OpenModelica 中的流体计算

Question

我正在尝试建立我的水力计算库。我对管道模型有疑问。

这就是我的管道模型的样子：

model pipe_v0

import Modelica.Units.SI;

  parameter SI.Area muF = 8e-5;
  parameter SI.Density rho = 998;
  parameter SI.SpecificHeatCapacityAtConstantPressure cp = 4200;
  SI.Pressure dp;
  parameter Real dt = 10;

SI.MassFlowRate G;
SI.Pressure pin, pout;
SI.Temperature tin, tout;

  Port.port_b port_b annotation(
    Placement(transformation(origin = {-100, 0}, extent = {{-5, -5}, {5, 5}}), iconTransformation(origin = {-100, 0}, extent = {{-10, -10}, {10, 10}})));
  Port.port_a port_a annotation(
    Placement(transformation(origin = {100, 0}, extent = {{-5, -5}, {5, 5}}), iconTransformation(origin = {100, 0}, extent = {{-10, -10}, {10, 10}})));
equation
G = muF*sqrt(2*rho*dp);
 
  pout = pin - dp;
  tout = tin + dt;
  
  port_b.p = pin;
  port_a.p = pout;

  port_b.h = tin*cp;
  port_a.h = tout*cp;

port_b.m = G;
port_a.m = -G;

port_b.H + port_a.H = 0;

annotation(
    Icon(graphics = {Rectangle( lineColor = {144, 144, 144}, fillColor = {190, 190, 190}, fillPattern = FillPattern.HorizontalCylinder, extent = {{-100, 10}, {100, -10}})}));
end pipe_v0;

这些是我的边界条件模型：

model bound_PT
extends Librero.Sourse.bound_base;
import Modelica.Units.SI;

parameter SI.Pressure p;
parameter SI.Temperature T;
SI.SpecificHeatCapacityAtConstantPressure cp = 4200;

equation
port_a.p = p;
T = port_a.h/cp;

annotation(
    Diagram,
    Icon(graphics = {Text(origin = {13, -61}, rotation = 30, extent = {{-100, 20}, {100, -20}}, textString = "%name", fontName = "GOST Common")}));
end bound_PT;

还有另一个：

model bound_mH
extends Librero.Sourse.bound_base;
import Modelica.Units.SI;

parameter SI.MassFlowRate m;
parameter SI.EnthalpyFlowRate H;


equation
port_a.m = m;
port_a.H = H;

annotation(
    Diagram,
    Icon(graphics = {Text(origin = {45, -49}, rotation = 33, extent = {{-100, 20}, {100, -20}}, textString = "%name", fontName = "GOST Common")}));
end bound_mH;

当我尝试计算一根管道（一个管道模型由两个边界条件封闭）时，一切正常。 如果我想合并流量，以便根据水力特性划分质量流量，则计算会出现以下错误：

[1] 18:07:22 Symbolic Error An independent subset of the model has imbalanced number of equations (18) and variables (17). variables:

尽管当我检查模型时（参见图片），它告诉我一切都很好：

[1] 18:07:21 Scripting Notification Check of Librero.poligon.st completed successfully. Class Librero.poligon.st has 56 equation(s) and 56 variable(s). 37 of these are trivial equation(s).

问题模型图片

怎么了？感谢您的帮助:-)

更新#1 这是连接器代码：

connector port_base
  import Modelica.Units.SI;
    SI.Pressure p;
    SI.SpecificEnthalpy h;
    flow SI.MassFlowRate m;
    flow SI.EnthalpyFlowRate H;
end port_base;

对于连接器模型，我简单地应用

extends Librero.Port.port_base;

并画了一个图标

Answer 1

我尝试删除所有

h

和

H

相关方程，并且该模型有效（具有 2 个压力输入和 1 个质量流量输出）。因此，这表明问题与模型的热部分有关。不知怎的，我不知道如何用当前的建模来解决混合点上游的

H

问题。

经过进一步思考，我无法理解为什么要定义两个流变量，因为

port.H

将直接链接到

port.m

和

port.h

。基于

Modelica.Fluid.Interfaces.FluidPort

的东西不是更实用吗？

  connector FluidPort

  flow Medium.MassFlowRate m_flow "Mass flow rate from the connection point into the component";
  Medium.AbsolutePressure p "Thermodynamic pressure in the connection point";
  stream Medium.SpecificEnthalpy h_outflow "Specific thermodynamic enthalpy close to the connection point if m_flow < 0";

  end FluidPort;