Variable diffuser and centrifugal compressor

Abstract

A variable diffuser and a centrifugal compressor are proposed. [Solution] This variable diffuser has an impeller (3) installed upstream and a volute casing (5) installed downstream, and includes a measurement point densification area for measuring the internal flow field of the variable diffuser and the upstream and downstream flow fields. The flow field measurement points of the variable diffuser are spaced apart along the fluid flow direction within the internal flow field of the variable diffuser and the upstream and downstream flow fields, and the spacing between the flow field measurement points installed within the measurement point densification area is smaller than the spacing between the flow field measurement points installed outside the measurement point densification area. Flow measurements are performed on the internal flow field of the variable diffuser and the upstream and downstream flow fields to obtain flow parameters and environmental parameters at each flow field measurement point of the variable diffuser. Comparative verification analysis of the measurement experiment results with the numerical simulation results improves the comprehensiveness, credibility, and reliability of the measurement results.

Description

[Technical Field]

[0001] The present invention relates to the technical field of compressors, and more particularly to variable diffusers and centrifugal compressors. [Background technology]

[0002] The centrifugal compressor is the core component of the multi-stage centrifugal compressor or axial-centrifugal compressor in the new pressure storage system, and the variable diffuser is the core stationary component of the centrifugal compressor, which can statically decelerate and boost the fluid and adaptively adjust the boost angle according to the fluid flow direction from the upstream impeller. Therefore, it is not possible to further efficiently optimize the design and highly accurately predict the performance of the variable diffuser.

[0003] Most of the existing technologies involve measurements of the external characteristics of the variable diffuser or simulation analyses that are not based on the actual environment of the entire aircraft. There is little detailed scientific research-level research on the internal flow mechanisms within the booster passage and upstream and downstream of the variable diffuser, making it impossible to accurately analyze the performance mechanisms of the variable diffuser and to further efficiently optimize the design. Summary of the Invention [Means for solving the problem]

[0004] In view of the above problems, the present invention proposes a variable diffuser that includes an impeller provided upstream, a volute casing provided downstream, and a measurement point densification region provided for measuring the internal flow field of the variable diffuser and the upstream and downstream flow fields, wherein the flow field measurement points of the variable diffuser are provided at intervals along the fluid flow direction in the internal flow field and the upstream and downstream flow fields of the variable diffuser, and the intervals between the flow field measurement points provided within the measurement point densification region are smaller than the intervals between the flow field measurement points provided outside the measurement point densification region.

[0005] Optionally, the spacing between adjacent flow field measurement points in a region of the volute casing close to the tongue is smaller than the spacing between adjacent flow field measurement points in a region of the volute casing far from the tongue.

[0006] Optionally, the flow field measurement points include a plurality of first groups of measurement points, in a booster chamber and a plurality of booster vanes circumferentially spaced apart within the booster chamber, variable volume booster passages are formed between the plurality of booster vanes, at least one first group of measurement points is provided in each booster passage along the fluid flow direction, the spacing between the first measurement points provided in the measurement point densification region is smaller than the spacing between the first measurement points provided outside the measurement point densification region, and the first measurement points are used to detect and acquire flow parameters and environmental parameters of the fluid within the booster passage.

[0007] Optionally, a first gap is provided between the variable diffuser and the impeller, and the flow field measurement points include a plurality of second groups of measurement points spaced apart in a circumferential direction of the first gap, the plurality of second groups of measurement points and the downstream booster passages are provided in one-to-one correspondence, the plurality of second measurement points in each group are provided along the fluid flow direction, the intervals between the second measurement points provided in the measurement point densification region are smaller than the intervals between the second measurement points provided outside the measurement point densification region, and the second measurement points are used to detect and acquire fluid flow parameters and environmental parameters in the first gap.

[0008] A second gap is optionally provided between the variable diffuser and the volute casing, and the flow field measurement points include a plurality of third measurement point groups spaced apart in the circumferential direction of the second gap, the plurality of third measurement point groups and each of the booster passages are provided in one-to-one correspondence, the plurality of third measurement points in each group are provided along the fluid flow direction, the spacing between the third measurement points provided in the measurement point densification region is smaller than the spacing between the third measurement points provided outside the measurement point densification region, and the third measurement points are used to detect and acquire fluid flow parameters and environmental parameters in the second gap.

[0009] Optionally, the first measurement point, the second measurement point, and the third measurement point are each provided with a detection sensor.

[0010] Optionally, the number of groups of the first measurement points is equal to the number of booster passages, the number of groups of the second measurement points is equal to the number of booster passages, and the number of groups of the third measurement points is equal to the number of booster passages.

[0011] Optionally, each of the first measurement point groups has at least two first measurement points, each of the second measurement point groups has at least three second measurement points, and each of the third measurement point groups has at least three third measurement points.

[0012] Optionally, the detection sensor includes at least one of a contact sensor and a non-contact sensor.

[0013] The present invention further provides a centrifugal compressor, including an overall inlet passage, an adjustable inlet guide vane, an impeller, a variable diffuser, a volute casing, and an overall outlet passage, wherein the adjustable inlet guide vane is disposed in the overall inlet passage, the impeller is disposed downstream of the adjustable inlet guide vane, the variable diffuser is disposed downstream of the impeller, the volute casing is disposed downstream of the variable diffuser, and the overall outlet passage is connected to the outlet of the volute casing.

[0014] Optionally, a tip clearance is provided between the impeller and the impeller cover, and a disc cavity is formed between the impeller on the side remote from the adjustable inlet guide vanes and the impeller cover.

[0015] The variable diffuser of the present invention selects a high-density measurement area for measuring the internal flow field of the variable diffuser and the upstream and downstream flow fields. During the measurement experiment stage, the flow field measurement points of the variable diffuser are spaced apart along the fluid flow direction in the internal flow field and the upstream and downstream flow fields of the variable diffuser. In this process, the interval between adjacent flow field measurement points in the area close to the tongue of the volute casing is made smaller than the interval between adjacent flow field measurement points in the area far from the tongue of the volute casing, and the interval between flow field measurement points in the high-density measurement area is made smaller than the interval between flow field measurement points outside the high-density measurement area. In other words, the flow field measurement points are spaced more densely in the high-density measurement area, and more and more fluid data is collected in the high-density measurement area. Finally, measurements are carried out on the internal flow field of the variable diffuser and the flow passing through it with respect to the upstream and downstream flow fields, and the flow parameters and environmental parameters at each measurement point of the variable diffuser flow field are obtained. The measurement experimental results are compared and analyzed with the numerical results of the simulation to improve the comprehensiveness, credibility, and reliability of the measurement results.

[0016] Additional features and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and obtained through the structure particularly pointed out in the description, claims and appended drawings. [Brief explanation of the drawings]

[0017] In order to more clearly describe the embodiments of the present invention or the technical solutions in the prior art, the drawings that need to be used in the description of the embodiments or the prior art are briefly described below. Obviously, the drawings in the following description are some embodiments of the present invention. Those skilled in the art can obtain other drawings based on these drawings without any creative efforts.

[0018] [Figure 1] FIG. 1 is a schematic diagram showing the arrangement of first, second and third measurement points in one embodiment of the present application. [Figure 2] FIG. 2 is a schematic diagram showing a partial structure of a centrifugal compressor according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the overall structure of a centrifugal compressor according to an embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart illustrating the main steps of a method for analyzing the internal flow field and the upstream and downstream flow fields of a variable diffuser in one embodiment of the present application. [Figure 5] FIG. 5 is a flowchart illustrating some steps of a method for analyzing the internal flow field and the upstream and downstream flow fields of a variable diffuser in one embodiment of the present application. [Figure 6] FIG. 6 is a partial simulation model diagram of adjustable inlet guide vanes in one embodiment of the present application. [Figure 7] FIG. 7 is a partial simulation model diagram of an impeller in one embodiment of the present invention. [Figure 8] FIG. 8 is a partial simulation model diagram of a disk cavity of an impeller in one embodiment of the present application. [Figure 9] FIG. 9 is a partial simulation model diagram of a variable diffuser in one embodiment of the present application. [Figure 10] FIG. 10 is a diagram of a simulation model of a volute casing in one embodiment of the present invention. [Figure 11] FIG. 11 is a schematic diagram of a first partial simulation of a variable diffuser in one embodiment of the present application. [Figure 12] FIG. 12 is a schematic diagram of a second partial simulation of a variable diffuser in one embodiment of the present application. [Figure 13] FIG. 13 is a schematic diagram of a third partial simulation of a variable diffuser in one embodiment of the present application. [Figure 14] FIG. 14 is a schematic diagram of a fourth partial simulation of a variable diffuser in one embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0019] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0020] As shown in Figures 1 and 2, the present invention provides a variable diffuser (4), which includes an impeller (3) provided upstream, a volute (5) provided downstream, and a measurement point densification region provided for measuring the internal flow field of the variable diffuser (4) and the upstream and downstream flow fields, the flow field measurement points of the variable diffuser (4) are provided at intervals along the fluid flow direction in the internal flow field of the variable diffuser (4) and the upstream and downstream flow fields, and the intervals between the flow field measurement points provided in the measurement point densification region are smaller than the intervals between the flow field measurement points provided outside the measurement point densification region.

[0021] The spacing between adjacent flow field measurement points in the region close to the tongue of the volute casing 5 is smaller than the spacing between adjacent flow field measurement points in the downstream region far from the tongue of the volute casing 5.

[0022] The variable diffuser 4 includes a booster chamber and a plurality of booster vanes 41 circumferentially spaced apart within the booster chamber, the angles of the booster vanes 41 being adjustable. Variable-volume booster passages 42 are formed between the booster vanes 41, and the flow field measurement points include a plurality of first measurement point groups 100, with at least one first measurement point group 100 provided within each booster passage 42 along the fluid flow direction, the spacing between the first measurement points 100 provided within the measurement point densification region being smaller than the spacing between the first measurement points 100 provided outside the measurement point densification region, and the first measurement points 100 are used to detect and acquire flow parameters and environmental parameters of the fluid within the booster passage 42.

[0023] The flow field measurement points include a plurality of first measurement points 100. At least one first measurement point 100 is provided in each pressure booster passage 42 along the fluid flow direction. The first measurement points 100 can be used to detect and acquire flow parameters and environmental parameters of the fluid in each pressure booster passage 42. Furthermore, because the spacing between the first measurement points 100 provided in the measurement point densification region is smaller than the spacing between the first measurement points 100 provided outside the measurement point densification region, more fluid data can be acquired and captured through the more densely packed first measurement points 100 provided in the measurement point densification region, thereby enabling the pressure boosting mechanism of the variable diffuser 4 to be analyzed.

[0024] The number of groups of first measurement points 100 is equal to the number of pressure boosting passages 42, i.e., one group of first measurement points 100 is provided for each pressure boosting passage 42. Specifically, at least two first measurement points 100 may be provided in each group. However, this is not a limitation. In other embodiments, the number of groups of first measurement points 100 and the number of points in each group can be set as needed.

[0025] In this embodiment, the first measurement points 100 in each group are spaced apart along the fluid flow direction in the booster passage 42. By spaced apart the first measurement points 100 in each group along the fluid flow direction in the booster passage 42, the change in the fluid flow direction characteristics in the booster passage 42 can be obtained, and the data can be easily compared and analyzed.

[0026] In some embodiments, a first gap 10 is provided between the variable diffuser 4 and the upstream impeller 3, and the flow field measurement points include a group of second measurement points 200 spaced apart along the first gap 10. The groups of second measurement points 200 correspond one-to-one to the downstream booster passages 42. The second measurement points 200 in each group are arranged along the fluid flow direction, and the spacing between the second measurement points 200 in the measurement point densification region is smaller than the spacing between the second measurement points 200 outside the measurement point densification region. The second measurement points 200 are used to detect and acquire fluid flow parameters and environmental parameters in the first gap 10.

[0027] The flow field measurement points include a group of multiple second measurement points 200 that are provided in a one-to-one correspondence with each of the upstream pressure boosting passages 42. The second measurement points 200 can be used to detect and acquire fluid flow parameters and environmental parameters in the first gap 10. Furthermore, because the spacing between the second measurement points 200 provided in the measurement point densification region is smaller than the spacing between the second measurement points 200 provided outside the measurement point densification region, more fluid data can be acquired and captured through the denser second measurement points 200 provided in the measurement point densification region, thereby enabling analysis of the fluid performance in the first gap 10.

[0028] In this embodiment, the number of groups of second measurement points 200 is equal to the number of pressure boosting passages 42, i.e., one group of second measurement points 200 is provided corresponding to each pressure boosting passage 42. Specifically, each group may be provided with at least three second measurement points 200, but is not limited to this. In other embodiments, the number of groups of second measurement points 200 and the number within each group can be set as needed.

[0029] In some embodiments, the second measurement points 200 in each group are spaced apart in the first gap 10 along the direction of fluid flow. By spaced apart the second measurement points 200 in each group in the first gap 10 along the direction of fluid flow, changes in the properties of the fluid in the first gap 10 can be obtained, facilitating comparative analysis of the data.

[0030] In some embodiments, a second gap 20 is provided between the variable diffuser 4 and the downstream volute casing 5, and the flow field measurement points include a group of multiple third measurement points 300 spaced apart along the second gap 20. The groups of multiple third measurement points 300 and the upstream booster passages 42 are provided in one-to-one correspondence. The multiple third measurement points 300 in each group are provided along the fluid flow direction, and the spacing between the third measurement points 300 in the measurement point densification region is smaller than the spacing between the third measurement points 300 outside the measurement point densification region. The third measurement points 300 are used to detect and acquire fluid flow parameters and environmental parameters in the second gap 20.

[0031] The flow field measurement points include a group of multiple third measurement points 300 provided in one-to-one correspondence with each downstream booster passage 42. The third measurement points 300 can be used to detect and acquire fluid flow parameters and environmental parameters in the second gap 20. Furthermore, because the spacing between the third measurement points 300 provided in the measurement point densification region is smaller than the spacing between the third measurement points 300 provided outside the measurement point densification region, more fluid data can be acquired and captured through the more densely packed third measurement points 300 provided in the measurement point densification region, thereby enabling analysis of the fluid performance in the second gap 20.

[0032] In this embodiment, the number of groups of third measurement points 300 is equal to the number of pressure boosting passages 42, i.e., one group of third measurement points 300 is provided corresponding to each pressure boosting passage 42. Specifically, each group may be provided with at least three third measurement points 300, but is not limited to this. In other embodiments, the number of groups of third measurement points 300 and the number within each group can be set as needed.

[0033] In some embodiments, the plurality of third measurement points 300 in each group are spaced apart in the second gap 20 along the direction of fluid flow. By spaced apart the plurality of third measurement points 300 in each group in the second gap 20 along the direction of fluid flow, changes in properties of the fluid in the second gap 20 can be obtained and data comparison and analysis can be facilitated.

[0034] The first measurement point 100, the second measurement point 200, and the third measurement point 300 are each provided with a detection sensor, which can detect the flowing fluid.

[0035] The detection sensor includes at least one of a contact sensor and a non-contact sensor.

[0036] The contact sensor may be at least one of a piezoresistive pressure sensor, a strain gauge pressure gauge, a thermocouple, a thermistor, a turbine flow meter, an electromagnetic flow meter, a differential pressure flow meter, a target flow meter, an accelerometer, a strain gauge, a conductivity sensor, a capacitance sensor, a rotational viscometer, a capillary viscometer, a multi-parameter composite sensor, a du Nouy method sensor, a plate method sensor, a contact microphone, a capacitance hygrometer, a stylus profiler, and a displacement sensor.

[0037] The non-contact sensor may be at least one of a piezoelectric pressure sensor, a capacitive pressure sensor, an infrared thermometer, an ultrasonic flow meter, a laser Doppler velocimeter (LDV), a non-contact electromagnetic flow meter, an ultrasonic flow meter, a laser vibrometer, a near-infrared spectrum sensor, a microwave sensor, a microwave / radio frequency sensor, a non-contact flow meter + viscosity sensor, a laser surface roughness sensor, a laser microphone, an infrared humidity sensor, a microwave humidity sensor, a laser interferometer, a white light interferometer, an ultrasonic thickness gauge, and an optical 3D scanner.

[0038] As shown in FIG. 2 , in some embodiments, flow parameters and environmental parameters of the fluid are acquired at a first measurement point 100 located in the booster passage 42, a second measurement point 200 located in the first gap 10, and a third measurement point 300 located in the second gap 20.

[0039] The processing results of the acquired flow parameters and environmental parameters are compared and analyzed with the numerical results of the simulation, and the comprehensive external performance of the whole machine under variable operating conditions is evaluated. The loss distribution in the booster passage 42 of the variable diffuser 4 and the upstream and downstream flow fields is analyzed, and the internal flow of the variable diffuser 4 and the upstream and downstream coupling loss mechanism are clarified, which further guides the design direction for optimizing the blade shape of the variable diffuser 4 and matching the coupling with the upstream and downstream.

[0040] The fluid flow parameters and environmental parameters are obtained at the first measurement point 100 located in the booster passage 42, the second measurement point 200 located in the first gap 10, and the third measurement point 300 located in the second gap 20. The processing results of the obtained flow parameters and environmental parameters are compared and analyzed with the numerical simulation results. This makes it possible to evaluate and analyze the overall external performance of the entire machine under variable operating conditions, the booster passage 42 of the variable diffuser 4, and the flow field loss distribution upstream and downstream. This clarifies the internal flow of the variable diffuser 4 and the upstream and downstream coupling loss mechanism, which can then be used to optimize the blade shape of the variable diffuser 4 and to guide design directions for matching the upstream and downstream coupling.

[0041] As shown in Figure 3, the present invention further provides a centrifugal compressor, including an overall inlet passage 1, an adjustable inlet guide vane 2, an impeller 3, a variable diffuser 4, a volute casing 5, and an overall outlet passage 6. The adjustable inlet guide vane 2 is disposed within the overall inlet passage 1, and the impeller 3 is disposed downstream of the adjustable inlet guide vane 2, with a tip clearance between the impeller 3 and the impeller cover, and a disk cavity is formed between the side of the impeller 3 away from the adjustable inlet guide vane 2 and the impeller cover. The variable diffuser 4 is disposed downstream of the impeller 3, and the volute casing 5 is disposed downstream of the variable diffuser 4. That is, the volute casing 5 is disposed downstream of the impeller 3, and the outlet passage is connected to the outlet of the volute casing 5. The step of measuring the flow passing through the flow fields inside, and upstream and downstream of, the variable diffuser 4 based on a measurement system for the overall centrifugal compressor and the internal flow field includes: Designing and constructing a centrifugal compressor overall and internal flow field measurement system; Measurements are carried out under all operating conditions and all internal flow fields for the inlet of the entire inlet passage 1 and the outlet of the entire outlet passage 6, the inlet / outlet and interior of the adjustable inlet guide vane 2, the inlet / outlet and interior of the impeller 3, the disk cavity of the impeller 3, the tip clearance of the impeller 3, the interior and upstream / downstream of the booster passage 42 of the variable diffuser 4, and the interior and upstream / downstream of the booster passage 42 of the volute casing 5 under different main flow rates, different angles of the adjustable inlet guide vane 2, different rotational speeds of the impeller 3, and different angles of the variable diffuser 4.

[0042] During the actual operation of a centrifugal compressor, a part of the main flow leaks from the disk cavity 20 and the tip clearance of the impeller 3. Therefore, in the measurement experiment stage of the present application, the influence of the leakage flow from the disk cavity 20 and the tip clearance of the impeller 3 is taken into consideration, and measurements of all operating conditions and all internal flow fields are carried out under different main flow rate conditions, different angles of the adjustable inlet guide vanes 2, different rotation speeds of the impeller 3, and different angles of the variable diffuser 4, so as to improve the accuracy of the measurement experiment results.

[0043] In some embodiments, the objects affected by the circumferential asymmetry due to the tongue include at least one of the volute casing 5 itself, the upstream and downstream internal flow fields, and the overall machine performance, and the range of influence includes at least one of the parts, the area, and the degree.

[0044] By limiting the objects affected by the circumferential asymmetry caused by the tongue to include at least one of the volute casing 5 itself, the internal flow fields on the upstream and downstream sides, and the overall machine performance, it is possible to more comprehensively analyze the effect of the circumferential asymmetry caused by the tongue on the internal flow field of the centrifugal compressor.

[0045] In this embodiment, the objects affected by the circumferential asymmetry caused by the tongue include at least one of the volute casing 5 itself, the internal flow fields on the upstream and downstream sides, and the overall machine performance, and the range of influence includes at least one of the parts, the area, and the degree.

[0046] Furthermore, as shown in FIG. 4, the variable diffuser of the present invention also provides a corresponding method for analyzing its internal flow field and upstream and downstream flow fields, which method includes: building a full-circle passage simulation model of the centrifugal compressor; Executing a simulation of all operating conditions of the entire passage area based on a full passage simulation model of the entire centrifugal compressor, preset fluid parameters, and preset boundary conditions; a step of obtaining the external performance and internal flow characteristics of the entire centrifugal compressor based on the numerical results of the simulation, and further analyzing and selecting a measurement point densification region provided for measuring the internal flow field and the upstream and downstream flow fields of the variable diffuser; a step of providing the flow field measurement points of the variable diffuser at intervals along the fluid flow direction in the internal flow field and the upstream and downstream flow fields of the variable diffuser, and making the intervals between the flow field measurement points located in the measurement point densification region smaller than the intervals between the flow field measurement points located outside the measurement point densification region; a step of measuring the flow passing through the internal flow field and the upstream and downstream flow fields of the variable diffuser 4 based on a measurement system for the entire centrifugal compressor and acquiring flow parameters and environmental parameters at each measurement point of the flow field of the variable diffuser 4, and comparing and verifying the numerical results of the simulation using the measurement experiment results; For the full-circumferential passage simulation model of the entire machine, simulations are performed under all operating conditions for the entire throughflow area, and when measurements are taken of the flow passing through the internal flow field of the variable diffuser 4 and the upstream and downstream flow fields, it is necessary to take into account the influence of the circumferential asymmetry caused by the tongue of the volute casing 5.

[0047] The present method for analyzing the internal flow field and upstream / downstream flow fields of a variable diffuser 4 involves performing a simulation of the entire pass-through region under all operating conditions for the constructed full-circle passage simulation model of the entire centrifugal compressor. Based on the numerical results of the simulation, the external performance and internal flow characteristics of the entire centrifugal compressor are obtained, and a measurement point densification region for measuring the internal flow field and the upstream / downstream flow fields of the variable diffuser 4 is analyzed and selected. During the measurement experiment phase, flow field measurement points of the variable diffuser 4 are spaced along the fluid flow direction in the internal flow field and the upstream / downstream flow fields of the variable diffuser 4. The spacing between the flow field measurement points located in the measurement point densification region is made smaller than the spacing between the flow field measurement points located outside the measurement point densification region. This arrangement of the flow field measurement points within the measurement point densification region allows for more accurate and more comprehensive collection of fluid data within the measurement point densification region. Finally, measurements are conducted on the internal flow field of the variable diffuser 4 and the flow fields upstream and downstream of the variable diffuser 4, and flow and environmental parameters are obtained at each measurement point in the flow field of the variable diffuser 4. The measured experimental results are then used to compare and verify the numerical results of the simulation. Therefore, this application combines simulation and experimental measurements, along with theoretical analysis, to perform overall performance evaluation and local quantitative analysis of the centrifugal compressor, deeply study the loss mechanism of the internal flow field of the through-flow section, and fully consider the adjustable characteristics of the diffuser vanes and their coupling mechanisms with the upstream and downstream, thereby improving the comprehensiveness, credibility, and reliability of the measurement results.

[0048] Specifically, the diffuser, as a component downstream of the impeller 3, converts part of the kinetic energy (dynamic pressure) of the high-speed, high-pressure gas at the impeller 3 outlet into static pressure (potential energy), thereby reducing the volumetric flow rate of the mainstream. The diffuser analysis includes dynamic and static clearances, as well as vaned and vaneless diffuser sections. Vaned diffuser blade shapes include wedge / passage, cascade, airfoil, conical, tapered disk-cover, and tubular. There are three main structural types: low-density, tandem, and half-height (cover-side, disk-side, and disk-cover staggered). Losses in the dynamic and static clearances and vaneless diffuser sections are primarily friction losses and separation losses, as well as coupled flow losses due to the nonuniformity of the airflow at the upstream impeller outlet and the circumferential asymmetry of the downstream volute casing. In addition to friction and separation losses, losses in vaned diffusers include leading-edge impact losses, wake mixing losses, secondary flow / blockage losses, and blade loading losses. The throat cross-section affects the compressor's stable operating range. Because the number of blades is less than, but not a multiple of, the number of blades in the impeller 3, a uniform circumferential airflow is generated in each booster passage 42, preventing resonance with the impeller 3. While fixed-vane diffusers offer higher design efficiency than vaneless diffusers, they have a narrower operating range and lower efficiency under variable operating conditions. Therefore, a variable-vane diffuser (i.e., the variable diffuser 4 of the present invention) is proposed. The angle of the booster vanes 41 in the diffuser can be adjusted to suit various flow rate operating conditions, achieving an ideal blade attack angle. This reduces flow losses within the diffuser while maintaining a high boost ratio and improving the compressor's stable operating range. The research subject of this invention is a low-density variable-vane diffuser for a centrifugal compressor.

[0049] In some embodiments, as shown in FIG. 5 , the step of constructing a full passage simulation model of the entire centrifugal compressor includes: constructing a full-circle passage simulation model of the full-circle entrance passage 1; Building a full-circle passage simulation model of the adjustable inlet guide vane 2 and placing it inside the full-circle passage simulation model of the entire machine inlet passage 1; constructing a full-passage simulation model of the impeller 3 and arranging it downstream of the full-passage simulation model of the adjustable inlet guide vanes 2; constructing a full-circle passage simulation model of the variable diffuser 4 and arranging it downstream of the full-circle passage simulation model of the impeller 3; constructing a full-circumferential passage simulation model of the volute casing 5 in consideration of the influence of the circumferential asymmetry caused by the tongue portion, and arranging the full-circumferential passage simulation model downstream of the full-circumferential passage simulation model of the variable diffuser 4; The method includes the steps of constructing a full-circumferential passage simulation model of the entire outlet passage 6 and connecting the full-circumferential passage simulation model of the outlet passage and the full-circumferential passage simulation model of the volute casing 5.

[0050] According to the above method, a full-circle passage simulation model of the inlet passage 1 of the entire machine, a full-circle passage simulation model of the adjustable inlet guide vane 2, a full-circle passage simulation model of the impeller 3, a full-circle passage simulation model of the variable diffuser 4, a full-circle passage simulation model of the volute casing 5, and a full-circle passage simulation model of the outlet passage 6 of the entire machine are established, that is, a full-circle passage simulation model of the centrifugal compressor is established, and a simulation is carried out based on the full-circle passage simulation model of the centrifugal compressor, which improves the accuracy and reliability of the simulation results.

[0051] In some embodiments, the step of constructing a full-circle passage simulation model of the entire centrifugal compressor further includes the step of constructing a full-circle passage simulation model of a disk cavity of the impeller 3, and connecting the leakage flow inlet of the full-circle passage simulation model of the disk cavity with the main flow outlet of the full-circle passage simulation model of the impeller 3, taking into account the influence of the leakage flow of the disk cavity of the impeller 3.

[0052] During the actual operation of a centrifugal compressor, a part of the main flow leaks from the disk cavity of the impeller 3. Therefore, in the simulation stage, the present application takes into consideration the influence of the leakage flow from the disk cavity of the impeller 3, and when constructing a full-circle passage simulation model of the entire centrifugal compressor, it also constructs a full-circle passage simulation model of the disk cavity of the impeller 3, and connects the leakage flow inlet of the full-circle passage simulation model of the disk cavity with the main flow outlet of the full-circle passage simulation model of the impeller 3, thereby improving the accuracy of the simulation results.

[0053] In some embodiments, the step of performing a simulation of all operating conditions of the entire pass-through area based on the entire pass-through simulation model of the entire centrifugal compressor, the preset fluid parameters, and the preset boundary conditions includes the step of building an entire pass-through area calculation model of the entire centrifugal compressor coupled with the disk cavities, and performing simulations of all operating conditions with different main flow rate and / or different rotation speed of the impeller 3 and / or different angles of the adjustable inlet guide vanes 2 and / or different angles of the variable diffuser 4.

[0054] By constructing a full-circumferential throughflow calculation model of the entire centrifugal compressor coupled with a disk cavity and performing simulations of all operating conditions with different main flow rates and / or different rotational speeds of the impeller 3 and / or different angles of the adjustable inlet guide vanes 2 and / or different angles of the variable diffuser 4, simulation data under different operating conditions of the entire centrifugal compressor coupled with a disk cavity can be obtained, and the comprehensiveness of the simulation data can be improved.

[0055] In some embodiments, the step of constructing a full-circumferential passage simulation model of the impeller cavity of the impeller 3 includes the following steps: Divide the disk cavity into a periodic, fully orthogonal hexahedral structure mesh using mesh preprocessing software, and match the mesh nodes of the leakage flow inlet of the full-circumferential passage simulation model of the disk cavity with the mesh nodes of the main stream outlet of the full-circumferential passage simulation model of the impeller 3; Close the leakage flow outlet of the full-circumferential passage simulation model of the disk cavity, and densify the meshes of the communication surface between the leakage flow inlet and the main stream outlet, the moving and stationary wall surfaces of the disk cavity, and the seal structure of the leakage flow outlet; Set the interior and moving wall surfaces of the disk cavity to a rotating region, and set the stationary wall surfaces of the disk cavity to a stationary region; Select the mixing plane method as the mesh calculation method for the communication surface between the leakage flow inlet and the main stream outlet.

[0056] According to the above method, the constructed full-circumferential passage simulation model of the disc cavity is more compatible with the full-circumferential passage simulation model of the impeller 3, and the leakage flow inlet / outlet, moving wall surface and stationary wall surface of the disc cavity are processed accordingly, so that the constructed full-circumferential passage simulation model of the disc cavity is more suitable for practical use.

[0057] Specifically, as shown in FIG. 8, FIG. 8 is a partial simulation model diagram of the disk cavity of the impeller 3 in one embodiment of the present application, and all the dark areas are mesh densification areas of the disk cavity.

[0058] In some embodiments, the step of constructing a full-circumference passage simulation model of the volute casing 5 involves using mesh preprocessing software to perform tetrahedral unstructured mesh division on the volute casing 5 with solid walls having boundary layers, densifying the mesh of the boundary layers, and partially densifying the mesh of the tongue.

[0059] By using the above method, a simulation model of the entire circumferential passage of the volute casing 5 is constructed, and the mesh at a specific position of the volute casing 5 is made denser to improve the accuracy of the simulation.

[0060] Specifically, as shown in FIG. 10, FIG. 10 is a simulation model diagram of the volute casing 5 in one embodiment of the present application, and all the dark areas are mesh densification areas of the volute casing 5.

[0061] The construction of a full-circumferential passage simulation model of the adjustable inlet guide vane 2, impeller 3, and variable diffuser 4 of a centrifugal compressor can be performed by referring to the disk cavity and volute casing 5 method, as shown in Figures 6, 7, and 9. Figure 6 is a partial simulation model diagram of the adjustable inlet guide vane 2 in one embodiment of the present invention, Figure 7 is a partial simulation model diagram of the impeller 3 in one embodiment of the present invention, and Figure 9 is a partial simulation model diagram of the variable diffuser 4 in one embodiment of the present invention. The dark areas in Figures 6, 7, and 9 are all mesh densification areas. Specifically, using mesh pre-processing software, the three parts, the adjustable inlet guide vane 2, impeller 3, and variable diffuser 4, are divided into a complete hexahedral structure mesh, with a body-fit H-type mesh used on the wall surface and an O-type mesh used at the boundary between the leading and trailing edges of the blade and the wall surface and the blade tip gap.

[0062] In this application, when constructing a full-circle passage simulation model of a centrifugal compressor, the same mesh topology and coarse mesh densification configuration are combined, and the full-circle passage mesh of the throughflow area of ​​the whole machine constructed 1:1 based on the original structural parameters of the research object must verify the independence of the mesh number.

[0063] In some embodiments, the steps of obtaining the external performance and internal flow characteristics of the entire centrifugal compressor based on the numerical simulation results, and analyzing and selecting a measurement point densification area for measuring the internal flow field and the upstream and downstream flow fields of the variable diffuser 4, include: analyzing the loss mechanism of the entire centrifugal compressor and the internal flow characteristics of each subcomponent under different operating conditions based on the numerical simulation results. In this analysis, the booster passage 42 and the upstream and downstream main flow field characteristics of the variable diffuser 4 are analyzed in detail, and the leakage flow characteristics in the gaps between each booster vane 41 of the variable diffuser 4 and the casing are used as auxiliary verification, thereby obtaining the external performance and internal flow characteristics of the entire centrifugal compressor. In addition, local region locations where the flow field characteristics inside the booster passage 42 of the variable diffuser 4 and the upstream and downstream show at least one of distortion, transition, and singularity are intentionally captured as the measurement point densification area.

[0064] Based on the numerical results of the simulation, the loss mechanism of the entire centrifugal compressor and the internal flow characteristics of each subcomponent under different operating conditions are analyzed, and the loss mechanism of the entire compressor and the internal flow characteristics of each subcomponent under variable operating conditions are evaluated. Areas with obvious local characteristics, including but not limited to distortions, transitions, and singularities, inside the variable diffuser 4 and upstream and downstream are intentionally captured, and these areas with obvious local characteristics are used as measurement point densification areas to analyze the coupling characteristics and internal flow structure of each flow-through component under variable operating conditions. Among them, the booster passage 42 of the variable diffuser 4 and the main flow field characteristics upstream and downstream are analyzed in detail, and the leakage flow characteristics in the gap between each booster vane 41 of the variable diffuser 4 and the casing are used as auxiliary verification.

[0065] 11 to 14, (a) of FIG. 11 shows a simulation data diagram of the change in static pressure when the fluid flows through the variable diffuser 4, and (b) of FIG. 11 shows a simulation data diagram of the change in total pressure when the fluid flows through the variable diffuser 4. (c) of FIG. 12 shows a simulation data diagram of the change in static temperature when the fluid flows through the variable diffuser 4, and (d) of FIG. 12 shows a simulation data diagram of the change in total temperature when the fluid flows through the variable diffuser 4. (e) of FIG. 13 shows a simulation data diagram of the change in density when the fluid flows through the variable diffuser 4, and (f) of FIG. 13 shows a simulation data diagram of the change in Mach number when the fluid flows through the variable diffuser 4. FIG. 14(g) shows a simulation data diagram of the change in viscosity of the fluid as it flows through the variable diffuser 4, and FIG. 14(h) shows a simulation data diagram of the change in turbulent kinetic energy of the fluid as it flows through the variable diffuser 4. The circled positions or regions where the gradient changes significantly are localized regions where the fluid exhibits at least one of distortion, transition, and singularity, i.e., measurement point densification regions. As can be seen from FIGS. 11 to 14, the static pressure, total pressure, and density on the blade surface of the variable diffuser 4 show clear gradients along the flow direction, and localized high-pressure and high-density regions are observed near the leading and trailing edges of the disk / cover. These are due to impingement loss and mixing loss, respectively. Both of these losses are significantly evident near the wall (only slightly indicated in the turbulent kinetic energy diagram). On the blade surface and in the passage of the variable diffuser 4, large gradients of static temperature and total temperature occur along the blade height direction, and the temperature on the side closer to the cover is significantly lower than the temperature on the side closer to the disk. This is because the cooling effect of the tip leakage vortex of the upstream impeller 3 acts mainly on the cover side of the variable diffuser 4. There is a significant increase in the gradients of static pressure, static temperature, and density along the radial direction within the passage of the variable diffuser 4, but there is also a significant decrease in the gradient of Mach number along the radial direction.This is due to the overlapping effects of deceleration, pressure buildup, and heating, and also to the large gradients of Mach number, viscosity, and turbulent kinetic energy along the axial direction, which are due to viscous dissipation in the wall boundary layer.

[0066] In some embodiments, the preset fluid parameters include fluid flow parameters and environmental parameters, where the fluid flow parameters include at least one of pressure, temperature, velocity, flow rate, vibration displacement, phase concentration, viscosity, Reynolds number, and surface tension of the fluid, and the fluid environmental parameters include at least one of sound pressure decibels, humidity, surface roughness, and wear of an environment in which the fluid is located.

[0067] The flow parameters reflect the flow characteristics of the fluid, and the environmental parameters reflect the characteristics of the environment in which the fluid is located, and since fluid detection includes both the flow parameters of the fluid and the environmental parameters of the fluid, the obtained fluid data is more accurate and comprehensive.

[0068] Specifically, pressure includes static pressure, total pressure, and differential pressure, temperature includes static temperature and total temperature, velocity includes mean velocity, instantaneous velocity, absolute velocity, relative velocity, and peripheral velocity, flow rate includes volumetric flow rate and mass flow rate, vibration displacement includes low frequency, medium frequency, and high frequency, phase concentration includes gas-liquid and liquid-solid, viscosity includes Newtonian and non-Newtonian, Reynolds number includes laminar flow, transitional flow, and turbulent flow, and surface tension includes static and dynamic.

[0069] Specifically, sound pressure decibels include fluid noise, mechanical noise, and electromagnetic noise, humidity includes absolute humidity and relative humidity, surface roughness includes average roughness and maximum height, and wear amount includes abrasive particles, adhesion, and fatigue.

[0070] In this embodiment, the fluid may be a medium in a gas phase, a liquid phase, or a gas-liquid two-phase flow, such as air, carbon dioxide gas, nitrogen gas, or helium gas.

[0071] In some embodiments, the preset boundary conditions include an inlet boundary condition, an outlet boundary condition, all contact wall boundary conditions, a periodic boundary condition, a rotating-stationary interaction boundary condition, and a turbulence model boundary condition. During the analysis phase of the simulation, the accuracy of the simulation results can be improved by limiting the relevant parameters of the preset boundary conditions. Specifically, the inlet boundary condition is set to the designed total temperature and total pressure boundary, and the turbulence intensity along the axial airflow direction is set to 5%. The outlet boundary condition is set to the mean static pressure at the start of the calculation, gradually increase the back pressure, and change to the designed mass flow rate as the total pressure ratio gradually increases. When the total pressure ratio begins to decrease, it is considered that the compressor is approaching its numerical stall point. The all contact wall boundary conditions are set to the adiabatic boundary condition and the no-slip boundary condition on the blade surface and the casing wall. The periodic boundary conditions are as follows: For single-passage calculations, the adjustable inlet guide vanes 2, impeller 3, disk cavity, and variable diffuser 4 are all single-blade passages, with rotating periodic surfaces along the circumferential boundaries on both sides of the passage. The full-circumference model is obtained by rotating and copying the single-blade model. The rotating-stationary interference boundary conditions are as follows: Commonly used boundary surface methods include the mixing plane method, frozen rotor method, and transient rotor-stator method. For single-passage calculations, the mixing plane method is used to circumferentially homogenize the physical quantities at the upstream boundary surface and transfer them to the downstream boundary surface, ignoring the effects of circumferential asymmetry. For full-circumference calculations, the frozen rotor method is used, where the rotor is analyzed in a rotating coordinate system and the stator in a stationary coordinate system. Information between the rotor and stator is transferred by interpolation, reflecting the effects of circumferential asymmetry on the upstream and downstream flow fields. The turbulence model boundary conditions are as follows: Using the SST turbulence model, the mass, momentum, and energy equations are discretized using second-order upwind finite difference. At least 10 mesh points are placed in the laminar sublayer region, and the wall function y+ is preferably close to 1.

[0072] Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that it is still possible to modify the technical solutions described in the above embodiments or to replace some of the technical features with equivalents, and such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions in the embodiments of the present invention. [Explanation of symbols]

[0073] 1 All aircraft entrance passage 2 adjustable inlet guide vanes 3 impeller 4 Variable Diffuser 5. Spiral casing 6 All aircraft exit passage 10 First gap 20 Second gap 41 Booster blade 42 Pressure booster passage 100 1st measurement point 200 2nd measurement point 300 3rd measurement point

Claims

1. 1. A variable diffuser having an impeller (3) provided upstream and a volute casing (5) provided downstream, the variable diffuser including a measurement point densification region provided for inspecting an internal flow field of the variable diffuser (4) and upstream and downstream flow fields, wherein flow field measurement points of the variable diffuser (4) are provided at intervals in the internal flow field of the variable diffuser and the upstream and downstream flow fields along a fluid flow direction, and the intervals between the flow field measurement points provided within the measurement point densification region are smaller than the intervals between the flow field measurement points provided outside the measurement point densification region.

2. 2. The variable diffuser according to claim 1, wherein a distance between adjacent flow field measurement points located closer to the tongue region of the volute casing is smaller than a distance between adjacent flow field measurement points located further from the tongue region of the volute casing.

3. 2. The variable diffuser according to claim 1, wherein the flow field measurement points include a plurality of first measurement point groups, wherein a booster chamber and a plurality of booster vanes are provided in the booster chamber at intervals in a circumferential direction, variable volume booster passages are formed between the plurality of booster vanes, and at least one first measurement point group is provided in each booster passage along a fluid flow direction, and an interval between the first measurement points provided within the measurement point densification region is smaller than an interval between the first measurement points provided outside the measurement point densification region, and the first measurement points are used to detect and acquire flow parameters and environmental parameters of the fluid in the booster passage.

4. 4. The variable diffuser according to claim 3, wherein a first gap (10) is provided between the variable diffuser (4) and the impeller (3), the flow field measurement points include a group of second measurement points (200) spaced apart in a circumferential direction of the first gap (10), the groups of second measurement points (200) are provided in one-to-one correspondence with each of the downstream pressure booster passages (42), the second measurement points (200) in each group are provided along a fluid flow direction, an interval between the second measurement points (200) provided within the measurement point densification region is smaller than an interval between the second measurement points (200) provided outside the measurement point densification region, and the second measurement points (200) are used to detect and acquire flow parameters and environmental parameters of the fluid in the first gap (10).

5. 5. The variable diffuser according to claim 4, wherein a second gap (20) is provided between the variable diffuser (4) and the volute casing (5), the flow field measurement points include a group of a plurality of third measurement points (300) spaced apart in a circumferential direction of the second gap (20), the groups of the third measurement points (300) and the pressure booster passages (42) are provided in one-to-one correspondence, the plurality of third measurement points (300) in each group are provided along a fluid flow direction, an interval between the third measurement points (300) provided within the measurement point densification region is smaller than an interval between the third measurement points (300) provided outside the measurement point densification region, and the third measurement points (300) are used to detect and acquire flow parameters and environmental parameters of the fluid in the second gap (20).

6. The variable diffuser according to claim 5, wherein the first measurement point (100), the second measurement point (200), and the third measurement point (300) are each provided with a detection sensor.

7. 6. The variable diffuser of claim 5, wherein the number of groups of the first measurement points is equal to the number of the booster passages, the number of groups of the second measurement points is equal to the number of the booster passages, and the number of groups of the third measurement points is equal to the number of the booster passages.

8. 6. The variable diffuser of claim 5, wherein each group of first measurement points (100) includes at least two first measurement points (100), each group of second measurement points (200) includes at least three second measurement points (200), and each group of third measurement points (300) includes at least three third measurement points (300).

9. 9. A centrifugal compressor comprising: the variable diffuser (4) according to any one of claims 1 to 8; an overall inlet passage (1); adjustable inlet guide vanes (2); an impeller (3); a volute casing (5); and an overall outlet passage (6), wherein the adjustable inlet guide vanes (2) are provided in the overall inlet passage (1); the impeller (3) is provided downstream of the adjustable inlet guide vanes (2); the variable diffuser (4) is provided downstream of the impeller (3); the volute casing (5) is provided downstream of the variable diffuser (4); and the overall outlet passage (6) is connected to an outlet of the volute casing (5).

10. 10. The centrifugal compressor according to claim 9, characterized in that a tip clearance is provided between the impeller (3) and the impeller cover, and a disc cavity is formed between the side of the impeller (3) remote from the adjustable inlet guide vanes (2) and the impeller cover.

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