Flywheel energy storage rotor and preparation method thereof

Abstract

The invention provides a flywheel energy storage rotor and a preparation method. The flywheel energy storage rotor comprises an inner layer, an outer layer and a middle layer located between the inner layer and the outer layer. The inner layer is a carbon fiber material layer, the middle layer is a composite material layer formed by combining high-strength carbon fibers and glass fibers, and the outer layer is a glass fiber layer; wherein transition layers are arranged between the inner layer and the middle layer and between the middle layer and the outer layer, and the transition layers are used for connecting the inner layer, the middle layer and the outer layer. The flywheel energy storage rotor is divided into the outer layer, the middle layer and the inner layer, the inner layer is the carbon fiber material layer and used for improving the structural strength and stability of the rotor, the composite material layer of the middle layer not only meets the strength requirement but also has flexibility, and the outer layer is further arranged on the outer side of the middle layer so that the toughness of the rotor can be enhanced, the impact resistance can be optimized, and meanwhile the service life of the rotor can be prolonged. And the cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flywheel energy storage rotor design, and particularly relates to a flywheel energy storage rotor and a preparation method thereof. Background Art

[0002] With the increasing prominence of energy shortages and environmental problems brought about by the development and utilization of traditional energy sources, renewable energy has developed rapidly. However, the intermittency and randomness of renewable energy have increased the burden of power grid frequency regulation and the difficulty of peak shaving.

[0003] As a new energy storage technology, the flywheel energy storage system has the advantages of high power density, fast charge and discharge speed, long service life, etc., and has broad application prospects in the power system.

[0004] In the flywheel energy storage system, the composite flywheel is one of the key components, and its performance directly affects the efficiency and reliability of the entire system. However, the existing composite flywheels have problems such as limited energy storage capacity, insufficient structural strength, and complex manufacturing processes, which limit their application in large-scale energy storage systems.

[0005] Based on this, the inventors of the present application propose a flywheel energy storage rotor and a preparation method thereof, in order to solve one or more of the above technical problems. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of limited energy storage capacity, insufficient structural strength and complex manufacturing process of the flywheel rotor in the prior art, and to provide a flywheel energy storage rotor and a preparation method thereof.

[0007] The present invention solves the above technical problems through the following technical solutions:

[0008] The present invention provides a flywheel energy storage rotor, which is characterized in that it includes:

[0009] An inner layer, an outer layer, and a middle layer located between the inner layer and the outer layer;

[0010] The inner layer is a carbon fiber material layer, the middle layer is a composite material layer combined with high-strength carbon fiber and glass fiber, and the outer layer is a glass fiber layer; wherein,

[0011] Transition layers are provided between the inner layer and the middle layer and between the middle layer and the outer layer, and the transition layers are used to connect the inner layer, the middle layer, and the outer layer.

[0012] According to an embodiment of the present invention, the transition layer is made by mixing an interfacial enhancer with resin.

[0013] According to an embodiment of the present invention, the thickness of the transition layer is 0.1 mm - 0.3 mm.

[0014] According to an embodiment of the present invention, the middle layer comprises a composite material layer formed by mixing high-strength glass fibers and T700 grade carbon fibers in a preset ratio;

[0015] Among them, in the composite material layer, the proportion of T700 grade carbon fibers is 70% to 90%, and the proportion of high-strength glass fibers is 10% to 30%.

[0016] According to an embodiment of the present invention, the fiber volume content of the inner layer, the outer layer and the middle layer is at least not less than 65% of the total volume content of the rotor;

[0017] The thickness of the rotor is between 30 mm and 95 mm.

[0018] According to an embodiment of the present invention, the thickness of the inner layer, the middle layer to the outer layer increases gradually.

[0019] According to an embodiment of the present invention, the rotor is formed by wet winding of fibers.

[0020] According to an embodiment of the present invention, the outer layer is made by 5 windings, with the thickness of each winding being 9 mm, and the interlayer pre-pressure is controlled by tension to be 8 MPa;

[0021] The middle layer is made by 4 windings. The thicknesses of the first and fourth layers are 7 mm respectively, and the thicknesses of the second and third layers are 8 mm respectively. The interlayer pre-pressure is controlled by tension to be 6 MPa;

[0022] The inner layer is made by 3 windings. The thicknesses of the first and second layers are 7 mm, and the thickness of the third layer is 6 mm. The interlayer pre-pressure is controlled by tension to be 3 MPa.

[0023] According to an embodiment of the present invention, the maximum tensile stress value of the outer layer is 9.95 MPa, and the maximum radial deformation is 0.48 mm.

[0024] The present invention also provides a method for preparing a flywheel energy storage rotor, comprising:

[0025] Step 1, winding carbon fiber materials to form an inner layer;

[0026] Step 2, arranging a mixture of a reinforcing agent and a resin on the outer side of the inner layer to form a first transition layer, and then winding high-strength carbon fibers and glass fibers on the transition layer to form a middle layer;

[0027] Step 3, arranging a mixture of a reinforcing agent and a resin on the middle layer to form a second transition layer, and continuously winding glass fibers to form an outer layer.

[0028] The positive and progressive effects of the present invention are as follows:

[0029] The flywheel energy storage rotor of the present invention is divided into an outer layer, a middle layer and an inner layer. The inner layer is a carbon fiber material layer, which is used to improve the structural strength and stability of the rotor. The composite material layer of the middle layer not only meets the strength requirements but also has flexibility. Further, an outer layer is provided on the outside of the middle layer to enhance the toughness of the rotor. While optimizing the impact resistance performance, the cost is reduced. Brief Description of the Drawings

[0030] The above and other features, properties and advantages of the present invention will become more apparent from the following description in conjunction with the drawings and embodiments, where:

[0031] Figure 1 is a schematic structural view of the flywheel energy storage rotor of the present invention;

[0032] Figure 2 is a schematic structural view of a wet fiber winding mold.

[0033] 1. Inner layer;

[0034] 2. Outer layer;

[0035] 3. Middle layer;

[0036] 4. Transition layer. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with specific embodiments and the drawings. More details are set forth in the following description in order to fully understand the present invention. However, the present invention is clearly capable of being practiced in many other different ways than those described herein. Those skilled in the art can make similar generalizations and deductions according to the actual application situation without departing from the connotation of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0039] Please refer to Figure 1 and Figure 2 , the present invention provides a flywheel energy storage rotor, including: an inner layer 1, an outer layer 2 and a middle layer 3 located between the inner layer 1 and the outer layer 2; wherein, the inner layer 1 is a carbon fiber material layer, the middle layer 3 is a composite material layer combined with high-strength carbon fiber and glass fiber, and the outer layer 2 is a glass fiber layer; wherein, a transition layer 4 is provided between the inner layer 1 and the middle layer 3 and between the middle layer 3 and the outer layer 2, and the transition layer 4 is used to connect the inner layer 1, the middle layer 3 and the outer layer 2.

[0040] It can be seen that carbon fiber has good structural strength and modulus, and can bear the large centrifugal force generated during the high-speed rotation of the rotor, which is used to greatly improve the structural strength and stability of the rotor. Therefore, the inner layer 1 is made of a carbon fiber material layer.

[0041] Glass fiber has good flexibility and cost advantages. While enhancing the toughness of the rotor and optimizing the impact resistance performance, it realizes reasonable cost control. Therefore, the outer layer 2 is made of a glass fiber layer. At the same time, a middle layer 3 is further arranged between the inner layer 1 and the outer layer 2. On the one hand, it is used to connect the inner layer 1 and the outer layer 2, and on the other hand, it can optimize and improve the anti-fatigue performance and the overall mechanical properties of the rotor.

[0042] Furthermore, epoxy resin has good bonding properties, good mechanical properties, low shrinkage rate, and good chemical corrosion resistance. It can be used as a matrix material, and the fluidity, curing processability, and toughness of the resin can be improved by adding a predetermined amount of curing agent, toughening agent, and diluent. Using epoxy resin as the matrix and combining it with glass fiber and carbon fiber can form the above-mentioned outer layer 2, middle layer 3, and inner layer 1.

[0043] Among them, in the modified resin, the content ratio of the curing agent is 10%-20%, the content ratio of the toughening agent is 5%-10%, and the content ratio of the diluent is 3%-5%. Thus, the connection strength requirements between layers are met.

[0044] Further, the inner layer 1 in the present invention uses epoxy resin as the matrix and selects a carbon fiber material layer to provide a stable core support for the rotor, ensuring better axial stability and torsional resistance.

[0045] The middle layer 3 uses a fiber material pre-impregnated with resin, and a composite material layer is formed by mixing high-strength glass fiber and T700-grade carbon fiber according to a preset ratio; among them, the proportion of T700-grade carbon fiber is 70%-90%, and the proportion of high-strength glass fiber is 10%-30%.

[0046] The pre-impregnation can be cured by methods such as hot pressing and vacuum forming, which are not limited here. The above process can ensure the uniform distribution of fibers and resin, and improve the quality and consistency of the composite material layer.

[0047] Furthermore, by adopting an optimized fiber laying angle, such as a symmetric laying method of 0°, 45°, 90°, -45°, the efficient bearing and uniform dispersion of radial and tangential stresses can be accurately realized, greatly improving the anti-fatigue performance and the overall mechanical properties of the rotor.

[0048] The outer layer 2 is made of fiberglass and combined with epoxy resin to form a fiberglass layer, which is used for protection and function optimization, facilitating resistance to external environmental erosion and foreign object impact. At the same time, the flexibility of the fiberglass is utilized to inhibit crack propagation, further enhancing the reliability and durability of the rotor.

[0049] By setting a transition layer 4 between adjacent layers, seamless and tight connection can be achieved, ensuring the smooth transfer and synergistic effect of stress, thereby avoiding the problem of failure between layers.

[0050] In one embodiment, the thickness of the transition layer 4 is 0.1 mm - 3 mm.

[0051] Since the material properties between the middle layer 3, the inner layer 1, and the outer layer 2 are different, stress concentration will occur. Setting the transition layer 4 can provide a gradually changing region between adjacent layers, thereby effectively dispersing stress. If the transition layer 4 is too thin, it is difficult to fully exert the stress buffering effect, while if the transition layer is too thick, it will increase the overall weight and volume of the rotor, which is not conducive to the high-speed rotation of the rotor.

[0052] Based on this, the present invention selects a transition layer 4 with a thickness of 0.1 mm - 3 mm. The specific thickness can be adjusted according to the overall thickness of the rotor. If the overall thickness of the rotor is too large, a transition layer close to 3 mm is selected, while if the rotor thickness is relatively small, a transition layer close to 0.1 mm is selected for the transition layer 4, thereby ensuring stress transition and maintaining the compactness of the rotor structure.

[0053] Optionally, the transition layer 4 is composed of a silane coupling agent and a glycidylamine epoxy resin mixed in a ratio of 1:0.5 to 1:1.

[0054] Optionally, the inner layer 1 is an M40 grade carbon fiber material layer; the middle layer 3 is a high-strength fiberglass - T700 grade carbon fiber material layer.

[0055] It can be seen that the M40 grade carbon fiber belongs to the high-modulus type carbon fiber. Using it for the inner layer 1 can provide greater anti-deformation ability for the entire rotor structure during the operation of the rotor. Since the inner layer 1 is the basic part that bears various stresses generated by the rotation of the rotor, the high-modulus characteristics of the M40 grade carbon fiber can ensure that the inner layer structure minimizes deformation as much as possible and maintains the accuracy of the overall shape of the rotor when rotating at high speed or under complex external forces, thereby ensuring the stable operation of the energy storage flywheel.

[0056] At the same time, the M40 grade carbon fiber has good comprehensive performance. Only a small amount is needed to meet the strict requirements of the inner layer for strength and stiffness. Thus, while ensuring high performance, a certain degree of lightweight can be achieved, improving the efficiency of the entire system.

[0057] T700 grade carbon fiber belongs to high-strength carbon fiber, with high strength and good cost performance. When compounded with high-strength glass fiber to form the middle layer 3, it can not only enhance the load-bearing capacity of the overall structure by virtue of the high strength of T700 grade carbon fiber, but also effectively control the material cost on the premise of ensuring performance by taking advantage of the relatively low cost of high-strength glass fiber.

[0058] Moreover, high-strength glass fiber has high tensile strength and good toughness. After being compounded with T700 grade carbon fiber, the properties of the two complement each other. The toughness of high-strength glass fiber can buffer the stress impact generated during high-speed rotation, preventing the T700 grade carbon fiber from breaking due to stress concentration; at the same time, the high strength of T700 grade carbon fiber can increase the load-bearing upper limit of the overall structure.

[0059] In addition, high-strength glass fiber also has good chemical stability and insulation, which can enhance the adaptability of the middle layer in different environments.

[0060] When manufacturing the middle layer, the two materials can work well together, which is convenient for operation and control during the manufacturing process, improving production efficiency and product quality stability.

[0061] Specifically, the fiber volume content of the inner layer 1, the outer layer 2 and the middle layer 3 is at least not less than 65% of the total volume content of the rotor; the thickness of the rotor is between 30mm and 95mm.

[0062] Thus, the rotor is formed by wet winding of fibers. It can be seen that in order to meet the manufacturing requirements of the wet winding process, a mold including a mandrel, a core mold and end plates is designed, and the structure is as Figure 2 shown.

[0063] Due to the large self-weight of the flywheel mold and the wound flywheel, the mandrel should have sufficient stiffness to ensure that the deformation of the mandrel itself is small during the winding process.

[0064] The geometric dimensions of the core mold and end plates determine the geometric dimensions of the flywheel product. If deformation occurs during the winding process, it will directly affect the geometric dimensions of the flywheel product. Therefore, the core mold and end plates should have sufficient stiffness.

[0065] It should be noted that the rotor is a key rotating component of the energy storage flywheel, and the control of its own unbalance amount is of great significance to the overall unbalance amount of the energy storage flywheel rotor. After the winding is completed, the resin between the fiber layers of the thermosetting epoxy resin is in a liquid state. By heating, the epoxy resin undergoes chemical cross-linking and curing. During the temperature rise of the liquid resin, its viscosity first decreases and then rises sharply. In the initial stage of the curing temperature rise, due to the decrease in the viscosity of the glue solution, the resin penetrates outward under the action of the pressure between the fiber layers. In order to prevent the influence of the deflection of the wound part and the uneven resin penetration on the unbalance amount of the composite flywheel, the composite flywheel is cured by a rotational curing process.

[0066] Based on this, the wet filament winding process proposed by the present invention winds the fibers on a rotating mandrel through a nozzle carrying the resin-impregnated fibers along a certain movement trajectory, and then completes the composite product, i.e., the rotor, through curing and demolding.

[0067] It can be seen that by adding a preset amount of curing agent, toughening agent and diluent to the epoxy resin, the present invention effectively improves the fluidity, curing process and toughness of the resin, thereby significantly enhancing the interfacial bonding strength between the matrix material and the limiting reinforcing material. The resin impregnated by the nozzle is the above-mentioned improved resin.

[0068] Specifically, through large-tension winding, there is a radial compressive stress between the wound fiber layers, and this compressive stress squeezes out the resin glue in the inner layer 1 during the winding process. The outward migration of the resin glue causes a partial loss of winding tension, which results in a reduction between the effective winding tension and the applied winding tension. The fiber winding tension reduction is considered in the winding tension design.

[0069] For example, through simulation, it is found that increasing the gap between fiber layers can reduce the winding tension reduction caused by the extrusion of resin glue. Therefore, in actual production, the winding process can be optimized by adjusting the spacing of fiber winding, reducing the adverse effects brought by the winding tension reduction. The specific way of considering the reduction is not limited here.

[0070] Furthermore, during a single winding process, as the number of winding layers increases, the proportion of fiber winding tension loss gradually increases. To ensure the uniformity of the fiber volume content, interlayer pressure and material quality of the composite material along the radial direction, a variable-tension and layer-by-layer curing process is adopted in the manufacture of the flywheel.

[0071] Specifically, the outer layer 2 is made by 5 windings, with a thickness of 9 mm for each winding, and the interlayer pre-pressure is controlled at 8 MPa through tension;

[0072] The middle layer 3 is made by 4 windings. The thicknesses of the first and fourth layers are 7 mm respectively, and the thicknesses of the second and third layers are 8 mm respectively. The interlayer pre-pressure is controlled at 6 MPa through tension;

[0073] The inner layer 1 is made by 3 windings. The thicknesses of the first and second layers are 7 mm, and the thickness of the third layer is 6 mm. The interlayer pre-pressure is controlled at 3 MPa through tension.

[0074] The following shows the material parameters of each layer of the rotor according to an embodiment of the present invention:

[0075]

[0076]

[0077] That is, the resin matrix of the present invention selects HBS-HTS40 resin, and the fiber content of the glass fiber layer, the inner layer and the middle layer is at least not less than 65%. The thicknesses are exemplified by 45, 30, and 20 respectively, and the specific data are not limited here.

[0078] Correspondingly, the circumferential modulus, radial modulus, Poisson's ratio and density of each layer are as shown in the above data examples.

[0079] It should be noted that the rotor is a key rotating component of the energy storage flywheel, and the control of its own unbalance amount is of great significance to the overall unbalance amount of the energy storage flywheel rotor. After the thermosetting epoxy resin is wound, the resin between the fiber layers is in a liquid state, and the epoxy resin is chemically crosslinked and cured by heating. During the temperature rise of the liquid resin, its viscosity first decreases and then rises sharply. In the initial stage of the curing temperature rise, due to the decrease in the viscosity of the adhesive liquid, the resin penetrates outward under the action of the pressure between the fiber layers. In order to prevent the influence of the deflection of the winding and the uneven penetration of the resin on the unbalance amount of the composite flywheel, the composite flywheel is cured by a rotational curing process.

[0080] In summary, the flywheel energy storage rotor of the present invention is divided into an outer layer 2, a middle layer 3 and an inner layer 1. The inner layer 1 is a carbon fiber material layer, which is used to improve the structural strength and stability of the rotor. The composite material layer of the middle layer 3 not only meets the strength requirements but also has flexibility at the same time. Further setting the outer layer 2 outside the middle layer 3 is to enhance the toughness of the rotor, optimize the impact resistance performance, and reduce the cost.

[0081] The present invention also provides a method for preparing a flywheel energy storage rotor, including:

[0082] Step 1: Wind the carbon fiber material to form an inner layer;

[0083] Step 2: Set a mixture of a reinforcing agent and a resin on the outside of the inner layer to form a first transition layer, and then continue to wind high-strength carbon fibers and glass fibers on the transition layer to form a middle layer;

[0084] Step 3: Set a mixture of a reinforcing agent and a resin on the middle layer to form a second transition layer, and continue to wind glass fibers to form an outer layer.

[0085] That is, the above method uses a flywheel winding mold (refer to Figure 2 ) to prepare a flywheel energy storage rotor, and through a wet winding process, the fiber nozzle with impregnated fiber winds the fiber on the rotating mandrel according to a certain movement trajectory, and then completes the preparation of the rotor through curing and demolding.

[0086] That is, the glue impregnated by the nozzle can be a mixture formed by adding a curing agent, a toughening agent and a diluent to the epoxy resin, thereby improving the interfacial bonding strength between the matrix material (epoxy resin) and the fiber material (carbon fiber and glass fiber).

[0087] Both the first transition layer and the second transition layer can be provided by coating or spraying, which is not limited herein. For example, after the inner layer winding is completed, the machine can be stopped and a mixture of an interface enhancer and resin (transition layer) can be coated and cured to form the first transition layer. Similarly, after the middle layer winding is completed, the machine can be stopped and a mixture of an interface enhancer and resin (transition layer) can be coated and cured to form the second transition layer, so as to improve the connection strength between layers and avoid failure.

[0088] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0089] The present application uses specific terms to describe the embodiments of the present application. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the present application can be appropriately combined.

[0090] Although the present invention is disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention all fall within the protection scope defined by the claims of the present invention.

Claims

1. A flywheel energy storage rotor, characterized in that, Comprising: An inner layer, an outer layer, and a middle layer located between the inner layer and the outer layer; The inner layer is a carbon fiber material layer, the middle layer is a composite material layer combined with high-strength carbon fiber and glass fiber, and the outer layer is a glass fiber layer; wherein, Transition layers are provided between the inner layer and the middle layer and between the middle layer and the outer layer, and the transition layers are used to connect the inner layer, the middle layer, and the outer layer.

2. The flywheel energy storage rotor according to claim 1, wherein, The transition layer is made by mixing an interface enhancer and resin.

3. The flywheel energy storage rotor according to claim 2, wherein, The thickness of the transition layer is 0.1 mm - 0.3 mm.

4. The flywheel energy storage rotor according to claim 1, wherein, The middle layer includes a composite material layer formed by mixing high-strength glass fiber and T700 grade carbon fiber in a preset ratio; Wherein, in the composite material layer, the proportion of T700 grade carbon fiber is 70% to 90%, and the proportion of high-strength glass fiber is 10% to 30%.

5. The flywheel energy storage rotor according to claim 1, wherein, The fiber volume content of the inner layer, the outer layer, and the middle layer is at least not less than 65% of the total volume content of the rotor; The thickness of the rotor is between 30 mm and 95 mm.

6. The flywheel energy storage rotor according to claim 5, wherein The thickness increases from the inner layer, the middle layer to the outer layer.

7. The flywheel energy storage rotor according to claim 1, wherein, The rotor is formed by wet winding of fibers.

8. The flywheel energy storage rotor according to claim 7, wherein, The outer layer is made by 5 windings, with each winding thickness of 9 mm, and the interlayer pre-pressure is controlled by tension to be 8 MPa; The middle layer is made by 4 windings. The thicknesses of the first layer and the fourth layer are 7 mm respectively, and the thicknesses of the second layer and the third layer are 8 mm respectively. The interlayer pre-pressure is controlled by tension to be 6 MPa; The inner layer is made by 3 windings. The thicknesses of the first layer and the second layer are 7 mm, and the thickness of the third layer is 6 mm. The interlayer pre-pressure is controlled by tension to be 3 MPa.

9. The flywheel energy storage rotor according to claim 1, characterized in that, The maximum tensile stress value of the outer layer is 9.95 MPa, and the maximum radial deformation is 0.48 mm.

10. A method for preparing a flywheel energy storage rotor, characterized in that, Comprising: Step 1: Wind the carbon fiber material to form an inner layer; Step 2: Set a mixture of an enhancer and resin on the outer side of the inner layer to form a first transition layer, and then wind high-strength carbon fiber and glass fiber on the transition layer to form a middle layer; Step 3: Set a mixture of an enhancer and resin on the middle layer to form a second transition layer, and continue to wind glass fiber to form an outer layer.

Images