今天在搞一个项目中的关于气体成分的设置

Gas composition
H2 Vol% 31.48
N2 Vol% 0.15
CH4 Vol% 3.2
CO2 Vol% 18.80
CO Vol% 46.1
C2H6 Vol% 0.1
C2H2 Vol% 0.14
C3H8 Vol% 0.03
Gas yield Nm3/h 25
Density kg/m3 0.94

下面是在REFPROP中按照当前的组分设置的混合物的到的热物性，用作参考和对比。

image-20260327213117962

thermophysicalProperties文件的设置

根据你的solver支持的情况，可以使用banana大法，看一下你的ThermoType都支持什么配置。我支持如下配置

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type         mixture                    transport   thermo       equationOfState           specie  energy                  

heRhoThermo  homogeneousMixture         const       hConst       incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  homogeneousMixture         const       hConst       perfectGas                specie  sensibleEnthalpy        
heRhoThermo  homogeneousMixture         sutherland  janaf        incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  homogeneousMixture         sutherland  janaf        perfectGas                specie  sensibleEnthalpy        
heRhoThermo  inhomogeneousMixture       const       hConst       incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  inhomogeneousMixture       const       hConst       perfectGas                specie  sensibleEnthalpy        
heRhoThermo  inhomogeneousMixture       sutherland  janaf        incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  inhomogeneousMixture       sutherland  janaf        perfectGas                specie  sensibleEnthalpy        
heRhoThermo  multiComponentMixture      const       hConst       incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  multiComponentMixture      const       hConst       incompressiblePerfectGas  specie  sensibleInternalEnergy  
heRhoThermo  multiComponentMixture      const       hConst       perfectGas                specie  sensibleEnthalpy        
heRhoThermo  multiComponentMixture      const       hConst       perfectGas                specie  sensibleInternalEnergy  
heRhoThermo  multiComponentMixture      polynomial  hPolynomial  icoPolynomial             specie  sensibleEnthalpy        
heRhoThermo  multiComponentMixture      polynomial  hPolynomial  icoPolynomial             specie  sensibleInternalEnergy  
heRhoThermo  multiComponentMixture      sutherland  janaf        incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  multiComponentMixture      sutherland  janaf        incompressiblePerfectGas  specie  sensibleInternalEnergy  
heRhoThermo  multiComponentMixture      sutherland  janaf        perfectGas                specie  sensibleEnthalpy        
heRhoThermo  multiComponentMixture      sutherland  janaf        perfectGas                specie  sensibleInternalEnergy  
heRhoThermo  reactingMixture            const       hConst       incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  reactingMixture            const       hConst       incompressiblePerfectGas  specie  sensibleInternalEnergy  
heRhoThermo  reactingMixture            const       hConst       perfectGas                specie  sensibleEnthalpy        
heRhoThermo  reactingMixture            const       hConst       perfectGas                specie  sensibleInternalEnergy  
heRhoThermo  reactingMixture            polynomial  hPolynomial  icoPolynomial             specie  sensibleEnthalpy        
heRhoThermo  reactingMixture            polynomial  hPolynomial  icoPolynomial             specie  sensibleInternalEnergy  
heRhoThermo  reactingMixture            sutherland  janaf        incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  reactingMixture            sutherland  janaf        incompressiblePerfectGas  specie  sensibleInternalEnergy  
heRhoThermo  reactingMixture            sutherland  janaf        perfectGas                specie  sensibleEnthalpy        
heRhoThermo  reactingMixture            sutherland  janaf        perfectGas                specie  sensibleInternalEnergy  
heRhoThermo  singleStepReactingMixture  sutherland  janaf        perfectGas                specie  sensibleEnthalpy        
heRhoThermo  singleStepReactingMixture  sutherland  janaf        perfectGas                specie  sensibleInternalEnergy  
heRhoThermo  veryInhomogeneousMixture   const       hConst       incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  veryInhomogeneousMixture   const       hConst       perfectGas                specie  sensibleEnthalpy        
heRhoThermo  veryInhomogeneousMixture   sutherland  janaf        incompressiblePerfectGas  specie  sensibleEnthalpy        
heRhoThermo  veryInhomogeneousMixture   sutherland  janaf        perfectGas                specie  sensibleEnthalpy

每一个配置都是代表了什么具体可以去User Guide中查询

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/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  4.x                                   |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      thermophysicalProperties;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

thermoType
{
    type            heRhoThermo;
    mixture         reactingMixture;
    transport       sutherland;
    thermo          janaf;
    energy          sensibleEnthalpy;
    equationOfState perfectGas;
    specie          specie;
}

dpdt no;
chemistryReader foamChemistryReader;
foamChemistryFile "$FOAM_CASE/constant/reactions";
foamChemistryThermoFile "$FOAM_CASE/constant/thermo.incompressiblePoly";
inertSpecie     CO;

liquids
{
}

solids
{
}

然后我选择的是这个配置。为什么选择这个配置呢，因为每个transport 和thermo的计算方法都需要配置对应的foamChemistryThermoFile， OF的tutorial中只有部分气体或者液体的热物性配置而且使用的transport和thermo的方式也都不对应，这个困扰了我很久。然后我发现了下面这个库。这里面是通过chemkinToFoam 转换其他数据库到OF的格式的。所以我就直接在其中搜寻了我需要的气体的配置，然后就套在了我的模拟中。

1
https://github.com/ZhangYanTJU/chemicalMechanisms
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//- C12H26_Yaos54r269.OFthermo
H2
{
    specie
    {
        nMoles          1;
        molWeight        2.01594;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           3500;
        Tcommon         1000;
        highCpCoeffs    ( 3.3372792 -4.94024731e-05 4.99456778e-07 -1.79566394e-10 2.00255376e-14 -950.158922 -3.20502331 );
        lowCpCoeffs     ( 2.34433112 0.00798052075 -1.9478151e-05 2.01572094e-08 -7.37611761e-12 -917.935173 0.683010238 );
    }
    transport
    {
        As              6.362e-07;
        Ts              72;
    }
    elements
    {
        H               2;
    }
}

N2
{
    specie
    {
        nMoles          1;
        molWeight        28.0134;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           5000;
        Tcommon         1000;
        highCpCoeffs    ( 2.92664 0.001487977 -5.684761e-07 1.009704e-10 -6.753351e-15 -922.7977 5.980528 );
        lowCpCoeffs     ( 3.298677 0.00140824 -3.963222e-06 5.641515e-09 -2.444855e-12 -1020.9 3.950372 );
    }
    transport
    {
        As              1.512e-06;
        Ts              120;
    }
    elements
    {
        N               2;
    }
}

CH4
{
    specie
    {
        nMoles          1;
        molWeight        16.04303;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           3500;
        Tcommon         1000;
        highCpCoeffs    ( 0.074851495 0.0133909467 -5.73285809e-06 1.22292535e-09 -1.0181523e-13 -9468.34459 18.437318 );
        lowCpCoeffs     ( 5.14987613 -0.0136709788 4.91800599e-05 -4.84743026e-08 1.66693956e-11 -10246.6476 -4.64130376 );
    }
    transport
    {
        As              1.512e-06;
        Ts              120;
    }
    elements
    {
        C               1;
        H               4;
    }
}

CO2
{
    specie
    {
        nMoles          1;
        molWeight        44.00995;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           3500;
        Tcommon         1000;
        highCpCoeffs    ( 3.85746029 0.00441437026 -2.21481404e-06 5.23490188e-10 -4.72084164e-14 -48759.166 2.27163806 );
        lowCpCoeffs     ( 2.35677352 0.00898459677 -7.12356269e-06 2.45919022e-09 -1.43699548e-13 -48371.9697 9.90105222 );
    }
    transport
    {
        As              1.572e-06;
        Ts              240;
    }
    elements
    {
        C               1;
        O               2;
    }
}


CO
{
    specie
    {
        nMoles          1;
        molWeight        28.01055;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           3500;
        Tcommon         1000;
        highCpCoeffs    ( 2.71518561 0.00206252743 -9.98825771e-07 2.30053008e-10 -2.03647716e-14 -14151.8724 7.81868772 );
        lowCpCoeffs     ( 3.57953347 -0.00061035368 1.01681433e-06 9.07005884e-10 -9.04424499e-13 -14344.086 3.50840928 );
    }
    transport
    {
        As              1.512e-06;
        Ts              120;
    }
    elements
    {
        C               1;
        O               1;
    }
}


C2H6
{
    specie
    {
        nMoles          1;
        molWeight        30.07012;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           3500;
        Tcommon         1000;
        highCpCoeffs    ( 1.0718815 0.0216852677 -1.00256067e-05 2.21412001e-09 -1.9000289e-13 -11426.3932 15.1156107 );
        lowCpCoeffs     ( 4.29142492 -0.0055015427 5.99438288e-05 -7.08466285e-08 2.68685771e-11 -11522.2055 2.66682316 );
    }
    transport
    {
        As              1.512e-06;
        Ts              120;
    }
    elements
    {
        C               2;
        H               6;
    }
}

C2H2
{
    specie
    {
        nMoles          1;
        molWeight        26.03824;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           3500;
        Tcommon         1000;
        highCpCoeffs    ( 4.14756964 0.00596166664 -2.37294852e-06 4.67412171e-10 -3.61235213e-14 25935.9992 -1.23028121 );
        lowCpCoeffs     ( 0.808681094 0.0233615629 -3.55171815e-05 2.80152437e-08 -8.50072974e-12 26428.9807 13.9397051 );
    }
    transport
    {
        As              1.512e-06;
        Ts              120;
    }
    elements
    {
        C               2;
        H               2;
    }
}

//- Smookes-16r35
C3H8
{
    specie
    {
        nMoles          1;
        molWeight        44.09721;
    }
    thermodynamics
    {
        Tlow            200;
        Thigh           5000;
        Tcommon         1000;
        highCpCoeffs    ( 7.525217 0.01889034 -6.283924e-06 9.179373e-10 -4.81241e-14 -16464.55 -17.8439 );
        lowCpCoeffs     ( 0.8969208 0.02668986 5.431425e-06 -2.126001e-08 9.24333e-12 -13954.92 19.35533 );
    }
    transport
    {
        As              1.512e-06;
        Ts              120;
    }
    elements
    {
        C               3;
        H               8;
    }
}

inertSpecie 是用来归一化使用的，如果你的组分总和<1的话，会使用你设置的这个组分来填补剩下的部分，我这个case就是用CO来填补。

在reaction 文件中，你要设置参与模拟的species,例如我的情况：

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species
(
    air
    H2
    N2
    CH4
    CO2
    CO
    C2H6
    C2H2
    C3H8
);

reactions
{}

0文件夹中要添加的文件

  1. Ydefault field，具体原因还没有搞清
  2. 其余气体都要创建一个scalar field。

在第2步的情况有个坑！这里面每个组分的比例使用的并不是体积百分比，也不是摩尔比，而是质量比！

下面部分再次是用AI生成的

在你的 thermoType 设置中，密度的计算逻辑主要由 heRhoThermo 和 perfectGas 这两个关键字决定。

以下是 OpenFOAM 内部处理密度的具体机制：

1. 计算核心：perfectGas (状态方程)

当你指定了 equationOfState perfectGas; 时，OpenFOAM 会在代码层面调用理想气体状态方程。对于混合气体，每一单元格的密度 $\rho$ 计算公式如下：

$$\rho = \frac{p}{R_{mix} T}$$

其中：

  • $p$: 该网格的瞬时压力。
  • $T$: 该网格的瞬时温度。
  • $R_{mix}$: 混合气体的比气体常数。

2. $R_{mix}$ 的来源 (组分耦合)

由于你使用的是 reactingMixture，OpenFOAM 会根据各个组分（$H_2, CO, CO_2$ 等）的实时质量分数 ($Y_i$) 来计算混合物的比气体常数：

$$R_{mix} = \sum_{i} (Y_i \cdot R_i) = \sum_{i} \left( Y_i \cdot \frac{R_{u}}{M_i} \right)$$

  • $R_{u}$: 通用气体常数 ($8.31446 \text{ J/(mol}\cdot\text{K)}$)。
  • $M_i$: 组分 $i$ 的摩尔质量（即你在 chemkin/therm.dat 或 thermophysicalProperties 中定义的 molWeight）。

3. heRhoThermo 的特殊性

你选择的 type 是 heRhoThermo：

  • 这种模型通常用于可压缩流动。
  • 它直接将密度 $\rho$ 作为基本热物理变量进行更新（相对于 hePsiThermo 使用压缩性系数 $\psi$）。
  • 在求解器（如 reactingFoam）的每个时间步中，程序会先根据能量方程解出温度 $T$，然后立即调用 equationOfState（即上面的公式）来更新 $\rho$。

在 OpenFOAM 中，组分的密度并不是在一个单一的“地方”简单定义的，而是通过热物理模型库 (Thermophysical Models) 及其关联的状态方程 (Equation of State) 动态计算出来的。

具体到你的情况（多组分气体），密度的计算逻辑如下：

1. 核心计算位置：状态方程 (Equation of State)

OpenFOAM 通过 src/thermophysicalModels 文件夹下的代码执行计算。对于气体，最常用的模型是 perfectGas（理想气体状态方程）：

$$p = \rho R T$$

在代码层面，每一层（Cell）的密度 $\rho$ 是由该网格当前的压力 $p$、温度 $T$ 以及该网格内混合气体的气体常数 $R$ 计算得出的。

2. 关键参数：混合气体的 $R$ (Gas Constant)

这是你之前结果出错的症结所在。混合气体的 $R$ 是根据各组分的质量分数 ($Y_i$) 加权平均计算的：

$$R_{mix} = \sum (Y_i \cdot R_i) = \sum \left( Y_i \cdot \frac{R_{universal}}{M_i} \right)$$

其中 $M_i$ 是各组分的摩尔质量（分子量）。

  • 如果你输错了 $Y_i$（比如把体积比当成质量比）：$R_{mix}$ 就会算错。
  • 计算链条：输入 $Y_i \rightarrow$ 计算 $R_{mix} \rightarrow$ 结合 $P, T \rightarrow$ 计算 $\rho$。