Method for Constructing a Medium Library for Dynamic Simulation of Liquid Rocket Engines Based on the Modelica Language

Abstract

The present invention relates to the simulation of liquid rocket engine systems, and mainly relates to a method for constructing a dynamic simulation medium library of liquid rocket engines based on the Modelica language. The purpose is to solve the technical problem that in the existing dynamic simulation of liquid rocket engines, there is a lack of a method for constructing a medium library that can cover various media involved in liquid rocket engines. Only by selecting the medium on the parameter panel can the physical properties be imported with one click. This method realizes the dynamic characteristic simulation of liquid rocket engines by establishing a complete medium library in the dynamic simulation model library, covering various media involved in liquid rocket engines, and only by selecting the medium on the parameter panel to realize the one-click import of component physical properties, separating the physical property library from the component model library. It is convenient and time-saving to operate, and can make the simulation results more reliable, providing a reference for subsequent engine scheme improvement and new model development.

Description

Technical Field

[0001] The present invention relates to the simulation of liquid rocket engine systems, mainly to a medium model library, and specifically to a method for constructing a dynamic simulation medium library of liquid rocket engines based on the Modelica language, which is applicable to the dynamic characteristic simulation of liquid rocket engines. Background Technique

[0002] The working media of liquid rocket engines involve liquids, gases, and combustion gases, and the temperature range involves normal temperature, low temperature, and high temperature. Adopting the modular modeling concept to construct a dynamic simulation model library of liquid rocket engines, and realizing the system model construction in a drag-and-drop modeling method for full-system simulation is one of the important means for improving the engine model scheme and developing new engines. However, when modeling using the modular modeling concept, it is necessary to set the physical properties of different components. If each component uses a single variable definition method such as density, viscosity, and thermal conductivity to set the physical properties, the modeling process will be extremely cumbersome. Therefore, there is an urgent need for a method for constructing a medium library for the dynamic simulation of liquid rocket engines, which can cover various media involved in liquid rocket engines, and components only need to select the medium on the parameter panel to achieve one-key import of physical properties. Summary of the Invention

[0003] The purpose of the present invention is to solve the technical problem that in the existing dynamic simulation of liquid rocket engines, there is a lack of a method for constructing a medium library that can cover various media involved in liquid rocket engines, and only by selecting the medium on the parameter panel, one-key import of physical properties can be achieved, and to provide a method for constructing a dynamic simulation medium library of liquid rocket engines based on the Modelica language.

[0004] To solve the above technical problems, the technical solution provided by the present invention is as follows:

[0005] A method for constructing a dynamic simulation medium library of liquid rocket engines based on the Modelica language is characterized in that it includes the following steps:

[0006] 1) Establish a physical property library in three layers:

[0007] The first layer is the data layer, which is used to store the physical properties of the medium in the standard environment; the data layer contains four types of basic data, namely liquid data, gas data, combustion product data, and solid propellant data;

[0008] The second layer is the method layer, which is used to configure the change function of the physical property in different temperature T and pressure p environments; the method layer corresponds to the data layer and contains the change functions of four types of media, namely the change function of liquid media, the change function of gas media, the change function of combustion product media, and the change function of solid propellant media;

[0009] The third layer is the instance layer. By calling the data layer and the method layer, the physical properties of the medium are instantiated as physical property options that can be directly called by the component library. The medium types included in the instance layer correspond one-to-one with the data layer and the method layer, corresponding to four types of media, namely liquid medium, gas medium, combustion product medium, and solid propellant medium.

[0010] 2) Associate the instance layer with the corresponding component models of the liquid rocket engine in the way of configuration items. The components corresponding to the component models include the component models of liquid components, gas components, thermal components, and solid propellant components. Configure liquid medium in the liquid components, gas medium in the gas components, combustion product medium in the thermal components, and solid propellant medium in the solid propellant components.

[0011] 3) Drag the component model into the modeling interface and select the medium in the parameter box. The instance layer of the physical property library will call the basic data of the selected medium in the data layer and the variation function in the method layer, assign the physical properties to the selected component model, and the obtained component model can be used for dynamic simulation.

[0012] Furthermore, in step 1), the liquid data includes the conventional liquid water and special liquid media used in liquid rockets. The special liquid media include nitrogen tetroxide, unsymmetrical dimethylhydrazine, methylhydrazine, nitric acid, liquid hydrogen, liquid oxygen, hydrazine, ethanol, liquid methane, ammonia, hydrogen peroxide, and kerosene. Define four physical property parameters, namely density rho, kinematic viscosity nu, bulk modulus of elasticity beta, and saturation vapor pressure p_vapour, of each liquid medium in its model under standard conditions.

[0013] Furthermore, in step 1), the gas data includes various gas media used in liquid rockets, including air, nitrogen, helium, hydrogen, oxygen, and methane. Define five physical property parameters, namely density rho, kinematic viscosity nu, specific heat at constant pressure Cp, gas constant Rg, and specific heat ratio kappa, of each gas medium in its model under standard conditions.

[0014] Furthermore, in step 1), the combustion product data includes five propellant combinations, namely nitrogen tetroxide - unsymmetrical dimethylhydrazine, nitrogen tetroxide - methylhydrazine, liquid oxygen - liquid hydrogen, liquid oxygen - kerosene, and liquid oxygen - methane. Configure three physical property parameters, namely gas constant Rg, specific heat ratio kappa, and temperature T, of each combustion product in its model during equivalent combustion.

[0015] Furthermore, in step 1), the solid propellant data includes the combustion parameters of solid propellant starters with two formulations. The solid propellant data refers to the combustion physical properties of solid propellant starters. Configure seven physical property parameters, namely density rho, burning rate coefficient a, pressure exponent n, gas constant Rg, constant pressure combustion temperature T, specific heat ratio kappa, and temperature sensitivity coefficient mu, of each solid propellant in its model.

[0016] Further, in step 2), in the variation function of the liquid medium, the input variables are defined as pressure p and temperature T, and the output variables are defined as density rho, kinematic viscosity nu, bulk modulus of elasticity beta, and saturation vapor pressure p_vapour. Then, a variation function of the output variables with respect to the input variables is constructed.

[0017] Further, in step 2), in the variation function of the gas medium, the input variables are defined as pressure p and temperature T, and the output variables are defined as density rho, kinematic viscosity nu, specific heat at constant pressure Cp, gas constant Rg, and specific heat ratio kappa. Then, a variation function of the output variables with respect to the input variables is constructed.

[0018] Further, in step 2), in the variation function of the combustion product medium, the input variables are defined as pressure p and mixture ratio Km, and the output variables are defined as gas constant Rg, specific heat ratio kappa, and temperature T. Then, a variation function of the output variables with respect to the input variables is constructed.

[0019] Further, in step 2), in the variation function of the solid propellant medium, only the output variables density rho, burning rate coefficient a, pressure exponent n, gas constant Rg, combustion temperature at constant pressure T, specific heat ratio kappa, and temperature sensitivity coefficient mu are defined, and the output variables are equal to the fixed values defined in the data layer.

[0020] The beneficial effects of the present invention compared with the prior art are as follows:

[0021] The method for constructing a dynamic simulation medium library of a liquid rocket engine based on the Modelica language provided by the present invention, by establishing a complete medium library in the dynamic simulation model library, covering various media involved in the liquid rocket engine, and only selecting the medium on the parameter panel to realize one-key import of component physical properties, separating the physical property library from the component model library, realizing the dynamic characteristic simulation of the liquid rocket engine, with convenient and time-saving operation, and making the simulation results more reliable, providing a reference for subsequent engine scheme improvement and new model development, overcoming the technical problem that when constructing a dynamic simulation model library of a liquid rocket engine based on the modular idea, the component model needs to configure physical properties for the adopted medium during system modeling, and establishing physical property variables in the component model makes the modeling process extremely cumbersome. Description of the Drawings

[0022] Figure 1 It is a dynamic simulation model of a liquid rocket engine generator based on the Modelica language of the present invention. Detailed Embodiments

[0023] The present invention will be further described below with reference to the embodiments.

[0024] A method for constructing a liquid rocket engine dynamic simulation medium library based on Modelica language includes the following steps:

[0025] 1) Establish a physical property library in three layers:

[0026] The first layer is the data layer (Data), which is used to store the physical properties of the medium under standard conditions (the physical properties stored here are the values ​​corresponding to the medium under standard pressure and temperature, which are constant values); the data layer contains four types of basic data, namely liquid data (LiquidData), gas data (GasData), combustion product data (CombustionProductsData) and solid gunpowder data (SolidData);

[0027] The liquid data covers conventional liquid water and special liquid media used in liquid rockets; the special liquid media include nitrogen tetroxide, unsymmetrical dimethyl hydrazine, methyl hydrazine, nitric acid, liquid hydrogen, liquid oxygen, hydrazine (hydrazine), ethanol, liquid methane, ammonia, hydrogen peroxide and kerosene, covering various liquid media used in liquid rockets, and can be expanded as needed; in the model of each liquid medium, four physical property parameters of density rho, kinematic viscosity nu, bulk elastic modulus beta and saturated vapor pressure p_vapour under standard conditions are defined, and the definitions of these four physical property parameters can meet the physical property configuration requirements of various liquid components in the dynamic simulation model;

[0028] The gas data covers various gas media used in liquid rockets, including air, nitrogen, helium, hydrogen, oxygen and methane, covering various gas media used in liquid rockets, and can be expanded as needed; in the model of each gas medium, five physical property parameters of density rho, kinematic viscosity nu, constant pressure specific heat capacity Cp, gas constant Rg and specific heat ratio kappa are defined under standard conditions. The definition of these five physical property parameters can meet the physical property configuration requirements of various gas components in the dynamic simulation model;

[0029] The combustion product data includes five propellant combinations, namely, dinitrogen tetroxide-uniform dimethyl hydrazine, dinitrogen tetroxide-methyl hydrazine, liquid oxygen-liquid hydrogen, liquid oxygen-kerosene, and liquid oxygen-methane. The combustion product data of the five propellant combinations cover various propellant combinations of liquid rocket engines in service and can be expanded as needed; in the model of each combustion product, three physical property parameters of the gas constant Rg, specific heat ratio kappa, and temperature T during equivalent combustion are configured; the definitions of these three physical property parameters can meet the calculation needs of the combustion process in the thermal component model;

[0030] The solid propellant data covers the media used in liquid rocket engines that currently adopt the propellant starter scheme, including the combustion parameters of solid propellant starters with two formulations and can be expanded as needed; the solid propellant data refers to the combustion physical properties of the solid propellant starter; in each solid propellant model, seven physical property parameters, namely density rho, burning rate coefficient a, pressure exponent n, gas constant Rg, constant pressure combustion temperature T, specific heat ratio kappa, and temperature sensitivity coefficient mu, are configured. The definitions of these seven physical property parameters can meet the physical property configuration requirements of the propellant starter in dynamic simulation;

[0031] The second layer is the method layer (PartialMedia), which is used to configure the variation function (input-output correspondence or two-dimensional interpolation table) of physical properties under different temperature T and pressure p environments. For example, to construct the variation function of liquid density with temperature and pressure, so as to obtain the calculation method of liquid density under different temperature and pressure environments); the method layer corresponds to the data layer, and the variation functions for four types of media are respectively the variation function of liquid medium (LiquidMedia), the variation function of gas medium (GasMedia), the variation function of combustion product medium (CombustionProductsMedia), and the variation function of solid propellant medium (SolidMedia);

[0032] In the liquid medium method (the variation function of the liquid medium), the input variables are defined as pressure p and temperature T, and the output variables are density rho, kinematic viscosity nu, bulk modulus of elasticity beta, and saturation vapor pressure p_vapour. Then, the variation function of the output variables with respect to the input variables is constructed;

[0033] In the gas medium method (the variation function of the gas medium), the input variables are defined as pressure p and temperature T, and the output variables are density rho, kinematic viscosity nu, specific heat at constant pressure Cp, gas constant Rg, and specific heat ratio kappa. Then, the variation function of the output variables with respect to the input variables is constructed;

[0034] In the combustion product medium method (the variation function of the combustion product medium), the input variables are defined as pressure p and mixture ratio Km, and the output variables are gas constant Rg, specific heat ratio kappa, and temperature T. Then, the variation function of the relationship between the output variables with respect to the input variables is constructed;

[0035] The change process of the physical properties of the solid propellant medium is not considered in the simulation. Therefore, in the solid propellant medium method (the variation function of the solid propellant medium), only the output variables density rho, burning rate coefficient a, pressure exponent n, gas constant Rg, constant pressure combustion temperature T, specific heat ratio kappa, and temperature sensitivity coefficient mu are defined, and the output variables are equal to the fixed values defined in the data layer;

[0036] The third layer is the instance layer (Media). By calling the data layer and the method layer, the physical properties of the medium are instantiated as physical property options that can be directly called by the component library. The types of media included in the instance layer correspond one-to-one with the data layer and the method layer, corresponding to four types of media, namely liquid media, gas media, combustion product media, and solid propellant media. For example, for the density physical property of the liquid oxygen medium in the instance layer, the constant value corresponding to the standard pressure and temperature is obtained by calling the data layer, and the calculation method of the density under different temperature and pressure environments is obtained by calling the instance layer. Finally, the physical properties of the instance layer are called by the component model, and the effect is that the liquid oxygen density of the component at the current temperature and pressure is calculated in real time.

[0037] 2) The instance layer is associated with the corresponding component models of the liquid rocket engine (such as Figure 1 the dynamic simulation model of the liquid rocket engine generator based on Modelica language in the present invention) in the form of configuration items. The components corresponding to the component models include the component models of liquid components, gas components, thermal components, and solid propellant components. Liquid media are configured in the liquid components, gas media are configured in the gas components, combustion product media are configured in the thermal components, and solid propellant media are configured in the pyrotechnic initiator (solid propellant component).

[0038] 3) Drag the component model into the modeling interface and select the medium in the parameter box. Once the medium is selected, the instance layer of the physical property library will call the basic data of the selected medium in the data layer and the change function in the method layer, and assign the physical properties to the selected component model. The obtained component model can be used for dynamic simulation.

[0039] Taking the combination of a certain combustion component and the physical property library as an example, the implementation method of the physical property library is described.

[0040] The first step: Establish the physical property library package file WorkingMedia;

[0041] The second step: Build the data layer in the physical property library package file WorkingMedia, including liquid data (LiquidData), gas data (GasData), combustion product data (CombustionProductsData), and solid propellant data (SolidData), a total of four categories. Define the physical property values of the medium under standard conditions;

[0042] Step 3: Construct the method layer corresponding to the data layer, including four categories: the method for liquid medium (LiquidMedia), the method for gas medium (GasMedia), the method for combustion product medium (CombustionProductsMedia), and the method for solid gunpowder medium (SolidMedia). Build the function of the change relationship between the output variables (physical property parameters) and the input variables (state parameters such as pressure, temperature, and mixing ratio), and obtain the calculation logic of the change of physical properties with state parameters.

[0043] Step 4: Rely on the method layer to instantiate the output instance layer, which also includes four categories: liquid medium (LiquidMedia), gas medium (GasMedia), combustion product medium (CombustionProductsMedia), and solid gunpowder medium (SolidMedia). The medium types included under each category also correspond one-to-one with the data layer and the method layer.

[0044] Step 5: Associate the instance layer with the component model in the form of configuration items. Configure the liquid medium in the liquid component, the gas medium in the gas component, the combustion product medium in the thermal component, and the solid gunpowder medium in the gunpowder initiator.

[0045] Step 6: Drag the component model into the modeling interface and select the medium in the parameter box. Once the medium is selected, the instance layer of the physical property library will call the basic data of the medium in the data layer and the input-output correspondence relationship in the method layer, assign the physical properties to the component model, and then dynamic simulation can be carried out.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. For those of ordinary professional skills in the art, the specific technical solutions recorded in the foregoing embodiments can be modified, or some of the technical features can be equivalently replaced. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions protected by the present invention.

Claims

1. A method for constructing a dynamic simulation medium library of a liquid rocket engine based on the Modelica language, characterized in that, It includes the following steps: 1) Establish a physical property library in three layers: The first layer is the data layer, which is used to store the physical properties of the medium under standard conditions; the data layer contains four types of basic data, namely liquid data, gas data, combustion product data, and solid propellant data; The liquid data includes the conventional liquid water and special liquid media used in liquid rockets; the special liquid media include dinitrogen tetroxide, unsymmetrical dimethylhydrazine, methylhydrazine, nitric acid, liquid hydrogen, liquid oxygen, hydrazine, ethanol, liquid methane, ammonia, hydrogen peroxide, and kerosene; four physical property parameters, namely density rho, kinematic viscosity nu, bulk modulus of elasticity beta, and saturated vapor pressure p_vapour, are defined in the model of each liquid medium under standard conditions; The gas data includes various gas media used in liquid rockets, including air, nitrogen, helium, hydrogen, oxygen, and methane; five physical property parameters, namely density rho, kinematic viscosity nu, specific heat at constant pressure Cp, gas constant Rg, and specific heat ratio kappa, are defined in the model of each gas medium under standard conditions; The combustion product data includes five propellant combinations, namely dinitrogen tetroxide-unsymmetrical dimethylhydrazine, dinitrogen tetroxide-methylhydrazine, liquid oxygen-liquid hydrogen, liquid oxygen-kerosene, and liquid oxygen-methane; three physical property parameters, namely gas constant Rg, specific heat ratio kappa, and temperature T, are configured in the model of each combustion product during equivalent combustion; The solid propellant data includes the combustion parameters of solid propellant starters with two formulations; the solid propellant data refers to the combustion physical properties of solid propellant starters; seven physical property parameters, namely density rho, burning rate coefficient a, pressure exponent n, gas constant Rg, combustion temperature at constant pressure T, specific heat ratio kappa, and temperature sensitivity coefficient mu, are configured in the model of each solid propellant; The second layer is the method layer, which is used to configure the variation function of physical properties under different temperature T and pressure p environments; the method layer corresponds to the data layer and includes the variation functions of four types of media, namely the variation function of liquid media, the variation function of gas media, the variation function of combustion product media, and the variation function of solid propellant media; The third layer is the instance layer. By calling the data layer and the method layer, the physical properties of the medium are instantiated as physical property options that can be directly called by the component library; the types of media included in the instance layer correspond one-to-one with the data layer and the method layer, corresponding to four types of media, namely liquid media, gas media, combustion product media, and solid propellant media; 2) Associate the instance layer with the corresponding component models of the liquid rocket engine in the form of configuration items. The components corresponding to the component models include the component models of liquid components, gas components, thermal components, and solid propellant components. Liquid media are configured in the liquid components, gas media are configured in the gas components, combustion product media are configured in the thermal components, and solid propellant media are configured in the solid propellant components; 3) Drag the component model into the modeling interface and select the medium in the parameter box. The instance layer of the physical property library will call the basic data of the selected medium in the data layer and the variation function in the method layer, assign the physical properties to the selected component model, and the obtained component model is used for dynamic simulation.

2. The method for constructing a dynamic simulation medium library of a liquid rocket engine based on the Modelica language according to claim 1, characterized in that: In step 2), define the input variables as pressure p and temperature T in the variation function of the liquid medium, and the output variables as density rho, kinematic viscosity nu, bulk modulus of elasticity beta, and saturation vapor pressure p_vapour, and then construct the variation function of the output variables with respect to the input variables.

3. The method for constructing a dynamic simulation medium library of a liquid rocket engine based on the Modelica language according to claim 2, characterized in that: In step 2), define the input variables as pressure p and temperature T in the variation function of the gas medium, and the output variables as density rho, kinematic viscosity nu, specific heat at constant pressure Cp, gas constant Rg, and specific heat ratio kappa, and then construct the variation function of the output variables with respect to the input variables.

4. The method for constructing a dynamic simulation medium library of a liquid rocket engine based on the Modelica language according to claim 3, characterized in that: In step 2), define the input variables as pressure p and mixture ratio Km in the variation function of the combustion product medium, and the output variables as gas constant Rg, specific heat ratio kappa, and temperature T, and then construct the variation function of the output variables with respect to the input variables.

5. The method for constructing a dynamic simulation medium library of a liquid rocket engine based on the Modelica language according to claim 4, characterized in that: In step 2), only define the output variables density rho, burning rate coefficient a, pressure exponent n, gas constant Rg, combustion temperature at constant pressure T, specific heat ratio kappa, and temperature sensitivity coefficient mu in the variation function of the solid propellant medium, and the output variables are equal to the fixed values defined in the data layer.

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