A method and system for quantitatively evaluating the online performance of thermal control multilayers

Abstract

Existing studies on thermal control multilayers have given the damage probabilities of thermal control multilayers corresponding to different average power densities. Correspondingly, the threshold power density of thermal control multilayers under different damage probabilities can be determined, but there is a lack of quantitative evaluation methods for the degree of damage to thermal control multilayers. The present invention proposes a method and system for quantitative evaluation of the online performance of thermal control multilayers from a quantitative perspective, that is, the performance is evaluated by fusing three types of data: surface imaging, temperature acquisition system, and equivalent emissivity, and the degree of damage to thermal control multilayers is graded, so that the severity of the damage can be quantitatively obtained. The present invention is funded by the Natural Science Foundation of Zhejiang Province, with project approval number LR24F030001.

Description

Technical Field

[0001] The present invention belongs to the field of thermal control multilayer, and in particular, relates to a method and system for quantitatively evaluating the online performance of thermal control multilayer. Background Art

[0002] Thermal control multilayer is a passive thermal control measure widely used in thermal design. It is not only used for heat preservation of instruments and equipment, but also can prevent high-temperature external heat flow (such as aerodynamic heating, solar radiation, plume heating of launch vehicles, etc.) from adversely affecting the instruments and equipment under its protection. Common thermal control multilayer materials are composed of reflective screens with low emissivity (such as aluminum foil, aluminized polyester film, etc.) and low thermal conductivity isolation layers (such as glass fiber paper, nylon mesh, plant fiber paper, etc.) alternately stacked on each other, usually 8-20 layers. Due to the particularity of the multilayer structure, it is very easy to be damaged.

[0003] Damage to thermal control multilayers will affect their thermal insulation capabilities. Existing studies on thermal control multilayers have given the probability of thermal control multilayer damage corresponding to different average power densities. Correspondingly, the threshold power density of thermal control multilayers under different damage probabilities can be determined, but there is a lack of relevant research on the quantitative evaluation of the degree of damage to thermal control multilayers. The present invention provides a method for quantitatively evaluating the online performance of thermal control multilayers from a quantitative perspective, that is, the performance is evaluated by fusing three types of data: surface imaging, temperature acquisition system, and equivalent emissivity, and the degree of damage to thermal control multilayers is graded. Using this method, the online performance evaluation level of thermal control multilayers can be obtained more accurately, avoiding the accidental errors caused by a single evaluation method. Summary of the invention

[0004] The existing thermal control multilayer patents provide the thermal control multilayer damage probability corresponding to different average power densities. Accordingly, the threshold power density of the thermal control multilayer under different damage probabilities can be determined, but there is a lack of relevant research on the quantitative evaluation of the degree of damage to the thermal control multilayer. The present invention provides a quantitative evaluation method for the online performance of the thermal control multilayer from a quantitative perspective, that is, the performance is evaluated by fusing three data, namely, surface imaging, temperature acquisition system and equivalent emissivity, and the online performance of the thermal control multilayer is graded.

[0005] A method for quantitatively evaluating the online performance of a thermal control multi-layer is disclosed. The method performs quantitative evaluation on the online performance of the thermal control multi-layer by fusing three data: surface imaging, temperature acquisition system, and equivalent emissivity. The method comprises: obtaining the thermal control multi-layer image by an observation method, judging the thermal control multi-layer image to obtain the proportion of undamaged area, judging based on the highest temperature data of the thermal control multi-layer to obtain the temperature hazard level, obtaining the initial emissivity of the thermal control multi-layer and the equivalent emissivity of the thermal control multi-layer after damage by simulation to obtain the emissivity ratio, fusing the proportion of undamaged area, the temperature hazard level, and the emissivity ratio to quantitatively obtain the online performance evaluation level of the thermal control multi-layer.

[0006] In the above technical solution, further, the thermal control multi-layer image to be evaluated is obtained and evenly divided into M units. The state of each unit is judged by observation, and the proportion of the intact area of ​​the thermal control multi-layer is obtained by statistics, that is, the proportion of the undamaged area is obtained.

[0007] Furthermore, the temperature T1 corresponding to the occurrence of blackening, carbonization and wrinkling of the thermal control multilayer material used and the melting point T m and vaporization point T v , retrieve the multi-layer temperature data of thermal control studied through the temperature acquisition system, and compare the highest temperature T max With T1, T m , T v The temperature hazard level is assessed based on the relationship between the sizes of the

[0008] Furthermore, the initial emissivity of the thermally controlled multilayer and the equivalent emissivity of the thermally controlled multilayer after damage are obtained by simulation to obtain the emissivity ratio, specifically including:

[0009] Establishing a simulation model of the thermal control multilayer to be evaluated; the simulation model at least includes a substrate and a material layer disposed on the substrate;

[0010] The thermally controlled multilayer substrate is heated by a heating plate under the substrate to obtain a thermally controlled multilayer heating temperature rise curve, and a first actual temperature rise rate is obtained through the temperature rise curve. Based on the simulation model, the material layer on the substrate is simulated with different emissivities at the same temperature rise starting point and heating power parameters to obtain the corresponding simulated temperature rise rate, and the working condition with the same first actual temperature rise rate is found, and the corresponding emissivity is recorded as the initial emissivity;

[0011] When the multilayer enters the shadow area, the heating sheet under the thermally controlled multilayer substrate is used to heat the material layer at the same temperature rise starting point and heating power parameters, and the thermally controlled multilayer heating temperature rise curve is obtained. The second actual temperature rise rate is obtained through the temperature rise curve. Based on the simulation model, the material layer on the substrate is simulated with different emissivities at the same temperature rise starting point and heating power parameters to obtain the corresponding simulated temperature rise rate, and the working condition with the same second actual temperature rise rate is found, and its corresponding emissivity is recorded as the equivalent emissivity;

[0012] Obtain the ratio of the equivalent emissivity to the initial emissivity.

[0013] Furthermore, the three evaluation data of surface imaging, temperature acquisition system and equivalent emissivity are integrated, different evaluation data are assigned different weights, and the quantitative thermal control multi-layer online performance evaluation level is obtained through comprehensive calculation through the weight method.

[0014] In addition, the present invention also provides a thermal control multi-layer online performance quantitative evaluation system for implementing any of the above-mentioned methods.

[0015] According to a specific embodiment of the present invention, the surface imaging performance evaluation may include the following steps: obtaining the surface morphology image of the thermal control multilayer by infrared imaging, and judging its surface state by observation method. The image is divided into a total of M units (M is determined according to the actual multilayer area size, and M is an integer ≥ 9), and the state of each unit is judged by observation. The state of the thermal control multilayer includes two situations, one is that the thermal control multilayer is not damaged, and the substrate or load under the multilayer is not directly exposed, and this state is recorded as 0; the other is that the thermal control multilayer is damaged, and the substrate or load under the multilayer is directly exposed, and this state is recorded as 1. The total number of undamaged states of the thermal control multilayer is S, which is calculated according to the formula P = S / M × 100%, that is, the proportion of intact area of ​​the thermal control multilayer. The online performance level of the thermal control multilayer is evaluated by the proportion of intact area of ​​the thermal control multilayer.

[0016] According to a specific embodiment of the present invention, the performance evaluation of the temperature acquisition system may include the following steps: The thermal control multilayer has different physical properties due to the different manufacturing processes and materials used. Here, a low-temperature thermal control multilayer with a total of 15 layers, which uses a more commonly used reflective screen as a double-sided aluminum-plated polyester film and a nylon mesh as an isolation layer, is taken as an example. If the surface temperature of the thermal control multilayer exceeds 127°C, blackening, carbonization, wrinkles and other phenomena may occur. When the surface temperature exceeds 269°C, ablation may occur. When the surface temperature exceeds 300°C, vaporization may occur. The temperature data of the thermal control multilayer under study is retrieved through the temperature acquisition system, and the online performance level of the thermal control multilayer is evaluated by comparing the maximum temperature of the thermal control multilayer with 127°C, 269°C, and 300°C.

[0017] According to a specific embodiment of the present invention, the performance evaluation of the equivalent emissivity of the thermally controlled multilayer may include the following steps: heating the lower substrate of the multilayer in the shadow area to obtain the heating temperature rise curve of the substrate, calculating the temperature rise rate through the temperature rise curve, and establishing a corresponding simulation model. The thermally controlled multilayer is equivalent to a coating attached to the substrate and in direct contact with the substrate. Based on the same heating starting point, the temperature rise change rate of the thermally controlled multilayer substrates with different emissivities is simulated and calculated to find the working condition with the same actual temperature rise rate. At this time, the corresponding emissivity is the equivalent emissivity. The online performance level of the thermally controlled multilayer is evaluated by the ratio of the equivalent emissivity to the emissivity of the thermally controlled multilayer in a good state.

[0018] According to a specific embodiment of the present invention, the effectiveness evaluation levels corresponding to three effectiveness evaluation methods can be scored respectively. Among them, Class Ⅳ (catastrophic) corresponds to a score of 75 < S ≤ 100, Class Ⅲ (fatal) corresponds to a score of 50 < S ≤ 75, Class Ⅱ (critical) corresponds to a score of 25 < S ≤ 50, and Class Ⅰ (minor) corresponds to a score of 0 ≤ S ≤ 25. Different weights are assigned to the three effectiveness evaluation methods. For example, the proportion of the effectiveness evaluation score of the surface imaging is 50%, the proportion of the effectiveness evaluation score of the temperature acquisition system is 30%, and the proportion of the effectiveness evaluation score of the equivalent emissivity is 20%. The comprehensive score of the multi-layer effectiveness evaluation level is calculated according to the weighting method to determine the effectiveness of the thermal control multi-layer.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The existing research on thermal control multi-layers has given the damage probabilities of thermal control multi-layers corresponding to different average power densities. Correspondingly, the threshold power density of thermal control multi-layers under different damage probabilities can be determined. However, there is a lack of relevant research on the quantitative evaluation of the damage degree of thermal control multi-layers. The present invention provides an on-line effectiveness evaluation method for thermal control multi-layers, that is, it is evaluated through the data fusion of surface imaging, temperature acquisition system and equivalent emissivity. Different weights are assigned to different evaluation methods, and the effectiveness level of thermal control multi-layers is comprehensively calculated by the weighting method.

[0021] Using this method reduces the accidental error caused by a single evaluation method, can quantitatively evaluate the effectiveness of thermal control multi-layers, and can obtain the on-line effectiveness level of thermal control multi-layers more accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the method flow of the present invention

[0023] Figure 2 Photo of the thermal control multi-layer of the present invention

[0024] Figure 3 Schematic diagram of the image equalization of the thermal control multi-layer of the present invention

[0025] Figure 4 Schematic diagram of the original thermal control multi-layer simulation model of the present invention

[0026] Figure 5 Temperature change diagram of the thermal control multi-layer of the present invention after damage DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] In order to make the above-mentioned purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation mode of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0028] In a preferred embodiment of the present invention, a method for quantitatively evaluating the online performance of a thermal control multilayer is provided. The method flow is as follows: Figure 1 As shown, the performance evaluation is performed from three perspectives: surface imaging, temperature acquisition system, and equivalent emissivity, and the corresponding evaluation data are then integrated to perform a quantitative evaluation of the online performance of thermal control multilayers.

[0029] Surface imaging performance evaluation includes the following steps:

[0030] Obtain thermally controlled multilayer surface morphology images through infrared imaging;

[0031] The images obtained must be thermally controlled multi-layer frontal morphological images;

[0032] The image is divided into a total of M units (M is determined according to the actual area size and shape of the thermal control multilayer, and M is an integer ≥ 9); according to an example of the present invention, the photo of the thermal control multilayer is as follows Figure 2 As shown, the effect after averaging is as follows Figure 3 As shown;

[0033] The actual thermal control multilayer may be of irregular shape, and when dividing the units, it should be ensured that there are no less than 3 units on each side;

[0034] By observing, determine the state of each unit, where there are only two unit states, recorded as 0 and 1 respectively;

[0035] The substrate or load under the thermal control multilayer is not directly exposed, the outer surface is intact or wrinkled, blackened, etc., and the thermal control multilayer is not damaged. This state is recorded as 0;

[0036] The substrate or load under the thermal control multilayer is exposed, and the thermal control multilayer is damaged. This state is recorded as 1;

[0037] The total number of thermal control multilayer units with a state of 0 is S;

[0038] The percentage of thermal control multi-layer intact area is calculated by the following formula;

[0039]

[0040] When P = 1, the outer surface of the thermal control multilayer is intact or blackened or wrinkled, and the substrate or load under the multilayer is not exposed, which has almost no effect on the temperature. This performance level is Class I;

[0041] When 50%≤P<1, damage occurs in a small range of the thermal control multilayer, and the substrate or load under the multilayer is exposed, but the operating temperature can still be maintained. This performance level is Class II;

[0042] When 0<P<50%, the thermal control multilayer is damaged in a large range, the substrate or load under the multilayer is exposed, the temperature exceeds the operating temperature range, and it cannot work normally. This performance level is Class III;

[0043] When P = 0, all the thermal control layers are ablated and vaporized, and the substrate or load under the layers is completely exposed, exceeding the working temperature range. The temperature is uncontrollable and may cause irreversible damage. This performance level is Class IV.

[0044] The temperature acquisition system performance evaluation includes the following steps:

[0045] The temperature collector retrieves the multi-layer temperature data of the thermal control being studied;

[0046] Find the highest temperature of the thermal control multilayer in the retrieved temperature data and record it as T max ;

[0047] According to the material characteristics of the thermally controlled multilayer, the temperature T1 corresponding to the blackening, carbonization, and wrinkling of the multilayer is obtained, and the melting point T m , vaporization point T v ;

[0048] Take the commonly used reflective screen as an example, which is a double-sided aluminum-coated polyester film, the isolation layer is a nylon mesh, and the total 15 layers of low-temperature thermal control multilayer, T1 is 127℃, T m 269℃, T v 300℃;

[0049] Compare T max With T1, T m , T v The size relationship of T max The temperature range in which it is located;

[0050] When T max When <T1, the highest temperature of the thermal control multilayer is lower than the temperature corresponding to the occurrence of blackening, carbonization, wrinkles and other phenomena in the multilayer. At this time, there is almost no effect on the temperature of the substrate or load under the thermal control multilayer. This performance level is Class I;

[0051] When T1≤T max <T mWhen the highest temperature of the thermally controlled multilayer is higher than the temperature T1 corresponding to the occurrence of blackening, carbonization, wrinkles, etc. in the multilayer, and lower than the melting point T m At this time, the substrate or load under the thermal control multilayer can still maintain the working temperature, and this performance level is Class II;

[0052] When T m ≤T max <T v When the maximum temperature of the thermal control multilayer is higher than the melting point of the material T m The corresponding temperature is lower than the vaporization point T of the material v At this time, the temperature of the substrate or load under the thermal control multilayer exceeds the operating temperature range and cannot work normally. This performance level is Class III;

[0053] When T max ≥T v When the highest temperature of the thermal control multilayer is higher than the vaporization point T of the material v The corresponding temperature, at this time, the substrate or load under the thermal control multilayer exceeds the working range temperature, the temperature is uncontrollable, and irreversible damage may be caused. This performance level is Class IV;

[0054] The thermal control multilayer equivalent emissivity performance evaluation includes the following steps:

[0055] When the thermal control multilayer enters the shadow area, the substrate or load under the thermal control multilayer begins to be heated at constant power, and the heating power Q1 at this time is recorded.

[0056] The temperature collector is used to obtain a curve chart showing the temperature of the thermally controlled multilayer substrate or load changing with time during the heating process; Figure 5 As shown;

[0057] Select two points S and E on the temperature rise curve with a larger slope, and the temperature rise rate V1 is calculated as follows:

[0058]

[0059] Where T E is the temperature corresponding to point E, °C;

[0060] Where Ts is the temperature corresponding to point S, °C;

[0061] where t E is the time corresponding to point E, s;

[0062] where t S is the time corresponding to point S, s;

[0063] Under the same starting point of temperature rise, the constant heating power of the substrate is Q1, and the temperature rise rate of the substrate with different equivalent emissivity is simulated and calculated;

[0064] Figure 4 A schematic diagram of a simulation model of a thermal control multilayer. The simulation model should at least include the thermal control multilayer and the substrate or load covered by the multilayer;

[0065] By adjusting different equivalent emissivities, the temperature rise curve of substrate heating is simulated and the simulated temperature rise rate V is obtained. 1-1 ;

[0066] Simulated temperature rise rate V 1-1 The acquisition method is the same as V1;

[0067] When the simulated temperature rise rate V 1-1 When the relative error δ with the actual temperature rise rate V1 is less than 0.1%, it can be considered that the corresponding emissivity at this time is the equivalent emissivity.

[0068]

[0069] Calculate the ratio of the equivalent emissivity to the original thermal control multilayer emissivity ε eff / ε;

[0070] When 1≤ε eff When / ε≤1.2, due to the 20% heating power design margin reserved in the thermal design, the substrate or load under the thermal control multilayer can still maintain the previous design temperature, and the equivalent emissivity ε eff When it increases, it has almost no effect on the temperature of the substrate or load under the thermal control multilayer, and this performance level is Class I;

[0071] When 1.2<ε eff When / ε≤2.93, due to the 20% heating power design margin and 20% temperature margin reserved in the thermal design, the temperature of the substrate or load under the multilayer will drop or rise, but it can still be maintained within the normal operating temperature range. This performance level is Class II;

[0072] When 2.93<ε eff When / ε≤19.2, the temperature of the substrate or load under the thermal control multilayer exceeds the normal operating temperature range, and the load cannot work normally. This performance level is Class III;

[0073] When ε eff / ε>19.2, and ε eff When the value is less than 1, the temperature of the substrate or load under the thermal control multilayer far exceeds the normal operating range, and the system temperature is uncontrollable, which may cause irreversible damage to the load under the thermal control multilayer. This performance level is Class IV.

[0074] Simulation equivalent emissivity ε under different conditions eff The calculation method of the ratio with the original emissivity ε is as follows:

[0075] When the thermal control multilayer reaches a thermal equilibrium state, the thermal equilibrium calculation method is shown in the following formula:

[0076]

[0077] Since the thermal equilibrium temperature T is much higher than the vacuum cold environment temperature T0 (3K), when calculating ε eff / ε, can be ignored At this point, the equilibrium formula can be simplified to:

[0078] Q=εAσT 4

[0079] When the thermal control layer changes, the equivalent emissivity increases, and the previous equilibrium temperature can still be maintained. In thermal design, a 20% heating power design margin is generally reserved. At this time, the thermal balance calculation formula is shown in the following formula, and ε is obtained. eff / ε=1.2;

[0080] (1+20%)Q=ε eff AσT 4

[0081] When the thermal control multilayer is partially damaged and the equivalent emissivity increases, the previous equilibrium temperature cannot be maintained. A 20% temperature margin is generally reserved in the thermal design, and the normal operating temperature can still be maintained. The thermal balance calculation formula is shown in the following formula to obtain ε eff / ε=2.93;

[0082] (1+20%)Q=ε eff Aσ(80%T) 4

[0083] When thermal control multilayer ablation is carried out over a large area, the equivalent emissivity continues to increase. At this time, the normal operating temperature of the instrument cannot be maintained. The thermal balance calculation formula is shown in the following formula to obtain ε eff / ε=19.2;

[0084] (1+20%)Q=ε eff Aσ(50%T) 4

[0085] According to Table 1, the multi-layer performance evaluation levels corresponding to the three methods are found.

[0086] Score the hazard levels corresponding to different effectiveness evaluation methods, with 100 points for Class IV, 75 points for Class III, 50 points for Class II, and 25 points for Class I; among them, the surface imaging effectiveness evaluation score accounts for 50%, the temperature acquisition system effectiveness evaluation score accounts for 30%, and the equivalent emissivity effectiveness evaluation score accounts for 20%; obtain the comprehensive score of the hazard level according to their respective weights, and determine which range the score falls into. Among them, Class IV (catastrophic) corresponds to a score of 75 < S ≤ 100, Class III (fatal) corresponds to a score of 50 < S ≤ 75, Class II (critical) corresponds to a score of 25 < S ≤ 50, and Class I (mild) corresponds to a score of 0 ≤ S ≤ 25; determine the damage hazard level of the thermal control multi-layer according to the comprehensive score of the hazard level.

[0087] Table 1 Thermal Control Multi-Layer Effectiveness Evaluation Level

[0088]

[0089] In addition, in another embodiment of the present invention, based on the same inventive concept as the above-mentioned online effectiveness quantitative evaluation method for thermal control multi-layers, an online effectiveness quantitative evaluation system for thermal control multi-layers is also provided, which is used to implement the online effectiveness quantitative evaluation method for thermal control multi-layers described in the present invention.

[0090] The above-described embodiments are only some preferred solutions of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical field can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for quantitatively evaluating the online performance of a thermal control multilayer, characterized in that: The online performance of thermal control multilayer is quantitatively evaluated by fusing three data, namely, surface imaging, temperature acquisition system and equivalent emissivity, including: obtaining thermal control multilayer images by observation method, judging the thermal control multilayer images to obtain the proportion of undamaged area; judging the temperature hazard level based on the highest temperature data of thermal control multilayer, first obtaining the temperature T1 corresponding to the occurrence of blackening, carbonization and wrinkling of the thermal control multilayer material used, and the melting point T m and vaporization point T v , retrieve the multi-layer temperature data of thermal control studied through the temperature acquisition system, and compare the highest temperature T max With T1, T m 、T v The temperature hazard level is evaluated by the relationship between the size of the thermal control multilayer and the thermal control multilayer equivalent emissivity after damage through simulation, and the emissivity ratio is obtained, including: Establishing a simulation model of the thermal control multilayer to be evaluated; the simulation model at least includes a substrate and a material layer disposed on the substrate; The thermally controlled multilayer substrate is heated by a heating plate under the substrate to obtain a thermally controlled multilayer heating temperature rise curve, and a first actual temperature rise rate is obtained through the temperature rise curve. Based on the simulation model, the material layer on the substrate is simulated with different emissivities at the same temperature rise starting point and heating power parameters to obtain the corresponding simulated temperature rise rate, and the working condition with the same first actual temperature rise rate is found, and the corresponding emissivity is recorded as the initial emissivity; When the multilayer enters the shadow area, the heating sheet under the thermally controlled multilayer substrate is used to heat the material layer at the same temperature rise starting point and heating power parameters, and the thermally controlled multilayer heating temperature rise curve is obtained. The second actual temperature rise rate is obtained through the temperature rise curve. Based on the simulation model, the material layer on the substrate is simulated with different emissivities at the same temperature rise starting point and heating power parameters to obtain the corresponding simulated temperature rise rate, and the working condition with the same second actual temperature rise rate is found, and its corresponding emissivity is recorded as the equivalent emissivity; Obtaining the ratio of the equivalent emissivity to the initial emissivity; The undamaged area ratio, temperature hazard level and emissivity ratio are integrated to quantitatively obtain the thermal control multi-layer online performance evaluation level.

2. The thermal control multi-layer online performance quantitative evaluation method according to claim 1, characterized in that: The thermal control multi-layer image to be evaluated is obtained and divided into M units. The state of each unit is judged by observation, and the proportion of the thermal control multi-layer intact area, that is, the proportion of the undamaged area, is obtained by statistics.

3. The thermal control multi-layer online performance quantitative evaluation method according to claim 1, characterized in that: The three evaluation data of surface imaging, temperature acquisition system and equivalent emissivity are integrated, different evaluation data are assigned different weights, and the quantitative thermal control multi-layer online performance evaluation grade is obtained through comprehensive calculation through the weight method.

4. A thermal control multi-layer online performance quantitative evaluation system, characterized in that: The system is used to implement the method according to any one of claims 1 to 3.

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