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CN-121993904-A - Imaging-non-imaging coupling concentrating collector with photon capturing cavity and design method

CN121993904ACN 121993904 ACN121993904 ACN 121993904ACN-121993904-A

Abstract

The invention discloses an imaging-non-imaging coupling concentrating collector with a photon capturing cavity and a design method, and belongs to the technical field of solar photo-thermal utilization. The heat collector comprises a linear heat absorber, a primary mirror below the linear heat absorber and an inverted secondary mirror above the linear heat absorber. The central reflection area of the primary reflector is configured to directly collect the near-axis light to the light-receiving surface of the linear absorber, and the edge reflection area is configured to guide the far-axis light to the secondary reflector. The wing plates at two sides of the secondary reflector extend downwards to form a semi-closed photon capturing cavity together with the linear heat absorber, and the semi-closed photon capturing cavity is used for intercepting marginal light and reflecting the marginal light to the backlight surface of the linear heat absorber for the second time. The invention realizes the uniform distribution of the energy flow in the circumferential direction of the linear heat absorber while improving the geometric light concentration ratio of the system through the synergistic optical path of 'bottom direct irradiation and top secondary reflection', eliminates the risks of heat bending and local heat transfer deterioration of the pipe wall from the source, and is suitable for high-flux and high-temperature working conditions such as supercritical carbon dioxide circulation.

Inventors

  • XU RUIHUA

Assignees

  • 济宁学院

Dates

Publication Date
20260508
Application Date
20260109

Claims (9)

  1. 1. An imaging-non-imaging coupled concentrator collector comprising a photon capturing cavity, comprising: a linear heat absorber (1) extending along a focal line; a primary mirror (2) arranged below the linear heat absorber (1), and A secondary mirror (3) disposed above the linear absorber (1) with its reflection surface facing downward; an open light transmission space is formed between the primary reflecting mirror (2) and the secondary reflecting mirror (3); the reflecting surface of the primary mirror (2) is divided in cross section into: A central reflection area (21) configured to directly reflect and concentrate the received paraxial incident light rays to the lower half surface of the linear heat absorber (1); edge reflection areas (22) located on both sides of the central reflection area (21) and configured to reflect the received far-axis incident light to the linear absorber (1) and secondary mirror (3); -the secondary mirror (3) is configured to intercept the light rays coming from the edge reflection zone (22) and reflect them to the upper half surface of the linear heat absorber (1); The two side edges of the secondary reflector (3) extend downwards to form wing plates, and the tail ends of the wing plates are not lower than the highest point of the linear heat absorber (1), so that the secondary reflector (3) and the upper surface of the linear heat absorber (1) jointly define a semi-closed photon capturing cavity (5).
  2. 2. The photon capturing cavity-containing imaging-non-imaging coupled concentrator collector of claim 1, wherein: the cross section outline of the central reflecting area (21) is parabolic, quasi-parabolic, circular arc or multi-section straight line fitting curve; The cross section outline of the edge reflection area (22) is a compound parabolic CPC type, a high-order polynomial curved surface type or a free curved surface type curve; the central reflection area (21) and the edge reflection area (22) are spatially connected in a continuous manner by C0 or C1 or have a gap therebetween.
  3. 3. The photon capturing cavity-containing imaging-non-imaging coupled concentrator collector of claim 1, wherein: The reflecting surface profile of the secondary reflecting mirror (3) is formed by connecting a plurality of sections of continuous curves; Any point Q i on the curve satisfies an optical path coupling condition that reflected light from a corresponding point P i on the edge reflection area (22) is tangential to the surface of the linear heat absorber (1) after being reflected by a point Q i .
  4. 4. The photon capturing cavity-containing imaging-non-imaging coupled concentrator collector of claim 1, wherein: the secondary reflecting mirror (3) is of a hollow structure or a thin shell structure, and a heat dissipation structure (32) is arranged on the backlight surface of the secondary reflecting mirror; The heat dissipation structure (32) includes heat dissipation fins arranged along an extending direction of the secondary mirror.
  5. 5. The photon capturing cavity-containing imaging-non-imaging coupled concentrator collector of claim 1, wherein: the linear heat absorber (1) comprises an inner heat absorbing pipe (11) and an outer light-transmitting vacuum cover (12); The projection opening width A ap of the primary mirror (2) has a geometric matching relationship with the radius r of the absorber tube (11) such that: At a given system receiving half angle theta a , the light cone reflected by the outermost end point of the edge reflection area (22) forms a light spot boundary after being reflected by the secondary reflector (3), and the light spot boundary falls in the section range of the heat absorption tube (11) or is tangential to the heat absorption tube (11).
  6. 6. The photon capturing cavity-containing imaging-non-imaging coupled concentrator collector of claim 1, wherein: The light reflected by the edge reflection area (22) forms a focal spot at the secondary reflector (3), and the lateral width of the secondary reflector (3) is larger than or equal to the theoretical width of the focal spot so as to cut off escaping light.
  7. 7. The photon capturing cavity-containing imaging-non-imaging coupled concentrator collector of claim 1, wherein: The photon capturing cavity (5) is configured to receive light rays from the edge reflection area (22), which are directed to a backlight area of the linear heat absorber (1) by at least one of: (a) Directly projected to the surface of the linear heat absorber (1); (b) Reflected once by the secondary reflector (3) and then projected to the surface of the linear heat absorber (1); (c) And the secondary reflector (3) and the linear heat absorber (1) are reflected for multiple times and then projected to the surface of the linear heat absorber (1).
  8. 8. A method of designing an imaging-non-imaging coupled concentrating collector comprising a photon capturing cavity as claimed in any one of claims 1 to 7, comprising the steps of: S1, defining design parameters, introducing a light source segmentation factor K, and mathematically decoupling a reflected light cone at the end point of the edge reflection region (22) into a direct component delta S 1 which is directly projected to the linear heat absorber (1) and a recapture component delta S 2 which is projected to the secondary reflector (3); s2, based on the principle of edge light, constructing the outline of the edge reflection area (22) by using the recapture component delta S 2 as a boundary condition; S3, determining the minimum theoretical radius and the center position of the linear heat absorber (1) according to the edge ray track of the edge reflection area (22) so as to meet a ray interception threshold; S4, constructing the outline of the central reflecting area (21) by taking the position of the linear heat absorber (1) as a focus; And S5, constructing the outline of the secondary reflector (3) by adopting a reverse iteration method, wherein for points on the outline, an equation is established according to an optical path conservation principle, so that the equation can simultaneously meet the requirements of receiving light rays from an edge reflection area (22) and reflecting and tangential to the surface of the linear heat absorber (1).
  9. 9. The method of designing an image-non-image coupled concentrating collector comprising a photon capturing cavity according to claim 8, wherein in step S5: And calculating a series of discrete points point by solving an optical path identity equation comprising an angle step length v and a linear absorber radius r, and splicing to form a quasi-elliptic curve profile of the secondary reflector (3).

Description

Imaging-non-imaging coupling concentrating collector with photon capturing cavity and design method Technical Field The invention relates to an imaging-non-imaging coupling concentrating collector with a photon capturing cavity and a design method thereof, belonging to the technical field of solar photo-thermal utilization. Background Currently, solar thermal power generation (CSP) technology is evolving towards high parameters (operating temperature >550 ℃) and Gao Guangre conversion efficiencies to adapt to new power cycles of supercritical carbon dioxide (scco 2) and the like. However, the most widely used trough parabolic collectors (PTC) in the field of medium and high temperature heat utilization face severe thermodynamic and mechanical challenges. Pain point I, high temperature heat loss bottleneck caused by low concentration ratio Traditional PTC is limited by imaging optics and solar aperture angle, with geometrical concentration ratios that stagnate 30-40 times over time. Because of the low light concentration ratio, the absorber tube must be kept at a large caliber (typically 70mm-90mm in diameter) to ensure the light interception rate, resulting in a large heat dissipation area. According to the theory of radiative heat transfer, the radiative heat loss is proportional to the fourth power of temperature. Therefore, when the operation temperature exceeds 450 ℃, the radiant heat loss of the conventional PTC increases exponentially, resulting in a drastic decrease in the photo-thermal conversion efficiency, and it is difficult to economically generate high temperature heat energy of 550 ℃ or more. Pain point two, thermal stress failure caused by unidirectional condensation Conventional PTC concentrates light only unidirectionally through the bottom, resulting in the lower semicircular surface of the absorber tube being subjected to extremely high fluence (peaks often exceeding 20 times the average), while the upper semicircular surface receives only weak direct light. The extreme energy flow difference generates a huge circumferential temperature gradient on the wall surface of the heat absorption pipe, and causes two serious consequences, namely, axial thermal bending deformation (i.e., banana effect) of the metal pipe, and severe shearing thermal stress at the glass-metal sealing position due to the huge temperature difference, so that glass sealing failure and pipe explosion (pipe explosion) are extremely easy to cause, and the safety of a power station is seriously influenced. Existing improvements and their drawbacks Attempts have been made in the prior art to solve the above problems, but all have significant drawbacks: (1) The prior secondary reflector is generally approximated by circular arc or standard geometric curve (such as CN201497202U and CN 101660845A), and cannot perfectly match with complex aberration generated by the edge of the primary reflector, so that the divergence of light spots is serious, and theoretical full reception is difficult to realize. The main purpose of the scheme is to approximate a high-precision optical surface by using a plane, an arc and other low-precision curved surfaces, and the processing cost is reduced, but the light spots are seriously scattered, and the geometric condensation ratio is difficult to break through by 30 times. In addition, the design light path is complex, part of light rays need to be reflected for 3 times or more, the optical efficiency loss is huge, and the requirements of high-temperature power generation on high energy flow density and low reflection loss cannot be met. (2) Solid media type scheme another prior art (e.g., U.S. patent application publication No. US 2011/0100419 A1) utilizes eccentric parabolic and solid transparent optical structures to achieve uniform irradiation of the photovoltaic cell surface. Defect analysis this solution relies on huge solid glass or plastic prisms for light transmission. In the photovoltaic field (small size) it is possible, but in large-scale photo-thermal power stations (collectors up to several hundred meters long), the weight of the solid medium is remarkable and the cost is extremely high, and the volumetric absorption loss of sunlight in the massive solid medium is remarkable. More importantly, the design mainly pursues low-power dodging (about 20 times), and does not have ultrahigh-power light gathering (> 70 times) and high-temperature tolerance required for high-temperature photo-thermal power generation. In summary, the prior art either compromises the condensing performance and leads to high optical losses, or fails to make large-scale and high-temperature applications due to the adoption of solid optical structures, while presenting significant weight and cost issues. At present, a novel heat collector based on a hollow reflector structure and capable of simultaneously realizing ultra-high light concentration ratio (low heat loss) and circumferentially uniform heating (low stress