Centrifugal compressor and its bladeless diffuser, parameter optimization method and related products

Abstract

The present application discloses a centrifugal compressor and its bladeless diffuser, a parameter optimization method and related products, which relate to the field of centrifugal compressor expansion stabilization control technology and improve the stall margin of the bladeless diffuser. The bladeless diffuser of the centrifugal compressor includes: 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; 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; the vortex generator is a rectangular vortex generator, and a plane formed by its length and width is fixed on the inner wall of the cover side as the installation surface of the vortex generator, and a plane formed by its length and height is used as the flow-facing surface of the vortex generator.

Description

Technical Field

[0001] The present application relates to the field of centrifugal compressor stabilization control technology, and in particular to a centrifugal compressor and its bladeless diffuser, a parameter optimization method, and related products. Background Art

[0002] Centrifugal compressors are crucial components in power engineering, primarily used to efficiently convert mechanical energy into the pressure and kinetic energy of gases, thereby providing high-pressure gas or driving fluid flow. They are widely used in the energy, transportation, and chemical industries. With the advancement of energy conservation, emission reduction, and green, low-carbon development goals, the demand for high-performance centrifugal compressors is becoming increasingly urgent.

[0003] However, centrifugal force and rapidly changing flow path shapes make the flow parameter distribution inside the centrifugal compressor very complex. With the improvement of centrifugal compressor performance (mainly reflected in improved efficiency, increased surge margin and increased pressure ratio), its end wall (i.e., the boundary wall that limits the fluid flow area) and the low-energy fluid in the boundary layer on the blade surface are very likely to undergo secondary flow under the action of 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 a centrifugal compressor (a key performance indicator for measuring a centrifugal compressor's stall resistance), one traditional approach is to give the centrifugal compressor's impeller endwall an asymmetric shaping effect. Asymmetric shaping optimizes the flow path within the cascade by adjusting the three-dimensional curved surface of the impeller endwall, reducing the lateral pressure differential within the flow channel, thereby weakening the intensity of the secondary flow in the boundary layer between the centrifugal compressor endwall and the blade surface, and reducing the scope of the recirculation zone. A second traditional approach is to install vortex generators within the cascade flow channel. Vortex generators generate induced vortices in the cascade flow channel to enhance the momentum exchange between the core flow (i.e., the high-momentum mainstream flow) and the low-energy fluid, increasing the momentum of the low-energy fluid, thereby resisting adverse pressure gradients, suppressing boundary layer separation, weakening the intensity of the secondary flow in the boundary layer between the centrifugal compressor endwall and the blade surface, and reducing the scope of the recirculation zone.

[0005] However, the above traditional solutions are not effective in situations where secondary flow phenomena are more complex and require stricter control (such as centrifugal compressors operating at high speeds, centrifugal compressors operating at low flow rates, and supercritical CO2 centrifugal compressors, especially supercritical CO2 centrifugal compressors operating at high speeds and low flow rates). The specific analysis is as follows:

[0006] Centrifugal compressor stall includes impeller stall and diffuser stall. Research has found that diffuser stall is more frequent than impeller stall and often occurs before impeller stall. Therefore, improving the diffuser's stall margin is crucial for improving centrifugal compressor operational stability.

[0007] The key to improving the stall margin of a diffuser lies in weakening the intensity of the secondary flow near the diffuser wall, thereby reducing the scope of the recirculation zone within the diffuser. Secondary flow near the diffuser wall refers to a lateral or circumferential flow of fluid near the diffuser wall caused by adverse pressure gradients, low-energy fluid aggregation, and geometric boundary effects. This flow is superimposed on the main flow and forms a recirculation zone under certain operating conditions. The presence of the recirculation zone directly reduces the effective flow area of ​​the flow channel, exacerbating flow separation and inducing diffuser stall.

[0008] A vaneless diffuser is a type of diffuser that consists of two parallel walls forming an annular channel. It lacks internal blades and converts kinetic energy of the gas into pressure energy solely through channel expansion. This article focuses on the study and analysis of vaneless diffusers.

[0009] When a centrifugal compressor operates at high speed, the airflow within the vaneless diffuser generates a significant circumferential component velocity. This causes severe circumferential deflection of the fluid and a large circumferential driving force, leading to a significant increase in the accumulation of low-energy fluid near the wall of the vaneless diffuser. Low-flow operating conditions reduce the primary velocity, weakening the fluid's ability to suppress secondary flows, and also significantly increasing the accumulation of low-energy fluid near the wall of the vaneless diffuser. The size effect of a supercritical CO2 centrifugal compressor (large relative clearance at the blade tips) also significantly increases the accumulation of low-energy fluid near the wall of the vaneless diffuser. In short, in applications where secondary flow phenomena are more complex and require stricter control, the intensity of the secondary flow near the wall of the vaneless diffuser increases significantly, and the area of ​​the recirculation zone formed increases significantly, making it possible for traditional asymmetric endwall shaping and vortex generators to maintain their effectiveness in reducing secondary flow near the wall of the vaneless diffuser. Summary of the Invention

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

[0011] A first aspect of the present application provides a vaneless diffuser for a centrifugal compressor, comprising: a plurality of vortex generators uniformly mounted on an inner wall of a cover side of the vaneless diffuser along the circumference of an annular inlet 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, and a plane formed by its length and width serves as the mounting surface of the vortex generator and is fixed to the inner wall of the cover side, and a plane formed by its length and height serves as the flow-facing 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 protrudes beyond the inlet boundary of the original vaneless diffuser, the vortex generator is installed at the inlet boundary of the original vaneless diffuser; the original vaneless diffuser refers to the vaneless diffuser before the vortex generator is installed;

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

[0018] In one 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, and the value range of β is: (90°-θ)-10° to (90°-θ)+10°; θ is the inlet flow angle of the original vaneless diffuser near the stall point;

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

[0020] The length l is determined based on 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 radial length r ranges from 1 / 16 to 1 / 2 times the radius of the vaneless diffuser;

[0021] 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;

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

[0023] A second aspect of the present application provides a centrifugal compressor, comprising: a bladeless diffuser of the centrifugal compressor according to the first aspect or any implementation of the first aspect.

[0024] In a possible implementation, the centrifugal compressor is a supercritical CO2 centrifugal compressor.

[0025] A third aspect of the present application provides a parameter optimization method, comprising:

[0026] By using computer simulation technology, the operating characteristics of the centrifugal compressor's bladeless diffuser under different working conditions are numerically simulated and analyzed to determine the near-stall point of the bladeless diffuser.

[0027] 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 generators are set; the structural parameters of the vortex generators are determined according to the stall margin requirements and energy loss control targets 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 its length and width form a plane. The surface is fixedly attached to the inner wall of the cover side as the mounting surface of the vortex generator, and a plane formed by its length and height serves as the front face 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 protrudes beyond the inlet boundary of the original vaneless diffuser, the vortex generator is installed at the inlet boundary of the original vaneless diffuser; the original vaneless diffuser refers to the vaneless diffuser before the vortex generator is installed; when the starting position of the recirculation zone in the original vaneless diffuser does not touch the inlet boundary of the original vaneless diffuser, the vortex generator is installed between the inlet boundary of the original vaneless diffuser and the starting position;

[0028] By using computer simulation technology, the operating characteristics of the vaneless diffuser with vortex generators installed under different working conditions were numerically simulated and analyzed to determine the near-stall point of the vaneless diffuser with vortex generators installed.

[0029] The operating characteristics of the vaneless diffuser near the stall point before and after the installation of the vortex generator are input into a pre-established performance analysis software model to obtain the model output results, including: the improvement in the stall margin and the increase in energy loss of the centrifugal compressor after the installation of the vortex generator;

[0030] and determining whether the stall margin improvement value and the energy loss increase value are both within a preset range; if not, modifying the structural parameters of the vortex generator, and returning to the step of determining the near-stall point of the vaneless diffuser after the vortex generator is installed; and if so, outputting the current structural parameters of the vortex generator.

[0031] In a fourth aspect, the present application provides a computer program product comprising computer-readable instructions. When the computer-readable instructions are executed on an electronic device, the electronic device implements the parameter optimization method described in the third aspect.

[0032] In a fifth aspect, 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.

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

[0034] The above and other features, advantages, and aspects of the various embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. 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 that the originals and elements are not necessarily drawn to scale.

[0035] Figure 1 A structural diagram of a bladeless diffuser of a centrifugal compressor provided in this application;

[0036] Figure 2 A kind of Figure 1 A partial enlarged view of the vaneless diffuser at point A is shown;

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

[0038] Figure 4 A kind of Figure 1Schematic diagram of the installation angle of the vortex generator in the vaneless diffuser shown;

[0039] Figure 5 This is a schematic diagram of a bladeless diffuser provided in the present application when no vortex generator is installed and a bladeless diffuser after vortex generators with lengths of PEW1, PEW2, and PEW3 are installed; wherein, Figure 5 (a) Schematic diagram of a vaneless diffuser without vortex generators installed; Figure 5 (b) Schematic diagram of the vaneless diffuser after the vortex generator with a length of PEW1 is installed; Figure 5 (c) Schematic diagram of the vaneless diffuser after the vortex generator with a length of PEW2 is installed; Figure 5 (d) Schematic diagram of the vaneless diffuser after the vortex generator with a length of PEW3 is installed;

[0040] Figure 6 The total pressure ratio-mass flow rate characteristic diagram of a supercritical CO2 centrifugal compressor when no vortex generator is installed on the vaneless diffuser provided in the present application, and when vortex generators of lengths PEW1, PEW2, and PEW3 are installed on the vaneless diffuser;

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

[0042] Figure 8 A flow chart of a parameter optimization method provided in this application;

[0043] Figure 9 This is a schematic diagram of the structure of a parameter optimization device provided in this application.

[0044] Reference numerals:

[0045] 1- vaneless diffuser; 2- annular inlet; 3- annular outlet; 4- vortex generator; 5- hub; 6- impeller inlet; 7- impeller casing; 8- cover side; 9- flow channel. DETAILED DESCRIPTION

[0046] The embodiments of the present application provide a centrifugal compressor and its bladeless diffuser, a parameter optimization method and related products, which are intended to weaken the secondary flow intensity near the wall of the bladeless diffuser of the centrifugal compressor, thereby reducing the scope of the recirculation zone formed in the bladeless diffuser and improving the stall margin of the bladeless diffuser. By improving the stall margin of the bladeless diffuser, the stall margin of the centrifugal compressor is also improved. Improving the stall margin of the centrifugal compressor (especially the stall margin under high speed and small flow working conditions) is the core task of the centrifugal compressor stabilization control, and its technological breakthrough is crucial to achieving efficient, reliable and wide-range operation of the centrifugal compressor.

[0047] The embodiment of the present application mainly improves the centrifugal compressor's stabilization effect by optimizing the structure of the centrifugal compressor's bladeless diffuser. Below, in conjunction with the accompanying drawings, a bladeless diffuser for a centrifugal compressor provided by the embodiment of the present application is first described in detail. It is known to those skilled in the art that with the development of technology and the emergence of new scenarios, the technical solutions provided by the embodiment of the present application are also applicable to similar technical problems.

[0048] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate and are merely used to describe the manner in which objects with the same attributes are described in the embodiments of this application.

[0049] Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a list of elements is not necessarily limited to those elements but may include other elements not expressly listed or inherent to such process, method, product, or apparatus.

[0050] In addition, the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0051] In addition, for easier understanding, the names of various directions are defined as follows:

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

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

[0054] Circumferential direction: The direction around the axis of the cylinder (perpendicular to the axis and also perpendicular to the cross-sectional radius).

[0055] See also Figure 1 A bladeless diffuser for a centrifugal compressor provided in an embodiment of the present application includes the following structural optimization design: a plurality of vortex generators 4 are evenly installed on the inner wall of the cover side of the bladeless diffuser 1 along the circumference of the annular inlet 2 of the bladeless diffuser 1; the structural parameters of the vortex generators 4 are determined according to the stall margin requirements and energy loss control targets of the centrifugal compressor; the structural parameters of each vortex generator 4 are the same.

[0056] Figure 2 for Figure 1 A partial enlarged view of point A of the vaneless diffuser shown. Figure 3 This is a schematic diagram of the structure of an acute angle area within the 360° circumferential range of the bladeless diffuser along the axial perspective. Figures 1 to 3 , the working principle of the embodiment of the present application is described in detail:

[0057] The flow path of a vaneless diffuser refers to the channel area inside the vaneless diffuser where the gas flows, that is, the space through which the gas flows from the annular inlet 2 to the annular outlet 3 in the vaneless diffuser. After flowing out of the impeller, the gas enters the annular inlet 2 of the vaneless diffuser directly or after passing through a gap. Figure 1 The reference numerals 5, 6, and 7 in the figure represent the hub, impeller inlet, and impeller casing, respectively. Figures 1-3 From the perspective shown, the cover and disk sides (the upper and lower walls of a vaneless diffuser, respectively) form an annular flow channel. This diffuser has no blades within the annular flow channel and converts the kinetic energy of the gas into pressure energy solely through channel expansion. The cover side, located near the impeller shroud (front cover), forms the outer wall of the annular flow channel, restricting the outer edge of the airflow. The disk side, located near the impeller disc (rear disc), forms the inner wall of the annular flow channel, constraining the inner edge of the airflow. Figure 3 Reference numeral 8 in FIG. 8 represents the cover side of the vaneless diffuser. Figure 3 Reference numeral 9 in the figure denotes an impeller and a flow passage of a 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 the momentum exchange of the fluid through a vortex-induced mixing mechanism, which can weaken the secondary flow intensity near the wall of the bladeless diffuser and reduce the scope of the recirculation zone. In addition, in view of the circumferential feature of the inlet of the bladeless diffuser, an embodiment of the present application uses multiple 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 vaneless diffuser cover, which is equivalent to adjusting the three-dimensional flow field of the inner wall of the vaneless diffuser cover. This adjustment makes it possible to optimize the flow path in the vaneless diffuser and further weaken the secondary flow intensity near the wall of the vaneless 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 is 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 clogging 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 low-energy fluid under 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 its shape, 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, all affect the flow characteristics within the vaneless diffuser. Through scientific theoretical analysis and numerical simulation, the optimal range of these structural parameters can be determined. This allows the momentum exchange to be fully enhanced and the flow path to be optimized 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 significantly weakened, the scope of the recirculation zone within the vaneless diffuser can be reduced, and the stall margin of the vaneless diffuser, and thus the stall margin of the centrifugal compressor, can be improved.

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

[0063] 1. The shape of the vortex generator

[0064] The shape of the vortex generator can be rectangular (i.e., cuboid) or trapezoidal. Compared with vortex generators of other shapes, rectangular vortex generators are easy to induce flow separation and effectively induce strong vortices due to their straight-edge and right-angle design. In addition, the regular shape is easy to process and has low cost. This high vortex strength and easy processing characteristics make it a balanced fit in scenarios such as bladeless diffusers that require efficient flow control and low-cost manufacturing. Based on this, in a possible implementation, still refer to Figures 1 to 3 In the embodiment of the present application, a rectangular vortex generator is used (a plane formed by its length l and width d is fixed to the inner wall of the cover side and a plane formed by its length l and height h is used as the flow-facing surface of the vortex generator, as shown in FIG. Figure 3 As shown in Figure 3), subsequent theoretical analysis and numerical simulation were carried out based on the rectangular vortex generator.

[0065] 2. Spacing between the vortex generator and the inlet boundary of the vaneless diffuser

[0066] The distance between the vortex generator and the inlet boundary of the vaneless diffuser is the specific location of the vortex generator. The method for determining the specific location of the vortex generator is as follows:

[0067] First, computer simulation technology was used to adjust the operating conditions of the original vaneless diffuser (the vaneless diffuser before the vortex generators were installed). Numerical simulations were then conducted on the original vaneless diffuser's operating characteristics under different operating conditions to determine its near-stall point. The near-stall point refers to the critical point in the operation of a vaneless diffuser where it approaches stall but has not yet fully stalled. This point is also known as the stall threshold.

[0068] Then, based on the operating characteristics of the original vaneless diffuser near the stall point, the extent of the recirculation zone within the original vaneless diffuser was determined. The extent of the recirculation zone can be determined by using radial velocity contours of sections at different axial heights of the original vaneless diffuser. Specifically, areas with radial velocities less than 0 m / s correspond to the recirculation zone. The larger the area of ​​this region, the more severe the flow separation. Based on this, multiple sections of the original vaneless diffuser along the flow direction (axial direction) were scanned to extract radial velocity distribution data and identify the extent of the recirculation zone.

[0069] When the starting position of the recirculation zone within the original vaneless diffuser touches or protrudes beyond the original vaneless diffuser's inlet boundary, the vortex generator is installed at the original vaneless diffuser's inlet boundary to suppress the recirculation as early as possible. When the starting position of the recirculation zone within the original vaneless diffuser does not touch the original vaneless diffuser's inlet boundary, the vortex generator is installed between the original vaneless diffuser's inlet boundary and the starting position, that is, the vortex generator is placed upstream of the starting position, thereby preemptively disturbing the airflow and preventing the recirculation zone from developing and expanding. This setting logic aims to optimize the vortex generator layout based on the positional relationship between the recirculation zone and the inlet boundary, achieving efficient control of flow separation.

[0070] 3. Installation angle of vortex generator

[0071] like Figure 4 As shown in the figure, the installation angle of the vortex generator 4 is the angle β between the radial velocity direction v (i.e., the radial direction of the vaneless diffuser) of the axial height section of the vaneless diffuser and the length of the vortex generator. The value of β ranges from (90° - θ) - 10° to (90° - θ) + 10°, where θ is the inlet flow angle of the original vaneless diffuser near the stall point. A larger β value increases the suppression effect on the recirculation zone.

[0072] 4. The length of the vortex generator l

[0073] When designing the vortex generator length, l, the optimal length must be selected by balancing the vortex generator's flow control function with the inherent flow losses and its impact on the flow field at low axial heights. The vortex generator length, l, is determined by the angle β and the radial length, r, of the vortex generator's central axis projected onto the meridional plane of the vaneless diffuser. The radial length, r, ranges from 1 / 16 to 1 / 2 the vaneless diffuser radius.

[0074] The meridian plane is a plane passing through the axis of a rotating machine (such as an impeller or diffuser) and is orthogonal to the plane perpendicular to the axis of rotation (i.e., the radial plane). The central axis of a vortex generator is the central symmetry line of its geometric structure. Changing the angle β changes the radial length r of the vortex generator's central axis projected on the meridian plane. Therefore, the length l of the vortex generator can be determined based on the angle β and the radial length r.

[0075] 5. Height of vortex generator h

[0076] The height h of the vortex generator should be slightly higher than the axial height of the original vaneless diffuser's recirculation zone near the stall point. Numerical simulations show that the axial height of the original vaneless diffuser's recirculation zone near the stall point is within 20% of the axial height of the vaneless diffuser, measured from the inner wall of the vaneless diffuser cover. Therefore, the height h of the vortex generator should be set within a range of 37.5% to 50% of the axial height of the vaneless diffuser, measured from the inner wall of the vaneless diffuser cover.

[0077] 6. Width d of vortex generator

[0078] To ensure that the vortex generators do not significantly affect the efficiency of the diffuser, the width d of the vortex generators should be as small as possible while ensuring ease of processing and meeting strength requirements. Excessive width d will result in increased energy loss from the vortex generators.

[0079] The above parameters represent the optimal range for vortex generators in vaneless diffusers commonly used in centrifugal compressors, derived through extensive data simulation. For a specific centrifugal compressor, this optimal range can be optimized within this range to quickly determine the optimal parameters.

[0080] The centrifugal compressor used in the embodiments of this application is, for example, a supercritical CO2 centrifugal compressor. A supercritical CO2 centrifugal compressor is one in which secondary flow phenomena are more complex and require stricter control. When the temperature and pressure of CO2 exceed its critical point (critical temperature 304.13K, or 31.0°C; critical pressure 7.38MPa), it enters a supercritical state. A centrifugal compressor using supercritical carbon dioxide as its working medium is called a supercritical CO2 centrifugal compressor.

[0081] Given the design parameters of a supercritical CO2 centrifugal compressor, as well as the specific location, installation angle, height h, and width d of the vortex generator, the performance of the supercritical CO2 centrifugal compressor before and after the addition of the vortex generator varies. For example, for a supercritical CO2 centrifugal compressor with the parameters shown in Table 1, with the vortex generator located at the inlet boundary of the vaneless diffuser, an included angle β of 85°, a height h of 37.5% of the axial height of the vaneless diffuser from the inner wall of the vaneless diffuser cover, and a width d of 0.4 mm, numerical simulation techniques reveal the operating characteristics of the supercritical CO2 centrifugal compressor when the lengths l are PEW1, PEW2, and PEW3 (PEW1, PEW2, and PEW3 represent vortex generators with radial lengths r of 1 / 8, 3 / 16, and 7 / 16 of the vaneless diffuser radius, respectively), as well as when the vaneless diffuser is not installed with the vortex generator.

[0082] Table 1 - Supercritical CO2 centrifugal compressor parameters

[0083]

[0084] Figure 5 Schematic diagrams of a vaneless diffuser without vortex generators installed (referred to as the "original state") and a vaneless diffuser with vortex generators having lengths l of PEW1, PEW2, and PEW3 installed. Figure 6The total pressure ratio-mass flow characteristic diagram of the supercritical CO2 centrifugal compressor is shown in the figure below when the vortex generator is not installed on the bladeless diffuser and when the vortex generators with lengths l of PEW1, PEW2 and PEW3 are installed on the bladeless diffuser. Figure 6 The stall margin ΔSM of the supercritical CO2 centrifugal compressor before and after adding the vortex generator can be determined, as shown in Table 2.

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

[0086]

[0087] As shown in Table 2, after adding the vortex generator with a length l of PEW1, the stall margin of the supercritical CO2 centrifugal compressor is increased by 7.76%, achieving the best stability expansion effect.

[0088] Figure 7 The backflow situation (two-dimensional streamline) on the cover side of the vaneless diffuser before and after the vortex generator with a length l of PEW1 is installed. Figure 7 It can be seen that compared with the original state, after adding the vortex generator, the vortex generator cuts off the backflow on the cover side, turning a large backflow area into one or two small backflow areas. From the streamline, its action mechanism is that the streamline below 70% of the axial height moves toward 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, if Figure 8 As shown, the embodiment of the present application provides a parameter optimization method, including:

[0090] Step S01: numerically simulating and analyzing the operating characteristics of a vaneless diffuser of a centrifugal compressor under different operating conditions using computer simulation technology to determine a near-stall point of the vaneless diffuser;

[0091] Step S02: Simulating and modeling the vaneless diffuser using computer simulation technology, including: evenly installing a plurality of vortex generators on the inner wall of the vaneless diffuser cover side along the circumference of the annular inlet of the vaneless diffuser, and setting structural parameters of the vortex generators;

[0092] Step S03: using computer simulation technology, numerically simulating and analyzing the operating characteristics of the vaneless diffuser after the vortex generator is installed under different operating conditions to determine the near-stall point of the vaneless diffuser after the vortex generator is installed;

[0093] Step S04: Inputting the operating characteristics of the vaneless diffuser near the stall point before and after the installation of the vortex generator into a pre-established performance analysis software model to obtain 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;

[0094] Step S05: Determine whether the stall margin improvement value and the energy loss increase value are both within a preset range; if not, proceed to step S06; if so, proceed to step S07;

[0095] Step S06: modifying the structural parameters of the vortex generator, and returning to step S03;

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

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

[0098] On a technical level, computer simulation technology, simulating the operating characteristics of a vaneless diffuser, allows for precise determination of the near-stall point, flexible adjustment of vortex generator structural parameters, and efficient numerical simulation analysis. Key data such as improved stall margin and increased energy loss can be quickly obtained through performance analysis software models.

[0099] In design optimization, if the indicators fall outside the preset range, the vortex generator structural parameters can be modified and reanalyzed, with continuous iterative optimization until the optimal parameters are obtained (i.e., the structural parameter values ​​corresponding to the stall margin improvement and energy loss increase both falling within the pre-set ranges). This shortens the R&D cycle and reduces design costs. Overall, this process provides a scientific and efficient approach for the design and optimization of vaneless diffusers for centrifugal compressors.

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

[0101] In one possible implementation, the centrifugal compressor provided in the embodiment of the present application is a supercritical CO2 centrifugal compressor.

[0102] like Figure 9 As shown, an embodiment of the present application further provides a parameter optimization device, comprising:

[0103] The near-stall point determination unit 100 before shaping is used to perform numerical simulation analysis on the operating characteristics of the vaneless diffuser of the centrifugal compressor under different working conditions through computer simulation technology to determine the near-stall point of the vaneless diffuser;

[0104] The simulation modeling unit 200 is used to simulate and model the bladeless diffuser through 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 its length and width are relatively large. A plane formed by the length and height of the vortex generator is fixed on the inner wall of the cover side as the installation surface of the vortex generator, and a plane formed by the length and height of the vortex generator is used as the flow-facing 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 recirculation zone in the original bladeless diffuser touches or protrudes from 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 recirculation 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;

[0105] The post-molding near-stall point determination unit 300 is used to perform numerical simulation analysis on the operating characteristics of the vaneless diffuser after the vortex generator is installed under different working conditions through computer simulation technology to determine the near-stall point of the vaneless diffuser after the vortex generator is installed;

[0106] The performance analysis and processing unit 400 is used to input the operating characteristics of the bladeless diffuser at the near-stall point before and after the installation of the vortex generator into a pre-established performance analysis software model to obtain 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 energy loss increase value are both within a pre-set range; if not, modify the structural parameters of the vortex generator and trigger the post-modeling near-stall point determination unit 300 again; if so, output the current structural parameters of the vortex generator.

[0107] A computer program product is also provided in an embodiment of the present application, including computer-readable instructions. When the computer-readable instructions are executed on an electronic device, the electronic device implements any parameter optimization method provided in the embodiment of the present application.

[0108] A computer-readable storage medium is also provided in an embodiment of the present application. 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 in the embodiment of the present application.

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

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

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

[0112] It should also be noted that the device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separate, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed across multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. In addition, in the drawings of the device embodiments provided in this application, the connection relationship between the modules indicates that there is a communication connection between them, 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 can also be implemented by special hardware including application-specific integrated circuits, special CPUs, special memories, special components, etc. In general, all functions performed by computer programs can be easily implemented with corresponding hardware, and the specific hardware structures used to implement the same function can also be diverse, such as analog circuits, digital circuits or special circuits, etc. However, for the present application, software program implementation is a better implementation method in most cases. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a readable storage medium, such as a computer's floppy disk, USB flash drive, mobile hard disk, ROM, RAM, magnetic disk or optical disk, etc., and includes a number of instructions to enable a computer device (which can be a personal computer, training equipment, or network equipment, etc.) to execute the methods described in each embodiment of the present application.

[0114] In the above embodiments, all or part of the embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented by software, all or part of the embodiments may be implemented 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 process or function described in the embodiment of the present application is 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 computer-readable storage medium. For example, the computer instructions can be transmitted from a website, a computer, a training device or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website, a computer, a training device or a data center. 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, a data center, etc. that includes one or more available media integrations. The available medium can be a magnetic medium, (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)).

[0116] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may 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 are not limited to the embodiments shown herein, but are intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bladeless diffuser for a centrifugal compressor, characterized in that: A plurality of vortex generators are evenly installed on the inner wall of the cover side of the vaneless diffuser along the circumference of the annular inlet of the vaneless diffuser; The vortex generator is a structural component that enhances fluid momentum exchange through a vortex-induced mixing mechanism. Enhancing fluid momentum exchange through the vortex-induced mixing mechanism means that when the airflow flows through the vortex generator, an induced vortex can be generated at the leading edge of the vortex generator; the induced vortex can promote mixing of the core flow and the low-energy fluid on the cover side of the vaneless diffuser to increase the momentum of the cover-side fluid, thereby enhancing the ability of the fluid near the wall of the vaneless diffuser to resist adverse pressure gradients and delay the occurrence of stall; moreover, the rotational motion of the induced vortex can divide and compress the recirculation area on the cover side to reduce the blockage of the flow area by the recirculation area; 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, and a plane formed by its length and width serves as the mounting surface of the vortex generator and is fixed to the inner wall of the cover side, and a plane formed by its length and height serves as the flow-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 protrudes beyond the inlet boundary of the original vaneless diffuser, the vortex generator is installed at the inlet boundary of the original vaneless diffuser; the original vaneless diffuser refers to the vaneless diffuser before the vortex generator is installed; When the starting position of the recirculation zone in the original vaneless diffuser does not touch the inlet boundary of the original vaneless diffuser, installing the vortex generator between the inlet boundary of the original vaneless diffuser and the starting position; 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, and the value range of β is: (90°-θ)-10° to (90°-θ)+10°; θ is the inlet flow angle of the original vaneless 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 based on 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 radial length r ranges from 1 / 16 to 1 / 2 times the radius of the vaneless 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 the minimum value that meets the processing convenience and strength requirements.

2. A centrifugal compressor, characterized in that: include: The vaneless diffuser for a centrifugal compressor according to claim 1.

3. The centrifugal compressor according to claim 2, characterized in that: The centrifugal compressor is a supercritical CO2 centrifugal compressor.

4. A parameter optimization method, characterized in that: include: By using computer simulation technology, the operating characteristics of the centrifugal compressor's 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 generators are set; the vortex generator is a structural component that enhances the fluid momentum exchange through the vortex induced mixing mechanism; enhancing the fluid momentum exchange through the vortex induced mixing mechanism means that when the airflow flows through the vortex generator, an induced vortex can 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 on the cover side of the bladeless diffuser to increase the momentum of the cover side fluid, thereby enhancing the ability of the near-wall fluid of the bladeless diffuser to resist the adverse pressure gradient and delay the occurrence of stall. and a plurality of vortex generators are used for the vortex generator, and a plurality of vortex generators are used for the vortex generator. The plurality of vortex generators are used for the vortex generator, and a plurality of vortex generators are used for the vortex generator. The plurality of vortex generators are used for the vortex generator, and a plurality of vortex generators are used for the vortex generator. The plane serves as the flow-facing 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 recirculation zone in the original bladeless diffuser touches or protrudes from 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 recirculation 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; the installation angle of the vortex generator is the radial velocity direction of the bladeless diffuser and the length direction of the vortex generator. The angle β of the vortex generator is in the range of (90°-θ)-10° to (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 projected on the meridian plane 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 ranges from 37.5% to 50% of the axial height of the bladeless diffuser from the inner wall of the bladeless diffuser cover; the width d is the minimum value that meets the processing convenience and strength requirements; By using computer simulation technology, the operating characteristics of the vaneless diffuser with vortex generators installed under different working conditions were numerically simulated and analyzed to determine the near-stall point of the vaneless diffuser with vortex generators installed. The operating characteristics of the vaneless diffuser near the stall point before and after the installation of the vortex generator are input into a pre-established performance analysis software model to obtain the model output results, including: the improvement in the stall margin and the increase in energy loss of the centrifugal compressor after the installation of the vortex generator; and determining whether the stall margin improvement value and the energy loss increase value are both within a preset range; if not, modifying the structural parameters of the vortex generator, and returning to the step of determining the near-stall point of the vaneless diffuser after the vortex generator is installed; and if so, outputting the current structural parameters of the vortex generator.

5. A computer program product, characterized in that The method comprises computer-readable instructions, which, when executed on an electronic device, enable the electronic device to implement the parameter optimization method according to claim 4.

6. 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 according to claim 4.

Images