CN117711511B - Mars gas finite rate chemical reaction model construction method and model data system - Google Patents
Mars gas finite rate chemical reaction model construction method and model data system Download PDFInfo
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Abstract
The invention discloses a Mars gas finite rate chemical reaction model construction method and a model data system, which belong to the field of aerodynamics and comprise the following steps: s1: normalizing the finite rate calculation formula; s2: constructing a sampling data set of a reverse reaction rate; s3: reconstructing an Arrhenius fitting coefficient of the reverse reaction rate; s4: reconstructing a Mars atmosphere MITCHELTREE chemical reaction model; s5: expanding a chemical model database and an I/O interface; s6: thermochemical unbalanced flow simulation and flow field acquisition based on Mars atmosphere MITCHELTREE improved model. The invention solves the problems of disordered calculation form, inconvenient use and difficult integration of the limited rate of the original MITCHELTREE chemical reaction model, and further establishes an improved Mars atmosphere MITCHELTREE chemical reaction model, and the new model has the advantages of high calculation and storage efficiency, unified interface design, simplicity, easiness in use and the like.
Description
Technical Field
The invention relates to the field of aerodynamics, in particular to a Mars gas finite rate chemical reaction model construction method and a model data system.
Background
The finite rate chemical reaction model has direct influence on the composition distribution of components in the real gas flow, and is a calculation model for accurately simulating the high hyperthermia chemical unbalanced flow and accurately predicting the aerodynamic thermal characteristics of the high hyperthermia chemical unbalanced flow. The different types of finite rate chemical reaction models have little difference in terms of the composition of the reaction formulas, but have obvious difference in terms of the calculation of the rate coefficients of the reaction formulas, which is also a main source of the calculation difference of the different types of chemical reaction models. At present, the expression form and the calculation mode of the chemical reaction rate coefficient mainly comprise two types, namely, the positive reaction rate coefficient and the reverse reaction rate coefficient are respectively expressed and calculated by adopting an Arrhenius empirical fit formula, and the positive reaction rate coefficient is expressed and calculated by adopting the Arrhenius empirical fit formula, but the reverse reaction rate coefficient is determined by calculating the ratio of the positive reaction rate coefficient to the equilibrium constant.
The mathematical expression modes of the balance constants are various, and the integration and expansion of the rate-limiting chemical reaction model are not facilitated, for example, when a new chemical model based on the balance constants is added, input/output module codes may need to be rewritten, even calculation modules such as chemical generation source items of a solver need to be changed, so that the method for expressing the reaction rate has poor adaptability and compatibility to the existing calculation framework of the hyperCFD software, and the function integration is complex. In contrast, in the first description method, the forward and reverse reaction rate coefficients are expressed and calculated by adopting Arrhenius experience fitting, so that the partial derivative calculation is simple, the programming is convenient to realize, the reading interface design is uniform, the chemical model expansion integration is convenient, and the like. The chemical reaction model constructed based on the method has high calculation and storage efficiency, and for any finite rate chemical reaction model, each reaction formula can completely express the finite rate calculation condition by only storing and reading 6 fixed parameter values. Therefore, most hyperCFD software adopts the method to design and construct a unified finite rate chemical model input/output interface.
In the original MITCHELTREE Mars atmospheric chemical reaction model, the inverse reaction rate coefficient of a part of reaction formulas is calculated by adopting an Arrhenius form, and the balance constant is calculated by adopting the other part, so that the confusion of the finite rate formulas in the expression forms brings a plurality of difficulties and inconveniences to the use integration of the chemical model, and therefore, an improved model with unified finite rate formulas, simplicity and easiness in use is needed to be constructed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a Mars gas limited rate chemical reaction model construction method and a model data system thereof, solves the technical problems of disordered limited rate calculation form, inconvenient use and difficult integration of an original MITCHELTREE chemical reaction model, and further establishes an improved Mars atmosphere MITCHELTREE chemical reaction model which has the advantages of high calculation and storage efficiency, unified interface design, simplicity, easiness in use and the like.
The invention aims at realizing the following scheme:
A Mars gas finite rate chemical reaction model construction method comprises the following steps:
S1: constructing a data set based on an original MITCHELTREE model, and standardizing a finite rate calculation formula by adopting Arrhenius fitting;
S2: constructing a sampling data set of the reverse reaction rate of the normalized finite rate calculation type;
s3: reconstructing an Arrhenius fitting coefficient of the reverse reaction rate based on the constructed data set;
s4: reconstructing a Mars atmosphere MITCHELTREE chemical reaction model by using the reconstructed coefficients to obtain a Mars atmosphere MITCHELTREE improved model;
S5: adding the Arrhenius fitting coefficient reconstructed by the chemical model into a chemical model database and expanding an I/O interface;
s6: based on step S5, a thermochemical unbalanced flow simulation based on the Mars atmosphere MITCHELTREE improved model and flow field acquisition are performed.
Further, in step S1, the constructing a dataset based on the original MITCHELTREE model, and normalizing the finite rate calculation formula by using an Arrhenius fitting method includes the following sub-steps: based on an original MITCHELTREE model, extracting all chemical reaction formulas to construct a new reaction formula dataset, wherein the positive and negative reaction rate coefficients of each chemical reaction formula are described by adopting an Arrhenius fitting formula to form a finite rate expression form with unified format specification.
Further, in step S2, the constructing the normalized sampling data set of the inverse reaction rate of the finite rate calculation formula includes the following sub-steps: based on an original MITCHELTREE model, extracting a reaction formula of a reverse reaction rate coefficient calculated by adopting a balance constant, respectively calculating a corresponding forward reaction rate and the balance constant according to the temperature interval step number, obtaining the reverse reaction rate according to the ratio of the forward reaction rate to the balance constant, and further establishing a sampling dataset of the reverse reaction rate.
Further, in step S3, reconstructing the inverse reaction rate Arrhenius fitting coefficient based on the constructed data set includes the following sub steps: based on the sampling data set in the step S2, three fitting curve types of an exponential function type, a power function type and a mixed type are adopted for a specified chemical reaction formula respectively, interpolation coefficients of each fitting formula are obtained according to least square interpolation, meanwhile, a best fitting curve is determined according to a mean square error minimum principle, and Arrhenius fitting formula coefficients of a reverse reaction rate are determined according to the best fitting curve.
Further, in step S4, the reconstructing the Mars atmospheric MITCHELTREE chemical reaction model by using the reconstructed coefficients includes the following sub-steps: and (3) reconstructing an improved Mars atmosphere MITCHELTREE chemical reaction model by adopting Arrhenius fitting coefficients obtained in the step S3 aiming at all chemical reaction formulas calculated by adopting equilibrium constants for the reverse reaction rate.
Further, in step S5, the adding the Arrhenius fitting coefficient after the chemical model reconstruction to the chemical model database and performing I/O interface expansion includes the sub-steps of: according to a standard and unified chemical model I/O interface module, adding Arrhenius fitting coefficients of all reaction formulas of the Mars atmosphere MITCHELTREE improvement model and positive and negative reaction rates into a chemical model database according to an array form, and adding corresponding I/O function interfaces for use by a high super CFD solver.
Further, in step S6, the developing a thermochemical unbalanced flow based on the Mars atmosphere MITCHELTREE improved model simulates its flow field acquisition, comprising the sub-steps of: in the hyperCFD solver, a chemical reaction generation source term is calculated based on an improved Mars atmosphere MITCHELTREE chemical reaction model, and parameters related to the concentration of flow field components are updated in a numerical iteration process until the flow field convergence condition is met, so that final required thermochemical unbalanced steady-state flow parameter distribution is obtained.
Further, in the reconstructed improved Mars atmosphere MITCHELTREE chemical reaction model, the inverse reaction rate Arrhenius fitting coefficients of chemical reaction formula R 1~R14 are respectively:
Wherein R 1~R14 represents a reaction formula, and A b、nb、Eb is respectively 3 coefficients of an Arrhenius fitting formula; in R 1~R10, the unit of the coefficient A b is Coefficient n b has no unit, coefficient E b has a unit of Kelvin K; for R 11~R14, the unit of coefficient A b is/>Coefficient n b has no units and coefficient E b has units of kelvin K.
A Mars gas finite rate chemical reaction model construction model data system comprising a computer program, the Mars gas finite rate chemical reaction model construction method according to any one of the preceding claims being implemented by running the computer program in a processor.
The beneficial effects of the invention include:
The improved Mars atmospheric MITCHELTREE chemical model adopts a standard and unified expression form aiming at the finite rate calculation, solves the problem of chaotic finite rate calculation form of the original model, is friendly to compatibility and adaptability of most hyperCFD software calculation frames, and is easy to be widely integrated and used.
The improved Mars atmosphere MITCHELTREE chemical model is described by Arrhenius fitting for the forward and reverse reaction rates, inherits the advantages of the Arrhenius fitting in numerical application, is simple in programming implementation when being adopted and used by the ultra CFD software, and has easy interface expansion and higher integration efficiency.
The reverse reaction rate reconstruction method provided by the invention is applicable to reconstruction of other chemical reaction models calculated by adopting equilibrium constants.
In the conception of the embodiment of the invention, 3 fitting curve types such as exponential function type, power function type and mixed type of exponent/power function are adopted, least square interpolation is adopted, and the least mean square error is selected as the best fitting curve for reconstructing Arrhenius fitting coefficients of reverse reaction rate, so that a limited rate chemical reaction model is reconstructed to meet the requirement of high-efficiency integrated use of high-super CFD software.
The improved Mars gas MITCHELTREE chemical reaction model constructed based on the method has the advantages of unified finite rate calculation formula, simplicity, easiness, compatibility and adaptability friendliness to most hyperCFD software and the like, can realize complete replacement of an original model in Mars atmospheric thermochemical unbalanced flow simulation, and can meet the requirements of engineering model simulation application in calculation accuracy.
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In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained according to these drawings without inventive faculty for a person skilled in the art.
FIG. 1 is a comparison of interpolation curves obtained by three different fitting methods according to equation 3 of the present invention;
FIG. 2 is a comparison of interpolation curves obtained by three different fitting methods according to equation 13 of the present invention;
FIG. 3 is a comparison of calculated wall pressure distribution of a two-primary chemical model and a modified chemical model according to an embodiment of the present invention;
FIG. 4 is a comparison of the calculated wall heat flow distribution of the original chemical model and the modified chemical model according to the second embodiment of the present invention.
Detailed Description
All of the features disclosed in all of the embodiments of this specification, or all of the steps in any method or process disclosed implicitly, except for the mutually exclusive features and/or steps, may be combined and/or expanded and substituted in any way.
The specific implementation process of the invention is as follows:
step S1, standardizing a finite rate calculation formula: based on an original MITCHELTREE model, extracting all chemical reaction formulas to construct a new reaction formula dataset, wherein the positive and negative reaction rate coefficients of each chemical reaction formula are described by adopting an Arrhenius fitting formula, so that a finite speed expression form with unified format specification, simplicity and easiness in use is formed.
The chemical reaction formula, forward/reverse reaction rate, equilibrium constant fitting coefficient, and trisomy collision coefficient of the original MITCHELTREE model are shown in tables 1, 2, and 3, respectively. It can be seen that the chemical reaction finite rate calculation form is more chaotic, the reaction formulas 1-14 adopt the combination of Arrhenius fitting formula and equilibrium constant, and the reaction formulas 15-24 respectively describe the Arrhenius fitting formula for the positive and the negative reaction rates, wherein the specific forms of the Arrhenius fitting formula and the equilibrium constant fitting formula are respectively as follows
(1)
Wherein the subscripts f and b are respectively indicative of a forward reaction and a reverse reaction, the subscript r is a chemical formula number, and the subscript eq is an abbreviation of equibrium. K f,r、Kb,r and K eq respectively represent the forward reaction rate, the reverse reaction rate and the equilibrium constant of the r reaction formula, and T is the temperature; a f,r、nf,r and E f,r are 3 coefficients of the forward reaction rate Arrhenius fit, respectively, and a b,r、nb,r and E b,r are 3 coefficients of the reverse reaction rate Arrhenius fit, respectively. In addition, B 1~B5 are 5 coefficients of a balance constant fitting type, and z=10000/T is a temporary parameter with respect to the temperature T, respectively. In the original MITCHELTREE model, specific values of the above coefficients can be seen in tables 1 and 2.
TABLE 1 original MITCHELTREE Mars gas 14 component 24 reaction chemistry model
TABLE 2MITCHELTREE equilibrium constant calculation parameters for Mars gas 14 component 24 reaction chemistry model
TABLE 3MITCHELTREE Mars gas 14 component 24 reaction chemistry model three-body Collision coefficient
Aiming at the problem that the chemical reaction finite rate calculation formula is confusing, the invention adopts a standardized and unified description mode to manage, namely, the forward/reverse reaction rates of all chemical reaction formulas are calculated and described by adopting an Arrhenius fitting formula. Therefore, the Arrhenius fitting coefficients in the gaps need to be filled for the chemical reaction formulas 1 to 14.
Step S2, constructing a sampling data set of a reverse reaction rate: based on an original MITCHELTREE model, extracting a reaction formula of a reverse reaction rate coefficient calculated by adopting a balance constant, respectively calculating a corresponding forward reaction rate and the balance constant according to the temperature interval step number, obtaining the reverse reaction rate according to the ratio of the forward reaction rate to the balance constant, and further establishing a sampling dataset of the reverse reaction rate.
For chemical reaction formulas 1-14, sampling calculation is performed in a temperature interval of 300-30000K, wherein the temperature values of the first 3 sample points are respectively 300K, 400K and 500K, then every 500K is taken, namely, the temperature values of the sample points are distributed in an arithmetic progression mode after 500K.
Based on the sample point temperature value mode, based on the coefficients given in tables 1 and 2, the forward reaction rate K f,r and the equilibrium constant K eq corresponding to the chemical reaction formula are calculated by adopting a formula (1), and then the reverse reaction rate K b,r=Kf,r/Keq is determined by adopting the ratio of the forward reaction rate K f,r to the equilibrium constant K eq.
And finally, constructing and generating an interpolation template data set based on the temperature sampling points according to the calculation result so as to be used for next interpolation calculation.
Step S3, reconstructing an Arrhenius fitting coefficient of the reverse reaction rate: based on a sampling data set, three fitting curve types including an exponential function type, a power function type, a mixed type and the like are adopted for a specified chemical reaction formula respectively, interpolation coefficients of each fitting formula are obtained according to least square interpolation, meanwhile, a best fitting curve is determined according to a mean square error minimum principle, and Arrhenius fitting formula coefficients of a reverse reaction rate are determined according to the best fitting curve.
And (3) respectively carrying out interpolation calculation by selecting 3 fitting curves such as an exponential function type, a power function type, a mixed type of an exponential/power function and the like based on the interpolation template data set in the step (S2). The expressions of the 3 target fitting curves of the exponential function type, the power function type, the mixed type and the like are respectively
(2)
Wherein x and y are independent variables and dependent variables respectively, and c 0~c2 is a fitting coefficient respectively. In the exponential fit, c 1 =0.0; in the power function type fitting equation, c 2 =0.0.
Secondly, a least square method is adopted to substitute a sample point temperature value T and a corresponding inverse reaction rate K b,r into a fitting mode, a linear equation set related to a coefficient c 1~c2 can be constructed and obtained, and a final coefficient c 1~c2 and a mean square error of a fitting curve can be obtained by adopting a Du Lite-mole decomposition method (Doolittle) to calculate. Taking chemical reaction formula 1 as an example, 3 curve fitting formulas obtained by using a least square method are respectively
(3)
In the middle ofIs the mean square error (used to describe the accuracy of the fitting method), defined as
(4)
Where N is the total number of sample points, and y i,real、yi,cal represents the actual value of sample point i and the value calculated using the fit equation, respectively.
And taking the smallest mean square value of the 3 calculated fitting curves as a target best fitting curve, and adopting the fitting curve to determine the Arrhenius fitting formula coefficient of the reverse reaction rate. The inverse reaction rate of equation 1 is then described as the best choice using a power function type fitting curve, and finally the Arrhenius fitting coefficient of its inverse reaction rate is determined as
(5)
Wherein c 1~c2 is an interpolation coefficient of a power function type fitting curve, and A b,r、nb,r and E b,r are inverse reaction rate Arrhenius fitting formula coefficients of reaction formula 1 respectively.
Step S4, reconstructing a Mars atmosphere MITCHELTREE chemical reaction model: and (3) aiming at all chemical reaction formulas of which the reverse reaction rate is calculated by adopting a balance constant, obtaining an Arrhenius fitting formula coefficient of the reverse reaction rate by adopting the step S3, and finally reconstructing to obtain an improved Mars atmosphere MITCHELTREE chemical reaction model.
And (3) aiming at chemical reaction formulas 2-14, processing by using the method in the step S3, and obtaining the Arrhenius fitting formula coefficients of the reverse reaction rates.
Finally, reconstructing a Mars atmosphere MITCHELTREE chemical reaction model, wherein the positive and negative reaction rates are calculated by adopting Arrhenius fitting, and the correlation coefficients are shown in Table 4.
TABLE 4 improved MITCHELTREE Mars gas 14 component 24 reaction chemistry model
Note that: the reverse reaction rate is obtained by least square interpolation.
Step S5, expanding a chemical model database and an I/O interface: according to the standard and unified chemical model I/O interface module design, adding the Arrhenius fitting coefficients of all reaction formulas of the improved model and the positive and negative reaction rates into a chemical model database according to an array form, and adding corresponding I/O function interfaces for use by a high super CFD solver.
Step S6, thermochemical unbalanced flow simulation and flow field acquisition based on Mars atmosphere MITCHELTREE improved model: in the hyperCFD solver, a chemical reaction generation source term is calculated based on an improved Mars atmosphere MITCHELTREE chemical reaction model, and related parameters such as flow field component concentration, transport coefficient and the like are updated in a numerical iteration process until the flow field convergence condition is met, so that final required thermochemical unbalanced steady-state flow parameter distribution is obtained.
The thermochemical unbalanced flow control equation related by the hyperCFD solver adopts a conservation integral form as
(6)
In the method, in the process of the invention,、/>Respectively representing the control body and the surrounding surface thereof, V is the unit volume of the control body, s is the area of the flow surface, n is the normal vector of the flow surface,/>To the incoming flow reynolds number. In addition, Q is a conservation vector, F, F v is a convection flux and a viscous flux, respectively, and W is an unbalanced source term.
The specific expressions of the constancy vector Q, the convection flux F, the viscous flux F v, and the unbalanced source term W are:
(7)
Wherein n= (n x,ny,nz) is the normal vector of the flow surface s, n x、ny、nz is the component of the normal vector n in the directions of the coordinate axes, The absolute velocity of the fluid is represented by u, v and w which are component values of the velocity in the directions of all coordinate axes respectively; c i、hi、eV,i、Di is mass fraction, specific enthalpy value, vibration energy and mass diffusion coefficient of each component i in the mixed gas respectively, i=1, 2, …, ns (ns is total number of the components of the mixed gas), ρ, p and T are density, pressure and temperature of the mixed gas respectively, H is total enthalpy of the mixed gas, E V and E are vibration energy and total internal energy of the mixed gas respectively, κ and κ V are translational mode heat conduction coefficient and vibration mode heat conduction coefficient of the mixed gas respectively, w i is a chemical reaction generation source item of the component i, and w V is a vibration unbalanced source item.
Furthermore, τ ij is the viscous stress tensor, τ xx、τyy、τzz、τxy、τxz、τyz is each component value of the viscous stress tensor, and u jτij satisfies:
(8)/>
where μ is the viscosity coefficient of the mixed gas, and u, v, and w are velocity component values of the velocity in three coordinate directions of the Cartesian coordinate system x, y, and z, respectively.
The specific association formula of the mixed gas energy system is as follows:
(9)
Wherein u, v and w are component values of the speed in directions of all coordinate axes, ρ, p, e and h are mixed gas density, pressure, total specific internal energy and enthalpy values, and e tr、eV is the kinetic energy and vibration energy of the mixed gas.
The calculation formula of the chemical reaction generation source term w i is as follows:
(10)
Wherein, the subscript r represents the number of the chemical reaction formula, the subscript i represents the number of the components, ns and nr are the total number of the components and the total number of the chemical reaction formula respectively, 、/>The stoichiometric coefficients of the component i in the r reaction formula in the forward and reverse reactions are respectively shown, M i is the molecular weight of the component i, ρ i is the density of the component i, and C r,i is the three-body collision coefficient of the component i in the r reaction formula. In addition, R r is the finite rate of the R-th reaction, and K r,f、Kr,b is the forward and reverse reaction rates of the R-th reaction, respectively. Here, K r,f、Kr,b was calculated using the Arrhenius fitting equation shown in formula (1), and the chemical reaction equation and its Arrhenius fitting equation coefficients are described in MITCHELTREE chemical reaction improvement model, as shown in table 4.
Finally, performing discrete and iterative solution by adopting an LU-SGS numerical format aiming at a thermochemical unbalanced flow control equation (6), and considering flow field calculation convergence when the average residual tends to be stable or reaches the maximum iterative step number, thereby obtaining various parameters of the chemical unbalanced steady flow, such as wall pressure distribution value, wall heat flow distribution value and the like. The LU-SGS numerical iteration format may be expressed as
(11)
In the formula, the superscript n represents the calculation time, the x represents the intermediate calculation amount, R is the right end term, L, D, U is a lower triangular matrix, a diagonal matrix and an upper triangular matrix respectively, deltaQ * is a temporary conservation amount increment, and DeltaQ n is a conservation amount increment calculated at the current n time.
It should be noted that, within the scope of protection defined in the claims of the present invention, the following embodiments may be combined and/or expanded, and replaced in any manner that is logical from the above specific embodiments, such as the disclosed technical principles, the disclosed technical features or the implicitly disclosed technical features, etc.
Example 1
The embodiment provides a Mars gas finite rate chemical reaction model construction method, which specifically comprises the following steps:
S1: constructing a data set based on an original MITCHELTREE model, and standardizing a finite rate calculation formula by adopting Arrhenius fitting;
S2: constructing a sampling data set of the reverse reaction rate of the normalized finite rate calculation type;
s3: reconstructing an Arrhenius fitting coefficient of the reverse reaction rate based on the constructed data set;
S4: reconstructing a Mars atmosphere MITCHELTREE chemical reaction model by using the reconstructed coefficients;
S5: adding the Arrhenius fitting coefficient reconstructed by the chemical model into a chemical model database and expanding an I/O interface;
s6: based on step S5, a thermochemical unbalanced flow simulation based on the Mars atmosphere MITCHELTREE improved model and flow field acquisition are performed.
The method of the embodiment is used for determining Arrhenius fitting coefficients of limited rate of a chemical model of Mars gas MITCHELTREE. Original Mars gas MITCHELTREE chemical model reference "Mitcheltree R A, Gnoffo P A. Wake Flow about a MESUR Mars Entry Vehicle. 6th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, AIAA-94-1958; 1994: 1-11.", Mars gas Park chemical model reference "Liu Qingzong. The detector enters numerical simulation of Mars atmospheric thermochemical unbalanced flow field [ D ]. Mianyang: china's aerodynamic research and development center research institute's major institute paper 2016:22-23 '. Sample point collection is carried out according to the sequence of 300, 400, 500, 1000, 1500, …, 25500 and 30000 in the temperature interval of 300-30000K, and meanwhile, the reverse reaction rate of the sampling points is obtained by calculating the forward reaction rate and the equilibrium constant of the original MITCHELTREE model. Based on the sampling point data sets of chemical reaction formulas 3 and 13, 3 fitting curves such as an exponential function type, a power function type, a mixed type of exponent/power function and the like are selected for interpolation calculation respectively.
Example 2
The embodiment provides a Mars gas finite rate chemical reaction model construction model data system, which is used for running the following steps:
S1: constructing a data set based on an original MITCHELTREE model, and standardizing a finite rate calculation formula by adopting Arrhenius fitting;
S2: constructing a sampling data set of the reverse reaction rate of the normalized finite rate calculation type;
s3: reconstructing an Arrhenius fitting coefficient of the reverse reaction rate based on the constructed data set;
S4: reconstructing a Mars atmosphere MITCHELTREE chemical reaction model by using the reconstructed coefficients;
S5: adding the Arrhenius fitting coefficient reconstructed by the chemical model into a chemical model database and expanding an I/O interface;
S6: based on step S5, a thermochemical unbalanced flow simulation based on the Mars atmosphere MITCHELTREE improved model and flow field acquisition are performed. The method is applied to a hypersonic CFD solver, and hypersonic thermochemical unbalanced flow simulation is carried out based on a Mars detector MESUR head cap model. Computational methods of the hyperCFD solver reference "Li Peng, chen Jianjiang, ding Mingsong, et al, LENS wind tunnel test return model aerodynamic thermal characteristics simulation, aviation journal, 42 (S1): 726400", computational model and experimental condition reference "Mitcheltree R A, Gnoffo P A. Wake Flow about a MESUR Mars Entry Vehicle. 6thAIAA/ASME Joint Thermophysics and Heat Transfer Conference, AIAA-94-1958; 1994: 1-11.". numerical simulation employ thermodynamic two temperature model and Mars gas 8-component chemistry model, convection flux selection Steger format and Vanalbada limiter, CFL number 200, wall condition radiation balance wall and carbon dioxide complete catalysis conditions (emissivity coefficient) =0.78), 16-Kernel parallel iteration steps 40000 steps.
FIG. 1 shows, based on example one, a comparison of interpolated curves for equation 3 using three different fitting methods, wherein the abscissa represents temperature in Kelvin (K); the ordinate indicates the reaction rate in cubic centimeters per square mole per second). It can be seen that the calculated curve of the hybrid fit matches the sample point values best, so the Arrhenius fit coefficients of the inverse reaction rate are determined using the hybrid fit coefficients. Compared with the power function type fitting coefficient adopted by the spark gas Park chemical model, the finite rate chemical model construction method provided by the invention is more comprehensive and reasonable, and the obtained inverse reaction rate Arrhenius fitting coefficient is more accurate.
FIG. 2 shows, based on example one, a comparison of interpolated curves for equation 13 using three different fitting methods, wherein the abscissa represents temperature in Kelvin (K); the ordinate indicates the reaction rate in cubic centimeters per mole per second). It can be seen that the calculated curve of the hybrid fitting type accords with the sample point value best, and the reliability of the finite rate chemical model construction method provided by the invention is further proved.
FIG. 3 shows, based on example two, a comparison of the calculated wall pressure distribution of the original chemical model and the modified chemical model, wherein the abscissa represents the arc length, i.e. the value of the length along the streamline of the model surface calculated from the standing point, in meters (m); the ordinate indicates the pressure in kilopascals (kPa). It can be seen that the calculated pressure distribution of the improved chemical model is consistent with that of the original model, and the effectiveness and the reliability of the MITCHELTREE chemical reaction improved model provided by the invention are proved, so that the requirements of the Mars atmospheric thermochemical unbalanced flow simulation can be met.
FIG. 4 shows, based on example two, a comparison of the calculated wall heat flow distribution of an original chemical model and a modified chemical model, wherein the abscissa represents the arc length, i.e. the value of the length along the streamline of the model surface calculated from the standing point, in meters (m); the ordinate indicates the heat flux density in watts per square centimeter (W/cm 2). It can be seen that the calculated heat flux density value of the improved chemical model is identical to that of the original model, and further shows that MITCHELTREE chemical reaction improved model does not influence the calculation result of Mars gas chemical reaction flow, so that the substitution of the original chemical model can be realized, and the requirements of integrated use of a hyperCFD solver and the simulation of Mars atmospheric thermochemical unbalanced flow can be met.
The units involved in the embodiments of the present invention may be implemented by software, or may be implemented by hardware, and the described units may also be provided in a processor. Wherein the names of the units do not constitute a limitation of the units themselves in some cases.
According to an aspect of embodiments of the present invention, there is provided a computer program product or computer program comprising computer instructions stored in a computer readable storage medium. The computer instructions are read from the computer-readable storage medium by a processor of a computer device, and executed by the processor, cause the computer device to perform the methods provided in the various alternative implementations described above.
As another aspect, the embodiment of the present invention also provides a computer-readable medium that may be contained in the electronic device described in the above embodiment; or may exist alone without being incorporated into the electronic device. The computer-readable medium carries one or more programs which, when executed by the electronic device, cause the electronic device to implement the methods described in the above embodiments.
Claims (6)
1. The method for constructing the Mars gas limited rate chemical reaction model is characterized by comprising the following steps of:
S1: constructing a data set based on an original MITCHELTREE model, and standardizing a finite rate calculation formula by adopting Arrhenius fitting;
In step S1, the constructing a data set based on the original MITCHELTREE model, and normalizing a finite rate calculation formula by using an Arrhenius fitting formula, including the following sub steps: based on an original MITCHELTREE model, extracting all chemical reaction formulas to construct a new reaction formula dataset, wherein the positive and negative reaction rate coefficients of each chemical reaction formula are described by adopting an Arrhenius fitting formula to form a finite rate expression form with unified format specification;
S2: constructing a sampling data set of the reverse reaction rate of the normalized finite rate calculation type;
In step S2, the constructing a sampling dataset of the inverse reaction rate of the normalized finite rate calculation formula includes the following sub-steps: based on an original MITCHELTREE model, extracting a reaction formula of a reverse reaction rate coefficient calculated by adopting a balance constant, respectively calculating a corresponding forward reaction rate and the balance constant according to the temperature interval step number, obtaining the reverse reaction rate according to the ratio of the forward reaction rate to the balance constant, and further establishing a sampling dataset of the reverse reaction rate;
s3: reconstructing an Arrhenius fitting coefficient of the reverse reaction rate based on the constructed data set;
In step S3, reconstructing the inverse reaction rate Arrhenius fitting coefficient based on the constructed data set, including the sub-steps of: based on the sampling data set in the step S2, respectively adopting three fitting curve types of an exponential function type, a power function type and a mixed type for a specified chemical reaction formula, obtaining an interpolation coefficient of each fitting formula according to least square interpolation, simultaneously determining a best fitting curve according to a mean square error minimum principle, and determining an Arrhenius fitting formula coefficient of a reverse reaction rate according to the best fitting curve;
s4: reconstructing a Mars atmosphere MITCHELTREE chemical reaction model by using the reconstructed coefficients to obtain a Mars atmosphere MITCHELTREE improved model;
S5: adding the Arrhenius fitting coefficient reconstructed by the chemical model into a chemical model database and expanding an I/O interface;
s6: based on step S5, a thermochemical unbalanced flow simulation based on the Mars atmosphere MITCHELTREE improved model and flow field acquisition are performed.
2. The method for constructing a finite rate chemical reaction model of Mars gas according to claim 1, wherein in step S4, the reconstructing a Mars atmospheric MITCHELTREE chemical reaction model using the reconstructed coefficients comprises the sub-steps of: and (3) reconstructing an improved Mars atmosphere MITCHELTREE chemical reaction model by adopting Arrhenius fitting coefficients obtained in the step S3 aiming at all chemical reaction formulas calculated by adopting equilibrium constants for the reverse reaction rate.
3. The method for constructing a finite-rate chemical reaction model of Mars gas according to claim 1, wherein in step S5, the step of adding the Arrhenius fitting coefficients after the reconstruction of the chemical model into a chemical model database and expanding the I/O interface comprises the following sub-steps: according to a standard and unified chemical model I/O interface module, adding Arrhenius fitting coefficients of all reaction formulas of the Mars atmosphere MITCHELTREE improvement model and positive and negative reaction rates into a chemical model database according to an array form, and adding corresponding I/O function interfaces for use by a high super CFD solver.
4. A method of constructing a finite rate chemical reaction model of Mars gas according to claim 3, wherein in step S6, said developing a thermochemical unbalanced flow based on the improved model of Mars atmosphere MITCHELTREE simulates its flow field acquisition, comprising the sub-steps of: in the hyperCFD solver, a chemical reaction generation source term is calculated based on an improved Mars atmosphere MITCHELTREE chemical reaction model, and parameters related to the concentration of flow field components are updated in a numerical iteration process until the flow field convergence condition is met, so that final required thermochemical unbalanced steady-state flow parameter distribution is obtained.
5. The method for constructing a finite rate chemical reaction model of Mars gas according to claim 2, wherein in the reconstructed modified Mars atmosphere MITCHELTREE chemical reaction model, the inverse reaction rate Arrhenius fitting coefficients of chemical reaction formula R 1~R14 are respectively:
Wherein R 1~R14 represents a reaction formula, and A b、nb、Eb is respectively 3 coefficients of an Arrhenius fitting formula; in R 1~R10, the unit of the coefficient A b is Coefficient n b has no unit, coefficient E b has a unit of Kelvin K; for R 11~R14, the unit of coefficient A b is/>Coefficient n b has no units and coefficient E b has units of kelvin K.
6. A system for constructing a model data of a finite-rate chemical reaction model of Mars gas, which is characterized by comprising a computer program, wherein the computer program is used for realizing the method for constructing the finite-rate chemical reaction model of Mars gas according to any one of claims 1-5 when running in a processor.
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