Numerical simulation method for on-orbit accurate measurement of residual propellant amount of plate-type storage tank based on heat capacity method

Abstract

The invention discloses a heat capacity method-based numerical simulation method for on-orbit accurate measurement of propellant surplus of a plate-type storage tank, which comprises the following steps of: firstly, constructing a three-dimensional calculation model of the plate-type storage tank, and setting surface tension between phase interfaces under microgravity, infiltration angles of a gas phase and a solid wall surface and environmental gravitational acceleration under an on-orbit flight working condition; carrying out numerical simulation on a gas-liquid flow process in the storage tank to obtain a stable distribution form of a propellant in the storage tank under a microgravity condition; secondly, carrying out two-phase heat exchange numerical simulation on the storage tank, and obtaining change data of the temperature of the wall surface of the storage tank along with time; different propellant filling ratios are set, and temperature change data of the outer wall of the storage tank are calculated; arranging the temperature change data under all packing ratios into a reference library; and carrying out a storage tank heat capacity method test under a microgravity condition, and comparing the measured temperature change data with the numerical simulation data in the reference library to obtain the residual amount of the propellant in the plate-type storage tank. According to the invention, accurate measurement of the residual amount of the propellant can be realized.

Description

Technical Field

[0001] The present invention relates to the field of satellite propellant remaining amount measurement, and particularly to a numerical simulation method for accurately measuring the remaining amount of propellant in an on-orbit plate-type tank based on the heat capacity method. Background Art

[0002] In space engineering, accurately grasping the remaining amount of propellant on a spacecraft is crucial for mission planning, orbit adjustment, and emergency handling. However, weighing methods, static pressure difference methods, float level gauges, etc. that rely on conventional gravitational acceleration, as well as radiation methods, optical methods, etc. that rely on determining the gas-liquid interface, cannot be applied in space. Because the microgravity condition will significantly affect the distribution and flow characteristics of fluids, resulting in a significant decrease in the measurement accuracy of traditional methods.

[0003] Currently, at home and abroad, more than a dozen detection methods have been proposed for the on-orbit autonomous and accurate measurement of the propellant amount, including: bookkeeping method, gas law method, volume excitation method, gas injection method, radioactive detection method, ultrasonic detection method, electromagnetic detection method, hydrodynamic method, and heat excitation method. Among them, the bookkeeping method, gas law method, and heat excitation method are three typical measurement methods. The heat excitation method has more advantages than the bookkeeping method and the gas law method at the end of the satellite's life, and for a multi-tank propulsion system, it can measure the remaining amount of a single tank, while the bookkeeping method and the gas law method can only measure the total remaining amount of the propellant. The heat excitation method can be divided into thermal response method (TPGT), heat capacity method (PGS), thermal metering method (TGM), and rapid measurement method (RPG). Among them, the heat capacity method has higher measurement accuracy because it uses a high-fidelity tank model for modeling and calculation. The establishment process of the high-fidelity tank model needs to include the internal propellant liquid level reconstruction process under on-orbit working conditions, and in the existing implementation methods of the heat capacity method, the application of the heat capacity method for reconstructing the liquid level under on-orbit microgravity conditions has not been carried out. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention proposes a numerical simulation method for accurately measuring the remaining amount of propellant in an on-orbit plate-type tank based on the heat capacity method. By comprehensively considering the geometric structure of the tank, the gas-liquid two-phase flow characteristics, and the heat conduction process under microgravity environment, a temperature data reference library for the heat capacity method measurement test of the tank under microgravity conditions is obtained, so as to use the measurement results to inversely deduce the remaining amount of propellant.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] A numerical simulation method for accurately measuring the remaining amount of propellant in an on-orbit plate-type tank based on the heat capacity method, comprising the following steps:

[0007] Step 1: Construct a detailed 3D model of the plate-type storage tank and perform mesh division. Input relevant physical properties of the propellant, including the density, viscosity, thermal conductivity, specific heat capacity of the propellant, and the pressure of the external environment, to ensure that the 3D model can accurately reflect the actual operating conditions;

[0008] Step 2: Consider the influence of surface tension on the gas-liquid two-phase flow characteristics under microgravity conditions. Set the surface tension between the phase interfaces under microgravity, the wetting angle between the gas-liquid interface and the solid wall, and the acceleration environment preset for the on-orbit flight condition. Set the propellant filling amount according to the propellant filling ratio resolution required for the actual on-orbit operation to achieve accurate numerical simulation of the gas-liquid flow process inside the plate-type storage tank and obtain the stable distribution pattern of the propellant inside the plate-type storage tank under microgravity conditions;

[0009] Step 3: Based on conditions including the area, power of the heating sheet, and the external environment temperature, construct a thermal analysis model of the plate-type storage tank and perform numerical simulation of two-phase heat transfer to obtain the data of the change in the wall temperature of the plate-type storage tank over time;

[0010] Step 4: Set different propellant filling percentages as variables and repeat Steps 2 to 3. For each filling percentage, calculate the data of the change in the outer wall temperature of the plate-type storage tank under the corresponding microgravity conditions. Organize the temperature change data under all filling ratios into a reference library to provide a comparison benchmark for implementing the on-orbit heat capacity method test;

[0011] Step 5: Implement the heat capacity method test for the storage tank under microgravity conditions. Compare the measured temperature change data with the numerical simulation data in the reference library, and select the filling amount of the propellant corresponding to the temperature change data closest to the numerical simulation data in the reference library as the remaining amount of the propellant inside the plate-type storage tank.

[0012] Further, in Step 2, based on the VOF gas-liquid two-phase flow model, the transient calculation is used to obtain the gas-liquid two-phase morphology inside the plate-type storage tank.

[0013] The beneficial effects of the present invention are as follows:

[0014] The numerical simulation method for accurately measuring the remaining amount of propellant in a plate-type storage tank based on the heat capacity method proposed by the present invention constructs the two-phase liquid level distribution inside the storage tank under on-orbit conditions through a high-precision on-orbit storage tank propellant liquid level reconstruction method. At the same time, based on the complex liquid level morphology inside the plate-type storage tank under microgravity, the application of the on-orbit storage tank heat capacity method is realized, thereby achieving high-precision measurement of the remaining amount of the on-orbit storage tank. Description of the Drawings

[0015] Figure 1 It is a flow schematic diagram of the numerical simulation method for accurately measuring the remaining amount of propellant in a plate-type storage tank based on the heat capacity method of the present invention.

[0016] Figure 2 It is the three-dimensional geometric model diagram of a certain plate-type storage tank in the embodiment.

[0017] Figure 3 It is the numerical calculation model of a certain plate-type storage tank in the embodiment.

[0018] Figure 4 It is the initial cloud diagram of a certain plate-type storage tank at filling ratios of 1%, 3%, 5%, and 7% in the embodiment.

[0019] Figure 5 It is the gas-liquid two-phase distribution diagram of a certain plate-type storage tank at filling ratios of 1%, 3%, 5%, and 7% under microgravity conditions.

[0020] Figure 6 It is the schematic distribution diagram of the heating sheet and 8 temperature measurement points on a certain plate-type storage tank.

[0021] Figure 7 It is the numerical simulation result of two-phase heat transfer of a certain plate-type storage tank. Among them, subgraphs (a) to (h) are the curves of the shell temperature of 8 temperature measurement points changing with time respectively. Specific implementation manner

[0022] The present invention will be described in detail below according to the attached drawings and preferred embodiments. The purpose and effect of the present invention will become clearer. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] As Figure 1 shown, the numerical simulation method for accurately measuring the remaining amount of propellant in a plate-type storage tank based on the heat capacity method of the present invention includes the following steps:

[0024] Step 1: Construct a detailed three-dimensional model of the plate-type storage tank and perform mesh division, and input relevant physical properties of the propellant, including the density, viscosity, thermal conductivity, specific heat capacity of the propellant, and the pressure of the external environment, to ensure that the three-dimensional model can accurately reflect the actual operating conditions.

[0025] As one of the embodiments of the present invention, given a certain plate-type storage tank, including the specific dimensions and thickness distribution of the accumulator, baffle plate, and outer shell, a detailed three-dimensional geometric model is constructed, as Figure 2 shown. Through the mesh division technology, a numerical calculation model of the storage tank is constructed, as Figure 3 shown, Figure 3 The left figure of 3 is the baffle plate, the middle figure is the accumulator, and the right figure is the overall numerical calculation model of the storage tank. Among them, the propellant is N2O4, and its density is 1444 kg / m -5Pa.S, with a surface tension coefficient of 26 dyn / cm and an external environmental pressure of 2 Mpa.

[0026] Step 2: Consider the influence of surface tension on the gas-liquid two-phase flow characteristics under microgravity conditions. Set the surface tension between the phase interfaces, the wetting angle between the gas-liquid interface and the solid wall, and the acceleration environment preset for the on-orbit flight condition. And set the propellant filling amount according to the propellant filling ratio resolution required for the actual on-orbit operation, so as to achieve an accurate numerical simulation of the gas-liquid flow process inside the plate-type tank and obtain a stable distribution pattern of the propellant inside the plate-type tank under microgravity conditions.

[0027] In this embodiment, the propellant filling ratio resolution required for the actual on-orbit operation is 2%. Therefore, when the filling ratios are set to 1%, 3%, 5%, and 7% respectively, the initialized cloud images obtained are as Figure 4 shown. The gas-liquid two-phase calculation model adopted in this embodiment is based on the VOF model and uses the PISO pressure correction algorithm. The stable distribution patterns of the propellant inside the tank under microgravity conditions at filling ratios of 1%, 3%, 5%, and 7% are as Figure 5 shown.

[0028] Step 3: Based on the conditions including the heating sheet area, power, and external environmental temperature, construct a thermal analysis model of the plate-type tank and conduct a numerical simulation of two-phase heat transfer to obtain the data of the change of the wall temperature of the plate-type tank over time.

[0029] In this embodiment, two heating sheets are symmetrically arranged on the tank shell, and bilateral equal-power (30 W) heating is adopted. The geometric size of the heating sheet is 200 mm × 400 mm. Eight temperature measurement points are selected on the tank shell. The setting positions of the heating sheets and the temperature measurement points in this embodiment are as Figure 6 shown.

[0030] Step 4: Set different propellant filling percentages as variables and repeat Steps 2 to 3. For each filling percentage, calculate the data of the change of the outer wall temperature of the plate-type tank under the corresponding microgravity conditions; organize the temperature change data under all filling ratios into a reference library to provide a comparison benchmark for implementing the on-orbit heat capacity method test.

[0031] As Figure 7 shown, it is the data of the change of the shell temperature over time in the two-phase heat transfer numerical simulation. Because at a filling ratio of 1%, the filling amount of the liquid is very small. After repositioning, the distribution of the liquid in the tank is scattered, resulting in most of the heat of the heating sheet being transferred to the metal shell. And because the heat transfer rate of the metal shell is relatively fast, the temperature of the monitoring point rises relatively fast, which is quite different from the temperature change trend over time at other filling ratios. For the visibility of the picture, Figure 7The data of the shell temperature change with time at a filling ratio of 1% is not shown, and only the data of the shell temperature change with time at eight temperature measurement points at filling ratios of 3%, 5%, and 7% are shown.

[0032] The temperature change data at all filling ratios are sorted into a reference library to provide a comparison benchmark for implementing the on-orbit heat capacity method test.

[0033] Step Five: Implement the heat capacity method test for the propellant tank under microgravity conditions. Compare the measured temperature change data with the numerical simulation data in the reference library, and select the filling amount of the propellant corresponding to the temperature change data closest to the numerical simulation data in the reference library as the remaining amount of the propellant in the plate-type propellant tank.

[0034] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art can still modify the technical solutions described in the foregoing examples or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included within the protection scope of the invention.

Claims

1. A numerical simulation method for accurate on-orbit measurement of the remaining amount of propellant in a plate tank based on the heat capacity method, characterized in that: The following steps are involved: Step 1: Build a detailed 3D model of the plate tank and perform meshing, input relevant propellant physical parameters, including the density, viscosity, thermal conductivity, specific heat capacity of the propellant, and the pressure of the external environment, to ensure that the 3D model can accurately reflect the actual operating conditions; Step 2: Considering the influence of surface tension on the gas-liquid two-phase flow characteristics under microgravity conditions, the surface tension between the phase interfaces under microgravity, the wetting angle between the gas-liquid interface and the solid wall, and the acceleration environment preset for the on-orbit flight conditions are set, and the propellant filling amount is set according to the propellant filling ratio resolution required for actual on-orbit operation, so as to achieve accurate numerical simulation of the gas-liquid flow process inside the plate tank, and obtain a stable distribution form of the propellant inside the plate tank under microgravity conditions; Step 3: Based on the conditions including the area, power and external ambient temperature of the heating plate, a thermal analysis model of the plate-type storage tank is constructed, a numerical simulation of two-phase heat exchange is performed, and data on the change of the wall temperature of the plate-type storage tank over time is obtained; Step 4: Set different propellant filling percentages as variables, repeat steps 2 to 3, and calculate the temperature change data of the outer wall of the plate tank under microgravity conditions for each filling percentage; organize the temperature change data under all filling ratios into a reference library to provide a comparison benchmark for the on-orbit heat capacity method test; Step 5: Conduct a tank heat capacity method test under microgravity conditions, compare the temperature change data obtained by measurement with the numerical simulation data in the reference library, and select the propellant filling amount corresponding to the temperature change data closest to the numerical simulation data in the reference library as the remaining amount of propellant in the plate tank.

2. The numerical simulation method for accurately measuring the remaining amount of propellant in a plate tank on orbit based on the heat capacity method according to claim 1 is characterized in that: In the step 2, based on the VOF gas-liquid two-phase flow model, transient calculation is used to obtain the gas-liquid two-phase state in the plate-type storage tank.

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