Spacecraft cable temperature prediction method

Abstract

The invention relates to a cable temperature prediction method for a spacecraft, and belongs to the technical field of aerospace crafts. Setting that the cable comprises n cable cores; when n is equal to 1, the insulation heat transfer coefficient h insulation of the cable is calculated; calculating the heating power P of the cable per unit length; calculating the surface temperature T when the cable reaches heat balance through a radiation heat conduction formula; calculating the internal and external temperature difference delta T1 of the cable insulation skin; calculating the center temperature T0 of the cable when n is equal to 1 according to the surface temperature T and the internal and external temperature difference delta T1; when n is greater than 1, calculating the heat transfer coefficient # imgabs0 # of the surface of the cable bundle, calculating the heat transfer coefficient # imgabs1 # of the inner surface of the cable, and iteratively calculating the center temperature T0'of the cable when n is greater than 1; the prediction of the center temperature of the cable under different n values is completed; the method adapts to the characteristics that the number of contacts in the spacecraft cable is large, and binding is fixed, the on-orbit temperature of the cable is accurately predicted in the early stage of design, and the method has huge advantages from the aspects of time cost, economic cost and reliability.

Description

Technical Field

[0001] The invention belongs to the technical field of aerospace vehicles and relates to a method for predicting the temperature of a cable used in a spacecraft. Background Art

[0002] Cables are an essential part of spacecraft. When the load is heavy, the cable temperature of the spacecraft is significantly higher than the ambient temperature in the cabin. Since the cables are bundled and fixed in sections, the cable heat dissipation ring at the bundling position will be even worse. If a short circuit or micro-short circuit occurs in the power supply equipment, the cable current will increase, which will cause the cable to heat up rapidly in a short period of time, and in severe cases, the cable may be damaged. The spacecraft power cable supplies power to the entire satellite equipment, with a large load current and high cable humidity. Therefore, it is particularly necessary to study the temperature rise change process of the power cable after power is turned on, so as to monitor the cable status and prevent failures.

[0003] In the current whole-star thermal design, the influence of cable heating is usually not considered, and it is stated in advance that "the heat conduction and radiation heat transfer of the connecting cables between devices are ignored." In the actual thermal analysis model, not only the heat conduction and radiation heat transfer of the cables are ignored, but also their heat capacity, heat consumption, etc. are not considered.

[0004] However, in certain situations, cable heating plays a significant role in the results of thermal design and thermal analysis. For example, in the error analysis of thermal balance tests, the influence of cable conduction leakage heat entering and leaving the satellite on the test results needs to be quantitatively considered; the heating of cables used to simulate external heat flow and heat consumption can cause the test results to deviate from the true value by more than 10°C. In addition, the current passing through the power cables on the satellite is very large when working, and the heat consumption reaches tens of watts. Its heating has a significant impact on the temperature of equipment in all compartments and cannot be ignored in analysis and calculation.

[0005] A lot of research has been conducted at home and abroad on the temperature rise of cables, but most of them are based on ground analysis. The heat dissipation method of ground cables is mainly convection, while the cables of spacecraft are in a vacuum environment and mainly rely on radiation to dissipate heat. The heat dissipation environment is worse than that of ground cables. In addition, the bundling, radiation and termination methods of cables will affect the heat dissipation model of cables, and their temperature rise is difficult to quantify.

[0006] Generally, during the whole-satellite thermal test phase, the cable temperature is measured by pasting thermistors, but this method is not suitable for measuring the temperature of spacecraft power cables. First, the method of pasting thermistors is suitable for equipment with large surfaces, while the outer diameter of the spacecraft cable bundle is small, which is not easy for thermistors to make good contact; second, spacecraft power cables often pass through cabins, and the temperature measurement point is far away from the temperature measurement equipment. Therefore, this indirect method of measuring the cable surface temperature is often used as a verification link and cannot be used as a reference for design elements. Summary of the invention

[0007] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and propose a temperature prediction method for spacecraft cables, which adapts to the characteristics of multiple connection points and binding fixation in spacecraft cables, and accurately predicts the on-orbit temperature of the cables in the early stage of design, which has great advantages in terms of time cost, economic cost and reliability.

[0008] The solution of the present invention is:

[0009] A method for predicting temperature of a spacecraft cable, comprising:

[0010] It is assumed that the cable includes n cable cores; n is a positive integer not less than 1;

[0011] When n is equal to 1, calculate the insulation heat transfer coefficient h of the cable 绝缘 ; Calculate the heating power P of the cable per unit length; Calculate the surface temperature T of the cable when it reaches thermal equilibrium by using the radiation heat conduction formula; Calculate the temperature difference ΔT1 between the inside and outside of the cable insulation; Based on the surface temperature T and the temperature difference ΔT1 between the inside and outside, calculate the cable center temperature T0 when n is equal to 1;

[0012] When n is greater than 1, calculate the heat transfer coefficient of the outer surface of the cable bundle Calculate the heat transfer coefficient of the cable inner surface Iterative calculation of the cable center temperature T0′ when n is greater than 1;

[0013] Complete the prediction of cable center temperature under different n values.

[0014] In the above-mentioned method for predicting the temperature of a spacecraft cable, the insulation heat transfer coefficient h 绝缘 The calculation method is:

[0015]

[0016] In the formula, δ is the thickness of the cable insulation layer, which can be obtained by looking up the table;

[0017] λ is the insulation thermal conductivity in vacuum environment.

[0018] In the above-mentioned method for predicting the temperature of a spacecraft cable, the calculation method of the heating power P is:

[0019] P=I 2 R

[0020] In the formula, I represents the current flowing through the cable;

[0021] R represents the impedance per unit length of cable.

[0022] In the above-mentioned spacecraft cable temperature prediction method, the surface temperature T is calculated according to the following formula:

[0023] I 2R=ε h σA C (T 4 -T0 4 )

[0024] In the formula, ε h is the hemispherical infrared emissivity of the outer surface of the cable insulation;

[0025] σ is the Stefan-Boltzmann constant;

[0026] T0 is the ambient temperature;

[0027] A C is the surface area per unit length of the cable.

[0028] In the above-mentioned method for predicting the temperature of a spacecraft cable, the surface area A per unit length of the cable C The calculation method is:

[0029] A C =πdL

[0030] Where d is the diameter of the cable with insulation;

[0031] L is the unit length.

[0032] In the above-mentioned method for predicting the temperature of a spacecraft cable, the calculation method of the diameter d of the insulating cable is:

[0033] d=2δ+d1

[0034] Where, δ is the thickness of the cable insulation layer;

[0035] d1 is the diameter of the cable core,

[0036] A is the cross-sectional area of ​​the cable core.

[0037] In the above-mentioned method for predicting the temperature of a spacecraft cable, the calculation method of the internal and external temperature difference ΔT1 is:

[0038]

[0039] Where Q is the power consumption per meter of the cable;

[0040] The cable center temperature T0 is:

[0041] T0=T+ΔT1.

[0042] In the above-mentioned spacecraft cable temperature prediction method, the heat transfer coefficient of the cable outer surface is The calculation method is:

[0043] In the formula, εh is the hemispherical infrared emissivity of the outer surface of the cable insulation;

[0044] σ is the Stefan-Boltzmann constant;

[0045] T0 is the ambient temperature;

[0046] T n is the cable outer surface temperature.

[0047] In the above-mentioned spacecraft cable temperature prediction method, the cable inner surface heat transfer coefficient The calculation method is:

[0048]

[0049] Where T1 is the inner surface temperature of the cable.

[0050] In the above-mentioned spacecraft cable temperature prediction method, the cable center temperature T0′ is calculated as follows:

[0051]

[0052] In the formula, q1 / q2 is the heating power of the two cables. Substituting it into the above formula, we can get the center cable temperature T0′.

[0053] The beneficial effects of the present invention compared with the prior art are:

[0054] (1) This invention is the first to conduct temperature analysis on spacecraft cables, which is used to predict the temperature of different cables on orbit and improve the thermal design of the entire satellite in the design stage;

[0055] (2) The single cable temperature prediction method proposed for the first time in this invention is a single cable simplification of the complex cable network of the entire satellite. Considering that radiation heat transfer is dominant in a vacuum environment, it is of great significance for the optimization design of the cable network.

[0056] (3) The temperature estimation model for the entire cable bundle proposed for the first time in this invention is an extension of the temperature prediction of a single cable. It takes the entire cable bundle as the research object, considers the factors of contact heat transfer, and is specifically designed for the binding of the entire cable bundle of the spacecraft. It has great advantages in terms of time cost, economic cost, and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a flow chart of temperature prediction of cables for spacecraft according to the present invention. DETAILED DESCRIPTION

[0058] The present invention will be further described below in conjunction with the embodiments.

[0059] The present invention provides a method for predicting the temperature of spacecraft cables, which is used to predict the operating temperature of each power cable of the entire satellite under a vacuum environment. It has important reference value for carrying out on-orbit spacecraft cable temperature prediction, cable network optimization design and cable inverse time protection.

[0060] Spacecraft cable temperature prediction methods, such as Figure 1 As shown, the specific steps include:

[0061] It is assumed that the cable includes n cable cores; n is a positive integer not less than 1.

[0062] When n is equal to 1, calculate the insulation heat transfer coefficient h of the cable 绝缘 .

[0063] Insulation heat transfer coefficient h 绝缘 The calculation method is:

[0064]

[0065] In the formula, δ is the thickness of the cable insulation layer, which can be obtained by looking up the table;

[0066] λ is the insulation thermal conductivity in vacuum environment.

[0067] Calculate the heating power P per unit length of cable.

[0068] The calculation method of heating power P is:

[0069] P=I 2 R

[0070] In the formula, I represents the current flowing through the cable;

[0071] R represents the impedance per unit length of cable.

[0072] The surface temperature T of the cable when it reaches thermal equilibrium is calculated using the radiation heat conduction formula.

[0073] Calculate the surface temperature T according to the following formula:

[0074] I 2 R=ε h σA C (T 4 -T0 4 )

[0075] In the formula, ε h is the hemispherical infrared emissivity of the outer surface of the cable insulation;

[0076] σ is the Stefan-Boltzmann constant;

[0077] T0 is the ambient temperature;

[0078] A Cis the surface area per unit length of the cable.

[0079] Surface area per unit length of cable A C The calculation method is:

[0080] A C =πdL

[0081] Where d is the diameter of the cable with insulation;

[0082] L is the unit length.

[0083] The calculation method of the diameter d of the cable with insulation is:

[0084] d=2δ+d1

[0085] Where, δ is the thickness of the cable insulation layer;

[0086] d1 is the diameter of the cable core,

[0087] A is the cross-sectional area of ​​the cable core.

[0088] Calculate the temperature difference ΔT1 between the inside and outside of the cable insulation.

[0089] According to the surface temperature T and the internal and external temperature difference ΔT1, calculate the cable center temperature T0 when n is equal to 1. The calculation method of the internal and external temperature difference ΔT1 is:

[0090]

[0091] Where Q is the power consumption per meter of the cable;

[0092] The cable center temperature T0 is:

[0093] T0=T+ΔT1.

[0094] When n is greater than 1, calculate the heat transfer coefficient of the outer surface of the cable bundle Heat transfer coefficient of the cable outer surface The calculation method is:

[0095]

[0096] In the formula, ε h is the hemispherical infrared emissivity of the outer surface of the cable insulation;

[0097] σ is the Stefan-Boltzmann constant;

[0098] T0 is the ambient temperature;

[0099] T n is the cable outer surface temperature.

[0100] Calculate the heat transfer coefficient of the cable inner surface Heat transfer coefficient of cable inner surface The calculation method is:

[0101]

[0102] Where T1 is the inner surface temperature of the cable.

[0103] Iteratively calculate the cable center temperature T0′ when n is greater than 1.

[0104] The calculation method of cable center temperature T0′ is:

[0105]

[0106] In the formula, q1 / q2 is the heating power of the two cables. Substituting it into the above formula, we can get the center cable temperature T0′.

[0107] Complete the prediction of cable center temperature under different n values.

[0108] Simulation verification

[0109] The power cables used in space exploration vehicles have three cable cores in each cable, and the current ranges from 0.1 to 30 A. Due to the harsh space environment in which they are used, the cable temperature may rise rapidly in a short period of time due to a short-term increase in current and binding, exceeding the upper limit of the cable's operating temperature; according to the cable manufacturer's manual, the cable's operating temperature is -40℃-100℃, and the thermal design of the entire satellite does not consider the heating effect of the cable.

[0110] 1) After the cable design and assembly are completed, arrange thermistor temperature measurement points;

[0111] 2) After the cable follows the whole satellite to participate in the thermal vacuum test, the temperature measurement point data are obtained as shown in the following table;

[0112]

[0113] 3) Compare the theoretical analysis temperature of the cable with the temperature of the measuring point measured by the thermal test:

[0114]

[0115] It has been verified that the cable temperature prediction model is in good agreement with the actual temperature of the cable in the thermal test. It can be concluded that the values ​​of environmental parameters and cable parameters are reasonable and the model prediction is accurate.

[0116] The present invention conducts temperature analysis on spacecraft cables for the first time, which is used to predict the temperatures of different cables on orbit, and improves the thermal design of the entire satellite in the design stage.

[0117] The single cable temperature prediction method proposed for the first time in this invention is a single cable simplification of the complex cable network of the entire satellite. Considering that radiation heat transfer is dominant in a vacuum environment, it is of great significance for the optimization design of the cable network.

[0118] The temperature estimation model for the entire cable bundle proposed for the first time in the present invention is an extension of the temperature prediction of a single cable. It takes the entire cable bundle as the research object, considers the factor of contact heat transfer, and is specifically designed for the binding of the entire cable bundle of spacecraft. It has great advantages in terms of time cost, economic cost, and reliability.

[0119] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for predicting the temperature of a spacecraft cable, characterized in that: include: It is assumed that the cable includes n cable cores; n is a positive integer not less than 1; When n is equal to 1, calculate the insulation heat transfer coefficient h of the cable 绝缘 ; Calculate the heating power P of the cable per unit length; calculate the surface temperature T of the cable when it reaches thermal equilibrium by using the radiation heat conduction formula; calculate the temperature difference ΔT1 between the inside and outside of the cable insulation; calculate the cable center temperature T0 when n is equal to 1 based on the surface temperature T and the temperature difference ΔT1 between the inside and outside; When n is greater than 1, calculate the heat transfer coefficient of the outer surface of the cable bundle Calculate the heat transfer coefficient of the cable inner surface Iterative calculation of the cable center temperature T0′ when n is greater than 1; Complete the prediction of cable center temperature under different n values.

2. A method for predicting temperature of a spacecraft cable according to claim 1, characterized in that: The insulation heat transfer coefficient h 绝缘 The calculation method is: In the formula, δ is the thickness of the cable insulation layer, which can be obtained by looking up the table; λ is the insulation thermal conductivity in vacuum environment.

3. A method for predicting temperature of a spacecraft cable according to claim 2, characterized in that: The calculation method of the heating power P is: P=I 2 R In the formula, I represents the current flowing through the cable; R represents the impedance per unit length of cable.

4. A method for predicting temperature of a spacecraft cable according to claim 3, characterized in that: Calculate the surface temperature T according to the following formula: I 2 R=ε h σA C (T 4 -T0 4 ) In the formula, ε h is the hemispherical infrared emissivity of the outer surface of the cable insulation; σ is the Stefan-Boltzmann constant; T0 is the ambient temperature; A C is the surface area per unit length of the cable.

5. A method for predicting temperature of a spacecraft cable according to claim 4, characterized in that: The surface area per unit length of the cable is A C The calculation method is: A C =πdL Where d is the diameter of the cable with insulation; L is the unit length.

6. A method for predicting temperature of a spacecraft cable according to claim 5, characterized in that: The calculation method of the diameter d of the insulated cable is: d=2δ+d1 Where, δ is the thickness of the cable insulation layer; d1 is the diameter of the cable core, A is the cross-sectional area of ​​the cable core.

7. A method for predicting temperature of a spacecraft cable according to claim 6, characterized in that: The calculation method of the internal and external temperature difference ΔT1 is: Where Q is the power consumption per meter of the cable; The cable center temperature T0 is: T0=T+ΔT1.

8. The method for predicting temperature of a spacecraft cable according to claim 1, characterized in that: Heat transfer coefficient of the cable outer surface The calculation method is: In the formula, ε h is the hemispherical infrared emissivity of the outer surface of the cable insulation; σ is the Stefan-Boltzmann constant; T0 is the ambient temperature; T n is the cable outer surface temperature.

9. A method for predicting temperature of a spacecraft cable according to claim 8, characterized in that: Heat transfer coefficient of cable inner surface The calculation method is: Where T1 is the inner surface temperature of the cable.

10. A method for predicting temperature of a spacecraft cable according to claim 9, characterized in that: The calculation method of cable center temperature T0′ is: In the formula, q1 / q2 is the heating power of the two cables. Substituting it into the above formula, we can get the center cable temperature T0′.

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