Dynamic startup and shutdown instant characteristic simulation method for engine high-altitude simulation test

Abstract

The invention provides a dynamic startup and shutdown instant characteristic simulation method for an engine high-altitude simulation test. The technical problem that the feasibility and accuracy of a test system cannot be truly reflected by an existing method is solved. The method comprises the following steps: 1, establishing a motion equation of gas-liquid two-phase particles, and calculating to obtain the evaporation capacity of water mist particles; 2, setting input conditions and boundary conditions on the basis of the step 1, and establishing a combustion flow field model for high-altitude simulation instantaneous characteristic analysis of the engine; 3, taking the time from the start of the engine to the shutdown delay as a time axis, and performing engine high-altitude simulation test transient change flow field simulation under a rated working condition; 4, judging whether the transient change of the high-altitude simulation test of the engine under the rated working condition is within a preset error range or not; 5, respectively simulating flow field structures of a pressure building section, a pressure stabilizing section and a pressure reducing section of the engine under rated working conditions; and 6, dynamic starting and shutdown instant characteristic simulation analysis of the high-altitude simulation test of the engine under different working conditions is completed respectively.

Description

Technical Field

[0001] The invention relates to an attitude control engine environment simulation test method, and in particular to a dynamic start-stop instantaneous characteristic simulation method for an engine high-altitude simulation test. Background Art

[0002] The attitude control engine is usually tested by high-altitude simulation test system, which uses diffuser, jet pump, etc. to eject gas, so as to ensure the vacuum pressure requirement of the vacuum chamber, and simulate the flight altitude of the attitude control engine to accurately evaluate the flight performance and consistency between the attitude control engine and the sky and the earth. In order to verify the feasibility and accuracy of the attitude control engine high-altitude simulation test system, simulation analysis is usually used to analyze and evaluate it.

[0003] The existing simulation analysis method is based on a separate analysis of a certain state of the engine. However, during the test, the working characteristics of the engine in the pressure building, pressure stabilization, pressure reduction and shutdown stages are different. If only a certain state is analyzed separately, it cannot truly reflect the feasibility of the test system. As a result, there is a large error between the analysis results and the actual situation of the test system, which ultimately affects the test system's accurate evaluation of engine performance.

[0004] In addition, there are back pressure and backfire phenomena during the startup and shutdown process of the engine, which can easily pose a serious threat to the engine nozzle and the test equipment and lines arranged in the vacuum chamber. The existing simulation analysis method does not conduct a specific analysis of this process. It can be seen that this method does not conduct a comprehensive and comprehensive analysis of the test system, and the accuracy of its analysis results cannot be verified. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that the existing simulation analysis method cannot truly reflect the feasibility and accuracy of the test system, and to provide a dynamic start-stop instantaneous characteristic simulation method for an engine high-altitude simulation test.

[0006] To achieve the above objectives, the technical solutions provided by the present invention are:

[0007] A method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test is special in that it includes the following steps:

[0008] Step [1], based on the combustion process and cooling process of the gas, the Reynolds average and conservation Navier-Stokes equations of multi-component chemical reactions are used, combined with the two-phase flow analysis model and the Lagrange-Euler method to establish the motion equations of the gas-liquid two-phase particles, and the evaporation amount of the water mist particles is calculated;

[0009] Step [2], based on step [1], based on the performance indicators and requirements of the engine high-altitude simulation test, combined with the parameters of the gas components and the parameters of each component of the test system, set the input conditions and boundary conditions, and establish a combustion flow field model for the engine high-altitude simulation transient characteristic analysis;

[0010] Step [3], based on the combustion flow field model established in step [2], combined with the SST kw model and the component transport model, with the time from before the engine starts to the shutdown delay as the time axis, perform a flow field simulation of transient changes in the engine high-altitude simulation test under rated conditions;

[0011] Step [4], determining whether the transient change of the engine high-altitude simulation test under the rated working conditions described in step [3] is within a predetermined error range, if so, proceeding to step [5], otherwise, returning to step [2] to modify the input conditions and boundary conditions, and re-establishing the combustion flow field model for the engine high-altitude simulation transient characteristic analysis;

[0012] Step [5], respectively simulate the flow field structures of the pressure building section, pressure stabilization section and pressure reducing section of the engine under rated working conditions, and control the pressure outlet boundary conditions, engine parameters and water injection volume through user-defined functions to realize the dynamic change analysis and simulation of outlet conditions and inlet conditions, thereby completing the dynamic start-up and shutdown instantaneous characteristics simulation analysis of the engine high-altitude simulation test under rated working conditions;

[0013] Step [6], according to the method of step [1] to step [5], complete the simulation analysis of the dynamic startup and shutdown instantaneous characteristics of the engine high-altitude simulation test 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 air chamber working pressures.

[0014] Furthermore, in step [1], the Reynolds-averaged and conservation Navier-Stokes equations for the multi-component chemical reaction are closed using a two-equation standard k-ε model, and discretized using a second-order upwind format, and the pressure and velocity are coupled using a Simple format.

[0015] Furthermore, in step [1], the motion equation of the gas-liquid two-phase particles is:

[0016]

[0017] In the formula, u p represents the gas velocity; t represents the time; f d represents the resistance of the water mist particles; u represents the speed of the water mist particles; g x represents the acceleration due to gravity; ρ p represents the gas density; ρ represents the density of water mist particles; fx represents the acceleration term.

[0018] Furthermore, in step [1], the evaporation amount of the water mist particles is calculated by the following formula:

[0019]

[0020] In the formula, is the evaporation rate of water mist particles; k c is the mass transfer coefficient of water mist particles, C t,s is the vapor molar concentration on the surface of liquid cooling water, C t,∞ is the vapor molar concentration of the gas phase.

[0021] Furthermore, in step [2], the input conditions and boundary conditions are specifically set as follows:

[0022] The calculation domain is taken from the engine nozzle inlet to the cooling channel outlet, and the calculation domain grid is divided by structured grid, and the grid near the wall and the water spray is encrypted; the gas flow rate, the velocity and the initial diameter of the water mist particles are set in combination with the incoming flow supply capacity; the nozzle inlet adopts a pressure inlet boundary, and the discrete phase is set to escape when it reaches the boundary; the solid wall surfaces in the model are all non-slip adiabatic walls; the symmetry axis adopts the axis boundary condition.

[0023] Furthermore, in step [2], the combustion flow field model for the instantaneous characteristic analysis of the engine at high altitude is established in a two-dimensional or three-dimensional mode, and the modeling and simulation are performed in an axisymmetric manner.

[0024] Furthermore, step [3] is specifically as follows: based on the combustion flow field model established in step [2], the SST kw model is used to perform turbulent steady-state simulation for the continuous phase in the entire calculation domain, while the discrete phase is calculated by discrete and phase-coupled methods using a density meter basis; for the fuel gas in the engine nozzle, the component transport model is used to simulate the diffusion and transport process of the fuel gas components; finally, the time between before the engine start and the shutdown delay is used as the time axis, thereby realizing the flow field simulation of transient changes in the engine high-altitude simulation test under rated conditions.

[0025] Furthermore, in step [6], the working chamber pressures of the different engine combustion chambers are 90% of the chamber pressure, 100% of the chamber pressure and 110% of the chamber pressure respectively.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention analyzes the instantaneous characteristics of the engine high-altitude simulation and establishes a combustion flow field model, and then performs transient simulation analysis of the engine high-altitude simulation working characteristics under rated conditions and different conditions (mainly under boundary conditions), and finally obtains the dynamic start-up and shutdown instantaneous characteristics simulation analysis of the engine high-altitude simulation test under different conditions, thereby providing real data support for evaluating the feasibility of the test system.

[0028] 2. The present invention adopts the Reynolds average and conservation type Navier-Stokes equations of multi-component chemical reactions as the basis for building the combustion flow field model. The equations can be established based on the analysis of the gas composition, and the impact / spray composite cooling method of discrete droplets is introduced into the continuous phase gas medium. In addition to solving the transport equation of the gas phase, by solving the discrete liquid phase, the purpose of accurately combining the analysis based on the gas composition with the solution of the overall flow and heat exchange of the flow field can be achieved, and its simulation performance is closer to the actual situation.

[0029] 3. When establishing a combustion flow field model, the present invention sets input conditions and boundary conditions to make the model more realistic. At the same time, the pressure and velocity are coupled in a Simple format, so that the pressure field and its corresponding velocity field can better satisfy the momentum equation during the next iteration, thereby obtaining the velocity correction value and the pressure correction value, improving the accuracy of the boundary condition input, and improving the accuracy of the simulation analysis.

[0030] 4. The present invention sets the time from before the engine starts to the shutdown delay as the time axis time, and evaluates the high-altitude simulated suction performance of the engine test system with the whole process of time characteristics, so as to obtain the instantaneous pressure balance and temperature balance calculation and characteristics of the system to meet the performance requirements of the engine high-altitude simulation test.

[0031] 5. The present invention controls boundary conditions such as pressure outlet, engine parameters, and water injection volume through UDF (User-Defined Function), thereby analyzing and simulating different boundary conditions of engine high-altitude simulation, realizing multi-state simulation during the dynamic working process of engine high-altitude simulation, and performance assessment verification analysis of boundary overload states, and possessing parameterized simulation and modeling analysis capabilities, so that its performance simulation has stronger applicability and applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0033] 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 used to limit the scope of protection of the present invention.

[0034] like Figure 1 As shown, this embodiment provides a method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test, comprising the following steps:

[0035] Step [1], based on the combustion process and cooling process of the gas, the Reynolds average and conservation Navier-Stokes equations of multi-component chemical reactions are used, combined with the two-phase flow analysis model and the Lagrange-Euler method to establish the motion equations of the gas-liquid two-phase particles, and the evaporation amount of the water mist particles is calculated.

[0036] In this embodiment, the Reynolds average and conservation Navier-Stokes equations for multi-component chemical reactions are closed using a two-equation standard k-ε model, and are discretized using a second-order upwind format, and the pressure and velocity are coupled using a Simple format.

[0037] The motion equation of the gas-liquid two-phase particles is obtained based on the two-phase flow analysis model DPM, and its solution method is the typical Lagrangian-Euler method, while the discrete phase is based on the Lagrangian method and is calculated by tracking a large number of particles. The motion equation of the gas-liquid two-phase particles in this embodiment is:

[0038]

[0039] In the formula, the first term on the right side of the equation represents the resistance of the particle, the second term represents gravity and buoyancy, and the third term represents other forces. p represents the gas velocity; t represents the time; f d represents the resistance of the water mist particles; u represents the speed of the water mist particles; g x represents the acceleration due to gravity; ρ p represents the gas density; ρ represents the density of water mist particles; f x represents the acceleration term.

[0040] At the same time, during the cooling process, the evaporation amount of the water mist particles is another important factor. The evaporation amount of the water mist particles in this embodiment is determined by the gas phase molar concentration gradient, which is calculated by the following formula:

[0041]

[0042] In the formula, is the evaporation rate of water mist particles; k c is the mass transfer coefficient of water mist particles, C t,sis the vapor molar concentration on the surface of liquid cooling water, C t,∞ is the vapor molar concentration of the gas phase.

[0043] When calculating the trajectory of gas-liquid two-phase particles, it is necessary to record the energy, mass and momentum values ​​gained or lost by the water mist particles when passing through the gas. These values ​​are introduced into the subsequent continuous phase as source terms for calculation. Therefore, when the continuous phase affects the discrete phase, the influence of the discrete phase trajectory is also added to the continuous phase. This two-way coupling is achieved by alternately solving the discrete phase and continuous phase equations until the solutions of the two phases stop changing.

[0044] Step [2]: Based on step [1], based on the performance indicators and requirements of the engine high-altitude simulation test, combined with the parameters of the gas components and the parameters of the various components of the test system, according to the flow field analysis software and finite element thinking, set the input conditions and boundary conditions, and establish a combustion flow field model for the instantaneous characteristic analysis of the engine high-altitude simulation.

[0045] In this embodiment, the input conditions and boundary conditions are specifically set as follows: the calculation domain is taken from the engine nozzle inlet to the cooling channel outlet, and the flow rate, the velocity of the water mist particles, and the initial diameter and other parameters are set in combination with the incoming flow supply capacity. The indoor area that will not affect the nozzle outlet flow field is intercepted as the atmospheric inlet. The atmospheric and nozzle inlets both use the pressure inlet boundary, and the discrete phase is set to escape when it reaches the boundary; the solid wall surfaces in the model all use the non-slip adiabatic wall surface; the symmetry axis uses the axis boundary condition. Among them, the calculation domain grid is divided by using the structured grid, and the grid near the wall and the water spray is encrypted to ensure the accuracy of the simulation.

[0046] The combustion flow field model for the analysis of the instantaneous characteristics of the engine at high altitude is generally established in a two-dimensional or three-dimensional mode, and the axisymmetric method is used for modeling and simulation.

[0047] Step [3], based on the combustion flow field model established in step [2], the finite volume method is used for calculation, wherein the continuous phase in the entire calculation domain is simulated by the SST kw model for turbulent steady-state simulation, while the discrete phase is calculated by discrete and phase-coupled method using a density meter basis; the combustion gas in the engine nozzle uses a component transport model to simulate the diffusion and transport process of the combustion gas components, and the calculation ignores the influence of gravity and chemical reactions that may occur during the flow process; finally, the time from before the engine is started to the shutdown delay is used as the time axis to realize the flow field simulation of transient changes in the engine high-altitude simulation test under rated conditions.

[0048] Step [4], determine whether the transient change of the engine high-altitude simulation test under the rated operating conditions described in step [3] is within the predetermined error range. If so, proceed to step [5]; otherwise, return to step [2] to modify the input conditions and boundary conditions, and re-establish the combustion flow field model for the engine high-altitude simulation transient characteristic analysis.

[0049] Step [5], respectively simulate the flow field structures of the pressure building section, pressure stabilization section and pressure reducing section of the engine under rated conditions, so as to realize the simulation analysis of the dynamic startup and shutdown instantaneous characteristics of the engine high-altitude simulation test under rated conditions.

[0050] Since there are back pressure and flashback during the engine startup and shutdown process, it is easy to pose a serious threat to the engine nozzle and the test equipment and lines arranged in the vacuum chamber. Therefore, it is necessary to perform transient flow field simulation throughout the engine passive injection high-altitude simulation test to ensure the accuracy of the simulation results. The transient flow field simulation of the entire engine passive injection high-altitude simulation test includes: simulating the flow field structure of the engine pressure building, pressure stabilization, decompression and vacuum chamber air replenishment stages during the test, simulating the flow field in the diffuser and vacuum chamber, and analyzing the flow field structure of each stage of the high-model test. Among them, the internal pressure of the engine is mainly divided into three stages: pressure building stage, pressure stabilization stage and pressure reduction stage. Therefore, this embodiment adopts a multi-stage model simulation to maintain the engine pressure, and the pressure outlet boundary condition is controlled by UDF (User-Defined Function), thereby realizing the dynamic change analysis and simulation of the outlet conditions, and the UDF control of boundary parameters such as engine parameters and water injection volume, thereby realizing the dynamic change analysis and simulation of the inlet boundary conditions, as well as the shutdown return cabin pressure and return pressure performance analysis.

[0051] Step [6], according to the method of step [1] to step [5], complete the simulation analysis of the dynamic startup and shutdown instantaneous characteristics of the engine high-altitude simulation test 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 air chamber working pressures.

[0052] In this embodiment, different engine combustion chamber working chamber pressures (90% chamber pressure, 100% chamber pressure and 110% chamber pressure) are selected for analysis, and different rear air chamber outlet pressures are selected according to the performance of the jet pump, and various working conditions are analyzed respectively; 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, and the ignition transient simulation analysis results of the engine test system from before startup to after shutdown are completed. The results include the instantaneous pressure, temperature, speed (Mach), density, streamline and flow velocity vector diagrams of the entire test system and sub-equipment (vacuum cabin, engine nozzle, diffuser, water spray cooler, front air chamber, tube bundle cooler, rear air chamber), as well as related dynamic vector curve charts, so as to achieve a comprehensive and accurate evaluation of the high-altitude simulated suction performance of the engine test system and meet the performance requirements of the high-altitude simulation test of the engine.

[0053] 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 dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test, characterized in that: The following steps are involved: Step [1], based on the combustion process and cooling process of the gas, the Reynolds average and conservation Navier-Stokes equations of multi-component chemical reactions are used, combined with the two-phase flow analysis model and the Lagrange-Euler method to establish the motion equations of the gas-liquid two-phase particles, and the evaporation amount of the water mist particles is calculated; Step [2], based on step [1], based on the performance indicators and requirements of the engine high-altitude simulation test, combined with the parameters of the gas components and the parameters of each component of the test system, set the input conditions and boundary conditions, and establish a combustion flow field model for the engine high-altitude simulation transient characteristic analysis; Step [3], based on the combustion flow field model established in step [2], combined with the SST kw model and the component transport model, with the time from before the engine starts to the shutdown delay as the time axis, perform a flow field simulation of transient changes in the engine high-altitude simulation test under rated conditions; Step [4], determining whether the transient change of the engine high-altitude simulation test under the rated working conditions described in step [3] is within a predetermined error range, if so, proceeding to step [5], otherwise, returning to step [2] to modify the input conditions and boundary conditions, and re-establishing the combustion flow field model for the engine high-altitude simulation transient characteristic analysis; Step [5], respectively simulate the flow field structures of the pressure building section, pressure stabilization section and pressure reducing section of the engine under rated working conditions, and control the pressure outlet boundary conditions, engine parameters and water injection volume through user-defined functions to realize the dynamic change analysis and simulation of outlet conditions and inlet conditions, thereby completing the dynamic start-up and shutdown instantaneous characteristics simulation analysis of the engine high-altitude simulation test under rated working conditions; Step [6], according to the method of step [1] to step [5], complete the simulation analysis of the dynamic startup and shutdown instantaneous characteristics of the engine high-altitude simulation test 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 air chamber working pressures.

2. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 1 is characterized by: In step [1], the Reynolds-averaged and conservation Navier-Stokes equations for the multi-component chemical reaction are closed using a two-equation standard k-ε model, and discretized using a second-order upwind format, and the pressure and velocity are coupled using a Simple format.

3. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 2 is characterized by: In step [1], the motion equation of the gas-liquid two-phase particles is: In the formula, u p represents the gas velocity; t represents the time; f d represents the resistance of the water mist particles; u represents the speed of the water mist particles; g x represents the acceleration due to gravity; ρ p represents the gas density; ρ represents the density of water mist particles; f x represents the acceleration term.

4. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 3 is characterized by: In step [1], the evaporation amount of the water mist particles is calculated by the following formula: In the formula, is the evaporation rate of water mist particles; k c is the mass transfer coefficient of water mist particles, C t,s is the vapor molar concentration on the surface of liquid cooling water, C t,∞ is the vapor molar concentration of the gas phase.

5. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 1 is characterized by: In step [2], the input conditions and boundary conditions are specifically set as follows: The calculation domain is taken from the engine nozzle inlet to the cooling channel outlet, and the calculation domain grid is divided by structured grid, and the grid near the wall and the water spray is encrypted; the gas flow rate, the velocity and the initial diameter of the water mist particles are set in combination with the incoming flow supply capacity; the nozzle inlet adopts a pressure inlet boundary, and the discrete phase is set to escape when it reaches the boundary; the solid wall surfaces in the model are all non-slip adiabatic walls; the symmetry axis adopts the axis boundary condition.

6. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 5 is characterized by: In step [2], the combustion flow field model for the instantaneous characteristic analysis of the engine at high altitude is established in a two-dimensional or three-dimensional mode, and the modeling and simulation are performed in an axisymmetric manner.

7. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 1 is characterized by: Specifically, step [3] is to use the SST kw model to perform steady-state turbulence simulation on the continuous phase in the entire calculation domain based on the combustion flow field model established in step [2], while the discrete phase is calculated by discrete and phase-coupled methods using a density meter basis; for the gas in the engine nozzle, the component transport model is used to simulate the diffusion and transport process of the gas components; finally, the time from before the engine is started to the shutdown delay is used as the time axis to realize the flow field simulation of transient changes in the engine high-altitude simulation test under rated conditions.

8. The method for simulating the dynamic startup and shutdown instantaneous characteristics of an engine high-altitude simulation test according to claim 1 is characterized by: In step [6], the working chamber pressures of the different engine combustion chambers are 90% chamber pressure, 100% chamber pressure and 110% chamber pressure respectively.

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