An airborne integrated air-cooled optical fiber cladding power stripper

Abstract

The invention discloses an airborne integrated air-cooled optical fiber cladding power stripper, comprising a total reflection parabolic mirror and a laser total absorption surface layer; the total reflection parabolic mirror is arranged inside a fuselage; the laser total absorption surface layer is integrally formed with a fuselage skin; the application adopts an integrated design of a cladding power stripper and a fuselage skin, and combines the design principle of a parabolic mirror to directly scatter stray light onto an inner wall of a cavity through a quartz glass tube, thereby greatly reducing the surface heat flux density of the stray light radiated to the absorption surface of the inner wall, and concentrating all the generated waste heat onto the inner surface of the skin, and then transferring it to the outer surface and utilizing the natural cold source of the airborne environment - high-altitude low-temperature and high-speed airflow for real-time heat dissipation, so that a large amount of waste heat generated by the stray light stripped from the optical fiber cladding can be efficiently dissipated in real time to meet the temperature control requirements of the cladding power stripper, and the cladding power stripper has a simple structure and a greatly reduced overall weight, thereby meeting the requirements of lightweight design.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber lasers, and in particular relates to an airborne integrated air-cooled optical fiber cladding power stripper. Background Art

[0002] Fiber lasers have been widely used in advanced manufacturing, medical treatment, industrial processing, military applications and other fields due to their obvious advantages such as high beam quality, good stability, compact structure and high conversion efficiency. For example, the application demand in airborne platforms is becoming more and more urgent. Double-clad fiber lasers are conducive to improving laser output power and pump coupling efficiency, but their output light contains certain stray light, which will seriously affect the spectral characteristics and beam quality of the laser, and directly or indirectly affect the reliability of the laser at high power, and need to be filtered out in time. Cladding Power Stripper (CPS) is one of the important devices in high-power double-clad fiber lasers. It has unique optical properties and is used to remove stray light in the fiber cladding, including core light leakage due to splicing loss or mode mismatch, unabsorbed pump light, leakage of higher-order modes in the core due to fiber bending, and amplified spontaneous radiation. CPS filters out the stray light transmitted in the fiber cladding, thereby eliminating the influence of this part of light on the quality of the laser beam. Its basic working principle is: CPS is a passive device used to filter out stray light in the optical fiber. The internal double-clad optical fiber segment is stripped into bare fiber, and the stray light generated by the laser operation is directly scattered outward without being gathered in the optical fiber cladding. These stray lights are scattered to the inner wall of the CPS shell and absorbed and converted into heat. The thermal radiation generated by these heats will cause the temperature of the bare fiber in the CPS to increase sharply. When it is higher than 200℃, the optical fiber core will melt, causing irreversible damage to the CPS and the laser system. Therefore, the design of the CPS heat dissipation structure is the key to the reliability design of the entire device; in addition, considering the presence of polymer colloid substances in the optical fiber, the operating temperature of the CPS should usually be less than 60℃.

[0003] Basic working principle of CPS:

[0004] CPS is a passive device used to filter out the cladding light in the optical fiber. The internal double-clad optical fiber segment is stripped into bare fiber, and the stray light generated by the laser operation is directly scattered outward instead of being gathered in the optical fiber cladding. These stray lights are scattered to the inner wall of the CPS shell and absorbed by it and converted into heat, which is then dissipated through media such as water. The typical structure of the existing CPS technical solution is as follows: Figure 4 and Figure 5 As shown, the optical fiber is sheathed in a quartz glass tube, which is sheathed in the cylindrical inner cavity of the housing. The optical fiber and the glass tube are supported and fixed at both ends by adhesive and sealing rings. Figure 4 , Figure 5As shown, a housing 1, air 2, a sealing ring 3, a rubber material 4, a quartz tube 5, and an optical fiber 6 are shown.

[0005] Existing CPS technical solution shell inner wall surface heat flux density:

[0006] In CPS design, the waste heat power consumption Q and the length L can be considered as constants, and the surface heat flux density q1 is inversely proportional to the inner wall diameter D3.

[0007] Considering the limited load capacity of airborne platforms and the high power of lasers used in airborne platforms, the lightweight design of fiber lasers and their heat dissipation problems (such as high-power heat-consuming devices CPS) are one of the key issues that need to be solved urgently. This problem can be solved by fully combining the platform environment characteristics and constraints. Based on the existing technical solutions, the CPS heat dissipation solutions currently used in airborne platforms mainly include air cooling (natural convection), liquid cooling, phase change heat storage and other thermal management solutions. The existing technical solutions are mainly as follows:

[0008] (1) Technical Solution 1: Air-cooled CPS. It mainly uses the heat conduction of the CPS metal shell to dissipate heat from the CPS through natural convection in the air.

[0009] (2) Technical Solution 2: Liquid-cooled CPS, including indirect liquid cooling and direct liquid cooling.

[0010] a) Schematic diagram of indirect liquid cooling CPS technology solution Figure 1 As shown, the working principle is to install the CPS on a heat sink, and the waste heat of optical fiber stripping is absorbed by the metal shell and conducted to the heat sink, and then the heat is taken away and dissipated by the liquid-cooled heat sink.

[0011] b) Schematic diagram of direct liquid cooling CPS technology solution Figure 2 As shown in the figure, its working principle is to place the quartz glass tube encapsulating the optical fiber in the cooling liquid, and take away and dissipate the heat through the liquid cooling system. Based on the traditional liquid-cooled CPS design, patent ZL201510323874.5 proposes a kilowatt-class optical fiber cladding power stripper based on microchannel water cooling, which is still based on liquid cooling to solve the heat dissipation problem of high heat flux density CPS.

[0012] (3) Technical Solution 3: Phase Change Thermal Storage CPS (Patent ZL201710567355.2), the schematic diagram of which is as follows Figure 3 As shown, its working principle is to fill the foam skeleton structure and phase change material (paraffin, etc.) inside the CPS, and use the phase change energy storage characteristics of the phase change material and the foam skeleton structure to increase the surface heat exchange area. The waste heat generated when the CPS is working is absorbed and temporarily stored by the phase change material, and then the stored waste heat is taken away and dissipated by the external coolant.

[0013] Disadvantages of the first existing technical solution: it uses natural convection in the air to dissipate heat, but the heat dissipation efficiency / effect is poor, and it is not suitable for situations where the air is thin or the laser power is high.

[0014] Disadvantages of the second existing technical solution: The heat dissipation effect of the indirect liquid-cooled CPS is poor, the stripping power is generally <300W, and it is subject to the performance of the cold plate; although the heat dissipation efficiency of the direct liquid-cooled CPS is greatly enhanced than that of the indirect liquid-cooled CPS, both adopt active thermal control. The entire cooling system contains numerous pump valve components, pipelines, etc. The system is more complex, and the required volume and weight are greatly increased.

[0015] The third disadvantage of the existing technical solution: When the phase change thermal storage CPS is working, it only uses the phase change material to absorb and temporarily store the waste heat. It still requires an additional cooling system to dissipate the waste heat (such as pump valve components may still be used for cooling). In addition, the phase change thermal storage CPS generally needs to store cold and keep warm before and after use. The cold storage time is generally long, and the usage scenarios are limited.

[0016] Cause:

[0017] Existing technical solution 1: Air-cooled CPS uses the CPS metal shell and natural convection of air to dissipate heat. Due to the limited heat capacity of the metal shell and the small natural convection heat transfer coefficient in the air, the heat dissipation capacity of the air-cooled CPS is very limited and is not suitable for occasions with high laser power and thin air.

[0018] Existing technical solution 2: Both indirect liquid-cooled and direct liquid-cooled CPS adopt active thermal control. The cooling system usually includes many pump valve components, pipelines, etc. The system is relatively complex, resulting in a significant increase in the overall volume and weight, which is not conducive to lightweight design.

[0019] Existing technical solution three: Phase change heat storage CPS uses the phase change latent heat of phase change materials to temporarily store the waste heat generated when the CPS is working. Its heat release process (such as when used in an airborne environment) still requires an additional cooling system to dissipate the waste heat, resulting in an increase in additional volume and weight; in addition, in order to fully utilize the phase change latent heat of phase change materials, it is necessary to fully consider the phase change temperature point to select phase change materials, resulting in the need to fully store cold and keep warm the phase change materials before and after use, and the CPS working interval may be longer.

[0020] Therefore, it is urgent to develop an airborne integrated air-cooled optical fiber cladding power stripper to solve the above problems. Summary of the invention

[0021] In order to solve the problems raised in the above background technology, the present invention provides an airborne integrated air-cooled optical fiber cladding power stripper.

[0022] To achieve the above object, the present invention provides the following technical solutions:

[0023] An airborne integrated air-cooled optical fiber cladding power stripper, comprising:

[0024] Total reflection parabolic mirror; the total reflection parabolic mirror is formed into an arc-shaped plate structure; the total reflection parabolic mirror is placed inside the fuselage;

[0025] Laser full-absorbing surface layer; the laser full-absorbing surface layer is integrally formed with the fuselage skin, and the laser full-absorbing surface layer forms an arc-shaped plate structure; the laser full-absorbing surface layer exchanges heat with the high-speed and low-temperature wind outside the fuselage; the total reflection parabolic mirror and the laser full-absorbing surface layer form a tubular structure; the optical fiber is placed in the tubular structure and is set in the same direction as the tubular structure.

[0026] Preferably, the center point of the optical fiber is placed at the focal point of the parabolic mirror.

[0027] Specifically, a quartz tube is sheathed outside the optical fiber, and air is filled between the optical fiber and the quartz tube.

[0028] Preferably, a heat insulating material is provided at the connection between the total reflection parabolic mirror and the laser total absorption surface layer.

[0029] Preferably, the side of the laser total absorption surface layer facing the total reflection parabolic mirror is coated with a thermal control coating material with high light absorption rate.

[0030] Furthermore, the side of the laser total absorption surface layer facing the total reflection parabolic mirror is also roughened.

[0031] Preferably, the thermal control coating material coated on the side of the laser total absorption surface layer facing the total reflection parabolic mirror is black nickel or organic black paint.

[0032] Further preferably, the organic black paint coated on the side of the laser total absorption surface layer facing the total reflection parabolic mirror is S731-SR107 black paint.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The design of the fully reflective parabolic mirror can not only prevent the radiation of stray light to the internal airborne equipment, but also radiate all the stray light to the surface of the cold source for real-time heat dissipation;

[0035] 2. Using the natural cold source of high altitude, low temperature and high speed (subsonic) on board to dissipate heat of the blanket power stripper in real time, it can meet the long-term working requirements of the blanket power stripper;

[0036] 3. The internal structure of the cladding power stripper does not require any cooling medium or sealing design, and the cladding power stripper is integrated with the fuselage skin. The structural design is simple, which can effectively reduce the structural weight of the cladding power stripper itself;

[0037] 4. Use low-temperature and high-speed airflow in the high altitude to dissipate waste heat in real time. There is no need to add additional cooling systems (such as pump valve components, pipelines, etc.). The entire heat dissipation system has a simple structure and the system weight can be greatly reduced to meet the needs of future lightweight design. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the technical solution of the indirect liquid-cooled cladding power stripper;

[0039] Figure 2 It is a schematic diagram of the technical solution of direct liquid-cooled cladding power stripper;

[0040] Figure 3 It is a schematic diagram of the technical solution of the phase change thermal storage blanket power stripper;

[0041] Figure 4 It is a typical cross-sectional structural diagram of the existing CPS technical solution;

[0042] Figure 5 It is a schematic diagram of a typical longitudinal section structure of an existing CPS technical solution;

[0043] Figure 6 This is a schematic diagram of the longitudinal cross-section structure of this application;

[0044] Figure 7 This is the reflection principle diagram of parabolic mirror;

[0045] Figure 8 Provide a finite element model for steady-state thermal analysis of the cladding power stripper;

[0046] In the figure: 1-shell, 2-air, 3-sealing ring, 4-rubber, 5-quartz tube, 6-optical fiber, 7-total reflection parabolic mirror, 8-skin, 81-laser full absorption surface layer, 9-thermal insulation material. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] The present invention provides the following technical solutions:

[0049] like Figure 6 As shown, an airborne integrated air-cooled optical fiber cladding power stripper comprises:

[0050] Total reflection parabolic mirror 7; the total reflection parabolic mirror 7 is formed into an arc-shaped plate structure; the total reflection parabolic mirror 7 is placed inside the fuselage;

[0051] Laser full absorption surface layer 81; the laser full absorption surface layer 81 is integrally formed with the fuselage skin 8, and the laser full absorption surface layer 81 is formed into an arc-shaped plate structure; the laser full absorption surface layer 81 exchanges heat with the high-speed and low-temperature wind outside the fuselage; the total reflection parabolic mirror 7 and the laser full absorption surface layer 81 form a tubular structure; the optical fiber is placed in the tubular structure and is consistent with the setting direction of the tubular structure.

[0052] like Figure 6 As shown, the center point of the optical fiber 6 is placed at the focal point of the parabolic mirror.

[0053] like Figure 6 As shown, a quartz tube 5 is sheathed outside the optical fiber 6, and air is filled between the optical fiber 6 and the quartz tube 5.

[0054] like Figure 6 As shown, a heat insulating material 9 is provided at the connection between the total reflection parabolic mirror 7 and the laser total absorption surface layer 81 .

[0055] like Figure 6 As shown, the side of the laser total absorption surface layer 81 facing the total reflection parabolic mirror 7 is coated with a thermal control coating material with high light absorption rate.

[0056] Furthermore, the side of the laser total absorption surface layer 81 facing the total reflection parabolic mirror 7 is also roughened.

[0057] Preferably, the thermal control coating material coated on the side of the laser total absorption surface layer 81 facing the total reflection parabolic mirror 7 is (stainless steel electroplating) black nickel or organic black paint.

[0058] Further preferably, the organic black paint coated on the side of the laser total absorption surface layer 81 facing the total reflection parabolic mirror 7 is S731-SR107 black paint.

[0059] In this application, combined with the special environmental characteristics and constraints of the airborne platform, for example, for subsonic aircraft, the flight speed is relatively high when flying at high altitudes (up to 160-300 km / h), and the ambient temperature inside and outside the cabin is relatively low (such as the ambient temperature of the standard atmosphere at an altitude of 6 km is about -24°C, and about -37°C at an altitude of 8 km). In this high-speed, low-temperature airflow environment, this patent solution is proposed.

[0060] The cladding power stripper, a device with large heat consumption, has the characteristics of high heat flux density. Combined with the basic working principle of the cladding power stripper, when the waste heat power Q and the fiber length L are determined, the aperture of the inner wall surface (i.e., the inner wall diameter D3) is increased. Figure 5 ), thereby reducing the heat flux density radiated to the inner wall surface.

[0061] like Figure 6 As shown, in this application,

[0062] (1) The cladding power stripper is designed to be conformally integrated with the inner surface of the fuselage skin. The right side ABCDEF of the cladding power stripper shares a common structure with the skin, and its inner surface is a laser full absorption surface. The surface is treated with blackening / roughening, etc., which absorbs all the stray light radiated to the surface and converts it into heat. The heat is then transferred to the outer surface through the inner surface of the skin and dissipated in real time through high-speed and low-temperature air cooling outside the skin.

[0063] (2) In order to prevent the stray light inside the cladding power stripper from radiating the onboard equipment inside the fuselage, a total reflection parabolic mirror is used on the left side FGHIJA of the cladding power stripper. The center point O of the optical fiber is placed at the focal position of the parabolic mirror. The laser radiated by the optical fiber to the FGHIJA surface will be emitted in parallel to the ABCDEF surface, where it will be absorbed and converted into heat. The heat will then be transferred to the outer surface through the inner surface of the skin and dissipated in real time through high-speed low-temperature air cooling outside the skin.

[0064] The basic principle of parabolic mirror is as follows Figure 7 As shown, the light point is placed on the main focus of the parabolic mirror, and the optical fiber is emitted parallel to the main axis after reflection by the mirror (for example, there is a parabolic mirror in the follow-up light and searchlight). When the light source is located at its focus, a parallel beam of directional illumination can be obtained; conversely, the incident light parallel to the main axis will converge at the focus after reflection by the parabolic mirror.

[0065] (3) Insulation materials are used at points A and F between the total reflection surface FGHIJA and the total absorption surface ABCDEF (inner surface) to insulate the wall surface, so as to prevent the heat converted from radiation to the ABCDEF surface from being transferred to the total reflection parabolic mirror, causing large thermal deformation or even damage to the parabolic mirror.

[0066] (4) Heat flux density of inner wall surface of this application: (This application design can be considered as L FGHIJA ≈0), adopting a unique cladding power stripper design concept, the stray light is directly scattered onto the inner wall of the cavity through the glass tube. ABCDEF , L FGHIJA Equal inner wall size (analogous to the general inner wall diameter D3, such as Figure 5 ), which greatly reduces the heat flux density of stray light radiated to the inner wall absorption surface, which is beneficial to the heat dissipation of the large heat consumption cladding power stripper.

[0067] (5) When a subsonic aircraft is cruising at high altitude, it can provide a natural cold source (low-temperature, high-speed airflow) for the cladding power stripper of the present application, which can dissipate heat for the device in real time and can theoretically continue to work.

[0068] (6) The present application adopts a passive thermal control structure. The internal structure design does not require phase change materials, water or other cooling media for heat extraction, does not require sealing design, and has a simple structural design (one side uses a parabolic mirror and the other side uses a shared skin structure). In addition, the heat release process of the cladding power stripper does not require the addition of other cooling systems, such as pump valve components, pipelines, etc. The system is simpler and the overall weight is greatly reduced, which is very conducive to lightweight design.

[0069] Preliminary simulation verification of the cooling effect of low-temperature and high-speed airflow:

[0070] Assuming that the stripping power of the cladding power stripper is 500W (that is, the waste heat power Q=500W), the calculation assumes that the heat flux density on the surface ABCDEF is cosine distribution, the heat flux density on both edges is 0, the heat flux density in the middle position is the maximum value, and the heat flux density is uniformly distributed along the length of the glass tube.

[0071] The length of the quartz glass tube is L = 150 mm. The skin is temporarily selected as a straight plane for analysis. The skin thickness is 1 mm and the material is aluminum alloy 6061. Considering the symmetry of the problem, only half of the fuselage skin structure is modeled, and its symmetry plane is parallel to the wind speed direction. The finite cloud model is as follows Figure 8 shown.

[0072] The calculation assumes that the wind speed V = 160km / h (a relatively small wind speed), the cruising altitudes are H = 2km and H = 7km respectively (the standard atmosphere is about 2°C at an altitude of 2km, and about -30.5°C at an altitude of 7km), and the thermal response of the blanket power stripper in steady state is calculated. The maximum temperature on the mounting surface of the blanket power stripper is shown in Table 1. It can be seen from the table that, except for the working conditions of the height H = 2km, the mounting surface length of 100mm, and the skin thickness of 1mm, the maximum temperature of the remaining blanket power strippers is less than 60°C, which can be easily solved by increasing the mounting surface length and skin thickness; it can be clearly seen from the preliminary simulation verification analysis that the design of the airborne integrated air-cooled blanket power stripper in this paper can fully meet the heat dissipation requirements of large heat consumption devices.

[0073] Table 1 Maximum temperature on the mounting surface of the cladding power stripper

[0074]

[0075]

[0076] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An airborne integrated air-cooled optical fiber cladding power stripper, characterized in that: include: Total reflection parabolic mirror; the total reflection parabolic mirror is formed into an arc-shaped plate structure; the total reflection parabolic mirror is placed inside the fuselage; Laser full-absorbing surface layer; the laser full-absorbing surface layer is integrally formed with the fuselage skin, and the laser full-absorbing surface layer forms an arc-shaped plate structure; the laser full-absorbing surface layer exchanges heat with the high-speed and low-temperature wind outside the fuselage; the total reflection parabolic mirror and the laser full-absorbing surface layer form a tubular structure; the optical fiber is placed in the tubular structure and is set in the same direction as the tubular structure.

2. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 1, characterized in that: The center point of the optical fiber is placed at the focus of the parabolic mirror.

3. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 1, characterized in that: A quartz tube is wrapped around the outside of the optical fiber, and air is filled between the optical fiber and the quartz tube.

4. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 1, characterized in that: A heat-insulating material is arranged at the connection between the total reflection parabolic mirror and the laser total absorption surface layer.

5. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 1, characterized in that: The side of the laser total absorption surface layer facing the total reflection parabolic mirror is coated with a thermal control coating material with high light absorption rate.

6. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 5, characterized in that: The side of the laser total absorption surface layer facing the total reflection parabolic mirror is also roughened.

7. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 5, characterized in that: The thermal control coating material coated on the side of the laser total absorption surface layer facing the total reflection parabolic mirror is black nickel or organic black paint.

8. The airborne integrated air-cooled optical fiber cladding power stripper according to claim 7, characterized in that: The organic black paint coated on the side of the laser total absorption surface layer facing the total reflection parabolic mirror is S731-SR107 black paint.

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