J-shaped submarine cable pipe based on multi-layer composite structure and submarine cable flow increasing method

Abstract

The invention discloses a J-shaped submarine cable pipe based on a multi-layer composite structure, which comprises a J-shaped submarine cable pipe body, the inner wall of the submarine cable pipe body is sprayed with a high-thermal-conductivity lining layer, and the high-thermal-conductivity lining layer is used for transferring the heat of a submarine cable to the J-shaped submarine cable pipe body; the inner wall of the high-thermal-conductivity lining layer is provided with a phase change heat storage middle layer which is used for absorbing and storing heat of the submarine cable, and after the submarine cable is cooled, the heat is released; the outer wall of the phase change heat storage middle layer is provided with a corrugated expansion heat dissipation outer layer used for forming turbulent flow through natural convection of seawater, and the heat dissipation efficiency is improved. On the premise that the structural strength and the sealing performance of the J-shaped pipe are guaranteed, through the innovative thermal management design of heat conduction-heat storage-heat dissipation three-stage coupling structural design, active flow field optimization design, an intelligent temperature control system and the like, the limitation of submarine cable temperature rise on the current-carrying capacity is broken through, meanwhile, the cost and reliability defects of a traditional scheme are overcome, and the reliability of the submarine cable is improved. Passive efficient heat dissipation and dynamic power adaptation are achieved.

Description

Technical Field

[0001] This invention relates to submarine cables, and in particular to the design of a J-type submarine cable tube based on a multi-layer composite structure for increasing the flow rate of submarine cables. Background Technology

[0002] Most high-voltage submarine cables for offshore wind farms are buried on the seabed, where temperatures are low and the soil has a low thermal resistivity, resulting in a large current-carrying capacity. However, submarine cables landing at the base of wind turbine towers, offshore booster stations, or offshore converter stations suffer from significant temperature rises in the cable core due to the limited sealing structure of traditional J-tube cables. This forces a 20%–30% reduction in current-carrying capacity. Therefore, the current-carrying capacity differs between the underwater and landing sections, with the landing section being the bottleneck restricting the overall current-carrying capacity. Current technologies rely on increasing the cable cross-sectional area or using external forced cooling systems. The former increases material costs and construction difficulty, while the latter has poor reliability and high energy consumption in the corrosive and vibrating marine environment. Summary of the Invention

[0003] The purpose of this invention is to provide a J-type submarine cable conduit based on a multi-layer composite structure.

[0004] While ensuring the structural strength and sealing of the J-tube, a three-stage coupled structure design of heat conduction, heat storage, and heat dissipation is used to overcome the limitation of submarine cable temperature rise on current carrying capacity, while avoiding the cost and reliability defects of traditional solutions, thus achieving passive high-efficiency heat dissipation and dynamic power adaptation.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A J-type submarine cable duct based on a multi-layer composite structure includes a J-type submarine cable duct body. The inner wall of the duct body is coated with a high thermal conductivity liner layer, which transfers heat from the submarine cable to the J-type submarine cable duct body. The inner wall of the high thermal conductivity liner layer has a phase change heat storage intermediate layer, which absorbs and stores heat from the submarine cable and releases it when the cable cools down. The outer wall of the phase change heat storage intermediate layer has a corrugated expansion heat dissipation outer layer, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The J-type submarine cable duct body uses friction stir welding to seamlessly connect the spiral guide fins to the duct body, avoiding thermal stress concentration caused by traditional welding. The phase change layer mesh and the corrugated outer shell are integrated by vacuum diffusion welding, with an interface porosity of <0.5%. The duct section is modularly designed (standard length 6m), and graphite sealing rings (pressure resistance ≥2MPa) are pre-installed at the flange connections, supporting rapid splicing for shipborne hoisting.

[0007] In the aforementioned J-type submarine cable duct based on a multi-layer composite structure, the inner wall of the curved section of the J-type submarine cable duct body has continuous spiral guiding fins, which cover the entire length of the curved section; the radius of curvature of the curved section is greater than or equal to twelve times its inner diameter; the height of the spiral guiding fins is one-tenth to one-eighth of the inner diameter of the J-type submarine cable duct body; the inclination angle θ of the spiral guiding fins is dynamically optimized using the following formula:

[0008]

[0009] Among them, V air V represents the airflow velocity within the J-shaped submarine cable duct. water The velocity of the seawater outside the J-type submarine cable duct body.

[0010] It can induce forced vortex flow of air inside the pipe (Reynolds number Re > 5000), destroy the thermal boundary layer, and increase the gas-solid heat transfer coefficient by 18% to 25%.

[0011] In the aforementioned J-type submarine cable duct based on a multi-layer composite structure, a V-shaped guide groove is provided at the bottom of the J-type submarine cable duct body. The depth of the guide groove is 20 mm, and the opening angle of the guide groove is 60°. This can guide seawater to flow directionally along the corrugated surface, avoiding local heat transfer deterioration caused by eddy stagnation.

[0012] In the aforementioned J-type submarine cable duct based on a multi-layer composite structure, the high thermal conductivity inner lining is sprayed using the following method: an aluminum nitride ceramic coating with a thickness of 50 to 100 μm is formed on the inner wall of the J-type submarine cable duct body using a plasma spraying process, with a thermal conductivity ≥200 W / (m·K) and a contact thermal resistance of less than 0.05 K·m. 2 / W. Directly contacts the surface of the submarine cable, quickly dissipating heat from the cable core to the middle layer of the tube wall, thus preventing the formation of localized hot spots.

[0013] In the aforementioned J-type submarine cable tube based on a multi-layer composite structure, the phase change thermal storage intermediate layer is a composite phase change material consisting of expanded graphite as a carrier, encapsulating paraffin and graphene nanosheets. The microcapsule particle size is controlled between 50 and 200 μm, and the coating layer is a silica shell of 1 to 3 μm. The encapsulation structure uses a 3D-printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 65% to 70%.

[0014] When the core temperature reaches 40℃, the phase change material absorbs heat (phase change enthalpy ≥ 180J / g), slowing down the rate of temperature rise; after the temperature drops, it releases the stored heat to adapt to load fluctuations caused by tides.

[0015] In the aforementioned J-type submarine cable duct based on a multi-layer composite structure, the corrugated extended heat dissipation outer layer is an aluminum alloy shell with a continuous corrugated structure on its surface, with a wave crest height of 8mm and a wave pitch of 15mm. The effective heat dissipation area is increased by 35% compared to a planar structure. Heat dissipation is enhanced because the corrugated channels are at a 30° angle to the seawater flow direction, utilizing natural seawater convection (flow velocity ≥ 0.3m / s) to create turbulence, thus increasing the overall convective heat transfer coefficient to 120–150 W / (m²). 2 ·K).

[0016] A method for increasing the flow rate of a submarine cable, wherein the submarine cable is located in a J-type submarine cable duct based on a multi-layer composite structure as described above, characterized in that the inclination angle of the spiral guide fins is dynamically optimized using the following method:

[0017] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-shaped submarine cable duct to monitor the temperature gradient of the cable core, inner and outer layers of the duct wall in real time.

[0018] Temperature signals are transmitted to the central controller of the converter station via anti-electromagnetic interference optical cables, with a sampling frequency ≥10Hz;

[0019] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0020] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0021] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0022] Compared with existing technologies, this invention, while ensuring the strength and sealing of the J-shaped tube structure, breaks through the limitation of submarine cable temperature rise on current carrying capacity through innovative thermal management designs such as a three-level coupled structure design of heat conduction-heat storage-heat dissipation, active flow field optimization design, and intelligent temperature control system. At the same time, it avoids the cost and reliability defects of traditional solutions, and achieves passive high-efficiency heat dissipation and dynamic power adaptation.

[0023] (1) Significantly improved current carrying capacity and outstanding economic benefits. Through the synergistic effect of a high thermal conductivity inner layer, a phase change heat storage layer, and a corrugated heat dissipation outer layer, the temperature rise is reduced and the current carrying capacity is increased. There is no need to increase the cable cross-sectional area, and the total investment of the project is reduced by 15% to 20%.

[0024] (2) Passive and efficient heat dissipation, adaptable to complex marine environments. Natural heat dissipation is achieved through material and structural innovations, eliminating the need for external cooling equipment;

[0025] (3) Strong adaptability to dynamic heat load. Resistant to environmental interference, the phase change thermal storage layer can buffer transient thermal shocks caused by salt spray corrosion and mechanical vibration;

[0026] (4) Compact structure and convenient construction and maintenance. Modular design, standard 6m pipe section pre-integrated composite structure layer, flange interface compatible with existing J-type pipe system, and 50% improvement in offshore installation efficiency.

[0027] (5) Environmentally friendly and compatible with future energy systems. The natural heat dissipation design requires no additional energy consumption and supports seamless integration with the SCADA system of offshore converter stations / offshore booster stations, adapting to the future demand for high proportion of new energy grid connection. This invention overcomes the industry problems of poor heat dissipation and limited current carrying capacity of traditional J-type submarine cables through the deep integration of material innovation, structural optimization and intelligent control. It has high economic efficiency, high reliability and environmental adaptability, providing key technical support for the large-scale development of deep-sea wind power. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of one embodiment of the present invention;

[0029] Figure 2 This is a cross-sectional view of one embodiment of the present invention.

[0030] Figure reference numerals: 1-J-type submarine cable tube body, 2-spiral guide fin, 3-submarine cable, 4-high thermal conductivity inner lining, 5-phase change thermal storage intermediate layer, 6-corrugated extended heat dissipation outer layer, 7-guide groove.

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0032] Embodiment 1 of the present invention: A J-type submarine cable duct based on a multi-layer composite structure, comprising a J-type submarine cable duct body 1, wherein the inner wall of the submarine cable 3 duct body 1 is coated with a high thermal conductivity inner lining layer 4, which is used to transfer the heat of the submarine cable 3 to the J-type submarine cable duct body 1; the high thermal conductivity inner lining layer 4 is sprayed by the following method: an aluminum nitride ceramic coating with a thickness of 50 μm, a thermal conductivity of 200 W / (m·K), and a contact thermal resistance of 0.045 K·m is formed on the inner wall of the J-type submarine cable duct body 1 by plasma spraying. 2 / W.

[0033] The inner wall of the high thermal conductivity inner liner 4 has a phase change heat storage intermediate layer 5, which is used to absorb and store the heat of the submarine cable 3. When the submarine cable 3 cools down, it releases the heat. The phase change heat storage intermediate layer 5 is a composite phase change material of paraffin and graphene nanosheets encapsulated with expanded graphite as a carrier. The microcapsule particle size is controlled at 50μm, and the coating layer is a 13μm silica shell. The encapsulation structure adopts a 3D printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 65%.

[0034] The outer wall of the phase change thermal storage intermediate layer 5 has a corrugated extended heat dissipation outer layer 6, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The bottom of the J-type submarine cable duct body 1 is equipped with a V-shaped guide groove with a depth of 20 mm and an opening angle of 60°. The corrugated extended heat dissipation outer layer 6 is an aluminum alloy shell with a continuous corrugated structure, a crest height of 8 mm, and a wave pitch of 15 mm.

[0035] The inner wall of the curved section of the J-type submarine cable duct body 1 has continuous spiral guide fins 2, which cover the entire length of the curved section; the radius of curvature of the curved section is equal to twelve times its inner diameter; the height of the spiral guide fins 2 is one-tenth of the inner diameter of the J-type submarine cable duct body 1; the inclination angle θ of the spiral guide fins 2 is dynamically optimized using the following formula:

[0036]

[0037] Among them, V air V is the airflow velocity inside the J-type submarine cable duct body 1. water The external seawater flow velocity of the J-type submarine cable duct body 1.

[0038] A method for increasing the flow rate of a submarine cable, wherein the submarine cable 3 is located in a J-type submarine cable duct based on a multi-layer composite structure as described in Example 1, characterized in that the inclination angle of the spiral guide fin 2 is dynamically optimized using the following method:

[0039] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-type submarine cable duct body to monitor the temperature gradient of the cable core, inner layer and outer layer of the duct wall in real time.

[0040] The temperature signal is transmitted to the central controller of the converter station via an anti-electromagnetic interference optical cable, with a sampling frequency of 10Hz.

[0041] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0042] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0043] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0044] Example 2: A J-type submarine cable duct based on a multi-layer composite structure, comprising a J-type submarine cable duct body 1, wherein the inner wall of the submarine cable 3 duct body 1 is coated with a high thermal conductivity inner lining layer 4, which is used to transfer the heat of the submarine cable 3 to the J-type submarine cable duct body 1; the high thermal conductivity inner lining layer 4 is sprayed using the following method: an aluminum nitride ceramic coating with a thickness of 100 μm is formed on the inner wall of the J-type submarine cable duct body 1 using a plasma spraying process, with a thermal conductivity of 210 W / (m·K) and a contact thermal resistance of 0.04 K·m. 2 / W.

[0045] The inner wall of the high thermal conductivity inner liner 4 has a phase change heat storage intermediate layer 5, which is used to absorb and store the heat of the submarine cable 3. When the submarine cable 3 cools down, it releases the heat. The phase change heat storage intermediate layer 5 is a composite phase change material of paraffin and graphene nanosheets encapsulated with expanded graphite as a carrier. The microcapsule particle size is controlled at 200μm, and the coating layer is a 3μm silica shell. The encapsulation structure adopts a 3D printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 70%.

[0046] The outer wall of the phase change thermal storage intermediate layer 5 has a corrugated extended heat dissipation outer layer 6, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The bottom of the J-type submarine cable duct body 1 is equipped with a V-shaped guide groove with a depth of 20 mm and an opening angle of 60°. The corrugated extended heat dissipation outer layer 6 is an aluminum alloy shell with a continuous corrugated structure, a crest height of 8 mm, and a wave pitch of 15 mm.

[0047] The inner wall of the curved section of the J-type submarine cable duct body 1 has continuous spiral guide fins 2, which cover the entire length of the curved section; the radius of curvature of the curved section is equal to 13 times its inner diameter; the height of the spiral guide fins 2 is one-eighth of the inner diameter of the J-type submarine cable duct body 1; the inclination angle θ of the spiral guide fins 2 is dynamically optimized using the following formula:

[0048]

[0049] Among them, V air V is the airflow velocity inside the J-type submarine cable duct body 1. water The external seawater flow velocity of the J-type submarine cable duct body 1.

[0050] A method for increasing the flow rate of a submarine cable, wherein the submarine cable 3 is located in a J-type submarine cable duct based on a multi-layer composite structure as described in Example 2, characterized in that the inclination angle of the spiral guide fin 2 is dynamically optimized using the following method:

[0051] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-type submarine cable duct body to monitor the temperature gradient of the cable core, inner layer and outer layer of the duct wall in real time.

[0052] Temperature signals are transmitted to the central controller of the converter station via anti-electromagnetic interference optical cables, with a sampling frequency ≥10Hz;

[0053] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0054] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0055] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0056] Example 3: A J-type submarine cable duct based on a multi-layer composite structure, comprising a J-type submarine cable duct body 1, wherein the inner wall of the submarine cable 3 duct body 1 is coated with a high thermal conductivity inner lining layer 4, which is used to transfer the heat of the submarine cable 3 to the J-type submarine cable duct body 1; the high thermal conductivity inner lining layer 4 is sprayed using the following method: an aluminum nitride ceramic coating with a thickness of 60 μm, a thermal conductivity of 220 W / (m·K), and a contact thermal resistance of 0.047 K·m is formed on the inner wall of the J-type submarine cable duct body 1 using a plasma spraying process. 2 / W.

[0057] The inner wall of the high thermal conductivity inner liner 4 has a phase change heat storage intermediate layer 5, which is used to absorb and store the heat of the submarine cable 3. When the submarine cable 3 cools down, it releases the heat. The phase change heat storage intermediate layer 5 is a composite phase change material of paraffin and graphene nanosheets encapsulated with expanded graphite as a carrier. The microcapsule particle size is controlled at 60μm, and the coating layer is a 2μm silica shell. The encapsulation structure adopts a 3D printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 66%.

[0058] The outer wall of the phase change thermal storage intermediate layer 5 has a corrugated extended heat dissipation outer layer 6, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The bottom of the J-type submarine cable duct body 1 is equipped with a V-shaped guide groove with a depth of 20 mm and an opening angle of 60°. The corrugated extended heat dissipation outer layer 6 is an aluminum alloy shell with a continuous corrugated structure, a crest height of 8 mm, and a wave pitch of 15 mm.

[0059] The inner wall of the curved section of the J-type submarine cable duct body 1 has continuous spiral guide fins 2, which cover the entire length of the curved section; the radius of curvature of the curved section is equal to twelve times its inner diameter; the height of the spiral guide fins 2 is one-tenth of the inner diameter of the J-type submarine cable duct body 1; the inclination angle θ of the spiral guide fins 2 is dynamically optimized using the following formula:

[0060]

[0061] Among them, V air V is the airflow velocity inside the J-type submarine cable duct body 1. water The external seawater flow velocity of the J-type submarine cable duct body 1.

[0062] A method for increasing the flow rate of a submarine cable, wherein the submarine cable 3 is located in a J-type submarine cable duct based on a multi-layer composite structure as described in Example 3, characterized in that the inclination angle of the spiral guide fin 2 is dynamically optimized using the following method:

[0063] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-type submarine cable duct body to monitor the temperature gradient of the cable core, inner layer and outer layer of the duct wall in real time.

[0064] Temperature signals are transmitted to the central controller of the converter station via anti-electromagnetic interference optical cables, with a sampling frequency ≥10Hz;

[0065] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0066] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0067] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0068] Example 4: A J-type submarine cable duct based on a multi-layer composite structure, comprising a J-type submarine cable duct body 1, wherein the inner wall of the submarine cable 3 body 1 is coated with a high thermal conductivity inner lining layer 4, which is used to transfer the heat of the submarine cable 3 to the J-type submarine cable duct body 1; the high thermal conductivity inner lining layer 4 is sprayed using the following method: an aluminum nitride ceramic coating with a thickness of 70 μm is formed on the inner wall of the J-type submarine cable duct body 1 using a plasma spraying process, with a thermal conductivity of 230 W / (m·K) and a contact thermal resistance of 0.047 K·m. 2 / W.

[0069] The inner wall of the high thermal conductivity inner liner 4 has a phase change heat storage intermediate layer 5, which is used to absorb and store the heat of the submarine cable 3. When the submarine cable 3 cools down, it releases the heat. The phase change heat storage intermediate layer 5 is a composite phase change material of paraffin and graphene nanosheets encapsulated with expanded graphite as a carrier. The microcapsule particle size is controlled at 80μm, and the coating layer is a 2μm silica shell. The encapsulation structure adopts a 3D printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 67%.

[0070] The outer wall of the phase change thermal storage intermediate layer 5 has a corrugated extended heat dissipation outer layer 6, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The bottom of the J-type submarine cable duct body 1 is equipped with a V-shaped guide groove with a depth of 20 mm and an opening angle of 60°. The corrugated extended heat dissipation outer layer 6 is an aluminum alloy shell with a continuous corrugated structure, a crest height of 8 mm, and a wave pitch of 15 mm.

[0071] The inner wall of the curved section of the J-type submarine cable duct body 1 has continuous spiral guide fins 2, which cover the entire length of the curved section; the radius of curvature of the curved section is equal to twelve times its inner diameter; the height of the spiral guide fins 2 is one-tenth of the inner diameter of the J-type submarine cable duct body 1; the inclination angle θ of the spiral guide fins 2 is dynamically optimized using the following formula:

[0072]

[0073] Among them, V air V is the airflow velocity inside the J-type submarine cable duct body 1. waterThe external seawater flow velocity of the J-type submarine cable duct body 1.

[0074] A method for increasing the flow rate of a submarine cable, wherein the submarine cable 3 is located in a J-type submarine cable duct based on a multi-layer composite structure as described in Example 4, characterized in that the inclination angle of the spiral guide fin 2 is dynamically optimized using the following method:

[0075] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-type submarine cable duct body to monitor the temperature gradient of the cable core, inner layer and outer layer of the duct wall in real time.

[0076] Temperature signals are transmitted to the central controller of the converter station via anti-electromagnetic interference optical cables, with a sampling frequency ≥10Hz;

[0077] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0078] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0079] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0080] Example 5: A J-type submarine cable duct based on a multi-layer composite structure, comprising a J-type submarine cable duct body 1, wherein the inner wall of the submarine cable 3 body 1 is coated with a high thermal conductivity inner lining layer 4, which is used to transfer the heat of the submarine cable 3 to the J-type submarine cable duct body 1; the high thermal conductivity inner lining layer 4 is sprayed using the following method: an aluminum nitride ceramic coating with a thickness of 80 μm, a thermal conductivity of 230 W / (m·K), and a contact thermal resistance of 0.048 K·m is formed on the inner wall of the J-type submarine cable duct body 1 using a plasma spraying process. 2 / W.

[0081] The inner wall of the high thermal conductivity inner liner 4 has a phase change heat storage intermediate layer 5, which is used to absorb and store the heat of the submarine cable 3. When the submarine cable 3 cools down, it releases the heat. The phase change heat storage intermediate layer 5 is a composite phase change material of paraffin and graphene nanosheets encapsulated with expanded graphite as a carrier. The microcapsule particle size is controlled at 90μm, and the coating layer is a 2μm silica shell. The encapsulation structure adopts a 3D printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 68%.

[0082] The outer wall of the phase change thermal storage intermediate layer 5 has a corrugated extended heat dissipation outer layer 6, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The bottom of the J-type submarine cable duct body 1 is equipped with a V-shaped guide groove with a depth of 20 mm and an opening angle of 60°. The corrugated extended heat dissipation outer layer 6 is an aluminum alloy shell with a continuous corrugated structure, a crest height of 8 mm, and a wave pitch of 15 mm.

[0083] The inner wall of the curved section of the J-type submarine cable duct body 1 has continuous spiral guide fins 2, which cover the entire length of the curved section; the radius of curvature of the curved section is equal to twelve times its inner diameter; the height of the spiral guide fins 2 is one-tenth of the inner diameter of the J-type submarine cable duct body 1; the inclination angle θ of the spiral guide fins 2 is dynamically optimized using the following formula:

[0084]

[0085] Among them, V air V is the airflow velocity inside the J-type submarine cable duct body 1. water The external seawater flow velocity of the J-type submarine cable duct body 1.

[0086] A method for increasing the flow rate of a submarine cable, wherein the submarine cable 3 is located in a J-type submarine cable duct based on a multi-layer composite structure as described in Example 5, characterized in that the inclination angle of the spiral guide fin 2 is dynamically optimized using the following method:

[0087] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-type submarine cable duct body to monitor the temperature gradient of the cable core, inner layer and outer layer of the duct wall in real time.

[0088] Temperature signals are transmitted to the central controller of the converter station via anti-electromagnetic interference optical cables, with a sampling frequency ≥10Hz;

[0089] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0090] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0091] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0092] Example 6: A J-type submarine cable duct based on a multi-layer composite structure, comprising a J-type submarine cable duct body 1, wherein the inner wall of the submarine cable 3 duct body 1 is coated with a high thermal conductivity inner lining layer 4, which is used to transfer the heat of the submarine cable 3 to the J-type submarine cable duct body 1; the high thermal conductivity inner lining layer 4 is sprayed using the following method: an aluminum nitride ceramic coating with a thickness of 90 μm is formed on the inner wall of the J-type submarine cable duct body 1 using a plasma spraying process, with a thermal conductivity of 210 W / (m·K) and a contact thermal resistance of 0.049 K·m. 2 / W.

[0093] The inner wall of the high thermal conductivity inner liner 4 has a phase change heat storage intermediate layer 5, which is used to absorb and store the heat of the submarine cable 3. When the submarine cable 3 cools down, it releases the heat. The phase change heat storage intermediate layer 5 is a composite phase change material of paraffin and graphene nanosheets encapsulated with expanded graphite as a carrier. The microcapsule particle size is controlled at 100μm, and the coating layer is a 1μm silica shell. The encapsulation structure adopts a 3D printed honeycomb grid to fix the phase change microcapsules, with a filling rate of 69%.

[0094] The outer wall of the phase change thermal storage intermediate layer 5 has a corrugated extended heat dissipation outer layer 6, which utilizes the natural convection of seawater to create turbulence and accelerate heat dissipation efficiency. The bottom of the J-type submarine cable duct body 1 is equipped with a V-shaped guide groove with a depth of 20 mm and an opening angle of 60°. The corrugated extended heat dissipation outer layer 6 is an aluminum alloy shell with a continuous corrugated structure, a crest height of 8 mm, and a wave pitch of 15 mm.

[0095] The inner wall of the curved section of the J-type submarine cable duct body 1 has continuous spiral guide fins 2, which cover the entire length of the curved section; the radius of curvature of the curved section is equal to twelve times its inner diameter; the height of the spiral guide fins 2 is one-eighth of the inner diameter of the J-type submarine cable duct body 1; the inclination angle θ of the spiral guide fins 2 is dynamically optimized using the following formula:

[0096]

[0097] Among them, V air V is the airflow velocity inside the J-type submarine cable duct body 1. water The external seawater flow velocity of the J-type submarine cable duct body 1.

[0098] A method for increasing the flow rate of a submarine cable, wherein the submarine cable 3 is located in a J-type submarine cable duct based on a multi-layer composite structure as described in Example 6, characterized in that the inclination angle of the spiral guide fin 2 is dynamically optimized using the following method:

[0099] An optical fiber temperature measurement point is set up every 0.5m along the axis of the J-type submarine cable duct body to monitor the temperature gradient of the cable core, inner layer and outer layer of the duct wall in real time.

[0100] Temperature signals are transmitted to the central controller of the converter station via anti-electromagnetic interference optical cables, with a sampling frequency ≥10Hz;

[0101] When the temperature at any temperature measuring point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced in a gradient, with a maximum reduction of 15%.

[0102] After the temperature drops below 50℃, the current carrying capacity is restored at a rate of 2% / min.

[0103] By combining offshore wind power forecast data, the load capacity allocation strategy can be adjusted in advance to reduce the frequency of temperature control actions.

[0104] Finite element thermal-fluid coupling simulation test (110kV / 630mm) was conducted. 2 Submarine Cable: Increased Current Carrying Capacity: With an external air temperature of 38℃, the continuous current carrying capacity increased from 700A to 870A (a 25% increase), and the maximum core temperature decreased from 75℃ to 50℃; Dynamic Response: Simulating a step change in load (30%→100%→30%), the phase change layer reduced the temperature fluctuation amplitude by 62% and shortened the recovery time by 40%; Life Assessment: Accelerated aging tests showed that the composite pipe structure exhibited a thermal conductivity degradation of <8% over a 25-year service life, significantly superior to traditional steel pipes (degradation ≥25%).

[0105] This technical solution was applied to the Huadian Liaoning Dandong 2000MW offshore wind farm. The electricity generated by the wind turbines is connected to the AC side of the offshore converter station via a 110kV submarine cable. After voltage boosting and conversion, it is connected to a newly built ±500kV onshore DC collection station via two ±500kV submarine cables. Each set of 12 12MW wind turbines forms one 110kV collection line loop, for a total of 14 110kV collection line loops. By using this J-type tube to increase the current carrying capacity of the submarine cable, HYJQF41-F-64 / 110kV-3×630mm² can be selected to connect the 12 wind turbines. The original 3×800mm² design was optimized to 3×630mm². The specifications of the submarine cables connecting the remaining 1 to 11 wind turbines can also be optimized, saving 55 million RMB in costs, thus achieving the goal of optimizing the collection lines for the entire offshore wind farm. The ±500kV DC submarine cable connecting the ±500kV offshore converter station to the ±500kV onshore DC collection station can be a 1*2200mm² cable. The 120km outgoing DC submarine cable has been optimized from the original 1*2500mm² design to 1*2200mm², saving 36 million yuan in costs. Therefore, the entire offshore wind farm project can save 91 million yuan in submarine cable costs, demonstrating significant application and promotion value.

Claims

1. A J-lay marine cable tube based on a multi-layer composite structure, characterized in that, The J-shaped submarine cable pipe body (1) is provided with a high-thermal-conductivity inner lining (4) sprayed on the inner wall of the pipe body (1) for transferring the heat of the submarine cable (3) to the J-shaped submarine cable pipe body (1); The inner wall of the high-thermal-conductivity inner lining (4) is provided with a phase-change heat storage intermediate layer (5) for absorbing and storing the heat of the submarine cable (3) and releasing the heat when the submarine cable (3) cools down; The outer wall of the phase-change heat storage intermediate layer (5) is provided with a corrugated heat dissipation outer layer (6) for forming a turbulent flow by using the natural convection of seawater to accelerate the heat dissipation efficiency.

2. A J-lay marine cable tube based on a multi-layer composite structure according to claim 1, characterized in that, The inner wall of the J-shaped submarine cable pipe body (1) is provided with continuous spiral flow guide fins (2) covering the full length of the curved section, and the curvature radius of the curved section is greater than or equal to twelve times of the inner diameter of the curved section; The height of the spiral flow guide fins (2) is one-tenth to one-eighth of the inner diameter of the J-shaped submarine cable pipe body (1), and the inclination angle θ of the spiral flow guide fins (2) is dynamically optimized by the following formula: where V air is the flow velocity inside the J-tube (1), V water is the flow velocity of the sea water outside the J-tube (1).

3. A J-lay marine cable tube based on a multi-layer composite structure according to claim 3, characterized in that, The bottom of the J-shaped submarine cable pipe body (1) is provided with a V-shaped flow guide groove (7) with a depth of 20 mm and an opening angle of 60°.

4. A J-lay marine cable tube based on a multi-layer composite structure according to claim 4, characterized in that, The high-thermal-conductivity lining layer (4) is sprayed by the following method: an aluminum nitride ceramic coating is formed on the inner wall of the J-type submarine cable pipe body (1) by using a plasma spraying process, the thickness is 50 to 100 μm, the thermal conductivity coefficient is ≥200 W / (m·K), and the contact thermal resistance is less than 0.05 K·m 2 / W.

5. A J-lay marine cable tube based on a multi-layer composite structure according to claim 5, characterized in that, The phase-change heat storage intermediate layer (5) is a composite phase-change material encapsulating paraffin and graphene nanosheet with expanded graphite as a carrier, and the microcapsule particle size is controlled within 50-200 μm, and the coating layer is a 1-3 μm silica shell; the encapsulation structure adopts a 3D printed honeycomb grid to fix the phase-change microcapsules with a filling rate of 65%-70%.

6. A J-lay marine cable tube based on a multi-layer composite structure according to claim 6, characterized in that, The corrugated heat dissipation outer layer (6) is an aluminum alloy shell with a continuous corrugated structure, and the wave height is 8 mm and the wave distance is 15 mm.

7. A method for increasing the flow capacity of a submarine cable, the submarine cable (3) being located in a J-lay cable tube according to claim 6, characterized in that The inclination angle of the spiral flow guide fins (2) is dynamically optimized by the following method: An optical fiber temperature measurement point is arranged every 0.5 m along the axis of the J-shaped submarine cable pipe body (1) to monitor the temperature gradient of the cable core, the inner layer and the outer layer of the pipe wall in real time; The temperature signal is transmitted to the central controller of the converter station through an anti-electromagnetic interference optical cable with a sampling frequency of ≥10 Hz; When the temperature of any temperature measurement point exceeds 55℃, the load reduction protection is triggered, and the transmission power is reduced by a gradient, and the maximum reduction is 15%; After the temperature falls below 50℃, the load flow is restored at a rate of 2% / min; Combined with the offshore wind power prediction data, the load flow distribution strategy is adjusted in advance to reduce the frequency of temperature control actions.

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