A method for rapid component deletion and database reconstruction for flame surface model

Abstract

The present invention belongs to the field of engines and computational fluid dynamics, and discloses a method for rapid component deletion and database reconstruction applicable to a flame surface model, comprising the following steps: setting a threshold as a criterion for determining whether a component should be eliminated; comparing the relative size of the component mass fraction and the threshold, eliminating the component corresponding to the component mass fraction, and saving a new laminar flame surface database file after eliminating the component information; updating the chemical reaction kinetic mechanism file; and reconstructing the component information in the CFD program. The method for rapid component deletion and database reconstruction applicable to a flame surface model proposed by the present invention can automatically identify and eliminate components, update the flame surface database file and chemical reaction kinetic file after eliminating the components, and reconstruct the component information in the CFD program, effectively improving the calculation efficiency of the flame surface model without reducing the flow field prediction accuracy.

Description

Technical Field

[0001] The invention belongs to the field of engines and computational fluid dynamics, and in particular relates to a component rapid deletion and database reconstruction method suitable for a flame surface model. Background Art

[0002] In the process of aerospace power design and numerical evaluation, how to correctly simulate combustion is one of the key technical issues. The combustion process includes fuel injection, atomization, evaporation, fuel vapor / air mixing, ignition, flame propagation, etc. It involves the intersection of multiple disciplines such as chemistry, multiphase fluid mechanics, computational fluid dynamics, and combustion. It is a very complex multi-physical field coupling process, and it is very difficult to simulate accurately, reliably, and efficiently.

[0003] At present, a variety of combustion models have been developed, such as the EBU model, EDC model, linear vortex model, conditional moment model, flame surface model, PDF model (including set type and transport type) and finite rate method based on Arrehinues formula. Among them, the finite rate method and flame surface model are the most widely used. Compared with the finite rate method, the flame surface model can use any detailed chemical reaction kinetic mechanism to describe more detailed combustion details, and considers the turbulent combustion interaction. It has shown good application prospects in the field of engineering applications and has directly served the design and evaluation of aerospace engines. However, when the chemical reaction kinetic mechanism used is more complex (the number of components is greater than 200), the computational efficiency of the flame surface model will be greatly affected.

[0004] Currently, there is an urgent need to develop a method for rapid component deletion and database reconstruction suitable for flame surface models. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for rapid component deletion and database reconstruction applicable to a flame surface model.

[0006] The method for rapid component deletion and database reconstruction applicable to the flame surface model of the present invention comprises the following steps:

[0007] S10. Set a threshold As a criterion for whether a component should be removed;

[0008] Setting Thresholds , as a component The criteria for judging whether to remove the product;

[0009] S20. Compare component mass fractions With threshold The relative size of the components is eliminated. The corresponding components , save the new laminar flame surface database file FL_new.dat after removing the component information;

[0010] Open the laminar flame surface database file FL.dat. The laminar flame surface database file FL.dat contains the component names And the corresponding component mass fraction ; Compare the mass fraction of each component in turn With threshold The relative size of the component determines whether it is necessary to delete the component And the corresponding component mass fraction , until all components are judged;

[0011] The specific steps are as follows: , if in all combustion conditions, the components Quality score Both are less than the set threshold , then delete the component in the laminar flame database file FL.dat And the corresponding component mass fraction ; Traverse all components until all components are judged; then, save the laminar flame surface database file FL.dat as a new laminar flame surface database file FL_new.dat;

[0012] S30. Update the chemical reaction kinetics mechanism file Reaction.inp;

[0013] According to the component names in the new laminar flame surface database file FL_new.dat, update the chemical reaction kinetic mechanism file Reaction.inp. The specific steps are as follows:

[0014] Select the first component name in Reaction.inp, and check whether the chemical reaction kinetics mechanism file Reaction.inp is included in FL_new.dat. If it is included, go to the next component for judgment; if not, delete the first component name; traverse all components of the chemical reaction kinetics mechanism file Reaction.inp until the judgment is completed; finally, save the chemical reaction kinetics mechanism file Reaction.inp as a new chemical reaction kinetics mechanism file Reaction_new.inp;

[0015] S40. Reconstruct component information in the CFD program;

[0016] According to the component names and component order in the new chemical reaction kinetic mechanism file Reaction_new.inp, the component information in the CFD program is reconstructed. The specific steps are as follows:

[0017] Select the first component of the CFD program, and find out whether the first component of the CFD program is included in Reaction_new.inp. If it is included, the first component of the CFD program is retained, and the ranking of the first component of the CFD program in the CFD program is updated. The specific ranking is determined by the order of the first component of the CFD program in Reaction_new.inp. At the same time, the thermochemical parameters corresponding to the first component of the CFD program are synchronously introduced. If it is not included, the first component of the CFD program and the corresponding thermochemical parameters are deleted until all components of the CFD program are judged.

[0018] Furthermore, the thermochemical parameters include component atomic weight, thermodynamic coefficient and transport coefficient.

[0019] The component rapid deletion and database reconstruction method applicable to the flame surface model of the present invention can automatically identify and eliminate components, update the flame surface database file and chemical reaction kinetics file after the components are eliminated, and reconstruct the component information in the CFD program, thereby effectively improving the calculation efficiency of the flame surface model without reducing the flow field prediction accuracy.

[0020] The component rapid deletion and database reconstruction method applicable to the flame surface model of the present invention is fully automatic in processing, does not require manual intervention, has strong operability, and has engineering practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic flow chart of a method for rapid component deletion and database reconstruction applicable to a flame surface model of the present invention;

[0022] Figure 2 The pressure distribution diagram along the wall of the engine flow field predicted by three different mechanisms;

[0023] Figure 3 The pressure distribution diagram along the wall of the engine flow field predicted by three different mechanisms. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0025] Example: Figure 1 As shown, the method for rapid component deletion and database reconstruction applicable to the flame surface model of this embodiment includes the following steps:

[0026] S10. Set a threshold As a criterion for whether a component should be removed;

[0027] Setting Thresholds , as a component The criteria for judging whether to remove the product;

[0028] S20. Compare component mass fractions With threshold The relative size of the components is eliminated. The corresponding components , save the new laminar flame surface database file FL_new.dat after removing the component information;

[0029] Open the laminar flame surface database file FL.dat. The laminar flame surface database file FL.dat contains the component names And the corresponding component mass fraction ; Compare the mass fraction of each component in turn With threshold The relative size of the component determines whether it is necessary to delete the component And the corresponding component mass fraction , until all components are judged;

[0030] The specific steps are as follows: , if in all combustion conditions, the components Quality score Both are less than the set threshold , then delete the component in the laminar flame database file FL.dat And the corresponding component mass fraction ; Traverse all components until all components are judged; then, save the laminar flame surface database file FL.dat as a new laminar flame surface database file FL_new.dat;

[0031] S30. Update the chemical reaction kinetics mechanism file Reaction.inp;

[0032] According to the component names in the new laminar flame surface database file FL_new.dat, update the chemical reaction kinetic mechanism file Reaction.inp. The specific steps are as follows:

[0033] Select the first component name in Reaction.inp, and check whether the chemical reaction kinetics mechanism file Reaction.inp is included in FL_new.dat. If it is included, go to the next component for judgment; if not, delete the first component name; traverse all components of the chemical reaction kinetics mechanism file Reaction.inp until the judgment is completed; finally, save the chemical reaction kinetics mechanism file Reaction.inp as a new chemical reaction kinetics mechanism file Reaction_new.inp;

[0034] S40. Reconstruct component information in the CFD program;

[0035] According to the component names and component order in the new chemical reaction kinetic mechanism file Reaction_new.inp, the component information in the CFD program is reconstructed. The specific steps are as follows:

[0036] Select the first component of the CFD program, and find out whether the first component of the CFD program is included in Reaction_new.inp. If it is included, the first component of the CFD program is retained, and the ranking of the first component of the CFD program in the CFD program is updated. The specific ranking is determined by the order of the first component of the CFD program in Reaction_new.inp. At the same time, the thermochemical parameters corresponding to the first component of the CFD program are synchronously introduced. If it is not included, the first component of the CFD program and the corresponding thermochemical parameters are deleted until all components of the CFD program are judged.

[0037] Furthermore, the thermochemical parameters include component atomic weight, thermodynamic coefficient and transport coefficient.

[0038] This embodiment uses a certain engine combustion field to test the effect of the present invention.

[0039] The engine flow conditions and injection conditions are shown in Table 1.

[0040] Table 1

[0041]

[0042] In order to reduce the amount of calculation, two-dimensional calculation is adopted, the grid volume is about 57,000, the wall adopts adiabatic wall conditions, the combustion model adopts flame surface model, and the kerosene chemical reaction kinetic mechanism adopts three sets of mechanisms for comparative calculation; among them, the first set of mechanisms is the original mechanism, including 203 components and 1592 steps of detailed reaction mechanism, the second set of mechanisms and the third set of mechanisms are automatically generated by applying the component rapid deletion and database reconstruction method suitable for the flame surface model of the present invention, among which the threshold value set for the second set of mechanisms is , containing 102 components, the threshold value set by the third set of mechanisms , containing 80 components.

[0043] Figure 2 The pressure distribution along the wall of the engine flow field predicted by three different mechanisms is given. Figure 3 The pressure distribution along the wall of the engine flow field predicted by three different mechanisms is given. Figure 2 , Figure 3It can be seen that compared with the original mechanism, although the number of components in the second set of mechanisms is halved, the flow field prediction results of the CFD calculation program are almost the same; because more components are deleted in the third set of mechanisms, the number of retained components is only 1 / 3 of the original mechanism, resulting in some differences in the local area prediction results from the original mechanism, but this can also be ignored.

[0044] Table 2 shows the time-consuming comparison of the calculations using three different mechanisms. It can be seen that the calculation time using the first mechanism is 120 hours; the calculation time using the second mechanism is 39 hours; and the calculation time using the third mechanism is 18 hours. It can be seen that after applying the method for rapid component deletion and database reconstruction applicable to the flame surface model of the present invention, the calculation time of the engine combustion field is shortened to 1 / 7 to 1 / 3 of the original, but the calculation accuracy is almost unaffected, indicating that the method for rapid component deletion and database reconstruction applicable to the flame surface model of the present invention can improve the calculation efficiency of the flame surface simulation, which can be increased by nearly an order of magnitude at most, confirming the technical feasibility and good effect of the present invention.

[0045] Table 2

[0046]

[0047] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and the embodiments, and can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional improvements and modifications can be easily realized without departing from the principles of the present invention. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A method for rapid component deletion and database reconstruction suitable for flame surface model, characterized in that: The following steps are involved: S10. Set a threshold As a criterion for whether a component should be removed; Setting Thresholds , as a component The criteria for judging whether to remove the product; S20. Compare component mass fractions With threshold The relative size of the components is eliminated. The corresponding components , save the new laminar flame surface database file FL_new.dat after removing the component information; Open the laminar flame surface database file FL.dat. The laminar flame surface database file FL.dat contains the component names And the corresponding component mass fraction ; Compare the mass fraction of each component in turn With threshold The relative size of the component determines whether it is necessary to delete the component And the corresponding component mass fraction , until all components are judged; The specific steps are as follows: , if in all combustion conditions, the components Quality score Both are less than the set threshold , then delete the component in the laminar flame database file FL.dat And the corresponding component mass fraction ; Traverse all components until all components are judged; then, save the laminar flame surface database file FL.dat as a new laminar flame surface database file FL_new.dat; S30. Update the chemical reaction kinetics mechanism file Reaction.inp; According to the component names in the new laminar flame surface database file FL_new.dat, update the chemical reaction kinetic mechanism file Reaction.inp. The specific steps are as follows: Select the first component name in Reaction.inp, and check whether the chemical reaction kinetics mechanism file Reaction.inp is included in FL_new.dat. If it is included, go to the next component for judgment; if not, delete the first component name; traverse all components of the chemical reaction kinetics mechanism file Reaction.inp until the judgment is completed; finally, save the chemical reaction kinetics mechanism file Reaction.inp as a new chemical reaction kinetics mechanism file Reaction_new.inp; S40. Reconstruct component information in the CFD program; According to the component names and component order in the new chemical reaction kinetic mechanism file Reaction_new.inp, the component information in the CFD program is reconstructed. The specific steps are as follows: Select the first component of the CFD program, and find out whether the first component of the CFD program is included in Reaction_new.inp. If it is included, the first component of the CFD program is retained, and the ranking of the first component of the CFD program in the CFD program is updated. The specific ranking is determined by the order of the first component of the CFD program in Reaction_new.inp. At the same time, the thermochemical parameters corresponding to the first component of the CFD program are synchronously introduced. If it is not included, the first component of the CFD program and the corresponding thermochemical parameters are deleted until all components of the CFD program are judged.

2. A method for rapid component deletion and database reconstruction suitable for flame surface model according to claim 1, characterized in that: The thermochemical parameters include component atomic weight, thermodynamic coefficient and transport coefficient.

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