A method for removing kerosene from the inner wall of a liquid rocket engine based on numerical simulation

Abstract

The present application relates to the technical field of aerospace engine utilization, and particularly relates to a method for removing kerosene from the inner wall of a liquid rocket engine based on numerical simulation, comprising the following steps: S1, establishing a three-dimensional model of an engine to be cleaned, and performing numerical simulation of the kerosene removal process to obtain simulated values of kerosene vapor concentration on the inner wall of the engine cavity under different working conditions; preparing a test piece of the engine to be cleaned, and performing a kerosene removal test under the same working conditions as the numerical simulation to obtain experimental values of kerosene vapor concentration on the inner wall of the engine cavity under different working conditions; S2, setting a standard error, and calculating the experimental error between the simulated values and the experimental values, and when the experimental error is less than the standard error, the engine uses the kerosene removal parameters in the numerical simulation for removal. The present application explores the mechanism problem in the treatment process and obtains the optimal treatment method by numerical simulation and experimental research on the process of removing the kerosene attached to the wall surface and the internal residual kerosene through cyclic blowing and suction operation of the engine cavity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of space engine utilization, in particular to a method for removing kerosene from the inner wall of a liquid rocket engine based on numerical simulation. BACKGROUND

[0002] Rockets are the main carrier for space activities in the world, and most rocket engines are disposable. Developing reusable and reusable rocket engines can save rocket exploration and development costs and shorten the development cycle. In order to reduce the launch cost of disposable launch vehicles, the aerospace industry has been working on developing reusable launch vehicles that can freely enter and exit space like airplanes. The engine, which accounts for one-third of the total cost of the rocket, is an important part of the reusable launch vehicle research.

[0003] After the test run of the rocket engine, the kerosene film will be attached to the engine cavity wall, which will cause fuel residue and cause liquid kerosene to adhere to the wall. Since the amount of kerosene remaining on the inner wall of the engine directly affects the performance of the next use, the problem of kerosene removal from the inner wall of the engine needs to be solved. The removal of residual kerosene from the inner wall of the rocket engine after testing is an important problem faced by reusable and reusable rocket engines.

[0004] The existing engine inner wall cleaning adopts a combination of hot nitrogen blowing and vacuum suction, and the selection of blowing time, vacuum suction time and vacuum degree still relies on traditional experience for operation. The existing cleaning operation has problems such as long time, unsatisfactory cleaning effect, etc., and lacks scientific theoretical guidance.

[0005] The current post-test removal process and steps are complex, including high-pressure nitrogen blowing and vacuum suction operations on different engine cavities. There are kerosene evaporation and diffusion and convective mass transfer phenomena during the removal process. The understanding of the evaporation and diffusion and convective mass transfer mechanism of the residual kerosene droplets on the wall is not perfect, and in engineering applications, empirical formulas are often used to study the evaporation and diffusion and convective mass transfer process of liquid droplets. Therefore, it is necessary to further study the evaporation and diffusion and convective mass transfer mechanism of hydrocarbons on the inner wall of the engine. SUMMARY

[0006] In view of the problem of complex kerosene removal process from the inner wall of the engine in the prior art, the present application provides a method for removing kerosene from the inner wall of a liquid rocket engine based on numerical simulation.

[0007] The present application is realized by the following technical solutions:

[0008] A method for removing kerosene from the inner wall of a liquid rocket engine based on numerical simulation, comprising the following steps:

[0009] S1, a three-dimensional model of the engine cavity to be cleaned is established, and numerical simulation of the kerosene cleaning process is performed to obtain simulated values of kerosene vapor concentration in the engine cavity under different working conditions;

[0010] S1, a three-dimensional model of the engine cavity to be cleaned is established, and numerical simulation of the kerosene cleaning process is performed to obtain simulated values of kerosene vapor concentration in the engine cavity under different working conditions;

[0011] S2, a standard error is set, and experimental errors between simulated values of kerosene vapor concentration in the engine cavity and experimental values of kerosene vapor concentration in the engine cavity under the same working conditions are calculated, and then the experimental errors are compared with the standard error to obtain the simulation results;

[0012] When the experimental error is less than the standard error, the simulated value of kerosene vapor concentration in the engine cavity is reliable, the parameter setting of the cleaning process corresponding to the simulated value of kerosene vapor concentration in the engine cavity is effective, and the engine adopts the kerosene cleaning parameters in the numerical simulation for cleaning; when the experimental error is greater than the standard error, the kerosene cleaning parameters in the numerical simulation are re-set until the experimental error is less than the standard error.

[0013] Preferably, in S1, the numerical simulation process of the engine to be cleaned is as follows:

[0014] S11, a three-dimensional model of the engine to be cleaned is established by using Solidworks, and the left end and the right end of the cavity are provided with gas inlets and gas outlets, and the middle of the cavity is provided with a suction port;

[0015] S12, the calculation grid of the three-dimensional model is divided by using the grid division software ICEM, and the calculation grid is a non-structured grid;

[0016] S13, the inlet and outlet boundary conditions, the operating parameters of the cleaning process, and the material parameters of the kerosene to be cleaned are set, the three-dimensional model after the calculation grid is divided is numerically simulated by using the volume method, and simulated values of kerosene vapor concentration in the three-dimensional model cavity of the engine are obtained.

[0017] Preferably, in S12, when the calculation grid is divided, each fluid domain is first separated, and then volume grid is generated for each fluid domain.

[0018] Preferably, in S13, the parameters in the cleaning process are as follows: the pressure in the blowing process is 1 MPa, the pressure in the suction process is 2 KPa; the suction and blowing process is 10 minutes / cycle, 20 minutes / cycle and 30 minutes / cycle, and the processing time is 120 min; the operating pressure is standard atmospheric pressure.

[0019] Preferably, the air inlet is set as a pressure inlet in the blowing process, and the gas outlet pressure is a pressure outlet; the suction port is set as a pressure outlet in the suction process.

[0020] Preferably, in S13, the boundary condition is a convection heat transfer boundary condition model.

[0021] Preferably, the blowing process and the suction process are both calculated by using an Eulerian two-fluid model.

[0022] Preferably, in S2, the calculation formula of the experimental error is:

[0023]

[0024] Preferably, in S2, the standard error is 20%.

[0025] Preferably, in S1, the size ratio of the three-dimensional model of the engine to be cleaned to the test piece of the engine to be cleaned is 1:1.

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

[0027] The simulation method for cleaning kerosene on the inner wall of a liquid rocket engine based on numerical simulation can study the blowing process of high-pressure nitrogen in the rocket engine cavity and the cleaning effect of the residual kerosene on the inner wall surface by the combined operation of high-pressure nitrogen blowing and low-pressure suction with different cycle times. In the experimental process, the kerosene vapor concentration in the gas phase in the cavity before and after treatment is measured by using gas chromatography to represent the cleaning effect and verify the simulation accuracy. Meanwhile, the mass transfer mechanism in the numerical simulation process is studied, and the influence law of the treatment effect of different cavities of the rocket engine after testing is obtained, and an efficient method for cleaning the residual kerosene on the inner wall surface of the rocket engine after testing is proposed.

[0028] Combined with experimental data, the evaporation and diffusion of hydrocarbons and the convection heat transfer and mass transfer mechanism are comprehensively analyzed and optimized, and an efficient engine cavity wall cleaning method is found.

[0029] The simulation method for cleaning kerosene on the inner wall of a liquid rocket engine based on numerical simulation can explore the evaporation and diffusion of kerosene on the inner wall of the engine and the heat transfer and mass transfer mechanism, and seek an optimization scheme of the post-test processing flow such as blowing and suction operation. The numerical simulation and experimental research are conducted on the process of cleaning the residual kerosene attached to the wall and inside the engine cavity by the cyclic blowing and suction operation, the mechanism problem in the processing process is explored, and the optimal processing method is obtained, and the influence law of the post-test processing result is obtained, thereby solving the problem of cleaning the residual kerosene on the inner wall of the engine after testing.

[0030] The application studies the cleaning effect of residual kerosene on the inner wall of the rocket engine through numerical calculation, and the cleaning effect of residual kerosene on the inner wall of the rocket engine under different cycle times of the combined operation of blowing and low-pressure pumping is studied. In the experiment, the kerosene vapor concentration in the gas phase in the cavity before and after treatment is used to represent the cleaning effect and to verify the accuracy of the simulation. At the same time, the mass transfer mechanism in the numerical simulation is studied, and the influence law of the treatment effect of different cavities of the rocket engine after test is obtained, and an efficient method for cleaning the residual kerosene on the inner wall of the rocket engine after test is proposed. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The flow chart of the numerical simulation method for the process of removing residual kerosene on the inner wall of the liquid rocket engine after test is shown in the figure.

[0032] Figure 2 The experimental equipment diagram for the process of removing residual kerosene on the inner wall of the liquid rocket engine after test in the embodiment of the application is shown in the figure.

[0033] Figure 3 The model diagram of the inner wall cavity of the rocket engine rectifier part for the process of removing residual kerosene on the inner wall in the embodiment of the application is shown in the figure.

[0034] Figure 4 The cavity grid diagram of the rocket engine rectifier part for the process of removing residual kerosene on the inner wall in the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0035] The application will be further described in detail below with specific examples, which are an explanation of the application rather than a limitation.

[0036] The application discloses a numerical simulation method for removing kerosene on the inner wall of a liquid rocket engine, which refers to Figure 1 , and comprises the following steps:

[0037] S1, a three-dimensional model of the engine inner wall cavity to be cleaned is established, and numerical simulation of the kerosene removal process is performed to obtain simulated values of kerosene vapor concentration in the engine cavity under different conditions, and the specific steps are as follows:

[0038] (1) a three-dimensional model of the engine to be cleaned is established by using Solidworks three-dimensional modeling software, and gas inlets and outlets are arranged at the left end and the right end of the cavity during modeling, and a pumping port is arranged in the middle of the cavity;

[0039] (2) the established cavity model is divided into calculation grids by using the grid division software ICEM, and the grid used is a non-structural grid; the established cavity model is divided into calculation grids by using the grid division software ICEM, and the grid used is a non-structural grid.

[0040] The structure elements irrelevant to analysis such as screw holes are omitted in the three-dimensional model. After the assembly of the geometric models of various parts is completed, the geometric model is converted into an "iges" format file recognized by the meshing software ICEM, so that the geometric model required in the meshing process can be obtained.

[0041] The liquid phase region and the gas phase region exist simultaneously in the simulation process calculation domain. When the calculation mesh is divided, the various fluid domains are separated first, and then the volume mesh is generated for each fluid domain. The internal region is the gas phase region, and the volume fraction of kerosene vapor at the initial moment can be defined for the region.

[0042] The interface between the liquid phase and the gas phase adopts the interior interface. The interface is virtual, and in the numerical calculation process, the gas can blow to the wall surface through the interface to act on the liquid phase. The liquid on the wall surface can also enter the cavity interior through the interface to be carried away by the gas flow, and the liquid on the wall surface can also undergo the evaporation diffusion and convection mass transfer process.

[0043] In order to check the independence of the cavity mesh used in the calculation, the mesh independence is verified by adjusting the number of nodes. The results show that the numerical results of the mesh number of 59w almost do not change with finer mesh, that is, the mesh number of 59w has reached the requirement of mesh independence. The calculation mesh used in the embodiment is shown in Figure 4 The region of 1mm close to the wall surface is set as the kerosene region, and the volume fraction of kerosene at the initial moment is defined as 1, that is, the region is full of liquid kerosene.

[0044] (3) The meshed model is imported into the simulation software Fluent, the inlet and outlet and wall boundary conditions, the operating parameters of the cleaning process and the material parameters of the kerosene to be cleaned are set, and the numerical simulation is carried out by using the volume method.

[0045] In the simulation process, the Fluent software is used to carry out three-dimensional numerical simulation on the blowing and suction heat and mass transfer law of the residual kerosene in the engine cavity. A compressible two-phase model considering phase change is established. According to the post-processing process, the inlet and outlet and wall boundary conditions, the blowing and suction process operating parameters and other settings are set, and the material parameters of the residual kerosene to be cleaned are set.

[0046] The cleaning of the engine inner wall includes the blowing process and the suction process. In the blowing process, the air inlet is set as a pressure inlet, and the gas outlet pressure is a pressure outlet. In the suction process, the suction port is set as a pressure outlet. The operating pressure is set as the standard atmospheric pressure 101.325KPa (absolute pressure), the pressure in the blowing process is 1MPa, the pressure in the suction process is 2KPa, the working condition of the engine cavity inner wall is: 10 minutes / cycle, 20 minutes / cycle and 30 minutes / cycle in the suction and blowing process, and the processing time is 120min.

[0047] All the wall surface selected the boundary condition of heat convection boundary condition model, the heat convection coefficient 10, the temperature was set as the average room temperature 293.15K under the test condition. The main physical and chemical properties of the residual kerosene and nitrogen gas at the test temperature were measured in the laboratory, and the measured data were set as the material property parameters in the simulation calculation.

[0048] The blowing process and the suction process were calculated by using the Eulerian two-fluid model, which can simulate multiphase flow and the interaction between phases, and the control equations were solved for each phase. The control equations involved are as follows:

[0049] Continuity equation:

[0050]

[0051] Momentum equation:

[0052]

[0053] Wherein: α i is the volume fraction of phase i, ρ i is the density of phase i, v i is the velocity of phase i, μ e,i is the effective viscosity of phase i. p is the total pressure, gi is the gravitational acceleration, F i is the total of the interphase force.

[0054] Energy equation:

[0055]

[0056] Wherein: λ eff is the effective thermal conductivity, S E is the heat source phase.

[0057] The test piece of the engine inner wall cavity to be cleaned (the size ratio of the three-dimensional model of the engine to be cleaned to the test piece of the engine to be cleaned is 1:1) was prepared, and a kerosene cleaning test was carried out under the same working condition as the numerical simulation, and the experimental value of the kerosene vapor concentration of the engine cavity inner wall under different working conditions was obtained.

[0058] S2, set the standard error, and calculate the experimental error between the simulation value of the kerosene vapor concentration of the engine cavity inner wall and the experimental value of the kerosene vapor concentration of the engine cavity inner wall under the same working condition, and then compare the experimental error with the standard error to obtain the simulation result.

[0059] When the experimental error is less than the standard error, the simulated value of the kerosene vapor concentration in the engine cavity inner wall is reliable, the parameter setting of the corresponding cleaning process is effective, and the kerosene cleaning parameters in the numerical simulation are used for cleaning; when the experimental error is greater than the standard error, the kerosene cleaning parameters in the numerical simulation are re-set until the experimental error is less than the standard error.

[0060] The calculation formula of the experimental error is:

[0061]

[0062] After using numerical simulation to calculate the process of removing the residual kerosene on the inner wall of the engine cavity by the combined operation of high-pressure nitrogen blowing and low-pressure suction with different cycle times, the experimental process is carried out under the same conditions, and the kerosene vapor concentration in the gas phase in the cavity before and after treatment is measured by using gas chromatography to represent the cleaning effect and verify the simulation accuracy.

[0063] The kerosene vapor concentration in the gas phase is measured by using gas chromatography, which is a high-sensitivity universal detector and almost responds to all organic matters. After the blowing and suction process is completed, the gas in the cavity is collected into a gas bag from the sampling port, and then the sample is prepared for simulation to obtain the kerosene vapor concentration in the cavity after different operations.

[0064] When there is a large amount of residual kerosene on the inner wall of the engine, the kerosene vapor concentration in the cavity is high through evaporation and diffusion. When there is a small amount of residual kerosene on the wall, the kerosene vapor concentration in the cavity is reduced through evaporation and diffusion, so that the amount of residual kerosene on the wall can be analyzed. The expression formula of the removal efficiency η is:

[0065]

[0066] In the formula, η is the removal efficiency; c0 is the kerosene vapor concentration in the cavity before cleaning; c1 is the kerosene vapor concentration in the cavity after cleaning.

[0067] After using numerical simulation to calculate the process of removing the residual kerosene on the inner wall of the engine cavity by the combined operation of high-pressure nitrogen blowing and low-pressure suction with different cycle times, the experimental process is carried out under the same conditions, and the kerosene vapor concentration in the gas phase in the cavity before and after treatment is measured by using gas chromatography to represent the cleaning effect and verify the simulation accuracy.

[0068] The engine cavity to be cleaned in the embodiment is as shown in Figure 3 The processing time in the embodiment is 120 minutes, and the suction and blowing process is 10 minutes / cycle, 20 minutes / cycle and 30 minutes / cycle in three working conditions. The kerosene vapor concentration in the cavity before and after treatment is measured by using gas chromatography (as shown in Figure 2As shown in the figure, the effect of the treatment under three operating conditions was judged. Simultaneously, the residual kerosene removal mechanism was studied using numerical simulation data, and an efficient treatment process was proposed. The kerosene vapor concentration inside the engine cavity before treatment was measured to be 4500 mg / m³. 3 The initial kerosene vapor concentration inside the cavity was set to 4500 mg / m³. 3 .

[0069] Reference Figure 4 The experimental result after 120 minutes of treatment and 10 minutes / cycle was 105 mg / m². 3 The simulation result is 124 mg / m³. 3 The error between the simulated and experimental values ​​was 18.09%; the experimental result for 30 minutes / cycle was 85 mg / m³. 3 The simulation result was 97 mg / m³. 3 The error between the simulated value and the experimental value is 14.11%.

[0070] The simulation process ends when the experimental error between the simulated and experimental values ​​is below 20%. This indicates that the numerical simulation model for removing residual kerosene from the inner wall of the liquid rocket engine after test firing, as described in this invention, is reliable, and its simulation results are valid and correct. The accuracy of the obtained simulation results can be used for mechanism analysis of the processing process in engineering practice, and the engine can be cleaned using the kerosene removal parameters from the numerical simulation.

[0071] Table 1 Comparison of simulated and experimental values ​​of kerosene vapor concentration inside the engine cavity after 120 minutes of treatment.

[0072]

[0073] Referring to Table 1, after 120 minutes of treatment, the cleaning efficiency was 97.86% for 30 minutes / cycle, 97.24% for 10 minutes / cycle, and 97.51% for 20 minutes / cycle. The proposed cleaning process can effectively remove residual kerosene from the engine's inner wall.

[0074] Analysis reveals that after 120 minutes of treatment, a 30-minute / cycle treatment yielded the best results, achieving a removal efficiency of 97.86%. The longer suction time during treatment is beneficial for removing residual kerosene because the lower suction pressure allows more kerosene remaining inside the cavity to evaporate and diffuse under low pressure. Simultaneously, the suction force within the low-pressure environment of the engine cavity is sufficiently strong to extract the kerosene-vapor-containing gas from the cavity. Therefore, in a 30-minute / cycle treatment within the engine cavity, the suction process lasts long enough, the internal pressure is lower, and the concentration of kerosene vapor in the gas decreases rapidly.

[0075] The application adopts Fluent 15.0 software to carry out three-dimensional numerical simulation on the heat and mass transfer law of engine cavity residual kerosene blowing and suction, so as to explore the evaporation diffusion and convection heat and mass transfer mechanism of hydrocarbons on the engine inner wall. The operation processes such as cycle blowing and vacuumizing of different engine cavities are simulated, the influence law of main influencing factors on post-test treatment on post-test treatment result is obtained, and the optimization result of post-test treatment process is sought.

[0076] The purpose of the application is to explore the kerosene removal effect of high-pressure nitrogen blowing and low-pressure suction process on the engine inner wall, and to seek the optimization scheme of post-test treatment process. First, the numerical calculation is used to study the cleaning effect of high-pressure nitrogen blowing and low-pressure suction combined operation with different cycle times on the residual kerosene on the inner wall.

[0077] In the experimental process, gas chromatography is used to measure the kerosene vapor concentration in the gas phase of the cavity before and after treatment, to characterize the cleaning effect and verify the simulation accuracy, to obtain the optimization method of residual kerosene cleaning on the inner wall of the complex structure cavity, and to obtain the influence law of post-test treatment effect of different cavities of the rocket engine, and to propose a method for cleaning the residual kerosene on the inner wall of the rocket engine after test.

[0078] The above is only the preferred embodiment of the application, and does not limit the technical solutions of the application in any way. Those skilled in the art should understand that the technical solutions can be modified and replaced in several simple ways without departing from the spirit and principles of the application, and these modifications and replacements also belong to the protection scope covered by the claims.

Claims

1. A method for removing kerosene from the inner wall of a liquid rocket engine based on numerical simulation, characterized in that, The method comprises the following steps: S1, a three-dimensional model of an engine cavity to be cleaned is established, and numerical simulation of the kerosene cleaning process is performed to obtain simulated values of kerosene vapor concentration in the engine cavity under different working conditions; An experimental piece of the engine cavity to be cleaned is prepared, and a kerosene cleaning test is performed under the same working conditions as the numerical simulation to obtain experimental values of kerosene vapor concentration in the engine cavity under different working conditions; The numerical simulation process of the engine to be cleaned is as follows: S11, a three-dimensional model of the engine to be cleaned is established by using Solidworks, and a gas inlet and a gas outlet are arranged at the left end and the right end of the cavity, and a suction port is arranged in the middle of the cavity; S12, the calculation grid of the three-dimensional model is divided by using a grid division software ICEM, and the calculation grid is a non-structural grid; S13, the inlet and outlet and the wall boundary conditions, the operating parameters of the cleaning process and the material parameters of the kerosene to be cleaned are set, the three-dimensional model after the calculation grid is divided is simulated by using the volume method to obtain simulated values of kerosene vapor concentration in the three-dimensional model cavity of the engine; S2, a standard error is set, and experimental errors between the simulated values of kerosene vapor concentration in the engine cavity and the experimental values of kerosene vapor concentration in the engine cavity under the same working conditions are calculated, and then the experimental errors are compared with the standard error to obtain the simulation result; When the experimental error is less than the standard error, the simulated values of kerosene vapor concentration in the engine cavity are reliable, the parameter settings of the cleaning process corresponding to the simulated values of kerosene vapor concentration in the engine cavity are effective, and the engine is cleaned by using the kerosene cleaning parameters in the numerical simulation; when the experimental error is greater than the standard error, the kerosene cleaning parameters in the numerical simulation are re-set until the experimental error is less than the standard error.

2. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 1, characterized in that, In S12, when the calculation grid is divided, first, each fluid domain is separated, and then the volume grid of each fluid domain is generated.

3. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 1, characterized in that, In S13, the parameters in the cleaning process are as follows: the pressure in the blowing process is 1 MPa, and the pressure in the suction process is 2 KPa; the suction and blowing process is 10 minutes / cycle, 20 minutes / cycle and 30 minutes / cycle, and the processing time is 120 min; the operating pressure is standard atmospheric pressure.

4. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 3, characterized in that, In the blowing process, the gas inlet is set as a pressure inlet, and the gas outlet pressure is a pressure outlet; in the suction process, the suction port is set as a pressure outlet.

5. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 4, wherein In S13, the boundary condition is a convection heat transfer boundary condition model.

6. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 4, wherein Both the blowing process and the suction process are calculated by using the Eulerian two-fluid model.

7. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 1, wherein, In S2, the calculation formula of the experimental error is as follows: 。 8. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 7, wherein, In S2, the standard error is 20%.

9. The method for removing kerosene from the inner wall of a numerical simulation liquid rocket engine according to claim 1, wherein, In S1, the size ratio of the three-dimensional model of the engine to be cleaned to the experimental piece of the engine to be cleaned is 1:1.

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