Database component simplification and reconstruction method suitable for flame surface model

Abstract

The invention belongs to the field of engine combustion and computational fluid mechanics, and discloses a database component simplification and reconstruction method suitable for a flame surface model. The database component simplification and reconstruction method suitable for the flame surface model comprises the following steps: giving names of reserved components; traversing the flame surface database, and deleting non-reserved components; calculating coefficients A1-A7; coefficients A1-A7 are newly added in the flame surface database, and a new flame surface database is formed; and the thermochemical parameters of the numerical simulation calculation program are re-assigned. According to the database component simplification and reconstruction method suitable for the flame surface model, seven new coefficients are stored, a large amount of useless component information is deleted at the same time, the storage amount of a flame surface database is reduced, the interpolation calculation amount of components is reduced, and on the basis that the prediction precision of a combustion flow field is not reduced, the prediction efficiency is improved. And the calculation efficiency of the flame surface combustion model is improved.

Description

Technical Field

[0001] The present invention belongs to the fields of engine combustion and computational fluid dynamics, and particularly relates to a method for reducing and reconstructing database components applicable to a flamelet model. Background Art

[0002] With the development of computational fluid dynamics, the role of numerical simulation in the design process of engine combustion chambers has become increasingly prominent. It can shorten the R & D cycle and reduce R & D costs, but at the same time, it also poses high requirements for both the accuracy and efficiency of numerical simulation. The key to numerical simulation of combustion chambers is the interaction between turbulence and combustion. Since the flamelet combustion model decouples turbulent flow and chemical reactions, it greatly reduces the computational amount. At the same time, detailed chemical reaction kinetic mechanisms can be used to depict the details of combustion flow, and it has been widely applied to the design and evaluation of engine combustion chambers.

[0003] The flamelet combustion model needs to store the component values corresponding to different mixture fractions and reaction progress variables in the flamelet database in advance. During calculation, the mass fractions of each component are obtained by looking up tables and interpolating according to the flow field parameters of the local grid, and then the temperature and density are calculated based on the mass fractions of the components. Currently, the fuels used in engines are usually large-molecule hydrocarbon fuels, and their chemical reaction kinetic mechanisms are very complex. For example, aviation kerosene is used as fuel in aeroengines, and the number of components in its chemical reaction kinetic mechanism is greater than 200. At this time, the computational efficiency of the flamelet combustion model will be greatly affected. To address this problem, it is necessary to reduce and reconstruct the database of the flamelet model without affecting the overall prediction accuracy to improve the computational efficiency of the flamelet combustion model.

[0004] Currently, there is an urgent need to develop a method for reducing and reconstructing database components applicable to the flamelet model. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for reducing and reconstructing database components applicable to the flamelet model.

[0006] The method for reducing and reconstructing database components applicable to the flamelet model of the present invention includes the following steps: Step1. Specify the names of the components to be retained; Specify N 0 names of the components that need to be retained in the flamelet database Flamelet.dat as the judgment criteria for whether a component needs to be removed; Step2. Traverse the flamelet database and delete the non-retained components; Open the flamelet database Flamelet.dat and iterate through the names of all components. If a component name is the same as the reserved component name, retain this component and its corresponding parameters; if it is different from the reserved component name, delete this component and its corresponding parameters from the flamelet database Flamelet.dat and store this component and its corresponding parameters in the temporary database Temp.dat. Step3. Calculate the coefficients A 1 ~ A 7 ; Based on the data in the temporary database Temp.dat, solve the coefficients respectively by solving the system of equations A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 ; Step4. Add the coefficients to the flamelet database A 1 ~ A 7 , forming a new flamelet database; Add the coefficients A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 to the flamelet database Flamelet.dat, forming a new flamelet database Flamelet_new.dat; Step5. Reassign the thermochemical parameters of the numerical simulation calculation program; According to the order of the components in the new flamelet database Flamelet_new.dat file, reassign the thermochemical parameters of the numerical simulation calculation program to ensure one-to-one correspondence; the thermochemical parameters include the names of each component, as well as the molecular weights, thermodynamic coefficients, and transport coefficients corresponding to the names of each component.

[0007] Furthermore, the coefficients in Step3 described aboveA 1 ~ A 7 The calculation process is as follows: Step301. Determine that the key technical parameter of the flamelet combustion model is the component mass fraction; The flamelet combustion model calculates the temperature value by combining the component mass fraction with the enthalpy value, calculates the density by combining the component mass fraction with the molar mass, determines that the key technical parameter of the flamelet combustion model is the component mass fraction, and obtains the component mass fraction by looking up the table and interpolating in the flamelet database; Step302. Define the coefficient A 1 ~ A 6 , and give a method for solving the temperature of the gas mixture; The product of fuel and air combustion is a gas mixture. For a gas mixture containing n species of components, the enthalpy h and the enthalpy of each component h i and the mass fraction Y i have the following relationship: ; The enthalpy of a single component in the gas mixture and the temperature T have the following relationship: ; Among them, M i is the molar mass of component i , R u is the universal gas constant, is the fitting coefficient of component i ; Assume that the components with mass fractions retained in the flamelet database are 1, 2... N 0 , and the components with deleted mass fractions are N 0 +1, N 0 +2... n , combining equations (1) and (2), we get: ; Let ; Then ; It can be seen from equation (10) that only components 1, 2... need to be stored in the flamelet databaseN 0 Mass fraction and coefficient of A 1 and A 2 and A 3 and A 4 and A 5 and A 6 , the temperature of the gas mixture can be solved by the enthalpy of the gas mixture without storing the mass fractions of components N 0 +1, N 0 +2... n ; Step303. Define the coefficient A 7 , and give a method for solving the density of the gas mixture; For a gas mixture containing n components, there is the following relationship between the pressure p and the density ρ : ; Let ; Then ; As can be seen from equation (13), in the flamelet database, only the mass fractions of components 1, 2... N 0 and the coefficient A 7 need to be stored, and the density of the gas mixture can be solved by the pressure and temperature of the gas mixture without storing the mass fractions of components N 0 +1, N 0 +2... n ; Step304. Obtain the coefficients A 1 to A 7 ; According to equations (4)-(9) and (12), solve the coefficients A 1 , A 2 , A 3 , A 4 respectively,A 5 , A 6 , A 7 .

[0008] The method for database component reduction and reconstruction applicable to the flamelet model of the present invention reduces the storage amount of the flamelet database and the interpolation calculation amount of components by storing seven new coefficients and deleting a large amount of useless component information, and improves the calculation efficiency of the flamelet combustion model without reducing the prediction accuracy of the combustion flow field. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a flowchart of a method for database component reduction and reconstruction applicable to the flamelet model of the present invention; Figure 2 is a comparison curve of the radial temperature distribution coefficients at the combustor outlet obtained by two flamelet database construction methods. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below with reference to the drawings and embodiments.

[0011] As Figure 1 shown, the method for database component reduction and reconstruction applicable to the flamelet model of the present invention includes the following steps: Step1. Specify the names of the components to be retained; Specify N 0 component names to be retained in the flamelet database Flamelet.dat as the judgment criteria for whether a component needs to be removed; Step2. Traverse the flamelet database and delete non-retained components; Open the flamelet database Flamelet.dat and traverse the names of all components. If the name of a component is the same as the name of the retained component, then retain this component and the corresponding parameters; if it is different from the name of the retained component, then delete this component and the corresponding parameters in the flamelet database Flamelet.dat and store this component and the corresponding parameters in the temporary database Temp.dat; Step3. Calculate the coefficients A 1 ~ A 7 ; Based on the data in the temporary database Temp.dat, solve the coefficients A 1 , A 2 , A3 , A 4 , A 5 , A 6 , A 7 ; Step4. Add coefficients A 1 ~ A 7 to the flamelet database to form a new flamelet database; Add coefficients A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 to the flamelet database Flamelet.dat to form a new flamelet database Flamelet_new.dat; Step5. Reassign the thermochemical parameters of the numerical simulation calculation program; According to the order of the components in the new flamelet database Flamelet_new.dat file, reassign the thermochemical parameters of the numerical simulation calculation program to ensure one-to-one correspondence; the thermochemical parameters include the names of each component, as well as the molecular weights, thermodynamic coefficients, and transport coefficients corresponding to the names of each component.

[0012] Further, the calculation process of the coefficients A 1 ~ A 7 in Step3 is as follows: Step301. Determine that the key technical parameter of the flamelet combustion model is the component mass fraction; The flamelet combustion model calculates the temperature value by combining the component mass fraction with the enthalpy value, calculates the density by combining the component mass fraction with the molar mass. Determine that the key technical parameter of the flamelet combustion model is the component mass fraction, and obtain the component mass fraction by looking up the table and interpolating in the flamelet database; Step302. Define coefficients A 1 ~ A 6 , and give a method for solving the temperature of the gas mixture; The products of fuel and air combustion are a gas mixture. For a gas mixture containing n components, the enthalpy h and the enthalpy of each component h i and mass fraction Y i have the following relationship: ; The enthalpy of a single component in the gas mixture and the temperature T have the following relationship: ; Among them, M i is the molar mass of component i , R u is the universal gas constant, is the fitting coefficient of component i ; Assume that the components with mass fractions retained in the flamelet database are 1, 2... N 0 , and the components with mass fractions deleted are N 0 +1, N 0 +2... n . Combining equations (1) and (2), we get: ; Let ; Then ; From equation (10), it can be seen that in the flamelet database, only the mass fractions of components 1, 2... N 0 and the coefficients A 1 , A 2 , A 3 , A 4 , A 5 , A 6 need to be stored to achieve the solution of the temperature of the gas mixture through the enthalpy of the gas mixture, without storing the mass fractions of components N 0 +1, N 0 +2... n ; Step303. Define coefficients A 7 , and give a method for solving the density of gas mixtures; For a gas mixture containing n components, there is the following relationship between the pressure p and the density ρ : ; Let ; Then ; As can be seen from Equation (13), in the flamelet database, only the mass fractions of components 1, 2,... N 0 and the coefficient A 7 need to be stored, and the density of the gas mixture can be solved through the pressure and temperature of the gas mixture, without storing the mass fractions of components N 0 +1, N 0 +2... n ; Step304. Obtain the coefficients A 1 ~ A 7 ; According to Equations (4)-(9) and (12), solve the coefficients A 1 , A 2 , A 3 , A 4 , A 5 , A 6 , A 7 .

[0013] Example: In this example, a single-head combustor is used to test the method for reducing and reconstructing the database components applicable to the flamelet model of the present invention.

[0014] The combustion medium of the single-head combustor is aviation kerosene, and the calculation adopts a detailed mechanism with 203 components and 1592 chemical reactions; the method for reducing and reconstructing the database components applicable to the flamelet model in this example retains 10 components, namely: CO 2 , CO, H 2 O, O 2 , N 2, H 2 , CH 4 , OH, CH and CH 2 O; Among them, the first level is the main product, including CO 2 and H 2 O; The second level is the intermediate product, including CO, OH, CH, H 2 , CH 4 and CH 2 O; The third level is the oxidant, including O 2 and N 2 ; In this embodiment, the radial temperature distribution coefficient at the combustor outlet is calculated by the traditional flamelet database construction method and the database component reduction and reconstruction method applicable to the flamelet model of the present invention respectively.

[0015] The inflow conditions of the single-head combustor are shown in Table 1. To reduce the calculation amount, gaseous fuel is used during calculation, fuel atomization is ignored, and at the same time, the cooling holes of the flame tube are simplified. The total number of grids is about 1.3 million.

[0016] Table 1 Inflow conditions of single-head combustor

[0017] Figure 2 The comparison curve of the radial temperature distribution coefficient at the combustor outlet obtained by the two flamelet database construction methods is given. It can be seen that the results obtained by the two flamelet database construction methods are completely coincident, indicating that the database component reduction and reconstruction method applicable to the flamelet model of the present invention has no influence on the accuracy of numerical simulation.

[0018] Table 2 gives the numerical simulation time consumed by the two flamelet database construction methods. It can be seen that the database component reduction and reconstruction method applicable to the flamelet model of the present invention shortens the calculation time by about 20% compared with the traditional flamelet database construction method, and the calculation efficiency is higher.

[0019] Table 2 Comparison of calculation time

[0020] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. For those skilled in the art, without departing from the principle of the present invention, all the features disclosed by the present invention, or all the steps in the disclosed methods or processes, except for the mutually exclusive features and / or steps, can be combined in any way. The present invention is not limited to the specific details and the illustrated examples here.

Claims

1. A method for simplifying and reconstructing database components suitable for flame surface models, characterized in that: The database component simplification and reconstruction method comprises the following steps: Step1. Give the name of the retained component; Given N 0 component names that need to be retained in the flame surface database Flamelet.dat as a criterion for determining whether a component needs to be removed; Step 2. Traverse the flame surface database and delete non-retained components; Open the flame surface database Flamelet.dat, traverse the names of all components, if a component name is the same as the reserved component name, then retain this component and the corresponding parameters; if it is different from the reserved component name, then delete this component and the corresponding parameters in the flame surface database Flamelet.dat, and store this component and the corresponding parameters in the temporary database Temp.dat; Step 3. Calculate the coefficient A 1~ A 7; Based on the data in the temporary database Temp.dat, the coefficients are solved separately through the simultaneous equations. A 1. A 2. A 3. A 4. A 5. A 6. A 7; Step 4. Add coefficients to the flame surface database A 1~ A 7. Form a new flame surface database; Added new coefficients to the flame surface database Flamelet.dat A 1. A 2. A 3. A 4. A 5. A 6. A 7. Form a new flame surface database Flamelet_new.dat; Step 5. Reassign the thermochemical parameters of the numerical simulation calculation program; According to the order of components in the new flame surface database Flamelet_new.dat file, the thermochemical parameters of the numerical simulation calculation program are reassigned to ensure one-to-one correspondence; the thermochemical parameters include the name of each component, as well as the molecular weight, thermodynamic coefficient and transport coefficient corresponding to each component name.

2. The method for simplifying and reconstructing database components suitable for flame surface model according to claim 1, characterized in that: The coefficient of Step 3 A 1~ A The calculation process of 7 is as follows: Step 301. Determine the key technical parameter of the flame surface combustion model is the component mass fraction; The flame surface combustion model calculates the temperature value by combining the mass fraction of the component with the enthalpy value, and calculates the density by combining the mass fraction of the component with the molar mass. The key technical parameter of the flame surface combustion model is determined to be the mass fraction of the component, and the mass fraction of the component is obtained by interpolation through the flame surface database lookup table; Step 302. Define coefficients A 1~ A 6. Give a method for solving the temperature of a gas mixture; The product of combustion of fuel and air is a gas mixture. n enthalpy of a gas mixture of h The enthalpy of each component h i and quality score Y i There are the following relationships between them: ； Enthalpy and temperature of individual components in a gas mixture T There are the following relationships between them: ； in, M i For components i The molar mass of R u is the universal gas constant, For components i The fitting coefficient of Assume that the mass fraction components retained in the flame surface database are 1, 2, ... N 0, the mass fraction of the deleted components is N 0+1, N 0+2…… n , combining equations (1) and (2), we get: ； make ； but ； From equation (10), we can see that only components 1, 2, ... need to be stored in the flame surface database. N 0 mass fraction and coefficient A 1. A 2. A 3. A 4. A 5. A 6, the temperature of the gas mixture can be solved by the enthalpy of the gas mixture without storing the components N 0+1, N 0+2…… n The quality score of Step 303. Define coefficients A 7. Give a method to solve the density of gas mixture; For containing n Gas mixture of components, pressure p With density ρ There are the following relationships between them: ； make ； but ； From equation (13), we can see that only components 1, 2, ... need to be stored in the flame surface database. N 0 mass fraction and coefficient A 7. The density of the gas mixture can be solved by the pressure and temperature of the gas mixture without storing the components N 0+1, N 0+2…… n The quality score of Step 304. Obtain coefficients A 1~ A 7; According to equations (4)-(9) and (12), the coefficients are solved respectively A 1. A 2. A 3. A 4. A 5. A 6. A 7.

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