Thermal design method used for laser cavity and giving consideration to thermal shielding and weight reduction effects

Abstract

The invention discloses a thermal design method with both thermal shielding and weight reduction effects for a laser cavity, and relates to the technical field of thermal design optimization. The method comprises the following steps: S1, determining an initial structure of a multi-layer nested heat shielding laser cavity; s2, performing thermal analysis on the cavity structure to obtain all thermal design parameters, and calculating a thermal time constant of the silicon crystal; s3, calculating the weight of the cavity according to the initial structure; s4, evaluating a thermal shielding effect by a time constant, evaluating a weight reduction effect by weight, and performing multi-target Pareto optimization on thermal design parameters; and S5, weighing the two effects to obtain an optimal thermal design method. The thermal design efficiency of the laser cavity is improved, the thermal shielding effect is improved, and the weight cost is saved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal design optimization, and in particular relates to a thermal design method for a laser cavity that takes into account both thermal shielding and weight reduction effects. Background Art

[0002] Satellite-borne optical clocks are key payloads for space quantum science to ensure high-precision time and frequency benchmarks. The frequency stability of optical clocks requires ultra-stable lasers to reduce external thermal noise. An ultra-stable laser cavity is usually used to improve the thermal shielding effect and provide a stable and reliable temperature environment for the ultra-stable laser. At the same time, the resources on the satellite are very limited. Statistics show that the mass of the thermal control system accounts for 3% to 5% of the total mass of the satellite. Therefore, when conducting thermal design, it is also necessary to reduce weight while ensuring the thermal shielding effect.

[0003] From a thermal perspective, the larger the heat capacity, the slower the temperature changes and the better the heat shielding effect. However, large heat capacity requires an increase in material mass, so the two goals of heat shielding effect and weight reduction are conflicting. Current thermal design optimization methods rely on the experience of thermal design engineers, cannot efficiently iterate calculation solutions, and are difficult to obtain the optimal solution under the two conflicting design goals, resulting in poor heat shielding effects or excessive time and weight costs. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a thermal design method for a laser cavity that takes into account both heat shielding and weight reduction effects. By determining the thermal time constant calculation method, taking the thermal time constant and weight as objective functions, and utilizing the Pareto frontier to obtain a multi-objective optimal solution, a thermal design solution that takes into account both heat shielding and weight reduction effects is efficiently obtained.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A thermal design method for a laser cavity that takes into account both heat shielding and weight reduction effects, the method comprising:

[0007] Step S1, determining the initial structure of the multi-layer heat shielding cavity;

[0008] Step S2, performing thermal analysis on the initial structure of the multi-layer heat shielding cavity to calculate the thermal time constant of the silicon crystal;

[0009] Step S3, calculating the weight of the cavity according to the initial structure of the multi-layer heat shielding cavity to obtain the total weight of the cavity;

[0010] Step S4, performing multi-objective Pareto optimization based on the thermal time constant and the total weight of the cavity to obtain a Pareto frontier curve;

[0011] Step S5: Analyze the Pareto frontier curve to find the optimal thermal design solution that takes into account both thermal shielding effect and weight reduction effect.

[0012] In a second aspect, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned thermal design method for a laser cavity that takes into account both thermal shielding and weight reduction effects.

[0013] In a third aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned thermal design method for a laser cavity that takes into account both thermal shielding and weight reduction effects.

[0014] The beneficial effects of the present invention are:

[0015] The present invention calculates the thermal time constant and total weight through Laplace transform, and combines the Pareto frontier to form a method for efficiently designing the optimal thermal structure scheme of the multi-layer thermal shielding cavity. The equivalent thermal conductivity is obtained through thermal analysis, and the thermal time constant is calculated by Laplace transform using Matlab to quickly iterate the thermal design scheme; through Pareto frontier analysis, a thermal design scheme that reduces weight and time costs is finally obtained while ensuring a good thermal shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a flow chart of a thermal design method for a laser cavity that takes into account both thermal shielding and weight reduction effects;

[0017] Figure 2 A simplified model diagram of a multi-layer heat shielding cavity in an embodiment of the present invention;

[0018] Figure 3 It is the Pareto frontier curve in the embodiment of the present invention.

[0019] Reference numerals:

[0020] 101. Vacuum layer; 102. External temperature control layer; 103. Internal temperature control layer; 104. Shielding layer; 105. Support frame; 106. Silicon crystal; 107. Support rod; 108. Interlayer support; 109. Epoxy fiberglass cup support. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0022] like Figure 1As shown, it is a flow chart of a thermal design method for a laser cavity that takes into account both heat shielding and weight reduction effects of the present invention, comprising the following steps:

[0023] Step S1, determining the initial structure of the multi-layer heat shielding cavity;

[0024] Step S2, performing thermal analysis on the initial structure of the multi-layer heat shielding cavity to calculate the thermal time constant of the silicon crystal;

[0025] Step S3, calculating the weight of the cavity according to the initial structure of the multi-layer heat shielding cavity to obtain the total weight of the cavity;

[0026] Step S4, performing multi-objective Pareto optimization based on the thermal time constant and the total weight of the cavity to obtain a Pareto frontier curve;

[0027] Step S5: Analyze the Pareto frontier curve to find the optimal thermal design solution that takes into account both thermal shielding effect and weight reduction effect.

[0028] Preferably, in step S1, Figure 2 As shown, determining the initial structure of the multi-layer heat shielding cavity includes: determining the first structural parameters of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the support frame 105 arranged in sequence from the outside to the inside, wherein the first structural parameters include at least one of the bottom area, height, thickness, material thermal conductivity, density, specific heat capacity property, and surface radiation property. Preferably, all the first structural parameters of each layer are determined; the silicon crystal 106 is surrounded by the support frame 105 through the support rod 107, and the interlayer support 108 is respectively located between the outer temperature control layer 102 and the inner temperature control layer 103, the inner temperature control layer 104 and the shielding layer 105. Between the control layer 103 and the shielding layer 104, and between the shielding layer 104 and the support frame 105, the support rod 107 is a polyimide insulation column, and the interlayer support 108 is supported by a polyimide screw sleeve insulation structure; the second structural parameters of the support rod 107, the interlayer support 108, and the epoxy glass fiber reinforced plastic cup support 109 are determined, and the second structural parameters include at least one of the length, contact area, and thickness. Preferably, all the second structural parameters of each support structure are determined; the outermost vacuum layer 101 and the outer temperature control layer 102 are supported by an epoxy glass fiber reinforced plastic cup support 109.

[0029] The vacuum layer 101 is further connected to a vacuum system to evacuate the system to a vacuum level below 10-9 mbar.

[0030] The interlayer support 108 includes two polyimide insulating pads and a screw. The two connection surfaces are connected by the screws, and the contact surface is heat-insulated by the polyimide insulating pad.

[0031] Preferably, step S2 comprises the following steps:

[0032] Step S201, calculating the equivalent heat transfer coefficient of each connection structure, such as the equivalent heat transfer coefficient of the support rod 107, the interlayer support 108, and the epoxy glass fiber reinforced plastic cup support 109;

[0033] Step S202, calculating the equivalent radiation heat transfer coefficient between each layer, such as the equivalent radiation heat transfer coefficient of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105;

[0034] Step S203, calculating the interlayer equivalent thermal conductivity according to step S201 and step S202;

[0035] Step S204, according to the specific heat capacity and the interlayer equivalent thermal conductivity, Laplace transform is implemented in Matlab through code to obtain a temperature response formula and a temperature response curve of the silicon crystal 106 as the external temperature changes;

[0036] Step S205 , when the external temperature steps by 1K, the time when the temperature rises by (1-1 / e)K in the temperature response curve of the silicon crystal 106 is read, which is the thermal time constant.

[0037] Preferably, step S3 comprises the following steps:

[0038] Step S301, calculating the volumes of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the support frame 105 according to the bottom area, height and thickness of the materials of each layer;

[0039] Step S302, multiplying the volume of each layer by the material density to obtain the weights of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the support frame 105 respectively;

[0040] Step S303, adding the weights of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105 to obtain a total weight.

[0041] Preferably, step S4 comprises the following steps:

[0042] Step S401, maximizing the thermal time constant obtained in step S205 as an objective function for measuring the thermal shielding effect;

[0043] Step S402, minimizing the total weight obtained in step S303 as an objective function for measuring the weight loss effect;

[0044] Step S403, modify the material and thickness of each layer of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105, modify the surface radiation properties of each layer of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105, modify the length, thickness, contact area, etc. of the connection structure of each layer to change the equivalent thermal conductivity, perform experimental design, iteratively calculate the thermal time constant and the total weight through the ilaplace function in Matlab, and obtain a data set;

[0045] Step S404: Process the data set using the Pareto frontier method based on normal boundary intersection to obtain Pareto frontier curves of different materials.

[0046] Preferably, step S5 comprises the following steps:

[0047] Step S501, analyzing the Pareto frontier curves of different materials, and finding a solution that takes into account both heat shielding effect and weight reduction effect while meeting thermal design indicators;

[0048] Step S502: Compare the results before and after the optimization to obtain the optimal thermal design solution.

[0049] Example

[0050] Step S1: Press Figure 2 The initial structure of the multi-layer heat shielding cavity is determined as shown;

[0051] Step S2, cavity thermal analysis and calculation of thermal time constant;

[0052] First, calculate the equivalent heat transfer coefficient of the connection structure between each layer :

[0053] ,

[0054] Among them, λ is the thermal conductivity of the material, A is the contact area, L is the length, and n is the number of groups of identical connection structures in each layer.

[0055] Then calculate the equivalent radiation heat transfer coefficient between each layer :

[0056] ,

[0057] Among them, B ij represents the viewing factor from surface i to surface j, A j represents the area of ​​surface j, ε j represents the emissivity of surface j, represents the Boltzmann constant, T i and T jare the temperatures of surface i and surface j respectively, and the superscript r indicates radiation heat transfer. Represents the radiation heat transfer between surface i and surface j.

[0058] Finally, the equivalent thermal conductivity between each layer is calculated :

[0059] ,i,j=1,2,3,4,i<j,

[0060] Let the cavity from the silicon crystal 106 to the outer temperature control layer 102 have temperatures T1 to T4 and heat capacities C1 to C4, respectively. When the temperature is stable, there is a heat balance equation:

[0061] ,

[0062] In the formula, the superscript · represents the first-order time derivative of the temperature function;

[0063] Perform a Laplace transform:

[0064] ,

[0065] In the formula, s represents the Laplace operator, and the superscript ~ represents the temperature function after Laplace transformation;

[0066] The temperature variation relationship between the silicon crystal 106 and the outer temperature control layer 102 can be obtained:

[0067] ,

[0068] The outer wall of the external temperature control layer 102 is given a step response , then the temperature of the silicon crystal 106 can be obtained Depends on the formula:

[0069] ,

[0070] Substituting the heat capacity in step S1 and the equivalent heat transfer coefficient calculated in step S2, and performing Laplace transform, we can get the following:

[0071] ,

[0072] The above equation represents the temperature response curve of silicon crystal 106, and t represents time. This process can be solved in Matlab using the ilaplace function. Then draw this curve, and when the temperature rises to (1-1 / e)K, read the time at this time, which is the thermal time constant. .

[0073] Step S3, calculating the cavity weight;

[0074] The volumes of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105 are calculated according to the material bottom area, height and thickness of each layer. The weights of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105 are obtained by multiplying the volume of each layer by the material density. The weights of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105 are added together to obtain the total weight W.

[0075] ,

[0076] In the formula, i represents the i-th layer of the cavity structure, and there are 4 layers in total: the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105. represents the density of the i-th layer of material, represents the thickness of the i-th layer, represents the surface area of ​​the i-th layer.

[0077] Step S4, multi-objective Pareto optimization of thermal design parameters;

[0078] Firstly, the material and thickness of each layer of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105 are modified, the surface radiation properties of each layer of the outer temperature control layer 102, the inner temperature control layer 103, the shielding layer 104 and the supporting frame 105 are modified, and the length, thickness, contact area, etc. of the connection structure of each layer are modified to change the equivalent thermal conductivity. The above parameters are called thermal design parameters, and the experimental design is carried out, and the thermal time constant and the total weight are iteratively calculated to obtain the data set;

[0079] Then define two main optimization objectives: thermal shielding effect objective and weight reduction effect objective. The thermal time constant is:

[0080] ,

[0081] In the formula, m represents a total of m iterative calculations, and a represents the ath calculation. , there are q thermal design parameters, represents the value of the qth thermal design parameter at the ath calculation, represents the value matrix of all thermal design parameters at the ath calculation, It shows the thermal time constant calculated at this time, which represents the situation that when the external environment changes, the silicon crystal 106 changes with the external environment. represents the objective function of the heat shielding effect at the a-th calculation, After m calculations, all iterative calculations are obtained. The resulting matrix. Indicates taking The maximum value in the matrix, that is, the thermal time constant of the silicon crystal 106 is the largest. At this time, the silicon crystal 106 is least affected by the external temperature change and the thermal shielding effect is the best.

[0082] The objective function of weight loss effect is expressed by weight:

[0083] ,

[0084] In the formula, represents the total weight of the system at the ath calculation, Represents the objective function of the single weight loss effect at this time, After m calculations, all iterative calculations are obtained. The resulting matrix. Representative The minimum value in the matrix is ​​the minimum value of the system weight, and the weight reduction effect is the best at this time.

[0085] The Pareto frontier method based on normal boundary intersection is used to process the data set to obtain the Pareto frontier curves of different materials, such as Figure 3 By moving along the Pareto frontier curve, all Pareto optimal solutions of the dual-objective problem can be found.

[0086] Step S5, obtaining the optimal thermal design solution;

[0087] according to Figure 3 , analysis shows that the Pareto frontier curve of aluminum material is located at the lower right of copper material, indicating that under the same thermal design, copper material has a shorter thermal response time and lower weight than aluminum, which means that aluminum can achieve better thermal shielding performance at a lower weight cost. However, compared with aluminum structure, the temperature gradient of copper structure may be smaller. Specifically, for copper material, a thermal design optimization effect with a thermal time constant of 95h and a minimum weight of about 19.62 kg can be achieved. For aluminum material, a thermal design optimization effect with a thermal time constant of 190h and a minimum weight of 10.77 kg can be achieved. The optimal design scheme of aluminum material is analyzed to obtain the best thermal design scheme.

[0088] In a second aspect, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned thermal design method for a laser cavity that takes into account both thermal shielding and weight reduction effects.

[0089] In a third aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enables the processor to implement the aforementioned thermal design method for a laser cavity that takes into account both thermal shielding and weight reduction effects.

[0090] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thermal design method for a laser cavity that takes into account both heat shielding and weight reduction effects, characterized in that: The method comprises: Step S1, determining the initial structure of the multi-layer heat shielding cavity; Step S2, performing thermal analysis on the initial structure of the multi-layer heat shielding cavity to calculate the thermal time constant of the silicon crystal; Step S3, calculating the weight of the cavity according to the initial structure of the multi-layer heat shielding cavity to obtain the total weight of the cavity; Step S4, performing multi-objective Pareto optimization based on the thermal time constant and the total weight of the cavity to obtain a Pareto frontier curve; Step S5, analyzing the Pareto frontier curve to find the optimal thermal design solution that takes into account both thermal shielding effect and weight reduction effect.

2. A thermal design method for a laser cavity that takes into account both heat shielding and weight reduction effects according to claim 1, characterized in that: The initial structure of the multi-layer heat shielding cavity in step S1 includes a vacuum layer, an outer temperature control layer, an inner temperature control layer, a shielding layer and a support frame arranged in sequence from the outside to the inside; the silicon crystal is surrounded by the support frame through support rods, and the interlayer supports are respectively located between the outer temperature control layer and the inner temperature control layer, between the inner temperature control layer and the shielding layer, and between the shielding layer and the support frame. The vacuum layer and the outer temperature control layer are supported by epoxy fiberglass cup supports.

3. A thermal design method for a laser cavity that takes into account both heat shielding and weight reduction effects according to claim 2, characterized in that: Determining the initial structure of the multi-layer heat shielding cavity in the step S1 includes determining the first structural parameters of the outer temperature control layer, the inner temperature control layer, the shielding layer and the support frame, wherein the first structural parameters include at least one of the bottom area, height, thickness, material thermal conductivity, density, specific heat capacity property, and surface radiation property; and determining the second structural parameters of the support rod, the interlayer support, and the epoxy fiberglass cup support, wherein the second structural parameters include at least one of the length, contact area, and thickness.

4. The thermal design method for a laser cavity taking into account both heat shielding and weight reduction effects according to claim 2, characterized in that: The support rod is a polyimide insulation column; the interlayer support adopts a polyimide screw sleeve insulation structure, including two polyimide insulation pads and a screw, the two connection surfaces are connected by the screws, and the contact surface is insulated by the polyimide insulation pad.

5. The thermal design method for laser cavity according to claim 1, characterized in that: The step S2 comprises: Step S201, calculating the equivalent heat transfer coefficient of the support rod, the interlayer support, and the epoxy glass fiber reinforced plastic cup support; Step S202, calculating the equivalent radiation heat transfer coefficient between each layer; Step S203, calculating the interlayer equivalent thermal conductivity according to the equivalent heat transfer coefficient and the equivalent radiation heat transfer coefficient; Step S204, performing Laplace transform and inverse Laplace transform according to the specific heat capacity and the interlayer equivalent thermal conductivity, to obtain a temperature response formula and a temperature response curve of the silicon crystal as the external temperature changes; Step S205 , when the external temperature steps by 1K, the time when the temperature rises by (1-1 / e)K in the temperature response curve of the silicon crystal is read, which is the thermal time constant.

6. The thermal design method for a laser cavity taking into account both heat shielding and weight reduction effects according to claim 1, characterized in that: The step S3 comprises: Step S301, calculating the volumes of the outer temperature control layer, the inner temperature control layer, the shielding layer and the support frame according to the bottom area, height and thickness of the materials of each layer; Step S302, multiplying the volume of each layer by the material density to obtain the weights of the outer temperature control layer, the inner temperature control layer, the shielding layer and the support frame respectively; Step S303: Add the weights of the outer temperature control layer, the inner temperature control layer, the shielding layer and the supporting frame to obtain a total weight.

7. The thermal design method for a laser cavity taking into account both heat shielding and weight reduction effects according to claim 1, characterized in that: The step S4 comprises: Step S401, maximizing the thermal time constant as an objective function for measuring the thermal shielding effect; Step S402, minimizing the total weight is used as the objective function to measure the weight loss effect; Step S403, modify the material and thickness of each layer of the outer temperature control layer, the inner temperature control layer, the shielding layer and the supporting frame, modify the surface radiation properties of each layer of the outer temperature control layer, the inner temperature control layer, the shielding layer and the supporting frame, modify the length, thickness and contact area of ​​the connection structure of each layer, perform experimental design, iteratively calculate the thermal time constant and the total weight through the ilaplace function in Matlab, and obtain a data set; Step S404: Process the data set using the Pareto frontier method based on normal boundary intersection to obtain Pareto frontier curves of different materials.

8. The thermal design method for a laser cavity taking into account both heat shielding and weight reduction effects according to claim 1, characterized in that: The step S5 comprises: Step S501, analyzing the Pareto frontier curves of different materials, and finding a solution that takes into account both heat shielding effect and weight reduction effect while meeting thermal design indicators; Step S502: Compare the results before and after the optimization to obtain the optimal thermal design solution.

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