Temperature noise suppression method using multi-layer composite structure

Abstract

The invention relates to a temperature noise suppression method using a multilayer composite structure, and belongs to the technical field of temperature noise control of space science detection devices. High-temperature noise is shifted out of a sensitive frequency interval through a high-specific-heat-capacity material, and temperature noise suppression is achieved based on a multi-layer composite structure of a low-heat-conductivity material and the high-specific-heat-capacity material; the thermal conductivity of the low-thermal-conductivity material is not greater than 0.05 W / (m.K); the phase change latent heat of the high-specific-heat-capacity material is not less than 100 J / g; the specific operation is as follows: (1) setting the total thickness of the multi-layer composite structure according to the thickness requirement of a spacecraft external thermal control material; (2) determining a high-specific-heat-capacity material and a low-heat-conductivity material; (3) placing the high-specific-heat-capacity material on the outer layer, and determining that the optimal proportion of the high-specific-heat-capacity material is 60%-70%; and (4) the number of layers of the composite material of the multi-layer composite structure is determined, the multi-layer composite structure is formed by alternately arranging more than four layers of low-heat-conductivity materials and more than five layers of high-specific-heat-capacity materials, and the suppressed temperature noise level meets the requirement.

Description

Technical Field

[0001] The invention belongs to the technical field of temperature noise control of space science detection devices, and in particular relates to a temperature noise suppression method using a multi-layer composite structure. Background Art

[0002] Gravitational waves are ripples in the structure of space and time. Gravitational wave detection is of great significance for exploring the origin of the universe and compact stars. At present, gravitational wave detection is mainly based on laser interferometry technology, which detects gravitational wave signals by detecting the phase difference between two co-source laser beams. There are certain limitations in ground-based gravitational wave detection: on the one hand, the current ground-based gravitational wave detectors have very low detection sensitivity below 100 Hz, and most gravitational waves are concentrated in the frequency range of 0.1 mHz to 0.1 Hz; on the other hand, the arm length of the ground-based gravitational wave detector is limited, and the phase difference between the two lasers is very small, which limits the sensitivity of ground-based gravitational wave detection. Space gravitational wave detection can greatly increase the arm length of the interferometer and avoid ground noise interference, so space gravitational wave detection is very necessary.

[0003] Space gravitational wave detection uses three synchronous satellites to build an interferometer arm length, and uses inertial sensors to sense the position changes between the detection masses, thereby detecting gravitational wave signals. Temperature fluctuations around the detection masses will produce temperature effects such as radiation pressure effect and thermal deformation fluctuations, reducing the sensitivity of inertial sensors to detect gravitational wave signals. These temperature effects can be called temperature noise. Temperature noise will produce stray forces and torques that vary with time on the detection mass, and acceleration noise on the detection mass, thereby changing the motion orbit of the detection mass, masking the distance changes of the detection mass caused by gravitational waves, and drowning out the signals from gravitational waves. Therefore, it is very important to suppress temperature noise.

[0004] Temperature noise comes from space heat flux noise mainly composed of solar radiation. As the satellite rotates around the earth and the sun, solar radiation irradiates the satellite periodically, generating a certain amount of heat flux noise. In the sensitive frequency band of gravitational wave detection, the heat flux noise of solar radiation is about 5W / (m 2 ·Hz 1 / 2 ), the heat flux noise generated by the Earth and the Moon is 10 -2 W / (m 2 ·Hz 1 / 2 ) and 10 -5 W / (m 2 ·Hz 1 / 2 ). Space heat flow acts on the satellite and propagates in the satellite's thermal protection layer through heat conduction. According to Fourier's law of heat conduction, the temperature noise frequency is determined by the heat source frequency. Research has found that in order to ensure the smooth development of space gravitational wave detection, the temperature noise should be controlled within μK / Hz 1 / 2 How to achieve an ultra-low temperature noise environment for space gravitational wave detectors is an urgent problem to be solved.

[0005] At present, the multi-layer materials used in spacecraft are composed of reflective layers (such as aluminum-coated polyimide film) and spacers (such as polyester mesh) arranged at intervals, mainly to form high thermal resistance to inhibit radiation heat transfer. In recent years, NASA Goddard Space Flight Center in the United States has integrated low thermal conductivity aerogels into multi-layer insulation materials to further improve the insulation performance. The current space multi-layer insulation materials are aimed at controlling the harsh temperature environment of 200°C to -180°C on the surface of the spacecraft to a temperature range that ensures the normal operation of the spacecraft and its instruments and equipment. However, they do not pay attention to temperature fluctuations in a small range. For example, when achieving a temperature control accuracy of ±1K, whether the temperature changes linearly or fluctuates within the temperature range of ±1K is not a concern, that is, the control of temperature noise is not a concern. However, the above issues need to be considered in thermal control during gravitational wave detection.

[0006] Due to the limited resources available for space exploration devices in space, at present, temperature noise control at home and abroad is mainly based on passive thermal insulation materials. For example, the LISA satellite uses a heat shield made of a thick layer of composite polyurethane material to suppress temperature noise, and the Taiji-1 satellite uses thermal insulation materials to reduce external thermal interference. Studies have shown that the lower the thermal conductivity and the higher the specific heat capacity of the passive thermal insulation material, the better the temperature noise suppression effect. Therefore, it is urgent to develop materials that meet both low thermal conductivity and high specific heat capacity in the target frequency band in space gravitational wave detection. Commonly used low thermal conductivity materials include aerogels, composite polyurethanes, etc., and related research focuses on reducing the thermal conductivity of thermal insulation materials; commonly used high specific heat capacity materials include phase change materials, and related research is committed to increasing the latent heat of phase change materials. However, it is difficult for a single thermal control material to be compatible with both low thermal conductivity and high specific heat capacity. At the same time, simply mixing low thermal conductivity materials and high heat capacity materials will increase the thermal conductivity of the composite material and reduce its specific heat capacity, weakening the advantages of each raw material. Based on the above analysis, the present invention proposes a temperature noise suppression method using a multilayer composite structure. Summary of the invention

[0007] In order to achieve passive thermal insulation material suppression within a target frequency band while being compatible with both low thermal conductivity and high specific heat capacity, the present invention provides a temperature noise suppression method using a multi-layer composite structure.

[0008] A temperature noise suppression method using a multi-layer composite structure uses low thermal conductivity materials to reduce the intensity of temperature noise, uses high specific heat capacity materials to move high temperature noise out of the sensitive frequency range, and suppresses temperature noise based on a multi-layer composite structure of low thermal conductivity materials and high specific heat capacity materials; The sensitive frequency range refers to the temperature noise frequency range greater than 1mHz; The multilayer composite structure is composed of high specific heat capacity materials and low thermal conductivity materials arranged alternately; The thermal conductivity of the low thermal conductivity material is not greater than 0.1 W / (m·K); The equivalent specific heat capacity of the high specific heat capacity material is not less than 4000 J / (kg·K).

[0009] The multi-layer composite structure is arranged alternately layer by layer in the order of high specific heat capacity materials and low thermal conductivity starting from the heat flow source and along the temperature noise transmission direction.

[0010] The high specific heat capacity material is a phase change material, the phase change latent heat of the phase change material is not less than 100 J / g, and the phase change temperature is near the controlled temperature.

[0011] The steps for temperature noise suppression based on multi-layer composite structure are as follows: Step (1): according to the thickness requirement of the spacecraft external thermal control material, the total thickness of the multi-layer composite structure is set, and the total thickness is 1-2 cm; that is, the sum of the thickness of more than four layers of low thermal conductivity materials and more than five layers of high specific heat capacity materials; Step (2): respectively determine the high specific heat capacity material and the low thermal conductivity material; Step (3): placing a high specific heat capacity material in the outer layer and determining the optimal proportion of the high specific heat capacity material, which is 60%-70%; Step (4): Under the premise of the optimal proportion of high specific heat capacity materials determined in step 3, the number of composite material layers of the multi-layer composite structure is increased in sequence, that is, more than four layers of low thermal conductivity materials and more than five layers of high specific heat capacity materials, so that the temperature noise level after suppression meets the requirements.

[0012] A further technical solution for the above temperature noise suppression operation is as follows: The gravitational wave detection frequency band of the spacecraft is between 0.1mHz and 1Hz.

[0013] The frequency band of the sensitive frequency interval is between 10mHz and 1Hz.

[0014] The low thermal conductivity material is a composite polyurethane material with a thermal conductivity of 0.044 W / (m·K), a specific heat capacity of 885 J / (kg·K), and a density of 100 kg / m 3 .

[0015] The high specific heat capacity material is a phase change material uniformly mixed with 70-80% by mass of paraffin, 5-10% by mass of expanded graphite, and 10-15% by mass of olefin block copolymer; the high specific heat capacity material has a thermal conductivity of 1.447 W / (m·K), an equivalent specific heat capacity of 4660 J / (kg·K), a phase change latent heat of 145.1 J / g, and a density of 919 kg / m 3 .

[0016] The mass fraction of the paraffin wax is 80%, the mass fraction of the expanded graphite is 5%, and the mass fraction of the olefin block copolymer is 15%.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are embodied in the following aspects: (1) The temperature noise suppression method of the present invention reduces the intensity of temperature noise through the low thermal conductivity characteristics, moves the high temperature noise out of the sensitive frequency range through the high specific heat capacity characteristics, and constructs a multi-layer composite structure based on low thermal conductivity materials and high specific heat capacity materials, thereby solving the problem of difficulty in developing materials with both low thermal conductivity and high specific heat capacity, and achieving temperature noise suppression. When the number of layers of the multi-layer composite structure is three and the proportion of high specific heat capacity materials is 60%-70%, the temperature noise suppression effect is the best, and the three-layer composite structure of high specific heat capacity material-low thermal conductivity material-high specific heat capacity material has a better effect. The results are shown in Figure 2 When the high specific heat capacity material accounts for 70%, the temperature noise of the high specific heat capacity material-low thermal conductivity material-high specific heat capacity material composite structure is only 15% of that of the low thermal conductivity material-high specific heat capacity material-low thermal conductivity material. For multi-layer composite structures with different numbers of layers, the more layers there are, the better the temperature noise suppression effect is. The effect is much stronger than the commonly used single-layer thermal insulation low thermal conductivity material. The temperature noise suppression effect in the frequency band of 0.001Hz tends to be stable when the number of layers is greater than three. The results are shown in Figure 3 .

[0018] (2) The present invention uses phase change material as a high specific heat capacity material for multilayer structure composite, because the phase change material has a high equivalent specific heat capacity due to its large latent heat of phase change.

[0019] (3) The present invention proposes an optimized arrangement of a multilayer composite structure with a high specific heat capacity material in the outer layer and a low thermal conductivity material in the inner layer. The high specific heat capacity material has the characteristics of heat storage and heat transfer delay, thereby moving the high temperature noise out of the sensitive frequency range. By combining it with the low thermal conductivity material, the ultra-low temperature noise can be suppressed.

[0020] The specific proof is as follows: The temperature noise suppression effect of multi-layer composite structure and single-layer thermal control material is compared. Figure 3 As shown, for temperature noise with a frequency of 0.001 and 0.005 Hz, when the composite structure is a single-layer composite structure, the temperature noise suppression effect of the high specific heat capacity material is better than that of the low thermal conductivity material. When the number of layers of the composite structure increases, the temperature noise suppression effect is significantly better than that of the single-layer structure. Therefore, the present invention creates a temperature noise suppression method using a multi-layer composite structure, combines high specific heat capacity materials with low thermal conductivity materials, and constructs a multi-layer composite structure, thereby achieving the suppression of ultra-low frequency temperature noise. Results are shown in Figure 3When the number of layers increases, the noises with frequencies of 0.001 and 0.005 Hz both show a downward trend, and the noise with frequency of 0.005 Hz decreases particularly significantly. The noise of the 7-layer composite material structure is only about 1 / 5 of that of the 3-layer composite material structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of a multi-layer composite structure with 7 layers.

[0022] Figure 2 This is a comparison chart of the temperature noise suppression effect when the high specific heat capacity material is in the inner (RCR) and outer (CRC) layers.

[0023] Figure 3 This is a comparison chart of the temperature noise suppression effect of multi-layer composite structure and single-layer thermal control material.

[0024] Figure 1 Medium sequence number: high specific heat capacity material 1, low thermal conductivity material 2, material outer surface 3. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Example 1 The Tianqin Project is to launch three satellites into an orbit 100,000 kilometers from the Earth, forming an equilateral triangle satellite array with the Earth as the center. During the mission, the Tianqin satellite needs to achieve a 10-second frequency response within the range of 0.1 MHz to 1 Hz. -5 K / Hz 1 / 2 Temperature noise control, using passive thermal control materials to suppress high-frequency temperature noise.

[0027] The steps to achieve temperature noise suppression using a multi-layer composite structure are as follows: Step (1): Set the total thickness of the multilayer composite structure according to the thickness requirements of the spacecraft external thermal control material In this embodiment 1, the total thickness of the high specific heat capacity material 1 and the total thickness of the low thermal conductivity material 2 are both 1 cm, and the total thickness of the multilayer composite structure is 2 cm.

[0028] Step (2): Select high specific heat capacity materials and low thermal conductivity materials as the base materials of the multilayer composite structure In this embodiment 1, the high specific heat capacity material is a shaped composite phase change material, which is made by uniformly mixing 80% by weight of paraffin wax, 5% by weight of expanded graphite and 15% by weight of olefin block copolymer. The high specific heat capacity material has a thermal conductivity of 1.447 W / (m·K), an equivalent specific heat capacity of 4660 J / (kg·K), a phase change latent heat of 145.1 J / g, and a density of 919 kg / m 3.

[0029] The low thermal conductivity material is a composite polyurethane material. The thermal conductivity of the composite polyurethane material is 0.044 W / (m·K), the specific heat capacity is 885 J / (kg·K), and the density is 100 kg / m 3 .

[0030] Step (3): Place the high specific heat capacity material on the outer layer and determine the optimal proportion of the high specific heat capacity material In this embodiment 1, the optimal high specific heat capacity material accounts for 65%.

[0031] By establishing a thermal simulation model of a multi-layer composite structure, numerical solutions are performed under periodic thermal boundary conditions, and the multi-layer composite structure is optimized with the temperature noise suppression index as the target. Under the condition that the thickness of the overall thermal control material remains unchanged, the influence of the arrangement mode and number of layers of the multi-layer composite structure is analyzed. Figure 1 As shown in Figure 2, the thermal simulation results show that the more layers there are, the better the performance. Figure 3 As shown, it is also found that the temperature noise suppression effect of the multilayer composite structure arrangement of the high specific heat capacity material 1 in the outer layer is better than the temperature noise suppression effect of the multilayer composite structure arrangement of the high specific heat capacity material in the inner layer, as shown in FIG. Figure 2 shown.

[0032] Step (4): Under the premise of the optimal ratio of high specific heat capacity materials, determine that the multilayer composite structure has a total of 9 layers, see Figure 1 , which is composed of five layers of high specific heat capacity material 1 and four layers of low thermal conductivity material 2 that are staggered, and the low thermal conductivity material 2 is located between two layers of high specific heat capacity material 1. The thermal simulation results show that in this embodiment 1, when the number of composite layers of the multi-layer composite structure is 9 layers, the temperature noise suppression requirement is met. Example 2

[0033] The Space Taiji Project is to launch three satellites into an orbit 50 million kilometers from the Earth, forming an equilateral triangle gravitational wave detection constellation around the Sun. During the mission, the Taiji satellites need to achieve a 10-Hz frequency range of 0.1mHz to 1Hz. -6 K / Hz 1 / 2 Temperature noise control, using passive thermal control materials to suppress high-frequency temperature noise.

[0034] The method for suppressing temperature noise using a multilayer composite structure comprises the following steps: Step (1): Set the total thickness of the multilayer composite structure according to the thickness requirements of the spacecraft external thermal control material In this embodiment 2, the total thickness of the high specific heat capacity material 1 and the total thickness of the low thermal conductivity material 2 are both 0.5 cm, the total thickness of the multilayer composite structure is 1 cm, and the rest is the same as in embodiment 1.

[0035] Step (2): Select high heat capacity material and low thermal conductivity material as the base material of the multilayer composite structure In this embodiment 2, the high specific heat capacity material is a shaped composite phase change material, which is the same as that in embodiment 1. The low thermal conductivity material is the same as that in embodiment 1.

[0036] Step (3): Place high heat capacity materials on the outer layer and determine the optimal proportion of high heat capacity materials In this embodiment 2, the optimal high specific heat capacity material accounts for 70%.

[0037] Step (4): Under the premise of the optimal proportion of high heat capacity materials, it is determined that the multilayer composite structure has 11 layers in total, which are composed of six layers of high specific heat capacity materials 1 and five layers of low thermal conductivity materials 2 that are alternately distributed.

[0038] By establishing a thermal simulation model of a multi-layer composite structure, numerical solutions are performed under periodic thermal boundary conditions, and the multi-layer composite structure is optimized with the temperature noise suppression index as the target. Under the condition that the thickness of the overall thermal control material remains unchanged, the influence of the arrangement mode and number of layers of the multi-layer composite structure is analyzed. The schematic diagram of the multi-layer composite structure is shown in Figure 1 As shown in Figure 2, the thermal simulation results show that the more layers there are, the better the performance. Figure 3 As shown, it is also found that the temperature noise suppression effect of the multilayer composite structure arrangement of high specific heat capacity materials in the outer layer is better than the temperature noise suppression effect of the multilayer composite structure arrangement of high specific heat capacity materials in the inner layer, as shown in Figure 2 The thermal simulation results show that the noise suppression requirement can be met at the 11th layer. Therefore, in this embodiment 2, the result of the multi-layer composite structure design method is to use a multi-layer composite structure with 11 layers of high specific heat capacity materials in the outer layer to suppress temperature noise.

Claims

1. A method for suppressing temperature noise using a multi-layer composite structure, characterized in that: The temperature noise suppression method uses low thermal conductivity materials to reduce the intensity of temperature noise, uses high specific heat capacity materials to move high temperature noise out of the sensitive frequency range, and suppresses temperature noise based on a multilayer composite structure of low thermal conductivity materials and high specific heat capacity materials; The sensitive frequency range refers to the temperature noise frequency range greater than 1mHz; The multilayer composite structure is composed of high specific heat capacity materials and low thermal conductivity materials arranged alternately; The thermal conductivity of the low thermal conductivity material is not greater than 0.1 W / (m·K); The equivalent specific heat capacity of the high specific heat capacity material is not less than 4000 J / (kg·K).

2. The method for suppressing temperature noise using a multi-layer composite structure according to claim 1, characterized in that: The multi-layer composite structure is arranged alternately layer by layer in the order of high specific heat capacity materials and low thermal conductivity starting from the heat flow source and along the temperature noise transmission direction.

3. The method for suppressing temperature noise using a multi-layer composite structure according to claim 1, characterized in that: The high specific heat capacity material is a phase change material, the phase change latent heat of the phase change material is not less than 100 J / g, and the phase change temperature is near the controlled temperature.

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