Centrifugal compressor, vaneless diffuser of centrifugal compressor, parameter optimization method and related products

Abstract

The invention discloses a centrifugal compressor, a vaneless diffuser of the centrifugal compressor, a parameter optimization method and related products, relates to the technical field of stability extension control of centrifugal compressors, and improves the stall margin of the vaneless diffuser. According to the vaneless diffuser of the centrifugal compressor, a plurality of vortex generators are evenly installed on the inner wall of the cover side of the vaneless diffuser in the circumferential direction of an annular inlet of the vaneless diffuser; the structural parameters of the vortex generator are determined according to the stall margin requirement and the energy loss control target of the centrifugal compressor; the structural parameters comprise the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the vaneless diffuser, the installation angle of the vortex generator and the geometric parameters of the vortex generator; the vortex generator is a rectangular vortex generator, a plane formed by the length and the width of the vortex generator serves as an installation face of the vortex generator to be attached and fixed to the inner wall of the cover side, and a plane formed by the length and the height of the vortex generator serves as an incident flow face of the vortex generator.

Description

Technical Field

[0001] This application relates to the technical field of centrifugal compressor stability extension control, and particularly relates to a centrifugal compressor, its vaneless diffuser, parameter optimization method and related products. Background Art

[0002] Centrifugal compressors are important components in power engineering, mainly used to efficiently convert mechanical energy into the pressure energy and kinetic energy of gas, so as to provide high-pressure gas for the system or drive fluid flow, and are widely used in the fields of energy, transportation and chemical industry. With the promotion of energy conservation, emission reduction and green and low-carbon development goals, the demand for high-performance centrifugal compressors is becoming increasingly urgent.

[0003] However, the centrifugal force and the rapidly changing flow path shape make the distribution of flow parameters inside the centrifugal compressor very complex. As the performance of the centrifugal compressor improves (mainly reflected in increased efficiency, increased surge margin and increased pressure ratio), the low-energy fluid in the boundary layer of the end wall (i.e., the boundary wall surface that defines the fluid flow region) and the blade surface is extremely prone to secondary flow under the action of the adverse pressure gradient. The secondary flow will drive the low-energy fluid to converge and accumulate in the corner area, resulting in boundary layer separation and the formation of a recirculation zone (i.e., the area where the radial velocity of the fluid is less than 0). The expansion of the recirculation zone will further induce corner separation, and even cause the centrifugal compressor to stall, seriously threatening the operating stability of the centrifugal compressor.

[0004] To improve the stall margin of the centrifugal compressor (a key performance indicator to measure the anti-stall ability of the centrifugal compressor), one of the traditional solutions is to perform asymmetric end wall shaping on the impeller end wall of the centrifugal compressor. The asymmetric end wall shaping optimizes the flow path inside the cascade by adjusting the three-dimensional curved surface shape of the impeller end wall, reduces the transverse pressure difference in the flow channel, thereby weakening the intensity of the secondary flow in the boundary layer of the centrifugal compressor end wall and the blade surface, and narrowing the recirculation zone. The second traditional solution is to install vortex generators in the cascade flow channel. The vortex generators strengthen the momentum exchange between the core flow (i.e., the high-momentum main flow) and the low-energy fluid by generating induced vortices in the cascade flow channel, increase the momentum of the low-energy fluid, thereby resisting the adverse pressure gradient, suppressing boundary layer separation, weakening the intensity of the secondary flow in the boundary layer of the centrifugal compressor end wall and the blade surface, and narrowing the recirculation zone.

[0005] However, the above traditional solutions are ineffective in situations where the secondary flow phenomenon is more complex and stricter control is required (such as centrifugal compressors under high-speed operating conditions, centrifugal compressors under small-flow operating conditions, supercritical CO 2 centrifugal compressors, especially supercritical CO 2 when the centrifugal compressor is under high-speed and small-flow operating conditions). The specific analysis is as follows:

[0006] Centrifugal compressor stall includes impeller stall and diffuser stall. Through research, it is found that diffuser stall occurs more frequently than impeller stall and often precedes impeller stall. Therefore, improving the stall margin of the diffuser is crucial for enhancing the operating stability of the centrifugal compressor.

[0007] To improve the stall margin of the diffuser, the key lies in weakening the intensity of the secondary flow near the diffuser wall surface, thereby reducing the scope of the recirculation zone inside the diffuser. The secondary flow near the diffuser wall surface refers to a lateral or circumferential flow of the fluid in the area near the wall surface inside the diffuser due to the influence of adverse pressure gradient, accumulation of low-energy fluid, and geometric boundaries. This flow is superimposed on the main flow and forms a recirculation zone under specific operating conditions. The existence of the recirculation zone will directly lead to a reduction in the effective flow area of the flow passage, exacerbate flow separation, and induce diffuser stall.

[0008] A vaneless diffuser is a diffuser that consists of two parallel wall surfaces to form an annular channel, without blades inside, and realizes the conversion of gas kinetic energy into pressure energy only through the expansion of the flow passage. The following mainly conducts research and analysis on the vaneless diffuser.

[0009] When the centrifugal compressor is operating at a high rotational speed, a large circumferential component velocity is generated in the airflow inside the vaneless diffuser. This causes severe circumferential deflection of the fluid, and the circumferential driving force received is relatively large, resulting in a significant increase in the accumulation of low-energy fluid near the wall surface of the vaneless diffuser. The small-flow operating condition will reduce the main flow velocity, weaken the inhibitory ability of the fluid on the secondary flow, and also lead to a significant increase in the accumulation of low-energy fluid near the wall surface of the vaneless diffuser. Supercritical CO 2 The size effect of the centrifugal compressor (relatively large tip clearance) will also cause a significant increase in the accumulation of low-energy fluid near the wall surface of the vaneless diffuser. In short, in situations where the secondary flow phenomenon is more complex and stricter control is required, the intensity of the secondary flow near the wall surface of the vaneless diffuser increases significantly, and the scope of the formed recirculation zone increases significantly, making the weakening effect of traditional asymmetric end-wall profiles and vortex generators on the secondary flow near the wall surface of the vaneless diffuser ineffective. Summary of the Invention

[0010] In view of the above problems, this application provides a centrifugal compressor, its vaneless diffuser, a parameter optimization method, and related products to improve the stall margin of the vaneless diffuser. The specific solutions are as follows:

[0011] In the first aspect of this application, a vaneless diffuser of a centrifugal compressor is provided, including: a plurality of vortex generators are evenly installed circumferentially along the annular inlet of the vaneless diffuser on the inner wall of the cover side of the vaneless diffuser;

[0012] The structural parameters of the vortex generator are determined according to the stall margin requirement and energy loss control target of the centrifugal compressor;

[0013] The structural parameters include: the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the vaneless diffuser, the installation angle of the vortex generator, and the geometric parameters of the vortex generator;

[0014] In terms of shape design, the vortex generator is a rectangular vortex generator. A plane formed by its length and width serves as the installation surface of the vortex generator and is fixedly attached to the inner wall of the cover side. A plane formed by its length and height serves as the oncoming flow surface of the vortex generator;

[0015] The distance between the vortex generator and the inlet boundary of the vaneless diffuser satisfies:

[0016] When the starting position of the recirculation zone in the original vaneless diffuser touches or extends beyond the inlet boundary of the original vaneless diffuser, install the vortex generator at the inlet boundary of the original vaneless diffuser; the original vaneless diffuser refers to the vaneless diffuser before installing the vortex generator;

[0017] When the starting position of the recirculation zone in the original vaneless diffuser does not touch the inlet boundary of the original vaneless diffuser, install the vortex generator between the inlet boundary of the original vaneless diffuser and the starting position.

[0018] In a possible implementation, the installation angle of the vortex generator is the angle β between the radial velocity direction of the vaneless diffuser and the length direction of the vortex generator. The value range of β is: (90° - θ) - 10° to (90° - θ) + 10°; θ is the inlet flow angle of the original vaneless diffuser at the near-stall point;

[0019] The geometric parameters of the vortex generator include length l, height h, and width d;

[0020] The value of the length l is determined according to the angle β and the radial length r of the central axis of the vortex generator projected on the meridian plane of the vaneless diffuser; the range of the radial length r is 1 / 16 to 1 / 2 times the radius of the vaneless diffuser;

[0021] The value range of the height h is: starting from the inner wall of the cover side of the vaneless diffuser, 37.5% to 50% of the axial height of the vaneless diffuser;

[0022] The value of the width d is the minimum value that meets the requirements of processing convenience and strength.

[0023] The second aspect of this application provides a centrifugal compressor, including: the vaneless diffuser of the centrifugal compressor according to the first aspect or any implementation manner of the first aspect.

[0024] In a possible implementation, the centrifugal compressor is a supercritical CO 2 centrifugal compressor.

[0025] The third aspect of this application provides a parameter optimization method, including:

[0026] Through computer simulation technology, numerically simulate and analyze the operating characteristics of the vaneless diffuser of a centrifugal compressor under different working conditions to determine the near-stall point of the vaneless diffuser;

[0027] Through computer simulation technology, perform simulation modeling on the vaneless diffuser, including: uniformly installing a plurality of vortex generators along the circumferential direction of the annular inlet of the vaneless diffuser on the inner wall of the cover side of the vaneless diffuser, and setting the structural parameters of the vortex generators; the structural parameters of the vortex generators are determined according to the stall margin requirement and energy loss control target of the centrifugal compressor; the structural parameters include: the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the vaneless diffuser, the installation angle of the vortex generator, and the geometric parameters of the vortex generator; in terms of shape design, the vortex generator is a rectangular vortex generator, and a plane formed by its length and width serves as the installation surface of the vortex generator and fits and fixes on the inner wall of the cover side, and a plane formed by its length and height serves as the upstream-facing surface of the vortex generator; the distance between the vortex generator and the inlet boundary of the vaneless diffuser satisfies: when the starting position of the recirculation zone in the original vaneless diffuser touches or extends beyond the inlet boundary of the original vaneless diffuser, install the vortex generator at the inlet boundary of the original vaneless diffuser; the original vaneless diffuser refers to the vaneless diffuser before installing the vortex generator; when the starting position of the recirculation zone in the original vaneless diffuser does not touch the inlet boundary of the original vaneless diffuser, install the vortex generator between the inlet boundary of the original vaneless diffuser and the starting position;

[0028] Through computer simulation technology, numerically simulate and analyze the operating characteristics of the vaneless diffuser after installing the vortex generators under different working conditions to determine the near-stall point of the vaneless diffuser after installing the vortex generators;

[0029] Input the operating characteristics of the vaneless diffuser before and after installing the vortex generators at the near-stall point into a pre-established performance analysis software model to obtain the model output results, including: the stall margin improvement value and the energy loss increase value of the centrifugal compressor after installing the vortex generators;

[0030] Judge whether both the stall margin improvement value and the energy loss increase value are within a pre-set range. If not, modify the structural parameters of the vortex generator and return to the step of determining the near-stall point of the vaneless diffuser after installing the vortex generators; if so, output the current structural parameters of the vortex generator.

[0031] A fourth aspect of the present application provides a computer program product, including computer-readable instructions, which, when running on an electronic device, enable the electronic device to implement the parameter optimization method described in the third aspect above.

[0032] A fifth aspect of the present application provides a computer storage medium, which carries one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device can implement the parameter optimization method described in the third aspect above.

[0033] By means of the above technical solution, in order to achieve refined flow regulation before the gas enters the vaneless diffuser, the present application arranges vortex generators on the inner wall of the cover side at the inlet of the vaneless diffuser. The vortex generator is a structural component that enhances the fluid momentum exchange through the vortex-induced mixing mechanism, which can weaken the intensity of the secondary flow near the wall of the vaneless diffuser and reduce the range of the recirculation zone. A plurality of vortex generators are evenly arranged circumferentially along the inner wall of the cover side at the inlet to ensure that the gas flow can be affected in the entire circumferential direction. In addition, the vortex generator is installed on the inner wall of the cover side of the vaneless diffuser, which is equivalent to adjusting the three-dimensional flow field of the inner wall of the cover side of the vaneless diffuser. This adjustment provides the possibility to optimize the flow path in the vaneless diffuser. The structural parameters of the vortex generator will affect the flow characteristics in the vaneless diffuser. Through scientific analysis and numerical simulation, the optimal range of these structural parameters can be determined, so as to fully weaken the intensity of the secondary flow near the wall of the vaneless diffuser, reduce the range of the recirculation zone, and improve the stall margin of the vaneless diffuser without significantly increasing the energy loss of the centrifugal compressor, thereby improving the stall margin of the centrifugal compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In combination with the drawings and with reference to the following specific embodiments, the above and other features, advantages and aspects of the various embodiments of the present disclosure will become more obvious. Throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the original components and elements are not necessarily drawn to scale.

[0035] Figure 1 It is a structural diagram of the vaneless diffuser of a centrifugal compressor provided by the present application;

[0036] Figure 2 It is a Figure 1 local enlarged view of point A of the vaneless diffuser shown;

[0037] Figure 3 It is a structural schematic diagram of an acute-angle region within a 360° circumferential range in the axial view of the vaneless diffuser provided by the present application;

[0038] Figure 4 It is a Figure 1Schematic diagram of the installation angle of the vortex generator in the shown vaneless diffuser;

[0039] Figure 5 Schematic diagrams provided by this application when no vortex generator is installed on the vaneless diffuser and after vortex generators with installation lengths of PEW1, PEW2, and PEW3 are installed on the vaneless diffuser; among them, Figure 5 (a) is the schematic diagram when no vortex generator is installed on the vaneless diffuser; Figure 5 (b) is the schematic diagram after a vortex generator with an installation length of PEW1 is installed on the vaneless diffuser; Figure 5 (c) is the schematic diagram after a vortex generator with an installation length of PEW2 is installed on the vaneless diffuser; Figure 5 (d) is the schematic diagram after a vortex generator with an installation length of PEW3 is installed on the vaneless diffuser;

[0040] Figure 6 Schematic diagrams provided by this application when no vortex generator is installed on the vaneless diffuser and after vortex generators with installation lengths of PEW1, PEW2, and PEW3 are installed on the vaneless diffuser, for the total pressure ratio - mass flow rate characteristic diagram of a supercritical CO 2 centrifugal compressor;

[0041] Figure 7 Schematic diagrams of the backflow situation on the cover side of the vaneless diffuser before and after a vortex generator with an installation length of PEW1 is installed, provided by this application; among them, Figure 7 (a) is the schematic diagram of the backflow situation on the cover side of the vaneless diffuser when no vortex generator is installed on the vaneless diffuser; Figure 7 (b) is the schematic diagram of the backflow situation on the cover side of the vaneless diffuser after a vortex generator with an installation length of PEW1 is installed;

[0042] Figure 8 Flowchart of a parameter optimization method provided by this application;

[0043] Figure 9 Schematic structural diagram of a parameter optimization device provided by this application.

[0044] Reference numerals:

[0045] 1 - vaneless diffuser; 2 - annular inlet; 3 - annular outlet; 4 - vortex generator; 5 - hub; 6 - impeller inlet; 7 - turbine casing; 8 - cover side; 9 - flow passage. Detailed implementation manners

[0046] The embodiments of the present application provide a centrifugal compressor, its vaneless diffuser, a parameter optimization method, and related products, aiming to weaken the intensity of the secondary flow near the wall of the vaneless diffuser of the centrifugal compressor, thereby reducing the range of the recirculation zone formed in the vaneless diffuser and increasing the stall margin of the vaneless diffuser. Increasing the stall margin of the vaneless diffuser also increases the stall margin of the centrifugal compressor. Increasing the stall margin of the centrifugal compressor (especially the stall margin under high-speed and small-flow operating conditions) is the core task of the centrifugal compressor stability extension control, and its technological breakthrough is crucial for achieving the efficient, reliable, and wide-range operation of the centrifugal compressor.

[0047] The embodiments of the present application mainly improve the centrifugal compressor stability extension effect by optimizing the structure of the vaneless diffuser of the centrifugal compressor. The following will detail a vaneless diffuser of a centrifugal compressor provided by the embodiments of the present application in conjunction with the accompanying drawings. Those of ordinary skill in the art know that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiments of the present application are equally applicable to similar technical problems.

[0048] The terms "first", "second", etc. in the description and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances, which is only a way of distinguishing objects with the same attributes when describing the embodiments of the present application.

[0049] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, so that a process, method, system, product, or device including a series of units does not have to be limited to those units, but may include other units not clearly listed or inherent to these processes, methods, products, or devices.

[0050] In addition, the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0051] In addition, for ease of understanding, the names of each direction are defined as follows:

[0052] Axial direction: along the axis direction of the cylinder;

[0053] Radial direction: along the radius direction of the cross-section (perpendicular to the axis);

[0054] Circumferential direction: Along the axis direction of the cylinder (perpendicular to the axis and also perpendicular to the section radius).

[0055] See Figure 1 As shown in, a vaneless diffuser of a centrifugal compressor provided by an embodiment of the present application includes the following structural optimization design: On the inner wall of the cover side of the vaneless diffuser 1, a plurality of vortex generators 4 are evenly installed circumferentially along the annular inlet 2 of the vaneless diffuser 1; the structural parameters of the vortex generators 4 are determined according to the stall margin requirements and energy loss control objectives of the centrifugal compressor; the structural parameters of each vortex generator 4 are the same.

[0056] Figure 2 For Figure 1 The partial enlarged view of the position A of the vaneless diffuser shown. Figure 3 It is a schematic structural diagram of an acute angle area within a 360° circumferential range from the axial view of the vaneless diffuser. Next, in combination with Figures 1 to 3 , the working principle of the embodiment of the present application will be described in detail:

[0057] The flow passage of the vaneless diffuser refers to the channel area where the gas flows inside the vaneless diffuser, that is, the space through which the gas passes during the process of flowing from the annular inlet 2 to the annular outlet 3 in the vaneless diffuser. After flowing out of the impeller, the gas directly enters the annular inlet 2 of the vaneless diffuser after passing through a section of gap or without passing through a gap; Figure 1 The reference numerals 5, 6, and 7 in represent the hub, the impeller inlet, and the turbine casing respectively. The vaneless diffuser is a diffuser that consists of two parallel wall surfaces (the cover side and the disk side respectively; from the orientation shown in Figures 1 to 3 , the cover side and the disk side are the upper and lower wall surfaces of the vaneless diffuser respectively) to form an annular flow passage. There are no blades inside the annular flow passage, and the conversion of gas kinetic energy into pressure energy is achieved only through the expansion of the flow passage. The cover side is the side close to the impeller shroud (front cover), which constitutes the outer wall surface of the annular flow passage and is used to limit the outer edge of the air flow; the disk side is the side close to the impeller disk (rear disk), which constitutes the inner wall surface of the annular flow passage and is used to restrict the inner edge of the air flow. Figure 3 The reference numeral 8 in represents the cover side of the vaneless diffuser, Figure 3 The reference numeral 9 in represents the flow passage of the impeller and the vaneless diffuser.

[0058] In order to achieve refined flow control before the gas enters the bladeless diffuser, an embodiment of the present application arranges a vortex generator on the inner wall of the cover side at the inlet of the bladeless diffuser (the inner wall of the cover side, i.e., the side of the cover side that contacts the flow channel of the bladeless diffuser). A vortex generator is a structural component that enhances fluid momentum exchange through a vortex-induced mixing mechanism, which can weaken the secondary flow intensity near the wall of the bladeless diffuser and reduce the range of the recirculation zone. In addition, in view of the circular feature of the inlet of the bladeless diffuser, an embodiment of the present application uses a plurality of vortex generators to be evenly arranged circumferentially along the inner wall of the cover side at the inlet of the bladeless diffuser to ensure that the gas flow can be affected in the entire circumferential direction. Its spatial layout is equivalent to the disturbance effect of multiple micro blades on the airflow, so the vortex generator can be called a "small blade". In addition, the vortex generator is installed on the inner wall of the bladeless diffuser cover, which is equivalent to adjusting the three-dimensional flow field of the inner wall of the bladeless diffuser cover. This adjustment makes it possible to optimize the flow path in the bladeless diffuser and further weaken the secondary flow intensity near the wall of the bladeless diffuser.

[0059] Among them, the fluid momentum exchange is enhanced through the vortex induced mixing mechanism, specifically: when the airflow flows through the vortex generator, an induced vortex will be generated at the leading edge of the vortex generator. The induced vortex can promote the mixing of the core flow and the low-energy fluid near the cover side of the bladeless diffuser, increase the momentum of the fluid near the cover side, and then enhance the ability of the fluid near the wall of the bladeless diffuser to resist the adverse pressure gradient, thereby delaying the occurrence of stall. Moreover, the rotational motion of the induced vortex can form a "squeezing" effect on the recirculation area near the cover side, dividing and compressing the large-scale recirculation area into smaller local recirculation areas, greatly reducing the blockage effect of the recirculation area on the flow area.

[0060] Flow field structure optimization specifically means: the leading edge of the vortex generator forms a specific angle of attack with the incoming flow, inducing local high-pressure and low-pressure areas near the inner wall of the cover side, weakening the lateral pressure difference in the recirculation area near the wall of the bladeless diffuser, and effectively suppressing the lateral migration trend of the low-energy fluid under the adverse pressure gradient, thereby weakening the secondary flow intensity near the wall of the bladeless diffuser.

[0061] The structural parameters of the vortex generator, such as the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the vaneless diffuser, the installation angle of the vortex generator, and the geometric parameters of the vortex generator, will affect the flow characteristics in the vaneless diffuser. The optimal range of the above structural parameters can be determined through scientific theoretical analysis, numerical simulation and other means, so as to fully enhance the momentum exchange and optimize the flow path without significantly reducing the flow capacity of the vaneless diffuser (which directly affects the energy loss of the centrifugal compressor). By fully enhancing the momentum exchange and optimizing the flow path, the secondary flow intensity near the wall of the vaneless diffuser can be fully weakened, the range of the recirculation zone in the vaneless diffuser can be reduced, and the stall margin of the vaneless diffuser can be improved, thereby improving the stall margin of the centrifugal compressor.

[0062] The following provides the optimal range of the above structural parameters and the achieved technical effects through theoretical analysis and numerical simulation:

[0063] I. Shape of the vortex generator

[0064] The shape of the vortex generator can be selected as rectangular (i.e., cuboid), trapezoidal, etc. Among them, compared with vortex generators of other shapes, the rectangular vortex generator is prone to flow separation to efficiently induce strong vortices due to its straight-edge and right-angle design, and its regular shape is convenient for processing and has low cost. The characteristics of high vortex intensity and simple processing make it achieve a balanced adaptation in scenarios such as vane-less diffusers that require efficient flow control and low-cost manufacturing. Based on this, in a possible implementation, still referring to Figures 1 to 3 , the embodiment of the present application adopts a rectangular vortex generator (a plane formed by its length l and width d serves as the installation surface of the vortex generator and is fixedly attached to the inner wall of the cover side, and a plane formed by its length l and height h serves as the oncoming flow surface of the vortex generator, as shown in Figure 3 ), and subsequent theoretical analysis and numerical simulation are carried out based on the rectangular vortex generator.

[0065] II. Spacing between the vortex generator and the inlet boundary of the vane-less diffuser

[0066] The spacing between the vortex generator and the inlet boundary of the vane-less diffuser, that is, the specific position of the vortex generator. The method for determining the specific position of the vortex generator is as follows:

[0067] First, through computer simulation technology, adjust the working conditions of the original vane-less diffuser (the vane-less diffuser before installing the vortex generator), and conduct numerical simulation analysis on the operating characteristics of the original vane-less diffuser under different working conditions, so as to determine the near-stall point of the original vane-less diffuser. The near-stall point refers to the critical point when the vane-less diffuser is operating and is close to but not yet fully stalled, and can also be called the stall critical point.

[0068] Then, according to the operating characteristics of the original vane-less diffuser at the near-stall point, determine the range of the internal recirculation zone in the original vane-less diffuser. The range of the recirculation zone can be determined by the radial velocity nephogram of different axial height sections of the original vane-less diffuser. Specifically: the area where the radial velocity is less than 0 m / s corresponds to the recirculation zone, and the larger the area of this region, the more serious the flow separation. Based on this, scan multiple sections of the original vane-less diffuser along the flow direction (axial direction), extract the radial velocity distribution data, and identify the range of the recirculation zone.

[0069] When the starting position of the recirculation zone in the original vaneless diffuser touches or extends beyond the inlet boundary of the original vaneless diffuser, install the vortex generator at the inlet boundary of the original vaneless diffuser to suppress recirculation as early as possible; when the starting position of the recirculation zone in the original vaneless diffuser does not touch the inlet boundary of the original vaneless diffuser, install the vortex generator between the inlet boundary of the original vaneless diffuser and the starting position, that is, place the vortex generator upstream of the starting position, so as to perturb and regulate the air flow in advance and prevent the development and expansion of the recirculation zone. This setting logic aims to optimize the layout of the vortex generator according to the positional relationship between the recirculation zone and the inlet boundary, and achieve efficient control of flow separation.

[0070] III. Installation Angle of Vortex Generator

[0071] As Figure 4 shown, the installation angle of the vortex generator 4 refers to the angle β between the radial velocity direction v (i.e., the radius direction of the vaneless diffuser) of the axial height section of the vaneless diffuser and the length direction of the vortex generator. The value range of β is: (90° - θ) - 10° to (90° - θ) + 10°, where θ is the inlet flow angle of the original vaneless diffuser at the near-stall point. The larger β is, the greater the inhibitory effect on the recirculation zone.

[0072] IV. Length l of Vortex Generator

[0073] When designing the length l of the vortex generator, it is necessary to balance the flow control effect of the vortex generator, the flow loss generated by itself, and the influence on the low-axial-height flow field, and select the optimal length. The length l of the vortex generator is determined according to the included angle β and the radial length r of the central axis of the vortex generator projected on the meridional plane of the vaneless diffuser. The range of the radial length r is 1 / 16 to 1 / 2 of the radius of the vaneless diffuser.

[0074] The meridional plane is a plane passing through the axis of the rotating machinery (such as the impeller and diffuser), and is orthogonal to the plane perpendicular to the rotating shaft (i.e., the radial plane). The central axis of the vortex generator refers to the central symmetry line of its geometric structure. When the included angle β changes, the radial length r of the central axis of the vortex generator projected on the meridional plane changes. Therefore, the length l of the vortex generator can be determined according to the included angle β and the radial length r.

[0075] V. Height h of Vortex Generator

[0076] The height h of the vortex generator should be slightly higher than the axial height of the recirculation zone of the original vaneless diffuser at the near-stall point. Through numerical simulation technology, the axial height of the recirculation zone of the original vaneless diffuser at the near-stall point is within 20% of the axial height of the vaneless diffuser starting from the inner wall of the cover side of the vaneless diffuser. Accordingly, the height h range of the vortex generator is set as: 37.5% to 50% of the axial height of the vaneless diffuser starting from the inner wall of the cover side of the vaneless diffuser.

[0077] VI. Width d of the Vortex Generator

[0078] To ensure that the vortex generator does not significantly affect the efficiency of the diffuser, the width d of the vortex generator should be as small as possible on the basis of being easy to process and meet the strength requirements. If the width d is too large, the additional energy loss generated by the vortex generator will increase.

[0079] The above parameters are the optimal ranges of the vortex generator of the vaneless diffuser for centrifugal compressors obtained through a large amount of data simulation. For a specific centrifugal compressor, optimization can be carried out within this optimal range to quickly determine the optimal parameters.

[0080] The centrifugal compressor applied in the embodiment of the present application is, for example, a supercritical CO 2 centrifugal compressor. The supercritical CO 2 centrifugal compressor is a centrifugal compressor with more complex secondary flow phenomena and requires more strict control. When the temperature and pressure of CO 2 exceed its critical point (critical temperature 304.13K, i.e., 31.0°C; critical pressure 7.38MPa), it enters the supercritical state. A centrifugal compressor with carbon dioxide in the supercritical state as the working medium is a supercritical CO 2 centrifugal compressor.

[0081] In the case where the design parameters of the supercritical CO 2 centrifugal compressor are given, and the specific position, installation angle, height h, and width d of the vortex generator are also given, when the length l of the vortex generator is different, the performance of the supercritical CO 2 centrifugal compressor before and after adding the vortex generator is different. For example, for a supercritical CO 2 centrifugal compressor with the parameters shown in Table 1, the specific position of the vortex generator is set at the inlet boundary of the vaneless diffuser; the included angle β of the vortex generator is 85°; the height h of the vortex generator is 37.5% of the axial height of the vaneless diffuser starting from the inner wall of the cover side of the vaneless diffuser; the width d of the vortex generator is 0.4mm. Then, through numerical simulation technology, when the lengths l are PEW1, PEW2, and PEW3 (PEW1, PEW2, and PEW3 respectively represent the vortex generators when the radial length r is 1 / 8, 3 / 16, and 7 / 16 times the radius of the vaneless diffuser) and when no vortex generator is installed on the vaneless diffuser, the operating characteristics of the supercritical CO 2 centrifugal compressor can be obtained.

[0082] Table 1 - Parameters of the Supercritical CO 2 Centrifugal Compressor

[0083]

[0084] Figure 5 Schematic diagrams of the vaneless diffuser without the installation of a vortex generator (referred to as the "original state") and after the installation of vortex generators with lengths l of PEW1, PEW2, and PEW3 respectively on the vaneless diffuser. Figure 6 For the vaneless diffuser without the installation of a vortex generator and after the installation of vortex generators with lengths l of PEW1, PEW2, and PEW3 respectively on the vaneless diffuser, supercritical CO 2 Total pressure ratio - mass flow rate characteristic diagram of a centrifugal compressor. According to this Figure 6 The stall margin ΔSM of the supercritical CO 2 centrifugal compressor before and after adding a vortex generator can be determined, as shown in Table 2.

[0085] Table 2 - Stall margins obtained with different lengths l

[0086]

[0087] As can be seen from Table 2, after adding a vortex generator with a length l of PEW1, the stall margin of the supercritical CO 2 centrifugal compressor is increased by 7.76%, achieving the best effect of stabilizing the flow.

[0088] Figure 7 For the flow condition (two - dimensional streamline) of the vaneless diffuser cover side before and after installing a vortex generator with a length l of PEW1. From Figure 7 it can be seen that compared with the original state, after adding a vortex generator, the vortex generator truncates the flow on the cover side, changing a large recirculation area into one or two small recirculation areas. From the perspective of the streamline, its mechanism of action is that the streamlines below 70% of the axial height move towards the cover side of the vaneless diffuser, thereby increasing the momentum near the cover side and driving the movement of the low - energy fluid on the cover side.

[0089] In addition, as Figure 8 shown, the embodiment of the present application provides a parameter optimization method, including:

[0090] Step S01: Through computer simulation technology, numerically simulate and analyze the operating characteristics of the vaneless diffuser of the centrifugal compressor under different working conditions to determine the near - stall point of the vaneless diffuser;

[0091] Step S02: Through computer simulation technology, perform simulation modeling on the vaneless diffuser, including: uniformly installing a plurality of vortex generators along the circumferential direction of the annular inlet of the vaneless diffuser on the inner wall of the cover side of the vaneless diffuser, and setting the structural parameters of the vortex generators;

[0092] Step S03: Through computer simulation technology, numerically simulate and analyze the operating characteristics of the vaneless diffuser with the installed vortex generator under different operating conditions, and determine the near-stall point of the vaneless diffuser with the installed vortex generator;

[0093] Step S04: Input the operating characteristics of the vaneless diffuser before and after installing the vortex generator at the near-stall point into a pre-established performance analysis software model, and obtain the model output results, including: the increase in stall margin and the increase in energy loss of the centrifugal compressor after installing the vortex generator;

[0094] Step S05: Determine whether both the increase in stall margin and the increase in energy loss are within a pre-set range. If not, go to Step S06; if so, go to Step S07;

[0095] Step S06: Modify the structural parameters of the vortex generator and return to Step S03;

[0096] Step S07: Output the current structural parameters of the vortex generator.

[0097] Figure 8 The method shown optimizes the structural parameters of the vortex generator based on computer simulation technology. Specifically:

[0098] At the technical level, by using computer simulation technology to simulate the operating characteristics of the vaneless diffuser, the near-stall point can be accurately determined, and the structural parameters of the vortex generator can be flexibly adjusted to efficiently carry out numerical simulation analysis. Through the performance analysis software model, key data such as the increase in stall margin and the increase in energy loss can be quickly obtained.

[0099] In terms of design optimization, if the indicators do not meet the preset range, the structural parameters of the vortex generator can be modified and re-analyzed, and continuously iteratively optimized until the best parameters (i.e., the structural parameter values corresponding to when both the increase in stall margin and the increase in energy loss are within the pre-set range) are obtained, shortening the R & D cycle and reducing the design cost. Overall, this process provides a scientific and efficient method for the design and optimization of the vaneless diffuser of the centrifugal compressor.

[0100] In addition, the embodiment of the present application also provides a centrifugal compressor, including: the vaneless diffuser of any centrifugal compressor provided in the above embodiment.

[0101] In a possible implementation, the centrifugal compressor provided in the embodiment of the present application is a supercritical CO 2 centrifugal compressor.

[0102] As Figure 9 shown, the embodiment of the present application also provides a parameter optimization device, including:

[0103] The near stall point determination unit 100 before shaping is used to numerically simulate and analyze the operating characteristics of the vaneless diffuser of a centrifugal compressor under different operating conditions through computer simulation technology, and determine the near stall point of the vaneless diffuser;

[0104] The simulation modeling unit 200 is used to perform simulation modeling on the vaneless diffuser through computer simulation technology, including: uniformly installing a plurality of vortex generators along the circumferential direction of the annular inlet of the vaneless diffuser on the inner wall of the cover side of the vaneless diffuser; and setting the structural parameters of the vortex generators; the structural parameters of the vortex generators are determined according to the stall margin requirement and energy loss control target of the centrifugal compressor; the structural parameters include: the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the vaneless diffuser, the installation angle of the vortex generator, and the geometric parameters of the vortex generator; in terms of shape design, the vortex generator is a rectangular vortex generator, and a plane formed by its length and width is used as the installation surface of the vortex generator to be fixedly attached to the inner wall of the cover side, and a plane formed by its length and height is used as the upstream-facing surface of the vortex generator; the distance between the vortex generator and the inlet boundary of the vaneless diffuser satisfies: when the starting position of the recirculation zone in the original vaneless diffuser touches or extends beyond the inlet boundary of the original vaneless diffuser, install the vortex generator at the inlet boundary of the original vaneless diffuser; the original vaneless diffuser refers to the vaneless diffuser before installing the vortex generator; when the starting position of the recirculation zone in the original vaneless diffuser does not touch the inlet boundary of the original vaneless diffuser, install the vortex generator between the inlet boundary of the original vaneless diffuser and the starting position;

[0105] The near stall point determination unit 300 after shaping is used to numerically simulate and analyze the operating characteristics of the vaneless diffuser after installing the vortex generator under different operating conditions through computer simulation technology, and determine the near stall point of the vaneless diffuser after installing the vortex generator;

[0106] The performance analysis and processing unit 400 is used to input the operating characteristics of the vaneless diffuser before and after installing the vortex generator at the near stall point into a pre-established performance analysis software model to obtain the model output results, including: the stall margin improvement value and the energy loss increase value of the centrifugal compressor after installing the vortex generator; determine whether both the stall margin improvement value and the energy loss increase value are within a pre-set range, if not, modify the structural parameters of the vortex generator, and trigger the near stall point determination unit 300 after shaping again; if so, output the current structural parameters of the vortex generator.

[0107] In an embodiment of the present application, a computer program product is further provided, including computer-readable instructions, which when running on an electronic device, enable the electronic device to implement any parameter optimization method provided in the embodiments of the present application.

[0108] In an embodiment of the present application, a computer-readable storage medium is further provided. The storage medium carries one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device can implement any parameter optimization method provided by the embodiment of the present application.

[0109] In addition, an embodiment of the present application further provides an electronic device, including: at least one processor and a memory connected to the processor, where:

[0110] The memory is used to store computer programs;

[0111] The processor is used to execute the computer programs so that the electronic device can implement any parameter optimization method provided by the embodiment of the present application.

[0112] It should be further noted that the device embodiments described above are only illustrative. The units described as separate components may or may not be physically separated. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the attached drawings of the device embodiments provided by the present application, the connection relationship between modules indicates that they have a communication connection, which can be specifically implemented as one or more communication buses or signal lines.

[0113] Through the description of the above embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software plus necessary general hardware, and of course, it can also be implemented by dedicated hardware including application-specific integrated circuits, dedicated CPUs, dedicated memories, dedicated components, etc. Generally, functions completed by computer programs can be easily implemented by corresponding hardware, and the specific hardware structures for implementing the same function can also be various, such as analog circuits, digital circuits or dedicated circuits. However, for the present application, in more cases, software program implementation is a better implementation method. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. The computer software product is stored in a readable storage medium, such as a floppy disk, USB flash drive, mobile hard disk, ROM, RAM, magnetic disk or optical disc of a computer, etc., and includes several instructions to enable a computer device (which can be a personal computer, training device, or network device, etc.) to execute the methods described in various embodiments of the present application.

[0114] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product.

[0115] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from a website, a computer, a training device, or a data center to another website, a computer, a training device, or a data center by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wirelessly (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can store or a data storage device such as a training device or a data center that includes one or more integrated available media. The available medium can be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid state disk (SSD)).

[0116] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the embodiments of the present application. Therefore, the embodiments of the present application will not be limited to the embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bladeless diffuser for a centrifugal compressor, characterized in that: On the inner wall of the cover side of the vaneless diffuser, a plurality of vortex generators are evenly installed along the circumference of the annular inlet of the vaneless diffuser; The structural parameters of the vortex generator are determined according to the stall margin requirement and energy loss control target of the centrifugal compressor; The structural parameters include: the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the vaneless diffuser, the installation angle of the vortex generator, and the geometric parameters of the vortex generator; In terms of shape design, the vortex generator is a rectangular vortex generator, a plane formed by its length and width is fixed on the inner wall of the cover as the mounting surface of the vortex generator, and a plane formed by its length and height is used as the frontal surface of the vortex generator; The distance between the vortex generator and the inlet boundary of the vaneless diffuser satisfies: When the starting position of the reflow zone in the original bladeless diffuser touches or protrudes beyond the inlet boundary of the original bladeless diffuser, the vortex generator is installed at the inlet boundary of the original bladeless diffuser; the original bladeless diffuser refers to the bladeless diffuser before the vortex generator is installed; When the starting position of the reflow zone in the original bladeless diffuser does not touch the inlet boundary of the original bladeless diffuser, the vortex generator is installed between the inlet boundary of the original bladeless diffuser and the starting position.

2. The bladeless diffuser for a centrifugal compressor according to claim 1, characterized in that: The installation angle of the vortex generator is the angle β between the radial velocity direction of the bladeless diffuser and the length direction of the vortex generator, and the value range of β is: (90°-θ)-10°~(90°-θ)+10°; θ is the inlet flow angle of the original bladeless diffuser near the stall point; The geometric parameters of the vortex generator include length l, height h and width d; The length l is determined according to the angle β and the radial length r of the central axis of the vortex generator on the meridian plane projection of the bladeless diffuser; the radial length r ranges from 1 / 16 to 1 / 2 times the radius of the bladeless diffuser; The height h is in the range of: 37.5% to 50% of the axial height of the vaneless diffuser from the inner wall of the vaneless diffuser cover; The width d is taken as the minimum value that meets the processing convenience and strength requirements.

3. A centrifugal compressor, characterized in that: include: A bladeless diffuser for a centrifugal compressor as claimed in any one of claims 1 to 2.

4. The centrifugal compressor according to claim 3, characterized in that: The centrifugal compressor is a supercritical CO2 centrifugal compressor.

5. A parameter optimization method, characterized in that: include: Through computer simulation technology, the operation characteristics of the centrifugal compressor bladeless diffuser under different working conditions are numerically simulated and analyzed to determine the near-stall point of the bladeless diffuser. The bladeless diffuser is simulated and modeled by computer simulation technology, including: on the inner wall of the cover side of the bladeless diffuser, a plurality of vortex generators are evenly installed along the circumference of the annular inlet of the bladeless diffuser, and the structural parameters of the vortex generator are set; the structural parameters of the vortex generator are determined according to the stall margin requirement and energy loss control target of the centrifugal compressor; the structural parameters include: the shape of the vortex generator, the distance between the vortex generator and the inlet boundary of the bladeless diffuser, the installation angle of the vortex generator and the geometric parameters of the vortex generator; in terms of shape design, the vortex generator is a rectangular vortex generator, and a plane formed by its length and width The surface is fixedly attached to the inner wall of the cover side as the installation surface of the vortex generator, and a plane formed by its length and height serves as the frontal surface of the vortex generator; the distance between the vortex generator and the inlet boundary of the bladeless diffuser satisfies: when the starting position of the reflow zone in the original bladeless diffuser touches or protrudes out of the inlet boundary of the original bladeless diffuser, the vortex generator is installed to the inlet boundary of the original bladeless diffuser; the original bladeless diffuser refers to the bladeless diffuser before the vortex generator is installed; when the starting position of the reflow zone in the original bladeless diffuser does not touch the inlet boundary of the original bladeless diffuser, the vortex generator is installed between the inlet boundary of the original bladeless diffuser and the starting position; Through computer simulation technology, the operating characteristics of the bladeless diffuser with vortex generators installed under different working conditions are numerically simulated and analyzed to determine the near-stall point of the bladeless diffuser with vortex generators installed. The operating characteristics of the vaneless diffuser before and after the installation of the vortex generator at the near-stall point are input into a pre-established performance analysis software model to obtain the model output results, including: the stall margin improvement value and energy loss increase value of the centrifugal compressor after the installation of the vortex generator; Determine whether the stall margin improvement value and the energy loss increase value are both within a preset range; if not, modify the structural parameters of the vortex generator, and return to the step of determining the near-stall point of the bladeless diffuser after the vortex generator is installed; if so, output the current structural parameters of the vortex generator.

6. A computer program product, characterized in that It comprises computer-readable instructions, and when the computer-readable instructions are executed on an electronic device, the electronic device implements the parameter optimization method as claimed in claim 5.

7. A computer-readable storage medium, characterized in that: The storage medium carries one or more computer programs, and when the one or more computer programs are executed by an electronic device, the electronic device can implement the parameter optimization method as claimed in claim 5.

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