in pure air, there are also components mainly composed of hydrocarbon fuels, such as methane, ethylene, aviation kerosene, etc. In particular, aviation kerosene is a mixture, including multi-molecular structures such as decane and benzene; the viscosity coefficient is not only related to temperature but also to the molar ratio of various components; the combustion flow field temperature of a ramjet engine generally does not exceed 5000K. Further, the present application uses a polynomial fraction to fit the viscous collision integral function, which can effectively shorten the calculation time of the viscosity coefficient of gas components, ensure the calculation accuracy, and improve the effect of the numerical simulation of the ramjet engine.

[0052] See Figure 1 As shown, the embodiments of the present invention disclose a numerical simulation method for a ramjet engine, including:

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

[0054] In the present application, the initial flow field of the ramjet engine contains multiple gas components, such as nitrogen, oxygen, fuel gas, etc. To calculate the viscosity coefficient of the gas components, it is first necessary to determine the dimensionless temperature of each gas component; the calculation process of the dimensionless temperature needs to combine 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 according to the gas components of the initial flow field to obtain the potential well depth corresponding to the gas components; determining the dimensionless temperature corresponding to the gas components based on the potential well depth and the preset simulation temperature corresponding to the ramjet. Specifically, the potential well depth corresponding to each gas component of the initial flow field can be found by querying a preset gas component transport coefficient database; for example, for a publicly available preset transport coefficient database, the potential well depth of the relevant gas components can be queried therefrom. After that, the dimensionless temperature of the relevant gas components can 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 means of 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] where is the molecular viscosity collision integral function.

[0059] Step S13: Determine 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 according to the molecular viscosity collision integral function may include: determining the viscosity coefficient of the gas component according to the gas molecular weight, collision diameter corresponding to the gas component, and the molecular viscosity collision integral function. Specifically, calculating the viscosity coefficient requires combining the gas molecular weight, collision diameter of the gas component, and the corresponding molecular viscosity collision integral function, etc.; calculating the viscosity coefficient of the i-th gas component uses the following formula (2):

[0061] ;

[0062] where is in Pa·s and W is the gas molecular weight. is the Lennard-Jones collision diameter, with the unit of (1 = 10 -10 m). The Lennard-Jones collision diameter can be queried from publicly available gas databases.

[0063] Further, in a specific embodiment, when the initial flow field is a multi-component mixed gas, in the process of determining the viscosity coefficient of the gas components according to the molecular viscous collision integral function, it may include: determining the viscosity coefficient of the mixed gas corresponding to the initial flow field according to the viscosity coefficient, molecular weight, and mole fraction of each gas component in the initial flow field, so as to perform numerical simulation operations on the ramjet engine using the viscosity coefficient of the mixed gas. Specifically, if it is a multi-component mixed gas, after obtaining the viscosity coefficient of each single gas component, the viscosity coefficient μ of the multi-component mixed gas can be calculated according to the Wilke mixing law formula; it can be understood that in the process of obtaining the mixed viscosity coefficient corresponding to the multi-component mixed gas, information such as the number of components, the viscosity coefficient, molecular weight, and mole fraction corresponding to each gas component is involved.

[0064] In a specific embodiment, the process of calculating the viscosity coefficient of the multi-component mixed gas according to the mixing law formula involves the following formulas (3) and (4):

[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 the 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 respectively, and the unit of both is 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 numerical simulation operations on the ramjet engine, it may further include: generating a flow field grid corresponding to the ramjet engine for the initial flow field; based on the viscosity coefficient, encrypting the flow field grid along the wall normal direction of the flow field grid to obtain the calculation grid corresponding to the ramjet engine. It can be understood that in order to simulate the turbulent boundary layer of the ramjet engine, it is necessary to encrypt the grid in the wall normal direction to ensure that the dimensionless normal height of the first layer of the grid (the dimensionless distance from the grid to the wall) Y + <5. Y + The calculation of requires the wall viscosity coefficient, and its calculation formula (5) is 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 the grid in the wall normal direction (i.e., the grid growth rate) is taken between 1.1 and 1.3.

[0071] It can be understood that in a specific embodiment, as Figure 2 shown, the calculation process of the gas viscosity coefficient specifically includes: querying the potential well depth and collision diameter corresponding to the gas components in the publicly available gas component transport coefficient database. If the corresponding data is queried, the dimensionless temperature can be calculated continuously. After that, 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 yet another specific embodiment, for the typical oncoming flow conditions of a supersonic ramjet engine: air with an oncoming flow temperature of 300K. The air components consist of 79% nitrogen and 21% oxygen by mole fraction, and the viscosity coefficient of the oncoming flow gas is calculated. Step 1: Calculate the dimensionless temperature of each component. Query the Lennard-Jones potential well depths of nitrogen N2 and oxygen O2 in the publicly available gas component transport coefficient database, which are 97.53K and 107.4K respectively. Therefore, the dimensionless temperatures of nitrogen N2 and oxygen O2 at 300K are 3.076 and 2.793 respectively; Step 2: Use the polynomial fraction in the above embodiment to calculate the molecular viscosity collision integral function Ω μ of each component (see formula ), the molecular viscosity collision integral functions of N2 and O2 can be obtained as 1.03 and 1.06 respectively at 300K; Step three: Combine the gas molecular weight and collision diameter to calculate the viscosity coefficient of the i-th gas component (see formula ), the viscosity coefficients of N2 and O2 can be obtained and . Step four: Combine the mixing law formula to calculate the viscosity coefficient of the multi-component mixed gas (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, W1 = 28 g / mol and W2 = 32 g / mol. According to the corresponding mixing law calculation formula, the viscosity coefficient of the mixed gas (i.e., air) is obtained as .

[0073] Step S14: Generate a computational grid for the ramjet based on the viscosity coefficient to perform numerical simulation operations on the ramjet.

[0074] In this application, the viscosity coefficients of 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, specifically involving the parameter solution of the grid model to analyze the performance of the ramjet and provide relevant data support for fuel ignition and structural design.

[0075] In a specific embodiment, during the process of performing numerical simulation operations on the ramjet, it may include: using the viscosity coefficient to perform calculation processing on the differential equation of viscous fluid motion to perform data simulation operations on the ramjet. Specifically, the numerical simulation of the ramjet involves control equations, gas models, chemical reaction mechanisms, and turbulence models. The control equation can be set as the multi-component viscous N-S equation, the gas model is set as a chemically non-equilibrium gas, and the corresponding chemical reaction mechanism is determined according to the fuel. The turbulence model adopts the two-equation eddy viscosity SST or turbulence model; Based on the viscosity coefficient obtained in the above steps, calculate and solve the corresponding differential equation of viscous fluid motion to perform relevant data simulation operations.

[0076] In another specific embodiment, during the numerical simulation operation, it may further include: calculating and processing the differential equation of viscous fluid motion in an iterative manner until the preset iteration condition is met; the preset iteration condition is to reach the residual convergence condition under steady-state calculation, or to reach the set end time under unsteady calculation. Specifically, during the process of solving the control equation, an iterative method can be adopted to perform numerical simulation operations according to the preset iteration conditions; it can be understood that during the iterative calculation process, the viscosity coefficient corresponding to the intermediate flow field of the iterative calculation is calculated and updated in real time, providing data for the solution of the differential equation of viscous fluid motion. Further, in steady-state calculation, the iteration is terminated until the residual converges; in unsteady calculation, it is necessary to calculate until the given time. After that, the relevant calculation results can be post-processed to calculate the drag or thrust of the ramjet engine, analyze the simulation situation of the ramjet engine, so as to evaluate the performance and structural design of the engine.

[0077] Thus, in the numerical simulation process of the ramjet engine of the present application, using a polynomial fraction to fit the viscous collision integral function can effectively shorten the calculation time of the gas viscosity coefficient and maintain the calculation accuracy to meet the usage requirements; moreover, it can adapt to the combustion flow field temperature requirements and component requirements of the ramjet engine, and can improve the efficiency of the numerical simulation of the ramjet engine.

[0078] As Figure 3 shown, the embodiment of the present application discloses a numerical simulation method for a ramjet engine, which involves a gas viscosity coefficient calculation module, a mesh generation module, a control equation solving module, and a post-processing module. Among them, the gas viscosity coefficient calculation module provides relevant data for mesh generation, control equation solving, and post-processing, and is used for the simulation calculation of the ramjet engine; specifically includes:

[0079] In this embodiment, based on the steps in the above embodiment, the gas viscosity coefficient calculation module can be used to calculate the multi-component gas viscosity coefficient; the mesh generation module can call the gas viscosity coefficient calculation module to obtain the wall viscosity coefficient, calculate the height ∆Y of the first layer of mesh corresponding to Y + = 1, and the spatial mesh is encrypted in the wall normal direction to ensure that the height of the first layer of mesh reaches ∆Y; the control equation solving module can calculate the preset multi-component N-S equation. The gas viscosity coefficient calculation module is called to obtain the viscosity coefficient of the spatial mesh during each calculation step; the post-processing calculation module can be used to calculate the drag or thrust of the ramjet engine, and the friction drag calculation needs to call the gas viscosity coefficient calculation module to obtain the viscosity coefficient of the wall mesh.

[0080] Furthermore, compared with other commonly used methods for calculating viscosity coefficients (Neufeld, Blottner, Gupta, Capitelli, and McBride), the viscosity coefficient calculation process in the technical solution of this application can effectively shorten the calculation time. Specifically, when making comparisons, the calculation time of a typical computational fluid dynamics software for calculating the flow field viscosity coefficient of 5 million grid cells can be simulated; 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 the Wilke mixing law is added, 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] Among them, the multiple is the ratio between the calculation time and the calculation time of this solution.

[0084] Table 2

[0085]

[0086] Among them, air is composed of nitrogen with a mole fraction of 79% and oxygen with a mole fraction of 21%.

[0087] Furthermore, compared with other commonly used methods for calculating viscosity coefficients, the viscosity coefficient calculation process in the technical solution of this application also ensures the calculation accuracy; other commonly used methods for calculating viscosity coefficients such as: Neufeld, Blottner, Gupta, Capitelli, McBride. Specifically, when making comparisons, the test data used covers the following temperature ranges, 300K to 4000K for air and N2, 300 to 1000K for methane and ethylene, and up to 2000K for CO2 and decane. The overall algorithm design supports seamless calculation of gas viscosity coefficients in the range of 300K to 5000K, with the uncovered part due to reference data limitations. For the viscosity coefficient of single-component N2, from Figure 4 and Table 3, it can be seen that the maximum deviation of this solution relative to other methods is 7.45%; for the viscosity coefficient of air, air can be regarded as nitrogen N2 with a molar ratio of 79% and oxygen O2 with a molar ratio of 21%. Since the Sutherland formula is accurate for calculating the viscosity coefficient of pure air within 2000K, the viscosity coefficient of air calculated by the Sutherland formula is also added here. From Figure 5As can be seen from Table 4, the maximum deviation of this solution compared to other methods is 5.15%. Among them, compared with the Sutherland formula, the maximum error of the calculation results of this solution is only 4.36%. For the viscosity coefficients of hydrocarbon fuels (such as methane, ethylene, and decane), Capitelli, Blottner, and Gupta did not give corresponding data, so the data of these methods are not available 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. Jos provided the data of the viscosity coefficients of methane, ethylene, and decane, the data of Carl L. Jos were added as a reference in Figures 6 - 8 and represented by Matheson. As can be seen from Figure 6 and Table 5, the maximum deviation of the viscosity coefficient of methane calculated by this solution compared to other methods is 3.3%; as can be seen from Table 6 and Figure 7 , the maximum deviation of the viscosity coefficient of ethylene calculated by this solution compared to other methods is 4.57%; as can be seen from Table 8 and Figure 7 , the maximum deviation of the viscosity coefficient of decane calculated by this solution compared to other methods is 4.9%; for the viscosity coefficient of CO2, the data within 2000K can be obtained from the website of a relevant research institute, and the data of the website are represented by NIST and "a certain research institute" in Table 8 and Figure 9 respectively. As can be seen from Table 8 and Figure 9 , the maximum deviation of the viscosity coefficient of CO2 calculated by this solution compared to other methods is 1.74%. The Lennard-Jones potential well depth and collision diameter used in the calculation of the components of this solution are shown in Table 9. To sum up, the errors of the viscosity coefficients of N2, air, methane, ethylene, decane, and CO2 calculated by this solution compared to other methods are all within 7.45%, and the errors of methane, ethylene, and decane are less than 5%. This shows that in the process of calculating the viscosity coefficients of gas components, the calculation accuracy of this solution is basically equivalent to that of other methods, and the calculation accuracy is guaranteed on the premise of shortening the calculation time.

[0088] Table 3

[0089]

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

[0091] Table 4

[0092]

[0093] Among them, oxygen O2 will undergo a dissociation reaction at 2000K, so only the data at temperatures from 300K to 2000K are compared.

[0094] Table 5

[0095]

[0096] Among them, Matheson only has data on methane at temperatures from 300K to 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 viscous calculation of multi-component gases can be applied to the numerical simulation of ramjet engines at temperatures from 300K to 5000K, and the gas components include ethylene, methane, decane, CO2, etc.; compared with other common methods for calculating viscosity coefficients, this solution can use a polynomial fraction to fit the viscous collision integral function during the numerical simulation of ramjet engines, which can shorten the calculation time while ensuring the calculation accuracy, and is applicable to the calculation of the viscosity coefficients of multi-component gases in the combustion flow field of ramjet engines, and can improve the efficiency of the numerical simulation of ramjet engines.

[0106] As Figure 10 shown, it is a schematic diagram of the dimensions of a two-dimensional combustion chamber model of a ramjet engine. The model is 500mm (millimeters) long and 100mm wide. The oncoming flow conditions are shown in Table 10. In the grid generation module, the computational grid can be generated using NNW-GridStar (a grid generation software for generating grids required for computational fluid dynamics analysis) software, and the total number of grids is 1.344 million. The wall viscous coefficient distribution is obtained using the gas viscosity coefficient calculation module in this solution. In order to ensure that Y + of the first grid layer on the wall is equal to 1 (see formula ), the spacing of the first grid layer in the wall normal direction needs to be controlled within 0.003mm, so the wall normal direction is encrypted according to the spacing of the first grid layer of 0.003mm. The grid growth rate in the wall normal direction is 1.3.

[0107] Table 10

[0108]

[0109] Furthermore, the pressure distribution on the centerline of the lower wall of the computational model is calculated. According to the control equation solving module, the calculation can be verified using a three-component gas (O2, N2, and H2O), without fuel, and without considering chemical reactions. The governing equations for the calculation are the steady multi-component Navier-Stokes equations. The time marching method uses the LU-SGS (an implicit algorithm for solving discrete linear equations) method. The inviscid flux uses the AUSMPW+ scheme. The turbulence model uses the BSL turbulence model. The wall uses a no-slip non-catalytic adiabatic wall model. The combustion chamber inlet is a supersonic inflow boundary, and the outlet is a supersonic outflow boundary. The calculation convergence criterion is that the L2 norm of the flow field density residual drops by four 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 calculation method of this scheme. From Figure 11 It can be seen that the pressure distribution on the wall centerline obtained by numerical calculation is consistent with the experimental value, and the maximum error is 10%. This shows the reliability of the calculation method of the gas viscosity coefficient of this scheme for predicting the flow field of a ramjet engine. Correspondingly, in this scheme and the gas viscosity coefficient calculation method of Neufeld, the influence on the calculation time of the ramjet engine flow field is as follows: The calculation is carried out on a self-built 112-core computing cluster. MPI is used to achieve 24-core parallel computing; in order to accelerate the calculation, the parallel computing program uses three-level optimized compilation. From Figure 12 It can be seen that at 10,000 iteration steps, the calculation time using the gas viscosity coefficient calculation method of this scheme is 2716 s (seconds), while the calculation time using the gas viscosity coefficient calculation method of Neufeld is 2798 s. It can save about 3% of the time. Further, in the post-processing solution module, the drag of this ramjet engine can be obtained as 193.8 N, of which the skin friction accounts for 70 N (Newtons). The calculation of the skin friction calls the gas viscosity coefficient calculation module. In addition, from Figure 13 It can also be seen from the distribution of the skin friction lines on the combustion chamber wall calculated by this scheme that there are two flow separation zones on the wall. The flow separation zone on the right can be used as a combustion chamber flame stabilizer by extending the fuel residence time; the pressure in front of the flow separation zone on the left is 1.5 atm (pressure), and the pressure after the separation zone reaches 3.4 atm. Due to the large pressure gradient, it needs to be considered in the structural design.

[0110] Thus, in the numerical simulation process of the ramjet engine, this scheme uses a polynomial fraction 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 calculation accuracy quite well, and improve the calculation efficiency of the ramjet engine numerical simulation.

[0111] Such as Figure 14As shown in the figure, an embodiment of the present application discloses a numerical simulation device for a ramjet engine, including:

[0112] A dimensionless temperature determination module 11, configured to determine the dimensionless temperature corresponding to the gas components of the initial flow field;

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

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

[0115] A numerical simulation module 14, configured to generate a computational grid for the ramjet engine based on the viscosity coefficient 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 in the present application, a polynomial fraction is used to fit the viscosity collision integral function, which can effectively shorten the calculation time of the gas viscosity coefficient and maintain the calculation accuracy to meet the usage requirements; moreover, it can adapt to the combustion flow field temperature requirements and component requirements of the ramjet engine, and 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 components of the initial flow field to obtain the potential well depth corresponding to the gas components;

[0119] A dimensionless temperature determination unit, configured to determine the dimensionless temperature of the gas components at each spatial position based on the potential well depth and the simulation temperature of the initial flow field corresponding to each spatial position.

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

[0121] A first viscosity coefficient determination unit, configured to determine the viscosity coefficient of the gas components according to the gas molecular weight, collision diameter corresponding to the gas components, and the molecular viscosity collision integral function.

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

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

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

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

[0126] A grid encryption module, configured to encrypt the flow field grid along the wall normal direction 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] A first processing unit, configured to perform calculation processing on the differential equation of viscous fluid motion by 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] A second processing unit, configured to perform calculation processing on the differential equation of viscous fluid motion in an iterative manner until a preset iteration condition is met; the preset iteration condition is to reach a residual convergence condition under steady-state calculation or to reach a set end time under unsteady calculation.

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

[0132] Figure 15 This is a schematic structural diagram of an electronic device 20 provided by 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. Among them, the memory 22 is used to store a computer program, and the computer program is loaded and executed by the processor 21 to implement the relevant steps in the ramjet engine numerical simulation method disclosed in any of the foregoing embodiments. In addition, 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 voltages for the various hardware devices on the electronic device 20; the communication interface 24 can create a data transmission channel between the electronic device 20 and external devices, and the communication protocol it follows can be any communication protocol applicable to the technical solution of this application, and specific limitations thereof are not provided herein; the input / output interface 25 is used to obtain external input data or output data to the outside, and the specific interface type thereof can be selected according to specific application requirements, and specific limitations are not provided herein.

[0134] In addition, the memory 22, as a carrier for resource storage, can be a read-only memory, a random access memory, a magnetic disk, an optical disk, etc., and 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] Among them, the operating system 221 is used to manage and control the various hardware devices and the computer program 222 on the electronic device 20, and it can be Windows Server, Netware, Unix, Linux, etc. The computer program 222 can further include a computer program capable of performing other specific tasks in addition to the computer program capable of performing the ramjet numerical simulation method executed by the electronic device 20 disclosed in any of the foregoing embodiments.

[0136] Furthermore, this application also discloses a computer-readable storage medium for storing a computer program; wherein, when the computer program is executed by a processor, the ramjet numerical simulation method disclosed above is implemented. For the specific steps of this method, reference can be made to the corresponding content disclosed in the foregoing embodiments, and details are not described herein again.

[0137] In this specification, the various embodiments are described in a progressive manner, and the key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and reference can be made to the description of the method part for related parts.

[0138] Those skilled in the art can further realize that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the components and steps of the examples have been generally described according to their functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.

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

[0140] Finally, it should also be noted that in this document, relational 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 actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is 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 expressly listed, or elements inherent to such process, method, article or device. Without further limitation, 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 technical solutions provided in this application have been introduced in detail above. Specific examples are used herein to illustrate the principles and implementation manners of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application; at the same time, for those of ordinary skill in the art, according to the idea of this application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. A numerical simulation method for a ramjet engine, characterized in that Including: Determine the dimensionless temperature corresponding to the gas components of the initial flow field; Based on the dimensionless temperature, determine the molecular viscous collision integral function of the gas components by means of polynomial fractional fitting; Determine the viscosity coefficient of the gas components according to the molecular viscous collision integral function; Generate a computational grid for the ramjet based on the viscosity coefficient to perform numerical simulation operations on the ramjet.

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

3. The numerical simulation method of a ramjet engine according to claim 1, characterized in that The determination of the viscosity coefficient of the gas components according to the molecular viscous collision integral function includes: Determine the viscosity coefficient of the gas components according to the gas molecular weight, collision diameter corresponding to the gas components, and the molecular viscous collision integral function.

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

5. The numerical simulation method of a ramjet engine according to claim 1, characterized in that The generation of the computational grid for the ramjet based on the viscosity coefficient includes: Generate a flow field grid for the ramjet corresponding to the initial flow field; Based on the viscosity coefficient, perform encryption processing on the flow field grid along the wall normal direction of the flow field grid to obtain the computational grid corresponding to the ramjet.

6. The numerical simulation method of a ramjet engine according to any one of claims 1 to 5, characterized in that The performance of numerical simulation operations on the ramjet includes: Perform computational processing on the viscous fluid motion differential equation using the viscosity coefficient to perform data simulation operations on the ramjet.

7. The numerical simulation method of a ramjet engine according to claim 6, characterized in that During the process of performing numerical simulation operations, it further includes: Perform computational processing on the viscous fluid motion differential equation in an iterative manner until the preset iteration conditions are met; the preset iteration conditions are to reach the residual convergence condition under steady-state calculation, or to reach the set end time under unsteady calculation.

8. A numerical simulation device for a ramjet engine, characterized in that, Including: A dimensionless temperature determination module for determining the dimensionless temperature corresponding to the gas components of the initial flow field; A polynomial fitting module for determining the molecular viscous collision integral function of the gas components by means of polynomial fractional fitting based on the dimensionless temperature; A viscosity coefficient determination module for determining the viscosity coefficient of the gas components according to the molecular viscous collision integral function; A numerical simulation module for generating a computational grid corresponding to the ramjet based on the viscosity coefficient to perform numerical simulation operations on the ramjet.

9. An electronic device, characterized in that, Including: A memory for storing a computer program; A processor for executing the computer program to implement the ramjet numerical simulation method according to any one of claims 1 to 7.

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

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