High-magnification composite cascade non-imaging condensation system and design method thereof

Abstract

The invention discloses a high-magnification composite cascade non-imaging condensation system and a design method thereof, and belongs to the technical field of solar photo-thermal utilization, and the system comprises a receiving body which is provided with a surface capable of receiving reflected light; the main reflecting mirror is configured to reflect incident light to a receiving body, and the outline of the main reflecting mirror is set as follows: under the condition of a given receiving half angle, paraxial edge light Ray1r in a reflecting light cone corresponding to any reflecting point on the main reflecting mirror points to the lower part or the bottom area of the light facing side of the receiving body after primary reflection; and the secondary reflecting mirror is configured to intercept and recycle the far-axis edge light ray Ray2r and the adjacent light rays in the reflecting light cone reflected by the main reflecting mirror, and reflect the far-axis edge light ray Ray2r and the adjacent light rays to the upper part of the light facing side or the backlight side area of the receiving body. Through the cascade cooperation that the main reflector covers the bottom area and the secondary reflector recycles the top escape light, the high geometric condensation ratio and the high uniformity of the circumferential energy flow of the receiver are realized under the condition of small receiving half angle.

Description

Technical Field

[0001] This invention relates to a high-magnification composite cascade non-imaging concentrating system and its design method, belonging to the field of solar optical concentrating technology. Background Technology

[0002] Line-focusing non-imaging concentrating systems are widely used in solar thermal power generation, high-temperature heat collection, and concentrated photovoltaics due to their relatively simple structure and ease of engineering implementation. In existing technologies, common line-focusing concentrating systems (such as parabolic trough PTC or composite parabolic CPC) typically include a circular tubular receiver and a reflector structure located below it. Their design is mostly based on the principle of edge rays, generating the reflector profile through geometric envelope under a given receiving half-angle condition.

[0003] However, in applications with a small receiving half-angle (such as tracking high-magnification focusing systems), existing non-imaging line focusing structures generally suffer from the following irreconcilable contradictions:

[0004] On the one hand, the energy flow distribution is extremely uneven. Traditional designs (such as PTC) tend to focus the light onto a focal line at the bottom of the receiver, or, like CPC, only ensure that the edge rays are tangent to the receiver. This results in a limited coverage area of ​​the reflected light cone on the receiver's cross-section, with energy often highly concentrated in a local area of ​​the receiver (usually the bottom), causing extremely high local heat flux density. This can lead to thermal stress deformation of the receiver tube (banana effect) or even the risk of tube bursting, while the top of the receiver is often in a dead zone of illumination.

[0005] On the other hand, there are limitations imposed by structural height and light concentration ratio. To achieve lossless capture at a small receiving half-angle, the height of the reflector designed according to the traditional CPC theory increases exponentially, resulting in huge material consumption, bulky structure, and significantly increased wind resistance, thus limiting its engineering application value. If the height is simply reduced by shortening the reflector, a large amount of light will escape from above the receiver, leading to a sharp drop in optical efficiency.

[0006] To address these issues, some existing technologies attempt to recover escaping rays by introducing secondary reflection structures. However, most of these solutions are merely simple "patchwork" designs based on the existing primary mirror, failing to fundamentally rebuild the spatial matching relationship between the primary mirror's reflected light cone and the receiver.

[0007] Existing technologies have not fully utilized the synergistic effect between "deliberately creating a specific direction for focusing (such as the bottom) by the primary reflector" and "directional retrieval by the secondary reflector (such as the top)" to simultaneously solve the three major challenges of height, efficiency, and uniformity. The design methodology is imperfect: it lacks a collaborative design logic for the primary and secondary reflectors, making it difficult to achieve a compact and lightweight system structure while ensuring light-gathering efficiency.

[0008] Furthermore, traditional parabolic trough concentrators (PTCs) are limited by their relatively low theoretical concentration ratio (typically less than 40), facing insurmountable thermodynamic bottlenecks when pursuing higher operating temperatures. According to the Stefan-Boltzmann law, the radiative heat loss of the receiver is proportional to the fourth power of its surface area and temperature. The relatively large receiver surface area of ​​PTCs leads to a sharp increase in heat loss in high-temperature working fluid applications (such as above 550°C), resulting in a significant decrease in photothermal conversion efficiency. This directly limits its application in next-generation high-efficiency solar thermal power generation technologies such as supercritical carbon dioxide (s-CO2) Brayton cycles, making it difficult to meet the needs of future high-temperature solar thermal power plants.

[0009] Therefore, there is an urgent need for a high-magnification composite cascade non-imaging focusing system that can simultaneously achieve efficient convergence of paraxial and far-axis light rays, has a compact structure, and a scientifically designed method. Summary of the Invention

[0010] The purpose of this invention is to propose a high-magnification composite cascade non-imaging focusing system and its design method, which solves the technical problems of severe far-axis edge light loss, low recovery efficiency of secondary mirrors, and lack of system design synergy in existing non-imaging focusing systems.

[0011] The high-magnification composite cascade non-imaging focusing system of the present invention comprises: The receiver has a surface capable of receiving reflected light. The primary reflector is configured to reflect incident light to the receiver. The profile of the primary reflector is set such that, under a given receiving half-angle, the paraxial edge light rays in the reflected light cone corresponding to any reflection point on the primary reflector point towards the lower or bottom region of the receiver on the light-facing side after one reflection. The secondary reflector is configured to intercept and recover the far-axis edge rays and adjacent rays in the reflected light cone reflected by the primary reflector, and reflect them to the upper part of the light-facing side or the back-light-facing area of ​​the receiver.

[0012] In this invention, the design logic of the primary reflector differs significantly from traditional designs. Traditional designs often aim for the center of the light cone to point towards the center of the receiver, while this invention creatively introduces a strong constraint of "paraxial edge ray Ray1r cutting". Although this constraint causes the overall upward shift of the reflected light cone, preventing some energy (especially the far-axis portion) from being directly intercepted by the receiver, it brings two significant advantages: first, it greatly reduces the distance between the primary reflector and the receiver, lowering the system height; second, it forces the reflected energy of the primary reflector to concentrate on the bottom of the receiver, leaving the top of the receiver empty for the secondary reflector to perform "secondary supplementary lighting", thus ensuring a uniform distribution of circumferential energy flow in the receiver in terms of physical mechanism.

[0013] In the aforementioned high-magnification cascaded non-imaging focusing system, the secondary mirror is not a redundant accessory, but rather a necessary complement based on the specific geometric configuration of the primary mirror: Because the primary reflector is constrained to a "Ray1r cut-off" configuration, as the reflection point extends towards the edge, the angular coverage of the reflected light cone gradually shifts upwards, inevitably causing the outer portion of the reflected light cone (with Ray2r as the boundary) to deviate from the top of the receiver. Therefore, this invention constructs a secondary reflector above the receiver specifically to intercept this particular escape light cone region and reflect it back to the top of the receiver. This collaborative working mode of "primary mirror handling the bottom, secondary mirror handling the top" achieves efficient capture and uniform distribution of light energy.

[0014] Preferably, the primary reflector is positioned below the receiver, and the secondary reflector is positioned above the receiver, with the reflecting surface of the secondary reflector facing the primary reflector.

[0015] Preferably, the primary reflector is configured such that the reflected light forms a coverage that at least partially overlaps with the receiver in the circumference of the receiver, the coverage being formed by the difference in the equivalent optical path from different reflection points of the primary reflector to the receiver.

[0016] Preferably, the profile of the primary reflector is composed of a continuous curve or a continuous surface, and adopts a parabola, involute, quasi-elliptic curve or a combination thereof.

[0017] Preferably, the secondary reflector has a pointed structure protruding from the center towards the receiver in cross-section, and wing-shaped reflective surfaces extend from the pointed point to both sides; its contour is constructed based on the principle of edge rays. For each escape light cone reflected from the edge segment of the primary reflector, its reflection point is regarded as an instantaneous virtual focal point, and the tangent point on the surface of the receiver is regarded as a moving real focal point. A curve adapted to the light cone is generated using the principle of constant optical path, and the curves are smoothly connected to form the continuous reflective surface of the secondary reflector.

[0018] Preferably, the primary reflector and the secondary reflector form a cascaded reflection structure in space, so that the incident light is guided to the receiver after one or more reflections.

[0019] Preferably, the receiver is a linear tubular structure, with its axial direction aligned with the linear focusing direction of the focusing system, and the cross-section of the receiver is circular, approximately circular, or other regular geometric shape.

[0020] The design method of the high-magnification composite cascade non-imaging focusing system of the present invention includes: The contour of the primary reflector is constructed based on the principle of light cone matching: According to the geometric parameters of the receiver and the receiving half angle of the system design, the geometric surface of the primary reflector is configured so that the edge ray of the side with a smaller angle deviating from the optical axis of the system, i.e., the paraxial edge ray Ray1r, in the reflected light cone corresponding to any reflection point on it, points to the lower part or bottom area of ​​the light-facing side of the receiver after one reflection. Identify the light escape area: Determine whether the far-axis edge light Ray2r and its adjacent light rays in the light cone reflected by the primary mirror, which deviate from the system's optical axis by a larger angle, cannot be directly captured by the receiver. Constructing a secondary reflector for light recovery: For the light area that cannot be directly captured, a secondary reflector is constructed above the receiver to reflect that portion of the light back to the receiver.

[0021] Preferably, the determination of the area where the reflected light is not directly captured is based on whether the far-axis edge ray Ray2r of the reflected light cone can be completely intercepted by the receiver under a single reflection condition.

[0022] Preferably, the contour construction process of the primary and secondary reflectors is achieved through one or more of the following methods: analytical calculation, numerical calculation, discrete iteration, or reverse ray tracing.

[0023] Compared with existing technologies, the high-magnification composite cascade non-imaging focusing system and its design method of the present invention exhibit the following beneficial effects in terms of technical performance and practical applications: 1. Highly Uniform Energy Flux Density Distribution: By employing a zoned mapping strategy of "primary reflector covering the bottom of the receiver and secondary reflector supplementing the top of the receiver," the drawback of traditional line focusing systems where energy is concentrated at the bottom is completely overcome. This invention achieves continuous coverage and uniformity of circumferential energy flux in the receiver, significantly reducing local peak heat flux density and effectively mitigating the risk of thermal stress deformation and glass breakage in the receiving tube.

[0024] 2. Balancing high light concentration ratio with low structural height: By utilizing the geometric constraints of the "Ray1r cut-off," the focal length and height of the primary reflector are forcibly compressed, allowing the system to maintain a low and compact structural form while achieving high light concentration (small receiving half-angle). This not only significantly reduces reflector material consumption but also significantly reduces the wind resistance load on the tracking system.

[0025] 3. High tolerance for light capture: The unique cascade recovery mechanism makes the system more flexible in handling far-axis edge rays. Even with certain tracking or manufacturing errors, the large top secondary mirror can effectively intercept escaping rays, ensuring the system's high optical interception factor.

[0026] 4. Strong engineering applicability: Compared with the solution using solid dielectric lenses, the present invention adopts a total reflection mirror structure, which has no dispersion and no absorption loss, and is lightweight and low in cost, making it particularly suitable for large-scale commercial promotion of solar thermal power generation and industrial heating.

[0027] 5. Spatial Release for the Auxiliary Optical System: Unlike solutions that use a "top-cutting" design with the primary mirror and confine the auxiliary mirror to a narrow space at the bottom of the receiver, the "bottom-cutting" design strategy of this invention shifts the light-receiving area to the top of the receiver. This open area removes the geometric limitations of the auxiliary mirror, allowing it to use a larger aperture or a more complex optical surface, thereby achieving more efficient light interception and energy redistribution while maintaining greater manufacturing tolerance.

[0028] 6. Breakthrough in concentrating power of traditional line-focusing systems. Thanks to the unique cascaded light cone matching mechanism of this invention, the system can effectively intercept and utilize off-axis light rays that are previously unavailable in single imaging or non-imaging systems. Under the same small receiving half-angle (e.g., 0.5°), the geometric concentration ratio of the system described in this invention significantly exceeds the theoretical limit of traditional parabolic trough (PTC) collectors. Compared to the typical concentration ratio limit of approximately 30-40 for traditional PTC systems, this invention achieves a performance improvement of several times (e.g., exceeding 90), thereby greatly enhancing the system's heat collection efficiency and work potential in high-temperature photothermal utilization scenarios.

[0029] 7. Significantly reduced heat loss, unlocking the potential for high-temperature thermal power generation applications. While achieving an ultra-high concentration ratio (e.g., 92), this invention essentially means a substantial reduction in the relative surface area of ​​the receiver (heat absorber) within the same aperture size. Compared to traditional PTC, this invention reduces the radiative and convective heat dissipation area at high temperatures by more than 60%. This characteristic allows the system to maintain extremely high heat collection efficiency even at higher operating temperatures (e.g., 700°C or higher), thus perfectly adapting to new high-efficiency thermal power generation cycles such as supercritical carbon dioxide (s-CO2), providing crucial optical hardware support for third- / fourth-generation solar thermal power generation technologies. Attached Figure Description

[0030] Figure 1 : A schematic diagram of the basic structure of the high-magnification composite cascade non-imaging focusing system of the present invention; Figure 2 : A schematic diagram of the optical path of the primary reflector in this embodiment of the invention when the critical condition for light escape has not been reached; Figure 3 : A schematic diagram of a light-concentrating system with a secondary reflector in an embodiment of the present invention; Figure 4: A schematic diagram comparing the reflected light coverage characteristics under different reflected optical path allocation states in the embodiments of the present invention; Figure 5 : A schematic diagram of the design method of the high-magnification composite cascade non-imaging focusing system of the present invention; Figure 6 : A schematic ray tracing diagram under small receiving half-angle conditions in an embodiment of the present invention; Figure 7 : A schematic diagram of the circumferential energy distribution of the receiver in this embodiment of the invention; Figure 8 : A diagram showing the definitional relationship between geometric variables in the trajectory equation of the mirror in this embodiment of the invention; In the diagram: 1. Receiver; 2. Primary reflector; 3. Secondary reflector. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Example 1: like Figures 1-3 As shown, the high-magnification composite cascade non-imaging focusing system of the present invention includes: Receiver 1 has a surface capable of receiving reflected light; The main reflector 2 is configured to reflect incident light to the receiver 1. The profile of the main reflector 2 is set such that, under a given receiving half angle, the paraxial edge ray Ray1r in the reflected light cone corresponding to any reflection point on the main reflector 2 points to the lower part or bottom area of ​​the light-facing side of the receiver 1 after one reflection. The secondary reflector 3 is configured to intercept and recover the far-axis edge ray Ray2r and its neighboring rays in the reflected light cone reflected by the primary reflector 2, and reflect them to the upper part of the light-facing side or the back-light-facing area of ​​the receiver 1.

[0033] The main reflector 2 is positioned below the receiver 1, and the secondary reflector 3 is positioned above the receiver 1, with the reflecting surface of the secondary reflector 3 facing the main reflector 2.

[0034] The primary reflector 2 is configured such that the reflected light forms at least partially overlapping coverage around the receiver 1, the coverage being formed by the difference in equivalent optical path from different reflection points of the primary reflector 2 to the receiver 1.

[0035] The profile of the primary reflector 2 is composed of a continuous curve or a continuous surface, and adopts a parabola, involute, quasi-elliptic curve or a combination thereof.

[0036] The profile of the secondary reflector 3 is constructed based on the inverse worst-case point iteration method. The light cone reflection point on the primary reflector 2 is regarded as the instantaneous fixed focus, and the tangent point on the surface of the receiver 1 is regarded as the moving focus, generating multiple curves.

[0037] The primary reflector 2 and the secondary reflector 3 form a cascaded reflection structure in space, so that the incident light is guided to the receiver 1 after one or more reflections.

[0038] In this embodiment, receiver 1 is a tubular receiver with a circular cross-section and a radius of r. The system is designed to receive a half-angle θ. a We selected 0.5° to suit high-precision tracking scenarios.

[0039] Receiver 1: A high-temperature resistant stainless steel vacuum tube with a standard circular cross-section and an axis arranged along the north-south direction to form a line-focusing structure. The tube is filled with heat-conducting oil as the heat transfer medium, and its surface is coated with a selective absorption coating, exhibiting an absorption rate of ≥95% for the solar spectrum and an infrared emissivity of ≤5%.

[0040] Primary reflector 2: Located directly below the receiver, it is made of high-reflectivity silver mirror material with a surface roughness Ra≤0.05μm. Its profile is composed of a combination of quasi-elliptic curves. By controlling the equivalent optical path difference from the reflection point to the receiver, the reflected light rays form a 40% overlap coverage around the receiver. The core design constraint of primary reflector 2 is that the paraxial edge ray Ray1r from any reflection point, after one reflection, is tangent to the bottom of the receiver (lower part of the light-facing side).

[0041] Secondary reflector 3: Located directly above the receiver, at a vertical distance of 1200mm from the primary reflector, it is made of anodized aluminum. Its profile is constructed based on the inverse worst-case iteration method, treating the light cone reflection point on the primary reflector as an instantaneously fixed virtual focal point and the tangent point on the receiver surface as a moving real focal point, generating 16 quasi-elliptic curve micro-elements and smoothly connecting them to form a continuous reflective surface.

[0042] Design principle explanation: (e.g.) Figure 2 As shown, in the intermediate design state with only the primary reflector and satisfying the aforementioned Ray1r tangent constraint, as the primary reflector extends outward, the coverage area of ​​the reflected light cone on the receiver surface gradually shifts upward. When the reflection point position exceeds the critical center-to-center distance (r / sinθ)... a When the light is reflected, the other side of the reflective cone—the far-axis edge ray (Ray2r)—begins to deviate from above the receiver, forming an escape ray.

[0043] To recover the inevitably escaped energy, this embodiment includes a secondary reflector 3 above the receiver 1. Its cascaded optical path is as follows: Figure 3As shown in the diagram: segment 2a is the light-free segment, and segment 2b is the light-leaking segment. The incident light cone L1 from the light source is reflected by the primary reflector 2 to form a primary reflection light cone L2. The lower half of the primary reflection light cone L2 is directly projected onto the receiver 1, while the upper part of the escaping light is intercepted by the secondary reflector 3 and converted into a secondary reflection light ray L3, which is finally guided to the top of the receiver 1. This cascaded cooperation achieves efficient capture of light energy.

[0044] Through this cascaded collaboration of "primary mirror targeting the bottom and secondary mirror blocking the top," this embodiment achieves efficient capture of incident light energy while significantly reducing the height of the primary reflector.

[0045] like Figure 4 As shown, this embodiment illustrates how adjusting the geometric control parameters of the primary reflector (such as the initial phase angle) can improve performance. The influence of s (or auxiliary constant C) on the structural characteristics of the system.

[0046] While keeping the core constraint of "Ray1r bottoming out" unchanged: Parameter Configuration A (Compact) (State A in the diagram): A smaller initial phase angle is selected, the primary reflector is closer to the receiver, and the system height is significantly reduced. Although this results in more top-escape rays, complete capture can still be achieved by matching a secondary reflector with a larger opening. This configuration is suitable for scenarios with extremely high wind resistance requirements.

[0047] Parameter configuration B (balanced type) (state B in the figure): Select a larger starting phase angle, the primary reflector is slightly further away from the receiver, the size of the secondary reflector is reduced, but the total height of the system is slightly increased.

[0048] This indicates that the present invention provides flexible optimization space for engineering design through the strategy of "primary mirror parameter adjustment + secondary mirror follow-up design".

[0049] like Figure 6 and Figure 7 As shown, numerical simulation analysis was performed on the system described in this invention.

[0050] Optical path verification: Numerical simulation analysis of the system was performed using ray tracing software. The results show that: Figure 6 The working mechanism of the cascaded optical path is clearly demonstrated. The primary reflector projects most of the light into the lower part of the receiver (green light), while the light that would have flown out from the top is precisely captured by the secondary reflector at the top and reflected back to the top of the receiver (red / dark light).

[0051] As is well known, for traditional parabolic trough concentrators (PTCs) using tubular receivers, their theoretical maximum geometric concentration ratio is limited by geometric optics principles and follows the formula:

[0052] Where φ e For the edge angle, θ a To receive half-width characters.

[0053] Receiving half angle θ a Set to 0.5° and take the maximum edge angle φ. e Under ideal extreme conditions of 90°, the theoretical upper limit of the concentration ratio of traditional PTC is only about 36.5.

[0054] Thanks to the cascaded non-imaging optical design described in this invention, through the extreme compression of paraxial rays by the primary mirror and the efficient recovery of off-axis rays by the secondary mirror, at the same receiving half-angle (θ)... a Under the condition of 0.5°, the effective geometric concentration ratio achieved by this system reached 92.

[0055] This breakthrough improvement in the light concentration ratio (from 36.5 to 92) is significant not only for the increase in optical efficiency, but also for the fundamental improvement in the thermodynamic performance of the system.

[0056] In solar thermal utilization, the heat loss (Qloss) of the receiver mainly consists of radiative heat loss and convective heat loss, both of which are proportional to the receiver's surface area (Areceiver). For a given aperture area, the geometric concentration ratio C is defined as C = Aaperture / Areceiver. Therefore, this invention increases the concentration ratio C to 2.5 times that of traditional PTC, meaning that while collecting the same amount of solar energy, the receiver's surface area (Areceiver) is reduced to 1 / 2.5 of that in traditional designs (i.e., a reduction of approximately 60% in heat dissipation area).

[0057] This change in geometric characteristics is crucial for high-temperature working fluid applications. Traditional PTCs, due to their large heat dissipation area, experience exponential increases in radiative heat loss when the working fluid temperature exceeds 550°C, leading to a sharp drop in system thermal efficiency and making it impossible to maintain high-temperature operation. In contrast, this invention, with its extremely small relative heat dissipation area, effectively suppresses radiative heat loss at high temperatures, enabling the heat transfer fluid to stably reach operating temperatures of 700°C or even higher.

[0058] This makes the composite cascade concentrating system described in this invention particularly suitable for supercritical carbon dioxide (s-CO2) Brayton cycle thermal power generation systems. The s-CO2 cycle is renowned for its compactness and high efficiency, but requires higher turbine inlet temperatures (typically >600°C) to realize its efficiency advantages. This invention fills the gap in existing line-focusing technology in this temperature range, enabling high-temperature, high-efficiency heat collection through a low-cost line-focusing structure without employing expensive and complex tower concentrating technology, thus possessing significant engineering application value.

[0059] Energy flow distribution: Figure 7 This figure illustrates a schematic trend of the circumferential energy distribution of a receiver under the influence of reflected light. The horizontal axis represents the relative circumferential position of the receiver, and the vertical axis represents the relative energy intensity. This figure is used to illustrate the continuous coverage characteristics of reflected light in the circumference of the receiver and does not represent specific numerical values, nor does it constitute a limitation on the form of energy distribution. Figure 7 Statistical results show that the energy flux density distribution curve on the receiver tube wall exhibits unique complementary characteristics—the energy peak contributed by the primary mirror is at the bottom, while the energy peak contributed by the secondary mirror is at the top. The superposition of these two features eliminates the extreme difference between the bottom and top of a traditional PTC receiver, achieving a high degree of uniformity in the circumferential energy flux.

[0060] The simulation results above demonstrate that the present invention effectively solves the problem of local thermal stress while achieving a high geometric concentration ratio.

[0061] Example 2: Based on Example 1, the design method of the high-magnification composite cascade non-imaging focusing system of the present invention includes: Based on the geometric parameters of receiver 1 and the receiving half angle of the system design, the outline of the main reflector 2 is constructed so that the paraxial edge ray Ray1r in the reflected light cone corresponding to any reflection point on the main reflector 2 points to the lower part or bottom area of ​​the light-facing side of receiver 1 after one reflection. Determine whether the far-axis edge ray Ray2r and its neighboring rays in the reflected light cone of the primary reflector 2, under given conditions, are not directly captured by the receiver 1; For areas of light that are not directly captured, a secondary reflector 3 is constructed to recover that portion of the light to the receiver 1.

[0062] The determination of the area where the reflected light is not directly captured is based on whether the far-axis edge light Ray2r of the reflected light cone can be completely intercepted by receiver 1 under a single reflection condition.

[0063] Since the primary mirror is generated based on a Ray1r cut-out, the reflected Ray2r rays do not converge at a single point but instead form a diverging caustic surface. Therefore, the profile of the secondary mirror 3 cannot use a standard conic section but must be constructed based on the inverse worst-case iteration method. Determine the starting point: The point where the Ray2r ray corresponding to the critical point where the light rays on the primary mirror begin to escape intersects with the Y-axis is taken as the vertex of the secondary mirror.

[0064] Establish constraints: For each infinitesimal element on the edge segment of the primary reflector, it is regarded as an instantaneous fixed virtual focus P, and the tangent point on the surface of the receiver is regarded as a moving real focus C.

[0065] Point-by-point generation: Based on the principle of edge rays, solve for the point Q that satisfies |PQ| + |QC| = Const (constant) to generate a quasi-elliptical infinitesimal element.

[0066] Curve fitting: Smoothly connect all the micro-points to form the final profile of the secondary reflector.

[0067] This method ensures that all escaping rays reflected by the primary mirror enter the receiver tangentially after being reflected once by the secondary mirror, theoretically eliminating the optical dead zone.

[0068] Specific operating steps are as follows: Figure 5 As shown: Input the core design parameters; First, it is necessary to clarify the basic design boundaries of the focusing system and input the key parameters of the receiver and the concentrator: Receiver 1 parameters: including the geometric dimensions of receiver 1 (such as pipe diameter and length) and spatial position coordinates (such as axis height and horizontal offset). Concentrator parameters: system design receiving half angle (i.e., the maximum angle range of incident light), and the coordinates of the starting and ending positions of the primary reflector (to determine the initial layout range of the reflector).

[0069] Establish rules for light reflection constraints; Based on the edge ray principle of non-imaging optics, determine the termination state and geometric constraints of the reflected ray: It is clear that after the paraxial edge rays are reflected once by the primary mirror, they must be precisely pointed to the lower or bottom area of ​​the light-facing side of the receiver; Define performance constraints such as the range of incident angles of reflected light on the surface of the receiver and the requirements for light spot coverage; Establish fundamental optical design principles such as constant optical path length and reversible ray tracing. Generate the profile of the primary reflector; Based on the input parameters and constraints, the profile of the primary reflector is constructed through analytical calculation or numerical simulation methods: Continuous reflective surfaces can be generated using parabolas, involutes, quasi-elliptic curves, or combinations thereof; Optimize the reflector curve so that the reflected light from different reflection points partially overlaps and covers the receiver around the perimeter, thus initially improving the uniformity of light reception; Optical performance risk assessment; The optical performance of the primary reflector was verified using ray tracing simulation: Analyze the coverage area and energy distribution uniformity of the reflected light on the surface of the receiver; The key focus is on determining whether there is a risk of light leakage from the far-axis edge rays escaping from above the receiver; If the light leakage rate exceeds the design threshold (e.g., >5%), then a light leakage risk is identified.

[0070] To further illustrate a feasible construction method for the primary mirror profile when satisfying the termination condition of the reflected light cone and the requirements of cascade reflection, an exemplary method for constructing the mirror trajectory equation is given below to illustrate the relationship between geometric variables when constructing the primary mirror profile in this invention. This invention does not limit the specific profile form of the mirror based on this trajectory equation.

[0071] It should be noted that the core of this invention does not lie in a specific analytical form of the mirror equation, but rather in constraining the termination state of the reflected light cone so that the reflected light cone corresponding to any reflection point on the primary mirror can be effectively intercepted by the receiver or secondary mirror after one or more reflections. The trajectory equation described in this embodiment is only used as an example to illustrate one possible implementation of the primary mirror profile under the above-mentioned reflected light cone constraint conditions, and does not constitute a limitation on the specific analytical form of the primary mirror.

[0072] In one exemplary embodiment, an auxiliary constant C may be introduced to characterize the equivalent geometric constraint relationship between the reflection point on the primary mirror and the receiver. This auxiliary constant can be expressed as:

[0073] Where r is the equivalent radius of the receiver, θ a The system is designed to receive half-width characters. s is the parameter angle used to determine the initial state of the primary reflector.

[0074] Based on this, the radial distance function ρ( ):

[0075] Furthermore, the profile of the primary mirror can be described by the following parametric equation:

[0076] in, The angle parameter corresponds to the reflection point.

[0077] It should be noted that the auxiliary constant C in the above formula is related to the initial parameter angle of the primary mirror. There is a direct coupling relationship between s (i.e., C is formed by...). s is uniquely determined), and together they constitute the core geometric control variables of this invention. Wherein, C physically corresponds to the initial optical path component in the optical path design, while s intuitively represents the spatial position of the physical starting point of the primary reflector.

[0078] Unlike traditional designs that fix these parameters, this invention releases them as independent design variables. In the high-magnification cascade system of this embodiment, different starting angles are selected. By adjusting s (and thus the constant C), the convergence point of the primary mirror on the paraxial peripheral ray Ray1r and the overall angle of the mirror can be directly controlled. This adjustment not only determines the structural height and compactness of the system, but more importantly, it defines the escape boundary of the off-axis peripheral ray Ray2r, thereby determining the required aperture size and supplementary lighting range of the upper secondary mirror, achieving precise geometric and optical cascading coordination between the primary and secondary mirrors.

[0079] It should be emphasized that the above trajectory equation is given only as an exemplary construction method. Those skilled in the art should understand that, without departing from the termination condition of the reflected light cone, the constraint of the most unfavorable point, and the concept of cascaded reflection of this invention, the profile of the primary reflector obtained by analytical calculation, numerical calculation, discrete iteration, or reverse ray tracing should be considered to fall within the protection scope of this invention.

[0080] like Figure 8 As shown, Figure 8 This diagram illustrates the defined relationships between geometric variables in the equation for the trajectory of a mirror. O represents the center of the receiver, P represents an exemplary reflection point on the primary mirror, and φ represents the parameter angle used to describe the position of the reflection point or the direction of reflection. Dashed lines in the diagram represent reference directions or lines used for parameter definition, while solid lines represent exemplary reflection directions. This diagram is not drawn to scale according to the specific equations and does not constitute a limitation on the shape of the mirror profile or the termination position of the reflected light ray.

[0081] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-magnification composite cascade non-imaging focusing system, characterized in that, include: The receiver (1) has a surface capable of receiving reflected light; The main reflector (2) is configured to reflect incident light to the receiver (1). The profile of the main reflector (2) is set such that, under a given receiving half angle, the paraxial edge light in the reflected light cone corresponding to any reflection point on the main reflector (2) points to the lower part or bottom area of ​​the light-facing side of the receiver (1) after one reflection. The secondary reflector (3) is configured to intercept and recover the far-axis edge rays and their adjacent rays in the reflected light cone reflected by the primary reflector (2), and reflect them to the upper part of the light-facing side or the back-light-facing area of ​​the receiver (1).

2. The high-magnification composite cascade non-imaging focusing system according to claim 1, characterized in that: The main reflector (2) is positioned below the receiver (1), and the secondary reflector (3) is positioned above the receiver (1), with the reflecting surface of the secondary reflector (3) facing the main reflector (2).

3. The high-magnification composite cascade non-imaging focusing system according to claim 1, characterized in that: The primary reflector (2) is configured such that the reflected light forms a coverage that at least partially overlaps with the receiver (1) in the circumference of the receiver (1), the coverage being formed by the difference in the equivalent optical path from different reflection points of the primary reflector (2) to the receiver (1).

4. The high-magnification composite cascade non-imaging focusing system according to claim 1, characterized in that: The profile of the main reflector (2) is composed of a continuous curve or a continuous surface, and adopts a parabola, an involute, a quasi-elliptic curve or a combination thereof.

5. The high-magnification composite cascade non-imaging focusing system according to claim 1, characterized in that: The secondary reflector (3) has a pointed structure protruding from the center towards the receiver (1) in cross-section, and extends from the pointed point to both sides to form a wing-shaped reflective surface; Its outline is constructed based on the principle of edge rays. For each escape light cone reflected by the edge segment of the main reflector (2), its reflection point is regarded as an instantaneous virtual focus, and the tangent point on the surface of the receiver (1) is regarded as a moving real focus. The principle of constant optical path is used to generate a curve that fits the light cone, and the curves are smoothly connected to form the continuous reflecting surface of the secondary reflector (3).

6. The high-magnification composite cascade non-imaging focusing system according to claim 2, characterized in that: The primary reflector (2) and the secondary reflector (3) form a cascaded reflection structure in space, so that the incident light is guided to the receiver (1) after one or more reflections.

7. The high-magnification composite cascade non-imaging focusing system according to any one of claims 1-6, characterized in that: The receiver (1) is a linear tubular structure, and its axial direction is consistent with the linear focusing direction of the light-concentrating system. The cross-section of the receiver (1) is circular, approximately circular, or other regular geometric shape.

8. A design method for a high-magnification composite cascade non-imaging focusing system as described in any one of claims 1-7, characterized in that, include: Construct the outline of the main reflector (2) based on the principle of light cone matching: According to the geometric parameters of the receiver (1) and the receiving half angle of the system design, configure the geometric surface of the main reflector (2) so that the edge light rays on the side of the light cone corresponding to any reflection point on it that deviate from the optical axis of the system by a smaller angle, i.e., the paraxial edge light Ray1r, point to the lower part or bottom area of ​​the light-facing side of the receiver (1) after one reflection. Identify the light escape area: Determine whether the light rays on the edge of the light cone reflected by the main reflector (2) that deviate from the optical axis of the system by a large angle, namely the far-axis edge light Ray2r and its neighboring light rays, cannot be directly captured by the receiver (1); Construct a secondary reflector (3) for light recovery: For the light area that cannot be directly captured, construct a secondary reflector (3) above the receiver (1) to reflect the light to the receiver (1).

9. The design method of the high-magnification composite cascade non-imaging focusing system according to claim 8, characterized in that: The determination of the area where the reflected light is not directly captured is based on whether the far-axis edge light Ray2r of the reflected light cone can be completely intercepted by the receiver (1) under the condition of a single reflection.

10. The design method of the high-magnification composite cascade non-imaging focusing system according to claim 8, characterized in that: The contour construction process of the primary reflector (2) and the secondary reflector (3) is achieved through one or more of the following methods: analytical calculation, numerical calculation, discrete iteration, or reverse ray tracing.

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