Full-system flow field performance simulation method for engine high-altitude simulation test

Abstract

The invention relates to a full-system flow field performance simulation method for an engine high-altitude simulation test, and mainly solves the technical problem that the real performance of a test system cannot be accurately obtained by an existing method. The method comprises the following steps: (1) performing simulation calculation on the stability of high-altitude simulation work of the engine; (2) performing simulation calculation on high-altitude simulation cooling characteristic distribution of the engine; (3) simulation calculation of high-altitude simulation working characteristics of the engine under different working conditions is completed; and (4) optimizing the design scheme of the test system according to the simulation result, and realizing the simulation analysis of the flow field performance of the whole system of the high-altitude simulation test of the engine. Through the method, the accuracy and feasibility of the test system scheme can be comprehensively and accurately analyzed, so that the correctness of the overall scheme of the engine high-altitude simulation test system is verified, the performance requirements of the test system are ensured, and finally engine test task assessment is completed.

Description

Technical Field

[0001] The invention relates to a liquid rocket engine environmental simulation test method, and in particular to a full-system flow field performance simulation method for an engine high-altitude simulation test. Background Art

[0002] The engine high-altitude simulation test system (hereinafter referred to as the "test system") consists of a vacuum chamber, a diffuser, a water spray cooler, a tube bundle cooler, and a steam injection system of a steam jet pump group. When conducting a high-altitude simulation test, the gas at the engine nozzle injection point passes through the diffuser, gas collection chamber, and tube bundle cooler of the test system in turn, and then is injected and pressurized to mix with water vapor in the jet pump, and finally discharged into the atmosphere through the jet pump injection. In this process, the supersonic airflow of the steam injection system needs to suck the pressure in the vacuum chamber to a certain vacuum degree (less than one atmosphere) before the engine nozzle works, so as to ensure the vacuum pressure requirements of the vacuum chamber; at the same time, the flight altitude of the engine is simulated to accurately evaluate its flight performance and consistency between the sky and the earth. Therefore, before conducting the engine high-altitude simulation test, it is necessary to ensure the feasibility of the overall plan of the test system.

[0003] In order to verify the feasibility and correctness of the overall plan of the engine high-altitude simulation test system, a simulation analysis method is usually used for comprehensive evaluation. The existing analysis method generally adopts a single-device simulation analysis method, that is, a single device in the test system is simulated and calculated separately, so as to infer the accuracy and feasibility of the overall plan of the test system. However, since this method lacks consideration of the boundary conditions of each device and a comprehensive analysis of the interaction between each device, it is easy to have inaccurate input conditions, which leads to errors and even large deviations between the results of the simulation analysis and the actual performance parameters of the test system, and ultimately the actual performance of the test system cannot be accurately obtained. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the existing method cannot accurately obtain the real performance of the test system, and to provide a method for simulating the flow field performance of the entire system of an engine high-altitude simulation test.

[0005] To achieve the above objectives, the technical solutions provided by the present invention are:

[0006] A method for simulating flow field performance of the entire system of an engine high-altitude simulation test, which is special in that it includes the following steps:

[0007] Step [1]: Establish a component model based on the composition of the fuel gas, calculate the input conditions, boundary conditions, and environmental parameters of the fuel gas flow process and pressure field of the engine steady-state working model, and then use the fluid mechanics calculation software to complete the simulation calculation of the engine high-altitude simulated working stability;

[0008] Step [2], based on the simulation calculation results of step [1], a discrete phase model is used to perform numerical simulation calculation on the process of mixing and cooling the gas and cooling water, thereby completing the simulation calculation of the distribution of the engine's high-altitude simulated cooling characteristics;

[0009] Step [3], according to the method of step [1] to step [2], respectively complete the simulation calculation of the engine high altitude simulation working characteristics under different working conditions; the different working conditions include different engine combustion chamber working pressures, different engine water spray cooling flow rates, different jet pump outlet pressures, different diffuser outlet pressures, and different plenum working pressures;

[0010] Step [4]: ​​Optimize the design of the engine high-altitude simulation test system based on the simulation results of step [3], and then realize the simulation analysis of the flow field performance of the entire system of the engine high-altitude simulation test.

[0011] Furthermore, step [1] is specifically as follows:

[0012] 1.1. Establish a component model based on the composition of the fuel gas, calculate and analyze the heat exchange between the fuel gas and cooling water, and obtain the input conditions of the engine steady-state analysis model;

[0013] 1.2. Based on step 1.1, the boundary conditions of the engine steady-state analysis model are calculated by combining the engine's fuel combustion process, interlayer cooling, gas heat exchange process, engine ejection, startup and shutdown states;

[0014] 1.3. On the basis of step 1.2, based on the shock wave effect and the axial symmetry of the gas flow field and the temperature field distribution, the environmental parameters of the gas flow process are calculated using the one-dimensional isentropic flow theory; the environmental parameters include the viscosity coefficient of the gas flow and the diffusion flux of each gas component;

[0015] 1.4. Input the input conditions obtained in step 1.1, the boundary conditions obtained in step 1.2, and the environmental parameters obtained in step 1.3 into the fluid mechanics calculation software to realize the simulation calculation of the engine's high-altitude simulated working stability.

[0016] Furthermore, in step 1.3, the calculation formula of the dynamic viscosity coefficient u of the gas flow is:

[0017]

[0018] Where ρ represents the gas density; k represents the turbulent kinetic energy of the gas; ε represents the turbulent dissipation rate; C u represents the model constant;

[0019] The calculation formula for the diffusion flux of each gas component is:

[0020]

[0021] Among them, J i is the diffusion flux of the i-th substance, i represents the number of gas components, i≥1; D i,m is the mass diffusion coefficient of the ith substance; u i is the turbulent dynamic viscosity coefficient of the i-th substance; Sc t is the Schmidt number of the i-th substance, which is defined as the ratio of the dynamic viscosity coefficient to the diffusion coefficient; △Y i is the mass fraction change of the ith substance; D T,i is the thermal diffusion coefficient of the ith substance; △T is the change in gas temperature, T is the temperature required for gas diffusion; t represents the time for gas diffusion.

[0022] Furthermore, in step 1.4, the fluid mechanics calculation software uses a component transport model for calculation and sets additional boundary conditions, wherein the additional conditions include the engine nozzle active ejector inlet, the diffuser outlet, the central axis and the no-slip wall, wherein the diffuser outlet leads to the atmosphere and the rest is set as the wall.

[0023] Furthermore, step [2] is specifically as follows:

[0024] 2.1. The gas flow field is obtained by using the standard k-ε turbulence model based on density basis, and the water spray cooling device of the test system is simulated by using the discrete phase model;

[0025] 2.2. Based on the simulation calculation results of step [1], the two-phase mixing and cooling process of gas and cooling water is numerically simulated, and the mixed physical field of gas and cooling water is coupled to obtain the flow field characteristics of the mixing and cooling process of gas and cooling water;

[0026] 2.3. Adjust the water spray angle, flow rate, injection area or flow rate respectively, and complete the simulation calculation of the engine high-altitude simulated cooling characteristic distribution according to the method in step 2.2.

[0027] Furthermore, in step [3], the working chamber pressures of the different engine combustion chambers are respectively 90% chamber pressure condition, 100% chamber pressure condition, and 110% chamber pressure condition.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] 1. The present invention completes the comprehensive simulation analysis of the test system process performance by simulating and calculating the stability of the engine's high-altitude simulation work, the distribution of the engine's high-altitude simulation cooling characteristics, and the working characteristics under different working conditions, thereby achieving a comprehensive analysis of the performance of each sub-equipment (vacuum chamber, engine nozzle, diffuser, water spray cooler, front air collecting chamber, tube bundle cooler, rear air collecting chamber) and the entire test system, and further truly verifies the correctness of the overall plan of the engine high-altitude simulation test system.

[0030] 2. The present invention simulates and analyzes the distribution of the engine's high-altitude simulated cooling characteristics, and compares and analyzes the changes in the cooling effect of water spray on the gas by adjusting the water spray angle, flow rate, injection area and flow rate, so as to comprehensively and accurately analyze the accuracy and feasibility of the cooling and temperature reduction scheme of the test system, and provide a reference basis for optimizing the design scheme.

[0031] 3. The present invention can realize the comprehensive evaluation of the ultimate design capacity and design index of each sub-equipment and the analysis of the performance overload capacity of the entire test system by simulating and analyzing the high-altitude simulated working characteristics of the engine under different working conditions, thereby verifying the matching of the boundary conditions of the engine high-altitude simulation test system and the engine performance verification, and the adaptability and feasibility of the overall scheme of the comprehensive simulation and analysis test system.

[0032] 4. The present invention can comprehensively and accurately evaluate the high-altitude simulated suction performance of the engine test system, so that the test system meets the performance index requirements of the engine high-altitude simulation test, providing a guarantee for the construction and application of the test system.

[0033] 5. The simulation method of the present invention can also obtain the pressure, temperature, speed (Mach), density, streamline and flow velocity vector diagrams of the entire test system and its sub-equipment, as well as related curve charts, and obtain the distribution of the temperature field and pressure field of the test system, thereby realizing the prediction of the performance of the test system and providing guidance for the construction of the test system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0036] Usually, in order to verify the correctness of the overall plan of the engine high-altitude simulation test system, it is necessary to carry out performance simulation calculation and analysis of the attitude control engine high-altitude simulation test system, which mainly involves the simulation analysis of the attitude control engine high-altitude simulation working stability, the simulation analysis of the attitude control engine high-altitude simulation cooling characteristics distribution and the simulation analysis of the attitude control engine high-altitude simulation working characteristics under different working conditions, to obtain the system pressure balance and temperature balance calculation and characteristics, comprehensively and accurately evaluate the high-altitude simulation suction performance of the engine test system, meet the performance requirements of the engine high-altitude simulation test, complete the engine test mission assessment, and ensure the performance requirements of the test bench.

[0037] Based on this, Figure 1 As shown, this embodiment provides a method for simulating the flow field performance of the entire system of an engine high-altitude simulation test, comprising the following steps:

[0038] Step [1]: Establish a component model based on the composition of the fuel gas, calculate the input conditions, boundary conditions, and environmental parameters of the fuel gas flow process and pressure field of the engine steady-state working model, and then use the fluid mechanics calculation software to complete the simulation calculation of the engine's high-altitude simulated working stability. Specifically:

[0039] 1.1. A component model is established based on the composition of the fuel gas, and the heat exchange between the fuel gas and the cooling water is calculated and analyzed to obtain the input conditions of the engine steady-state analysis model.

[0040] 1.2. Based on step 1.1, a comprehensive analysis is conducted on the engine's fuel combustion process, interlayer cooling, gas heat exchange process, engine ejection, startup and shutdown states, and the boundary conditions of the engine steady-state analysis model are calculated.

[0041] 1.3. On the basis of step 1.2, based on the shock wave effect and the axial symmetry of the gas flow field and temperature field distribution, the environmental parameters of the gas flow process are calculated using the one-dimensional isentropic flow theory. The environmental parameters generally include the viscosity coefficient of the gas flow and the diffusion flux of each gas component.

[0042] In this embodiment, the one-dimensional isentropic flow theory and the turbulence model Navier-Stokes equation of the environmental parameters of the gas flow process and the pressure field are simplified into a two-dimensional axisymmetric form:

[0043]

[0044] In the formula: F is the external force on the x-axis (such as gravity, pressure gradient, etc.); G is the external force on the y-axis (such as gravity, pressure gradient, etc.); t is time; x is the axial coordinate; y is the axial coordinate; U is the velocity vector; H is the product of pressure and gravitational acceleration.

[0045] Based on the conservation of momentum and energy, the turbulence model Navier-stokes needs to be applied. This numerical simulation uses the standard k-ε equation model, and the calculation formula of the dynamic viscosity coefficient u of the gas flow is expressed as:

[0046]

[0047] Where ρ represents the gas density; k represents the turbulent kinetic energy of the gas; ε represents the turbulent dissipation rate; C u Represents the model constant.

[0048] Since the working media of the engine and ejector are different in the high-altitude simulation test of the engine, a component transport model is used to simulate the mixing and transport behaviors of different gas components in the flow field by solving the conservation equations describing the convection, diffusion and reaction sources of each component substance, and the mass fraction of each substance is obtained by estimating the gas convection-diffusion equation.

[0049] The general form of the conservation equation is:

[0050]

[0051] Where Y i is the mass fraction of the i-th substance; v is the velocity vector of the flow field; J i is the diffusion flux of the ith substance; R i is the net production rate of the chemical reaction of the i-th substance; S i for the ith species via discrete phases and user-defined source terms.

[0052] The calculation formula for the diffusion flux of each gas component (i.e. each substance) is:

[0053]

[0054] Among them, J i is the diffusion flux of the i-th substance, i represents the number of gas components, i≥1; D i,m is the mass diffusion coefficient of the ith substance; u i is the turbulent dynamic viscosity coefficient of the i-th substance; Sc t is the Schmidt number of the i-th substance, which is defined as the ratio of the dynamic viscosity coefficient to the diffusion coefficient; △Y i is the change in mass fraction of the ith substance; D T,i is the thermal diffusion coefficient of the ith substance; △T is the temperature change, T is the temperature required for the gas to diffuse; t represents the total time required for the gas to diffuse.

[0055] 1.4. Input the input conditions obtained in step 1.1, the boundary conditions obtained in step 1.2, and the environmental parameters obtained in step 1.3 into the fluid mechanics calculation software to realize the simulation calculation and analysis of the engine's high-altitude simulated working stability.

[0056] This embodiment is based on commercial computational fluid dynamics software (FLUENT software), and adopts SST k-omega, DPM, component transport and other models for simulation calculation, and sets additional boundary conditions, wherein the additional conditions include the engine nozzle active ejector inlet (pressure-inlet), diffuser outlet (pressure-outlet), central axis (axis) and no-slip wall (wall), wherein the diffuser outlet leads to the atmosphere, and the rest is set to the wall.

[0057] The calculation method is set as follows: the solver is set to use the compressible NS equations for solving the two-dimensional steady-state mass, momentum, and energy transport, the turbulence model uses the standard k-ε model, the spatial discretization method uses the implicit Roe-fds flux, the difference format is the second-order upwind format, and the fluid properties are the ideal air gas model.

[0058] Step [2]: Based on the simulation calculation results of step [1], a discrete phase model is used to perform numerical simulation calculations on the process of mixing and cooling the gas and cooling water, thereby completing the simulation calculation analysis of the distribution of the engine's high-altitude simulated cooling characteristics. Specifically:

[0059] 2.1. The gas flow field is obtained using the density-based standard k-ε turbulence model, and the discrete phase model (DPM) is used to simulate the water spray cooling device of the test system.

[0060] 2.2. Based on the simulation calculation results of step [1], the two-phase mixing and cooling process of gas and cooling water is numerically simulated, and the mixed physical field of gas and cooling water is coupled to obtain the flow field characteristics of the mixing and cooling process of gas and cooling water, so as to realize the analysis of the cooling effect of the engine high-altitude simulated operation and the equipment protection characteristics.

[0061] 2.3. Adjust the water spray angle, flow rate, injection area or flow rate respectively, and complete the simulation calculation and analysis of the engine high-altitude simulated cooling characteristic distribution according to the method in step 2.2.

[0062] This embodiment analyzes the influence of water spray angle, flow rate, injection area and flow rate on the cooling effect of gas flow, and simulates the influence of two-stage water spray cooling on the cooling effect of gas flow. By analyzing the water spray flow field, the coupling effect and cooling effect of discrete phases on the gas phase are simulated. On this basis, by adjusting the water spray angle, flow rate, injection area and flow rate, the changes in the cooling effect of gas by water spray are compared and analyzed. After obtaining various factors of water spray cooling, the high-altitude simulated cooling performance of the engine test system is analyzed and evaluated, so as to comprehensively and accurately analyze the accuracy and feasibility of the cooling and cooling scheme of the test system, and provide a reference for optimizing the design scheme.

[0063] Step [3]: According to the methods of step [1] to step [2], complete the simulation calculation and analysis of the high-altitude simulated working characteristics of the engine under different working conditions, and then realize the simulation calculation and analysis of the flow field performance of the whole system of the engine high-altitude simulation test.

[0064] This embodiment conducts a comprehensive analysis on the engine limit assessment, overload or abnormal conditions of each test equipment, and the boundary capacity of the entire test system, and selects different engine combustion chamber working pressures (90%, 100%, 110% working conditions), different engine water spray cooling flow rates, different jet pump outlet pressures, different diffuser outlet pressures, different air collecting chamber working pressures and other working conditions for analysis.

[0065] Step [4]: ​​Optimize the design of the engine high-altitude simulation test system based on the simulation results of step [3], so as to realize the simulation analysis of the flow field performance of the entire system of the engine high-altitude simulation test, and provide strong theoretical support for the reliability of the test system.

[0066] First, according to the performance of the jet pump, different outlet pressures of the rear plenum chamber are selected for multi-condition analysis. Secondly, different engine water spray cooling flow rates are selected to simulate and analyze the cooling effect of the high-altitude simulated gas flow of the attitude control engine. After that, the simulation analysis results of the ignition working stability of the engine test system are obtained by combining different jet pump outlet pressures, different diffuser outlet pressures, and different plenum chamber working pressures, so as to obtain the pressure, temperature, speed (Mach), density, streamline and flow velocity vector diagrams of the entire test system and sub-equipment (vacuum chamber, engine nozzle, diffuser, water spray cooler, front plenum chamber, tube bundle cooler, rear plenum chamber) under different working conditions, as well as related curve charts, etc., so as to achieve a comprehensive performance evaluation of the ultimate design capacity and design indicators of the sub-equipment.

[0067] Based on this, it is also possible to analyze the performance overload capacity of the entire test system, verify the matching of the boundary conditions of the attitude control engine high-altitude simulation test system with the engine performance verification, comprehensively simulate and analyze the adaptability and feasibility of the overall plan of the test system, and comprehensively and accurately evaluate the high-altitude simulated suction performance of the engine test system to meet the performance index requirements of the engine high-altitude simulation test, providing guarantees for the construction and application of the test system.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for simulating the flow field performance of the entire system of an engine high-altitude simulation test, characterized in that: The following steps are involved: Step [1]: Establish a component model based on the composition of the fuel gas, calculate the input conditions, boundary conditions, and environmental parameters of the fuel gas flow process and pressure field of the engine steady-state working model, and then use the fluid mechanics calculation software to complete the simulation calculation of the engine high-altitude simulated working stability; Step [2], based on the simulation calculation results of step [1], a discrete phase model is used to perform numerical simulation calculation on the process of mixing and cooling the gas and cooling water, thereby completing the simulation calculation of the distribution of the engine's high-altitude simulated cooling characteristics; Step [3], according to the method of step [1] to step [2], respectively complete the simulation calculation of the engine high altitude simulation working characteristics under different working conditions; the different working conditions include different engine combustion chamber working pressures, different engine water spray cooling flow rates, different jet pump outlet pressures, different diffuser outlet pressures, and different plenum working pressures; Step [4]: ​​Optimize the design of the engine high-altitude simulation test system according to the simulation results of step [3], so as to realize the simulation analysis of the flow field performance of the whole system of the engine high-altitude simulation test.

2. The method for simulating the flow field performance of the entire system of an engine high-altitude simulation test according to claim 1 is characterized in that: Step [1] is as follows: 1.

1. Establish a component model based on the composition of the fuel gas, calculate and analyze the heat exchange between the fuel gas and cooling water, and obtain the input conditions of the engine steady-state analysis model; 1.

2. Based on step 1.1, the boundary conditions of the engine steady-state analysis model are calculated by combining the engine's fuel combustion process, interlayer cooling, gas heat exchange process, engine ejection, startup and shutdown states; 1.

3. On the basis of step 1.2, based on the shock wave effect and the axial symmetry of the gas flow field and the temperature field distribution, the environmental parameters of the gas flow process are calculated using the one-dimensional isentropic flow theory; the environmental parameters include the viscosity coefficient of the gas flow and the diffusion flux of each gas component; 1.

4. Input the input conditions obtained in step 1.1, the boundary conditions obtained in step 1.2, and the environmental parameters obtained in step 1.3 into the fluid mechanics calculation software to realize the simulation calculation of the engine's high-altitude simulated working stability.

3. The method for simulating the flow field performance of the entire system of an engine high-altitude simulation test according to claim 2 is characterized by: In step 1.3, the calculation formula of the dynamic viscosity coefficient u of the gas flow is: Where ρ represents the gas density; k represents the turbulent kinetic energy of the gas; ε represents the turbulent dissipation rate; C u represents the model constant; The calculation formula for the diffusion flux of each gas component is: Among them, J i is the diffusion flux of the i-th substance, i represents the number of gas components, i≥1; D i,m is the mass diffusion coefficient of the ith substance; u i is the turbulent dynamic viscosity coefficient of the i-th substance; Sc t is the Schmidt number of the i-th substance, which is defined as the ratio of the dynamic viscosity coefficient to the diffusion coefficient; △Y i is the mass fraction change of the ith substance; D T,i is the thermal diffusion coefficient of the ith substance; △T is the temperature change, T is the temperature required for the gas to diffuse; t represents the time for the gas to diffuse.

4. The method for simulating the flow field performance of the entire system of an engine high-altitude simulation test according to claim 2 or 3, characterized in that: In step 1.4, the fluid mechanics calculation software uses a component transport model for calculation and sets additional boundary conditions, which include the engine nozzle active ejector inlet, diffuser outlet, central axis and no-slip wall, wherein the diffuser outlet leads to the atmosphere and the rest is set as the wall.

5. The method for simulating the flow field performance of the entire system of an engine high-altitude simulation test according to claim 1 is characterized in that: Step [2] is as follows: 2.

1. The gas flow field is obtained by using the standard k-ε turbulence model based on density basis, and the water spray cooling device of the test system is simulated by using the discrete phase model; 2.

2. Based on the simulation calculation results of step [1], the two-phase mixing and cooling process of gas and cooling water is numerically simulated, and the mixed physical field of gas and cooling water is coupled to obtain the flow field characteristics of the mixing and cooling process of gas and cooling water; 2.

3. Adjust the water spray angle, flow rate, injection area or flow rate respectively, and complete the simulation calculation of the engine high-altitude simulated cooling characteristic distribution according to the method in step 2.

2.

6. The method for simulating the flow field performance of the entire system of an engine high-altitude simulation test according to claim 1 is characterized by: In step [3], the working chamber pressures of the different engine combustion chambers are respectively 90% chamber pressure condition, 100% chamber pressure condition, and 110% chamber pressure condition.

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