Pneumatic design method for low-temperature compressor

Abstract

The present application provides a pneumatic design method for a low-temperature compressor. The pneumatic design method comprises: acquiring design input parameters of a centrifugal compressor, wherein the design input parameters comprise a design flow coefficient, a design Mach number, and a head coefficient; determining the model stage of the centrifugal compressor on the basis of the design flow coefficient; and on the basis of the design input parameters and the model stage of the centrifugal compressor, determining design parameters of flow components of the centrifugal compressor. The pneumatic design method of the present application can enable a centrifugal compressor to better satisfy the performance requirements of LNG low-temperature marine centrifugal compressor products, thereby improving design efficiency.

Description

Aerodynamic design method for cryogenic compressor TECHNICAL FIELD

[0001] The present application relates to the technical field of compressors, in particular to an aerodynamic design method for a cryogenic compressor. BACKGROUND

[0002] Liquefied natural gas (LNG) is regarded as an important transitional product for the future development of non-fossil energy, as a clean and efficient fossil energy, and its share in the global energy market is gradually expanding. At the same time, LNG is an energy source that is easy to transport and store, and can be transported by sea to all parts of the world, making the LNG transportation industry grow rapidly, and the demand for LNG ships as an important transportation tool has surged.

[0003] LNG cryogenic marine centrifugal compressor is a key equipment of LNG ship, the compressor is installed in the hold, and the space and safe operation of the unit are extremely high, which is significantly different from the conventional centrifugal compressor used in traditional chemical and refining processes. According to its role in the process, it can be divided into high-load centrifugal compressors and low-load centrifugal compressors. High-load centrifugal compressors are mainly used in different process flows such as gas displacement, cargo hold warming, LNG loading and unloading, etc. The compressor inlet operating temperature varies from -140℃ to 20℃, the medium molecular weight varies from 16 to 28, the minimum volumetric flow is about 40% of the maximum volumetric flow, and the fixed speed operation is adopted, so the high-load centrifugal compression needs to have high Mach number, wide range, high efficiency operation performance and flow regulation capacity. Low-load centrifugal compressors are mainly used for power system gas supply, the compressor inlet operating temperature varies from -90℃ to 20℃, the medium composition and volumetric flow are constant, and the fixed speed operation is adopted, so the low-load centrifugal compressor needs to have high efficiency and curve regulation capacity at variable Mach number. The existing conventional centrifugal compressor cannot meet the requirements of LNG cryogenic marine centrifugal compressor in structure and operating range.

[0004] SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, one object of the present application is to provide an aerodynamic design method for a cryogenic compressor, so that the centrifugal compressor designed thereby can better meet the performance requirements of LNG ships and improve design efficiency.

[0006] Embodiments of the first aspect of the application provide a method for aerodynamic design of a cryogenic compressor, the method comprising: obtaining design input parameters of the centrifugal compressor, the design input parameters comprising a design flow coefficient, a design Mach number, and an energy head coefficient; in response to the design flow coefficient being greater than or equal to 0.06 and less than or equal to 0.175, determining a model stage of the centrifugal compressor as a first model stage, the flow passage components of the first model stage comprising an adjustable inlet guide vane, an impeller, a fixed blade diffuser, a bend, an axial diffuser, and a discharge volute; in response to the design flow coefficient being less than 0.06, determining the model stage of the centrifugal compressor as a second model stage, the flow passage components of the second model stage comprising the impeller, an adjustable blade diffuser, the bend, and the discharge volute; and determining design parameters of the flow passage components of the centrifugal compressor according to the design input parameters and the model stage of the centrifugal compressor.

[0007] In some embodiments, the machine Mach number of the first model stage is greater than or equal to 0.9 and less than or equal to 1.1, and the energy head coefficient of the first model stage is greater than or equal to 0.7 and less than or equal to 0.8.

[0008] In some embodiments, the determining of the design parameters of the flow passage components of the centrifugal compressor according to the design input parameters and the model stage of the centrifugal compressor comprises: determining structural design parameters and aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters comprising an outlet flow angle of the impeller and an outlet cross-sectional average Mach number of the impeller; and determining structural design parameters of the fixed blade diffuser and the axial diffuser according to the structural design parameters and the aerodynamic parameters of the impeller.

[0009] In some embodiments, the determining of the structural design parameters and the aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters comprising the outlet flow angle of the impeller and the outlet cross-sectional average Mach number of the impeller, comprises: determining the structural design parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor; determining a position of maximum static pressure difference of the impeller under a design point operating condition and a flow state of the gas in a flow passage of the impeller according to the structural design parameters of the impeller; in response to the position of maximum static pressure difference being located within a range of 50%-100% of a blade length and the flow state of the gas in the flow passage being free of flow separation, obtaining the aerodynamic parameters of the impeller; otherwise, returning to the previous step and readjusting the structural design parameters of the impeller.

[0010] In some embodiments, the determining the structural design parameters of the fixed blade diffuser and the axial guide vane according to the structural design parameters and the aerodynamic parameters of the impeller comprises: determining initial design parameters of the fixed blade diffuser and the axial guide vane according to the structural design parameters and the aerodynamic parameters of the impeller; determining a first performance judgment parameter and a gas flow state according to the initial design parameters of the fixed blade diffuser and the axial guide vane; the first performance judgment parameter comprises an outlet flow angle of the fixed blade diffuser, an outlet cross-section average Mach number of the fixed blade diffuser, an inlet flow angle of the axial guide vane, and an inlet cross-section average Mach number of the axial guide vane; in response to the first performance judgment parameter and the gas flow state satisfying a preset judgment condition, determining the initial design parameters as the structural design parameters of the fixed blade diffuser and the axial guide vane, otherwise, readjusting the initial design parameters of the fixed blade diffuser and the axial guide vane and redetermining the design performance judgment parameter; wherein the preset judgment condition comprises one or more of the following: at a design Mach number design point, the outlet flow angle of the fixed blade diffuser is uniformly distributed, and the average value of the outlet flow angle is greater than or equal to 34° and less than or equal to 39°, the outlet cross-section average Mach number of the fixed blade diffuser is greater than or equal to 0.31 and less than or equal to 0.38, and the gas flow in the flow passage between the outlet of the fixed blade diffuser and the inlet of the axial guide vane is not separated; within a design Mach number high-efficiency region, the outlet flow angle of the fixed blade diffuser is uniformly distributed, and the average value of the outlet flow angle is greater than or equal to 32° and less than or equal to 45°, the outlet cross-section average Mach number of the fixed blade diffuser is greater than or equal to 0.28 and less than or equal to 0.52, and the gas separation in the meridian plane of the small flow region occurs on the shaft disc side; at the design Mach number design point, the inlet flow angle of the axial guide vane is uniformly distributed, and the average value of the inlet flow angle is greater than or equal to 34° and less than or equal to 39°, the inlet cross-section average Mach number of the axial guide vane is greater than or equal to 0.24 and less than or equal to 0.31, the blade installation angle of the axial guide vane exceeds 90°, the gas appears local separation within 30% to 70% of the blade height and the separation area disappears before entering the exhaust volute; within the design Mach number high-efficiency region, the inlet flow angle of the axial guide vane is uniformly distributed, and the average value of the inlet flow angle is greater than or equal to 32° and less than or equal to 40°, the inlet cross-section average Mach number of the axial guide vane is greater than or equal to 0.22 and less than or equal to 0.44; the design Mach number high-efficiency region refers to a flow range in which the polytropic efficiency of the first model stage from the inlet of the impeller to the outlet of the exhaust volute is greater than or equal to 70% at the design Mach number.

[0011] In some embodiments, the first performance determining parameter further comprises: an outlet flow angle of the impeller, an outlet cross-section average Mach number of the impeller, an inlet flow angle of the exhaust volute, and an inlet cross-section average Mach number of the exhaust volute; and wherein the preset determining condition further comprises one or more of: in the design Mach number efficient zone, the outlet flow angle of the impeller is uniformly distributed, and an average value of the outlet flow angle of the impeller is greater than or equal to 20° and less than or equal to 32°, the outlet cross-section average Mach number of the impeller is greater than or equal to 0.67 and less than or equal to 0.74; in the design Mach number efficient zone, the gas has no flow separation in the meridian flow passage at the bend; in the design Mach number efficient zone, the inlet flow angle of the exhaust volute is uniformly distributed, and an average value of the inlet flow angle of the exhaust volute is greater than or equal to 87° and less than or equal to 93°, the inlet cross-section average Mach number of the exhaust volute is greater than or equal to 0.15 and less than or equal to 0.28.

[0012] In some embodiments, the blades of the fixed-vane diffuser are full-height wedge-shaped blades, a ratio of an inlet diameter D3 of the fixed-vane diffuser to a diameter D2 of the impeller satisfies: 1.15≤D3 / D2≤1.25; a ratio of an outlet diameter D4 of the fixed-vane diffuser to the diameter D2 of the impeller satisfies: 1.60≤D4 / D2≤1.70; a ratio of an inlet width b3 of the fixed-vane diffuser to an outlet width b2 of the impeller satisfies: 0.85≤b3 / b2≤1; a ratio of an outlet width b4 of the fixed-vane diffuser to the inlet width b3 of the fixed-vane diffuser satisfies: b4 / b3=1; a number of the blades of the fixed-vane diffuser is greater than or equal to 7 and less than or equal to 13; and the number of the blades of the fixed-vane diffuser is less than a number of the blades of the impeller; an inlet installation angle of the fixed-vane diffuser is greater than an outlet flow angle of the impeller, and a difference between the two is greater than or equal to 12° and less than or equal to 15°.

[0013] In some embodiments, a ratio of an inlet width b5 of the axial flow director to an outlet width b4 of the fixed-vane diffuser satisfies: 0.75≤b5 / b4≤0.8; a ratio of a blade length L of the axial flow director to the diameter D2 of the impeller satisfies: 0.2≤L / D2≤0.25; a ratio of a center diameter D5 of the axial flow director to the diameter D2 of the impeller satisfies: 1.85≤D5 / D2≤1.90; a ratio of an inlet relative position L5 of the axial flow director to the diameter of the impeller satisfies: 0.2≤L5 / D2≤0.25; an outlet installation angle of the axial flow director is greater than or equal to 100° and less than or equal to 110°, and an inlet installation angle of the axial flow director is substantially consistent with an outlet installation angle of the fixed-vane diffuser; a number of the blades of the axial flow director is greater than or equal to 33 and less than or equal to 53.

[0014] In some embodiments, the polytropic efficiency of the first model stage from the inlet of the impeller to the outlet of the discharge volute at the design Mach number and the design flow coefficient is greater than or equal to 0.83 and less than or equal to 0.85, and the high efficiency flow range of the first model stage is 80%-115% of the design point.

[0015] In some embodiments, the guide vane opening of the adjustable inlet guide vanes is -70° to +20°, and the high efficiency flow range of the first model stage is 40%-120% of the design point.

[0016] In some embodiments, the machine Mach number of the second model stage is greater than or equal to 0.9 and less than or equal to 1.2, and the energy head coefficient of the second model stage is greater than or equal to 0.7 and less than or equal to 0.8.

[0017] In some embodiments, the design parameters of the flow components of the centrifugal compressor are determined according to the design input parameters and the model stage of the centrifugal compressor, including determining the structural design parameters and aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters including the outlet flow angle of the impeller and the outlet Mach number of the impeller; and determining the structural design parameters of the adjustable blade diffuser according to the structural design parameters and the aerodynamic parameters of the impeller.

[0018] In some embodiments, the structural design parameters and aerodynamic parameters of the impeller are determined according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters including the outlet flow angle of the impeller and the outlet Mach number of the impeller, including: determining the structural design parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor; determining the position of the maximum static pressure difference of the impeller at the design point working condition and the flow state of the gas in the flow passage of the impeller according to the structural design parameters of the impeller; obtaining the aerodynamic parameters of the impeller in response to the position of the maximum static pressure difference being located in the range of 50%-100% of the blade length and the gas not appearing flow separation in the flow passage; otherwise, returning to the previous step and readjusting the structural design parameters of the impeller.

[0019] In some embodiments, the determining the structural design parameters of the adjustable blade diffuser according to the structural design parameters and the aerodynamic parameters of the impeller comprises: determining initial design parameters of the adjustable blade diffuser according to the structural design parameters and the aerodynamic parameters of the impeller, the initial design parameters of the adjustable blade diffuser including an initial installation angle and an angle adjustment range; determining second performance judgment parameters at different angles and performance curves of the second model stage at different angles according to the initial design parameters of the adjustable blade diffuser, the second performance judgment parameters including an inlet flow angle, an inlet cross-sectional average Mach number, an outlet flow angle, and an outlet cross-sectional average Mach number of the adjustable blade diffuser; in response to the second performance judgment parameters and the performance curves satisfying a preset judgment condition, determining the initial design parameters as the structural design parameters of the adjustable blade diffuser, otherwise, readjusting the initial design parameters of the adjustable blade diffuser and redetermining the second performance judgment parameters; wherein the preset judgment condition includes one or more of the following: in an initial angle design Mach number efficient region, an average value of the inlet flow angle of the adjustable blade diffuser is greater than or equal to 15° and less than or equal to 30°, and an outlet cross-sectional average Mach number of the adjustable blade diffuser is greater than or equal to 0.58 and less than or equal to 0.80; in the initial angle design Mach number efficient region, an average value of the outlet flow angle of the adjustable blade diffuser is greater than or equal to 45° and less than or equal to 55°, and the outlet cross-sectional average Mach number of the adjustable blade diffuser is greater than or equal to 0.16 and less than or equal to 0.35; in a regulated angle design Mach number, a change range of an average value of the inlet flow angle of the adjustable blade diffuser compared to an average value of the inlet flow angle at the initial angle is less than 10°, and a change range of an average value of the outlet flow angle of the adjustable blade diffuser compared to an average value of the outlet flow angle at the initial angle is less than 20°.

[0020] In some embodiments, the second performance judgment parameters further include: a flow separation area ratio of the gas in the meridian flow passage at the bend, an inlet flow angle of the exhaust volute, and a ratio of a tangential velocity of the gas at the inlet of the exhaust volute to a peripheral velocity of the impeller; and wherein the preset judgment condition further includes one or more of the following: in the design Mach number efficient region, the flow separation area ratio of the gas in the meridian flow passage at the bend is less than 50%, and the separation area is concentrated on the shroud side; in the design Mach number efficient region, the inlet flow angle of the exhaust volute is uniformly distributed, and an average value of the inlet flow angle is greater than or equal to 45° and less than or equal to 60°, and the ratio of the tangential velocity of the gas at the inlet of the exhaust volute to the peripheral velocity of the impeller is less than 0.155.

[0021] In some embodiments, the blades of the adjustable blade diffuser are full height wedge-shaped blades; the ratio of the initial angle inlet diameter D3 of the adjustable blade diffuser to the diameter D2 of the impeller satisfies: 1.15≤D3 / D2≤1.25; the ratio of the initial angle outlet diameter D4 of the adjustable blade diffuser to the diameter D2 of the impeller satisfies: 1.90≤D4 / D2≤1.95; the ratio of the initial angle inlet width b3 of the adjustable blade diffuser to the outlet width b2 of the impeller satisfies: 0.93≤b3 / b2≤1; the ratio of the initial angle outlet width to the inlet width of the adjustable blade diffuser is 1; the initial angle blade number of the adjustable blade diffuser is greater than or equal to 7 and less than or equal to 13, and the initial angle blade number of the adjustable blade diffuser is less than the blade number of the impeller; the initial installation angle of the inlet of the adjustable blade diffuser is less than or equal to the outlet flow angle of the impeller, and the difference between the two is greater than or equal to 0 and less than or equal to 5°; the initial installation angle of the outlet of the adjustable blade diffuser is greater than the initial installation angle of the inlet of the adjustable blade diffuser, and the difference between the two is greater than or equal to 15° and less than or equal to 25°; the angle adjustment range is ±10° of the initial installation angle; the adjustment center of the adjustable blade diffuser is located at 30%-40% of the blade centerline of the adjustable blade diffuser, and after the adjustment angle, the ratio of the inlet diameter D3 of the adjustable blade diffuser to the diameter D2 of the impeller satisfies: D3 / D2≥1.1, and the initial installation angle of the inlet of the adjustable blade diffuser is greater than or equal to 5°.

[0022] In some embodiments, the two ends of the curved channel in the second model stage are connected to the adjustable blade diffuser and the exhaust volute, the outlet flow of the adjustable blade diffuser enters the exhaust volute after a 90° turn through the curved channel, the circular arc inlet of the curved channel is tangent to the wheel cover and shaft disc of the straight line segment of the outlet of the adjustable blade diffuser, and the ratio of the inlet width b5 of the curved channel to the initial angle outlet width b4 of the adjustable blade diffuser satisfies: 0.8≤b5 / b4≤2.5.

[0023] In some embodiments, the polytropic efficiency of the second model stage at the design Mach number and the design flow coefficient is greater than or equal to 0.79 and less than or equal to 0.82, and the high efficiency flow range applicable from the inlet of the impeller to the outlet of the exhaust volute of the second model stage is 80%-115% of the design point.

[0024] In some embodiments, the opening of the adjustable blade diffuser is controlled between -10° and +10°, and the high efficiency flow range applicable by the second model stage is 40%-135% of the design point.

[0025] In some embodiments, the exhaust volute is an equal cross-section volute with equal through-flow cross sections in the circumferential direction.

[0026] The above description is only a summary of the technical solutions of the present application. In order to make the technical means of the present application more clearly understood and implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0027] In the drawings, like reference numerals refer to same or similar components throughout the several views, unless otherwise indicated. These drawings are not necessarily to scale. It should be understood that these drawings only depict some embodiments in accordance with the disclosure and should not be considered as limiting the scope of the disclosure.

[0028] Fig. 1 is a flow chart of a method for aerodynamic design of a centrifugal compressor for LNG carrier according to an embodiment of the present application;

[0029] Fig. 2 is a schematic diagram of a first model stage of a centrifugal compressor for LNG carrier according to an embodiment of the present application;

[0030] Fig. 3 is a schematic diagram of a second model stage of a centrifugal compressor for LNG carrier according to an embodiment of the present application;

[0031] Fig. 4 is a schematic diagram of inlet and outlet angles of a fixed blade diffuser of the first model stage of a centrifugal compressor for LNG carrier according to an embodiment of the present application;

[0032] Fig. 5 is a schematic diagram of inlet and outlet angles of an axial inducer of the first model stage of a centrifugal compressor for LNG carrier according to an embodiment of the present application;

[0033] Fig. 6 is a meridional relative velocity distribution diagram of the first model stage according to an embodiment of the present application;

[0034] Fig. 7 is a static pressure distribution diagram of a shroud side pressure surface and a suction surface of an impeller of the first model stage according to an embodiment of the present application;

[0035] Fig. 8 is a relative velocity distribution diagram of a 10% blade height cross section of the impeller of the first model stage according to an embodiment of the present application;

[0036] Fig. 9 is a relative velocity distribution diagram of a 50% blade height cross section of the impeller of the first model stage according to an embodiment of the present application;

[0037] Fig. 10 is a relative velocity distribution diagram of a 90% blade height cross section of the impeller of the first model stage according to an embodiment of the present application;

[0038] Fig. 11 is a relative velocity distribution diagram of a 10% blade height cross section of a blade diffuser of the first model stage according to an embodiment of the present application;

[0039] Fig. 12 is a relative velocity distribution diagram of a 50% blade height cross section of the blade diffuser of the first model stage according to an embodiment of the present application;

[0040] Fig. 13 is a relative velocity distribution diagram of a 90% blade height section of the blade diffuser of the first model stage according to the embodiment of the present application;

[0041] Fig. 14 is a flow angle distribution diagram of an outlet section of the blade diffuser of the first model stage according to the embodiment of the present application;

[0042] Fig. 15 is a relative velocity distribution diagram of a 10% blade height section of the axial guide vane of the first model stage according to the embodiment of the present application;

[0043] Fig. 16 is a relative velocity distribution diagram of a 50% blade height section of the axial guide vane of the first model stage according to the embodiment of the present application;

[0044] Fig. 17 is a relative velocity distribution diagram of a 90% blade height section of the axial guide vane of the first model stage according to the embodiment of the present application;

[0045] Fig. 18 is a velocity distribution diagram of a center section of the exhaust volute of the first model stage according to the embodiment of the present application;

[0046] Fig. 19 is a velocity distribution diagram of any section of the exhaust volute of the first model stage according to the embodiment of the present application;

[0047] Fig. 20 is a relative velocity distribution diagram of the meridian flow passage of the second model stage according to the embodiment of the present application;

[0048] Fig. 21 is a static pressure distribution diagram of the impeller of the second model stage according to the embodiment of the present application on the pressure surface and the suction surface of the shaft cover disc side;

[0049] Fig. 22 is a relative velocity distribution diagram of a 10% blade height section of the impeller of the second model stage according to the embodiment of the present application;

[0050] Fig. 23 is a relative velocity distribution diagram of a 50% blade height section of the impeller of the second model stage according to the embodiment of the present application;

[0051] Fig. 24 is a relative velocity distribution diagram of a 90% blade height section of the impeller of the second model stage according to the embodiment of the present application;

[0052] Fig. 25 is a relative velocity distribution diagram of a 10% blade height section of the blade diffuser of the second model stage according to the embodiment of the present application;

[0053] Fig. 26 is a relative velocity distribution diagram of a 50% blade height section of the blade diffuser of the second model stage according to the embodiment of the present application;

[0054] Fig. 27 is a relative velocity distribution diagram of a 90% blade height section of the blade diffuser of the second model stage according to the embodiment of the present application;

[0055] Fig. 28 is a velocity distribution diagram of a center section of the exhaust volute of the second model stage according to the embodiment of the present application;

[0056] Figure 29 is a velocity profile of any cross section of the second model level exhaust volute according to an embodiment of the present application. DETAILED DESCRIPTION

[0057] The embodiments of the present application will be described in detail with reference to the drawings. The following examples are only used to more clearly illustrate the technical scheme of the present application, thus only serve as examples, and cannot be used to limit the protection scope of the present application.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the specification herein is for describing particular embodiments only and is not intended to be limiting of the application; the use herein of terms such as "comprise" and "comprising", and "have" and "having", and any variations thereof, is intended to cover the presence of successively stated integers or features but not to preclude the presence of other integers or features. The use of "including", "containing" or "comprising" and variations thereof herein is meant to encompass the presence for the stated feature, integer or step but not to preclude the presence or addition of one or more other features, integers, steps or groups thereof.

[0059] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0060] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearance of the phrase in various places in the specification is not necessarily all referring to the same embodiment, or to the same alternative embodiment, nor is it necessary that all embodiments include the same feature, structure or characteristic. It will be explicitly understood by those of ordinary skill in the art that the embodiments described herein can be combined with other embodiments.

[0061] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0062] In the description of the embodiments of the present application, the term "a plurality of" refers to two or more (including two), and similarly, "a plurality of groups" refers to two or more groups (including two groups), and "a plurality of pieces" refers to two or more pieces (including two pieces).

[0063] In the description of the embodiments of the present application, the orientations or positional relationships indicated by the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0064] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0065] As shown in FIG. 1, the embodiments of the present application provide a pneumatic design method 100 of a cryogenic compressor, which comprises:

[0066] Step S110: obtaining design input parameters of the centrifugal compressor, the design input parameters comprising a design flow coefficient, a design Mach number and an energy head coefficient.

[0067] Step S120: in response to the design flow coefficient being greater than or equal to 0.06 and less than or equal to 0.175, determining that the model stage of the centrifugal compressor is a first model stage, the flow passage components of the first model stage comprising an adjustable inlet guide vane, an impeller, a fixed blade diffuser, a bend, an axial flow guide and an exhaust volute; in response to the design flow coefficient being less than 0.06, determining that the model stage of the centrifugal compressor is a second model stage, the flow passage components of the second model stage comprising an impeller, an adjustable blade diffuser, a bend and an exhaust volute.

[0068] Step S130: determining the design parameters of each flow passage component of the centrifugal compressor according to the design input parameters and the model stage of the centrifugal compressor.

[0069] In step S120, according to the process flow function of the LNG cryogenic marine centrifugal compressor, the specific structure of the model stage is divided into two categories according to different design flow coefficients: the first model stage and the second model stage.

[0070] As shown in FIG. 2, along the gas flow direction, the flow passage components of the first model stage include an adjustable inlet guide vane 1, an impeller 2, a fixed blade diffuser 3a, a bend 4, an axial flow guide 5, and an exhaust volute 6. The bend 4 serves to connect the fixed blade diffuser 3a and the axial flow guide 5, and guides the gas flow at the outlet of the fixed blade diffuser 3a into the axial flow guide 5. The first model stage can be extended to the modeling design of low-temperature marine compressor products with a flow coefficient satisfying 0.06≤φ≤0.175.

[0071] As shown in FIG. 3, along the gas flow direction, the flow passage components of the second model stage include an impeller 2, an adjustable blade diffuser 3b, a bend 4, and an exhaust volute 6; the bend 4 of the second model stage serves to connect the adjustable blade diffuser 3b and the exhaust volute 6, and the gas flow at the outlet of the adjustable blade diffuser 3b enters the exhaust volute 6 after a 90° turn. The second model stage can be extended to the modeling design of low-temperature marine compressor products with a flow coefficient φ<0.06.

[0072] In some embodiments, the machine Mach number of the first model stage is greater than or equal to 0.9 and less than or equal to 1.1, and the energy coefficient of the first model stage is greater than or equal to 0.7 and less than or equal to 0.8.

[0073] In some embodiments, the step S130 comprises:

[0074] According to the design input parameters and the model stage of the centrifugal compressor, the structural design parameters and the aerodynamic parameters of the impeller are determined, the aerodynamic parameters including the outlet flow angle of the impeller and the outlet cross-section average Mach number of the impeller;

[0075] According to the structural design parameters and the aerodynamic parameters of the impeller, the structural design parameters of the fixed blade diffuser and the axial flow guide are determined.

[0076] When designing the structural size of the flow passage components of the centrifugal compressor, the structural design parameters of the impeller 2 can be calculated first, and the aerodynamic parameters at the outlet of the impeller 2 are calculated according to the structural design parameters, for the subsequent calculation of the structural design parameters of the flow passage components.

[0077] In some embodiments, according to the design input parameters and the model stage of the centrifugal compressor, the structural design parameters and the aerodynamic parameters of the impeller are determined, the aerodynamic parameters including the outlet flow angle of the impeller and the outlet cross-section average Mach number of the impeller comprising:

[0078] According to the design input parameters and the model stage of the centrifugal compressor, the structural design parameters of the impeller are determined.

[0079] According to the structural design parameters of the impeller, the position with the maximum static pressure difference of the impeller under the design point working condition and the flow state of the gas in the flow passage of the impeller are determined.

[0080] In response to the position of the maximum static pressure difference being in the range of 50%-100% of the blade length and the gas not appearing to be separated in the flow passage, the aerodynamic parameters of the impeller are obtained; otherwise, return to the previous step and re-adjust the structural design parameters of the impeller.

[0081] The impeller 2 can be a three-dimensional impeller, and the blades can be long and short blades. The position of the maximum static pressure difference of the impeller at the design point working condition can be obtained by computer fluid simulation, for example, by calculating the static pressure distribution diagram of the impeller at the shaft cover disc side pressure surface and the suction surface to determine the position of the maximum static pressure difference. In some embodiments, the position of the maximum static pressure difference of the impeller at the design point working condition is in the range of 50%-100% of the blade length, which means that the load is concentrated in the middle and rear part of the impeller, so that the first model stage has high efficiency and a wide working condition range. At the same time, the impeller design also needs to ensure that the gas does not appear to be separated in the flow passage. Specifically, the flow state of the impeller at different positions can be detected or calculated by test or calculation simulation, so as to determine whether the flow is separated.

[0082] In the process of determining the structural design parameters of the impeller, the structural design parameters of the impeller need to be iteratively calculated according to the design size requirements of the first model stage until all the above evaluation conditions are met.

[0083] In some embodiments, determining the structural design parameters of the fixed blade diffuser 3a and the axial guide 5 according to the structural design parameters and the aerodynamic parameters of the impeller 2 comprises:

[0084] determining the initial design parameters of the fixed blade diffuser 3a and the axial guide 5 according to the structural design parameters and the aerodynamic parameters of the impeller 2;

[0085] determining the first performance judgment parameters and the gas flow state according to the initial design parameters of the fixed blade diffuser 3a and the axial guide 5; the first performance judgment parameters include the outlet flow angle of the fixed blade diffuser 3a, the outlet section average Mach number of the fixed blade diffuser 3a, the inlet flow angle of the axial guide 5, and the inlet section average Mach number of the axial guide 5;

[0086] In response to the first performance judgment parameters and the gas flow state satisfying the preset judgment condition, the initial design parameters are determined as the structural design parameters of the fixed blade diffuser 3a and the axial guide 5; otherwise, the initial design parameters of the fixed blade diffuser 3a and the axial guide 5 are re-adjusted, and the design performance judgment parameters are re-determined.

[0087] The preset judgment condition includes one or more of the following:

[0088] (i) At the design Mach number design point, the outlet flow angle distribution of the fixed-blade diffuser 3a is uniform, and the average value of the outlet flow angle is greater than or equal to 34° and less than or equal to 39°, the average Mach number of the outlet section of the fixed-blade diffuser 3a is greater than or equal to 0.31 and less than or equal to 0.38, and the gas flow in the flow passage between the outlet of the fixed-blade diffuser 3a and the inlet of the axial guide vane is not separated;

[0089] (ii) In the design Mach number efficient region, the outlet flow angle distribution of the fixed-blade diffuser 3a is uniform, and the average value of the outlet flow angle is greater than or equal to 32° and less than or equal to 45°, the average Mach number of the outlet section of the fixed-blade diffuser 3a is greater than or equal to 0.28 and less than or equal to 0.52, and the separation of the gas in the low-flow region meridian plane occurs on the shaft side;

[0090] (iii) At the design Mach number design point, the inlet flow angle distribution of the axial diffuser 5 is uniform, and the average value of the inlet flow angle is greater than or equal to 34° and less than or equal to 39°, the average Mach number of the inlet section of the axial diffuser 5 is greater than or equal to 0.24 and less than or equal to 0.31, the blade installation angle of the axial diffuser 5 exceeds 90°, the gas appears local separation in the range of 30% to 70% of the blade height and the separation area disappears before entering the exhaust volute 6;

[0091] (iv) In the design Mach number efficient region, the inlet flow angle distribution of the axial diffuser 5 is uniform, and the average value of the inlet flow angle is greater than or equal to 32° and less than or equal to 40°, the average Mach number of the inlet section of the axial diffuser 5 is greater than or equal to 0.22 and less than or equal to 0.44.

[0092] The design Mach number efficient region refers to a flow range in which the polytropic efficiency from the inlet of the impeller to the outlet of the exhaust volute is greater than or equal to 70% at the design Mach number.

[0093] For the first model stage, the fixed-blade diffuser 3a and the axial guide vane 5 can be jointly designed, the inlet structure of the fixed-blade diffuser 3a depends on the aerodynamic parameters at the outlet of the impeller 2, the outlet structure is jointly designed with the inlet structure of the axial guide vane 5, and the flow angle and the Mach number between the two are strictly controlled in a suitable range, and the outlet structure of the axial guide vane 5 depends on the exhaust volute 6 capable of meeting the requirements of the marine compressor. Through iterative calculation, the flow loss in the diffuser 3a is small, there is no obvious separation, the gas flows smoothly and efficiently into the axial guide vane 5, the flow loss in the axial guide vane 5 is small, and the outlet flow angle is not obviously changed under various working conditions.

[0094] After the initial design parameters of the fixed-vane diffuser 3a and the axial flow guide 5 are determined, the first performance determination parameter can be calculated, and whether the parameters of the fixed-vane diffuser 3a and the axial flow guide 5 meet the requirements can be determined according to whether the first performance determination parameter and the gas flow state meet the preset determination condition. In some embodiments, the preset determination condition can include one or more of the above (i) to (iv), or all of the above (i) to (iv).

[0095] In some embodiments, the first performance determination parameter further includes the outlet flow angle of the impeller 2, the outlet cross-section average Mach number of the impeller 2, the inlet flow angle of the exhaust volute 6, and the inlet cross-section average Mach number of the exhaust volute 6. And the preset determination condition further includes one or more of the following:

[0096] (i) In the design Mach number efficient region, the outlet flow angle of the impeller 2 is uniformly distributed, and the average value of the outlet flow angle of the impeller 2 is greater than or equal to 20° and less than or equal to 32°, the outlet cross-section average Mach number of the impeller 2 is greater than or equal to 0.67 and less than or equal to 0.74;

[0097] (ii) In the design Mach number efficient region, the gas has no flow separation in the meridian flow passage at the bend 4;

[0098] (iii) In the design Mach number efficient region, the inlet flow angle of the exhaust volute 6 is uniformly distributed, and the average value of the inlet flow angle of the exhaust volute 6 is greater than or equal to 87° and less than or equal to 93°, the inlet cross-section average Mach number of the exhaust volute 6 is greater than or equal to 0.15 and less than or equal to 0.28.

[0099] In addition to the above-mentioned key aerodynamic parameters that directly affect the performance of the combined design of the fixed-vane diffuser 3a and the axial flow guide 5, the first performance determination parameter can also include other aerodynamic parameters of the throughflow cross-section, such as the outlet flow angle of the impeller, the outlet cross-section average Mach number, the inlet flow angle of the exhaust volute 6, and the inlet cross-section average Mach number. These aerodynamic parameters also have an important influence on the performance of the model stage, so when calculating the structural design parameters, the above-mentioned aerodynamic parameters can also be included in the first performance determination parameter for consideration.

[0100] In some embodiments, as shown in FIG. 4, the vanes 31 of the fixed-vane diffuser 3a are full-height wedge-shaped vanes, and the fixed-vane diffuser 3a can be designed according to the following requirements: the ratio of the inlet diameter D3 of the fixed-vane diffuser 3a to the diameter D2 of the impeller 2 satisfies: 1.15≤D3 / D2≤1.25; the ratio of the outlet diameter D4 of the fixed-vane diffuser 3a to the diameter D2 of the impeller 2 satisfies: 1.60≤D4 / D2≤1.70; the ratio of the inlet width b3 of the fixed-vane diffuser 3a to the outlet width b2 of the impeller 2 satisfies: 0.85≤b3 / b2≤1; the ratio of the outlet width b4 of the fixed-vane diffuser 3a to the inlet width b3 of the fixed-vane diffuser 3a satisfies: b4 / b3=1; the number of vanes of the fixed-vane diffuser 3a is greater than or equal to 7 and less than or equal to 13; the number of vanes of the fixed-vane diffuser 3a is less than the number of vanes of the impeller 2; the inlet installation angle of the fixed-vane diffuser 3a is greater than the outlet flow angle of the impeller 2, and the difference between the two is greater than or equal to 12° and less than or equal to 15°.

[0101] In some embodiments, as shown in FIG. 5, the ratio of the inlet width b5 of the axial flow guide 5 to the outlet width b4 of the fixed-vane diffuser 3a satisfies: 0.75≤b5 / b4≤0.8; the ratio of the vane length L of the vanes 51 of the axial flow guide 5 to the diameter D2 of the impeller 2 satisfies: 0.2≤L / D2≤0.25; the ratio of the center diameter D5 of the axial flow guide 5 to the diameter D2 of the impeller 2 satisfies: 1.85≤D5 / D2≤1.90; the ratio of the inlet relative position L5 of the axial flow guide 5 to the diameter of the impeller 2 satisfies: 0.2≤L5 / D2≤0.25; the outlet installation angle of the axial flow guide 5 is greater than or equal to 100° and less than or equal to 110°, and the inlet installation angle of the axial flow guide 5 is substantially consistent with the outlet installation angle of the fixed-vane diffuser 3a; the number of vanes of the axial flow guide 5 is greater than or equal to 33 and less than or equal to 53.

[0102] The "substantially consistent" inlet installation angle of the axial flow guide 5 with the outlet installation angle of the fixed-vane diffuser 3a means that the installation angles of the two components are designed to match each other to ensure that the fluid can maintain low flow loss and good flow characteristics when it smoothly transitions from the diffuser to the flow guide. "Substantially consistent" does not mean that the two angles must be exactly the same, but rather that they are designed to coordinate with each other, allowing for a certain tolerance range to accommodate actual conditions during manufacturing and assembly. This design approach ensures efficient and stable operation of the entire fluid transmission system.

[0103] In some embodiments, the polytropic efficiency of the first model stage from the inlet of the impeller to the outlet of the exhaust volute at the design Mach number and the design flow coefficient is greater than or equal to 0.83 and less than or equal to 0.85, and the high-efficiency flow range applicable to the first model stage is 80%-115% of the design point.

[0104] In some embodiments, the guide vane opening of the adjustable inlet guide vane 1 is -70° to +20°, and the high-efficiency flow range applicable to the first model stage is 40%-120% of the design point.

[0105] The high-efficiency flow range applicable to the first model stage generally refers to a flow range within which the impeller machine can work with high efficiency. For example, the high-efficiency flow range refers to a flow range within which the polytropic efficiency of the model stage from the inlet of the impeller to the flange outlet is higher than 70%.

[0106] By setting the adjustable inlet guide vane 1 and the corresponding guide vane opening, the applicable flow range of the first model stage can be significantly widened.

[0107] In some embodiments, the machine Mach number of the second model stage is greater than or equal to 0.9 and less than or equal to 1.2, and the energy head coefficient of the second model stage is greater than or equal to 0.7 and less than or equal to 0.8.

[0108] In some embodiments, step S130 comprises: determining the structural design parameters and aerodynamic parameters of the impeller 2 according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters including the outlet flow angle of the impeller 2 and the outlet Mach number of the impeller 2; and determining the structural design parameters of the adjustable blade diffuser 3b according to the structural design parameters and the aerodynamic parameters of the impeller 2.

[0109] For the case where the design flow coefficient is less than 0.06, the second model stage is selected and the structural design parameters of the flow passage components are calculated, mainly including the structural design of the impeller 2 and the structural design of the adjustable blade diffuser 3b. The design of the adjustable blade diffuser 3b can achieve the requirements of wide model stage range and high efficiency, and can be applied to different machine Mach numbers, and can adapt to the case where the inlet temperature deviation of the LNG ship compressor operating at a constant speed is up to 140℃.

[0110] In some embodiments, the determining the structural design parameters and the aerodynamic parameters of the impeller 2 according to the design input parameters and the model stage of the centrifugal compressor includes: determining the structural design parameters of the impeller 2 according to the design input parameters and the model stage of the centrifugal compressor; determining a position of maximum static pressure difference of the impeller 2 at the design point operating condition and a flow state of the gas in the flow passage of the impeller 2 according to the structural design parameters of the impeller 2; in response to the position of maximum static pressure difference being located in a range of 50%-100% of the blade length and the gas not appearing flow separation in the flow passage, obtaining the aerodynamic parameters of the impeller 2; otherwise, returning to the previous step and readjusting the structural design parameters of the impeller 2.

[0111] The impeller 2 can be a three-dimensional impeller, and the position of maximum static pressure difference of the impeller 2 being located in a range of 50%-100% of the blade length means that the load of the impeller 2 is concentrated in the middle and rear part. After the structural design parameters of the impeller 2 are determined, the aerodynamic parameters of the outlet of the impeller 2 are extracted, because the outlet structure of the impeller 2 needs to be adapted to the inlet structure of the adjustable blade diffuser 3b, which can be used for subsequent determination of the structural design parameters of the adjustable blade diffuser 3b.

[0112] In some embodiments, the determining the structural design parameters of the adjustable blade diffuser 3b according to the structural design parameters and the aerodynamic parameters of the impeller 2 includes: determining initial design parameters of the adjustable blade diffuser 3b according to the structural design parameters and the aerodynamic parameters of the impeller 2, the initial design parameters of the adjustable blade diffuser 3b including an initial installation angle and an angle adjustment range; determining second performance judgment parameters at different angles and performance curves of the second model stage at different angles according to the initial design parameters of the adjustable blade diffuser 3b, the second performance judgment parameters including an inlet flow angle, an inlet cross-sectional average Mach number, an outlet flow angle and an outlet cross-sectional average Mach number of the adjustable blade diffuser 3b; in response to the second performance judgment parameters and the performance curves satisfying a preset judgment condition, determining the initial design parameters as the structural design parameters of the adjustable blade diffuser 3b, otherwise, readjusting the initial design parameters of the adjustable blade diffuser 3b and redetermining the second performance judgment parameters.

[0113] The performance curves of the second model stage present the following regularities: (a) as the machine Mach number of the model stage increases, the performance curves move in the direction of increasing flow rate; (b) when the adjustable blade diffuser is adjusted within ±0-5°, the performance curves move as a whole through CFD analysis, and the trend presented at different machine Mach numbers is basically consistent with (a); (c) when the adjustable blade diffuser is adjusted within ±5-10°, the performance of the model stage is basically to the maximum adjustable range, and the performance curves at smaller machine Mach numbers present the characteristics of a wider range.

[0114] In some embodiments, the preset judgment condition of the second model stage includes one or more of the following:

[0115] (I) in the initial angle design Mach number efficient region, the average value of the inlet flow angle of the adjustable blade diffuser is greater than or equal to 15° and less than or equal to 30°, and the average Mach number of the outlet section of the adjustable blade diffuser is greater than or equal to 0.58 and less than or equal to 0.80;

[0116] (II) in the initial angle design Mach number efficient region, the average value of the outlet flow angle of the adjustable blade diffuser is greater than or equal to 45° and less than or equal to 55°, and the average Mach number of the outlet section of the adjustable blade diffuser is greater than or equal to 0.16 and less than or equal to 0.35;

[0117] (III) in the regulated angle design Mach number, the change range of the average value of the inlet flow angle of the adjustable blade diffuser 3b compared with the average value of the inlet flow angle in the initial angle is less than 10°, and the change range of the average value of the outlet flow angle of the adjustable blade diffuser 3b compared with the average value of the outlet flow angle in the initial angle is less than 20°.

[0118] When the second performance determination parameter and the performance curve cannot meet the preset determination condition, the initial design parameters of the adjustable blade diffuser 3b can be adjusted within a preset range, and the second performance determination parameter and the performance curve under different angles are recalculated according to the adjusted initial design parameters, so as to continuously iterate and optimize, and finally obtain the structure design parameters which can completely meet the preset determination condition.

[0119] In some embodiments, the second performance determination parameter further includes: the flow separation area ratio of the gas in the meridian flow passage at the bend 4, the inlet flow angle of the exhaust volute 6, and the ratio of the tangential velocity of the gas at the inlet of the exhaust volute 6 to the blade peripheral velocity. Correspondingly, the preset determination condition further includes one or more of the following:

[0120] (IV) in the design Mach number efficient region, the flow separation area ratio of the gas in the meridian flow passage at the bend 4 is less than 50%, and the separation area is concentrated on the shroud side;

[0121] (V) in the design Mach number efficient region, the inlet flow angle of the exhaust volute 6 is uniformly distributed, and the average value of the inlet flow angle is greater than or equal to 45° and less than or equal to 60°, and the ratio of the tangential velocity of the gas at the inlet of the exhaust volute 6 to the blade peripheral velocity is less than 0.155.

[0122] In some embodiments, the blades of the adjustable blade diffuser 3b are full height wedge-shaped blades; the ratio of the initial angle inlet diameter D3 of the adjustable blade diffuser 3b to the diameter D2 of the impeller 2 satisfies: 1.15≤D3 / D2≤1.25; the ratio of the initial angle outlet diameter D4 of the adjustable blade diffuser 3b to the diameter D2 of the impeller 2 satisfies: 1.90≤D4 / D2≤1.95; the ratio of the initial angle inlet width b3 of the adjustable blade diffuser 3b to the outlet width b2 of the impeller 2 satisfies: 0.93≤b3 / b2≤1; the ratio of the initial angle outlet width to the inlet width of the adjustable blade diffuser 3b is 1; the initial angle blade number of the adjustable blade diffuser 3b is greater than or equal to 7 and less than or equal to 13, and the initial angle blade number of the adjustable blade diffuser 3b is less than the blade number of the impeller 2; the initial installation angle of the inlet of the adjustable blade diffuser 3b is less than or equal to the outlet flow angle of the impeller 2, and the difference between the two is greater than or equal to 0 and less than or equal to 5°; the initial installation angle of the outlet of the adjustable blade diffuser 3b is greater than the initial installation angle of the inlet of the adjustable blade diffuser 3b, and the difference between the two is greater than or equal to 15° and less than or equal to 25°; the angle adjustment range is ±10° of the initial installation angle; the adjustment center of the adjustable blade diffuser 3b is located at 30%-40% of the blade centerline of the adjustable blade diffuser 3b, and after the adjustment angle, the ratio of the inlet diameter D3 of the adjustable blade diffuser 3b to the diameter D2 of the impeller 2 satisfies: D3 / D2≥1.1, and the initial installation angle of the inlet of the adjustable blade diffuser 3b is greater than or equal to 5°.

[0123] In some embodiments, the two ends of the curved channel 4 in the second model stage are connected to the adjustable blade diffuser 3b and the exhaust volute 6, and the outlet flow of the adjustable blade diffuser 3b enters the exhaust volute 6 after a 90° turn of the curved channel. The circular arc inlet of the curved channel 4 is tangent to the wheel cover and shaft disc of the straight line segment at the outlet of the adjustable blade diffuser 3b, and the ratio of the inlet width b5 of the curved channel 4 to the initial angle outlet width b4 of the adjustable blade diffuser 3b satisfies: 0.8≤b5 / b4≤2.5.

[0124] In some embodiments, the polytropic efficiency of the second model stage at the design Mach number and the design flow coefficient is greater than or equal to 0.79 and less than or equal to 0.82, and the high efficiency flow range of the second model stage from the inlet of the impeller 2 to the outlet of the exhaust volute 6 is 80%-115% of the design point.

[0125] It can be understood that the high efficiency flow range refers to the flow range in which the polytropic efficiency of the second model stage from the inlet of the impeller 2 to the outlet of the exhaust volute 6 is higher than 70%.

[0126] In some embodiments, the opening of the adjustable blade diffuser is controlled between -10° and +10°, and the high efficiency flow range of the second model stage is 40%-135% of the design point.

[0127] By the opening control of the adjustable blade diffuser, the application range of the second model stage can be significantly widened, so as to better meet the performance requirements of the LNG ship centrifugal compressor under the condition that the inlet temperature deviation is up to 140℃ when the centrifugal compressor is operated at a constant speed.

[0128] In some embodiments, the exhaust volute 6 is an equal cross-section exhaust volute with equal cross-sectional areas in the circumferential direction.

[0129] The exhaust volute is used to collect the compressed medium discharged from the impeller and guide the medium to flow to the outlet, and further diffuses the gas to improve the pressure of the gas. The equal cross-section exhaust volute refers to the cross-sectional area of the fluid passing through the volute remaining unchanged within a certain length range. The equal cross-section exhaust volute is characterized in that at least one section of the cross-sectional area inside the volute remains unchanged. This design helps to reduce the resistance loss during gas flow, thereby improving the efficiency of gas flow.

[0130] The aerodynamic design method of the centrifugal compressor of the embodiments of the present application will be further described below in combination with specific design examples.

[0131] Embodiment 1

[0132] The design input parameters of the first model stage of the LNG cryogenic ship centrifugal compressor include: design Mach number Ma 2u = 1.0, energy coefficient τ = 0.78, design flow coefficient φ = 0.08, the structure design of the main flow components is carried out according to the following steps, which specifically includes:

[0133] Step one: impeller design. The impeller 2 is selected as a three-dimensional impeller, and full-length blades are adopted. The load is concentrated in the middle and rear part of the impeller 2, so that the model stage has high efficiency and wide working condition range. As shown in FIGS. 6-10, according to the computational fluid dynamics (CFD) simulation, detailed analysis of the internal flow of the impeller can be provided, including pressure distribution and flow separation, the static pressure distribution of the pressure surface and the suction surface of the shaft cover disc side of the impeller 2 under the design point working condition is obtained, and according to the static pressure distribution, it can be determined that the position with the largest static pressure difference is at 75%-90% blade length. At the same time, the gas in the flow passage has no flow separation at 10%, 50%, and 90% blade height sections, and the polytropic efficiency of the impeller 2 can reach 94.7%, and the extracted outlet flow angle β2 = 26.5°, and the outlet Mach number Ma 2c = 0.689.

[0134] Step two: Fixed blade diffuser design. In the embodiment of the present application, the meridian of the hub and the shroud side of the fixed blade diffuser 3a is composed of a straight line which is perpendicular to the axial direction, the ratio of the inlet width b3 of the fixed blade diffuser 3a to the outlet width b2 of the impeller 2 satisfies: b3 / b2=0.97, the ratio of the inlet diameter D3 of the fixed blade diffuser 3a to the diameter D2 of the impeller 2 satisfies: D3 / D2=1.2, the inlet installation angle matches the outlet flow angle of the impeller 2, which ensures that the outlet flow of the impeller 2 can smoothly enter the fixed blade diffuser 3a. The ratio of the outlet width b4 of the fixed blade diffuser 3a to the inlet width b3 satisfies: b4 / b3=1, the ratio of the outlet diameter D4 of the fixed blade diffuser 3a to the diameter D2 of the impeller 2 satisfies: D4 / D2=1.65, the number of blades is 11, and the outlet installation angle α4A of the fixed blade diffuser 3a and the inlet installation angle α3A satisfy: α4A=α3A+14°. This design can reduce the flow loss in the fixed blade diffuser 3a and suppress the flow separation on the shroud side of the fixed blade diffuser 3a, as shown in FIG. 6. On the 10%, 50%, and 90% blade height sections, the gas has no flow separation in the flow passage, as shown in FIGS. 11-13. From the structural point of view, the fixed blade diffuser 3a adopts a wedge-shaped diffuser, and low-speed separation will occur in the outlet part. The outlet flow angle α4 of the fixed blade diffuser 3a is extracted as 37.81°, and the distribution is shown in FIG. 14. The outlet Mach number Ma 4c =0.34 of the fixed blade diffuser 3a, if the Mach number is too high, the impact loss in the bend 4 and the axial diffuser 5 will increase, and if the Mach number is too low, the separation loss in the bend 4 and the axial diffuser 5 will increase. After calculation, the related parameters and flow state in the first performance judgment parameter can meet the preset judgment condition. If any parameter does not meet the preset judgment condition, the structure needs to be changed and iteratively calculated until all parameters meet the preset judgment condition.

[0135] Step three: Bend design. The bend 4 is tangent to the straight line segment of the outlet of the blade diffuser 3a, and after a 90° turn, it enters the axial diffuser 5. After the gas flow passes through the bend 4, the flow angle is more uniform, and the Mach number distribution is more uniform, which ensures that the gas enters the axial diffuser 5 more uniformly and suppresses the impact loss caused by high speed. As shown in FIG. 4, the CFD analysis result shows that under the design Mach number and design flow coefficient working condition, there is no flow separation in the bend 4.

[0136] Step four: axial inducer design. The meridian lines of the hub and the shroud of the axial inducer 5 are both composed of a straight line parallel to the axial direction, the blade is a full height airfoil blade, and the number of blades is 47. The ratio of the inlet width b5 of the axial inducer 5 to the outlet width b4 of the fixed blade diffuser 3a satisfies: b5 / b4=0.78, the ratio of the central diameter D5 of the axial inducer 5 to the diameter D2 of the impeller 2 satisfies: D5 / D2=1.89, the relative position L5 of the inlet of the axial inducer 5 to the diameter D2 of the impeller 2 satisfies: L5 / D2=0.22, the installation angle of the inlet of the axial inducer 5 is consistent with the installation angle of the outlet of the fixed blade diffuser 3a, and the installation angle of the outlet is 105°. First, the inlet flow angle α5 of the axial inducer 5 is extracted under the design Mach number and the design flow coefficient working condition, that is, α5=38.25°, the Mach number Ma 5c =0.27, and through calculation, the related parameters and the flow state in the first performance judgment parameter can satisfy the preset judgment condition. If any parameter does not satisfy the preset judgment condition, the iteration calculation needs to return to step two until all satisfy.

[0137] As shown in FIG. 6, there is no flow separation on the meridian flow passage of the axial inducer 5. On the 10%, 50%, and 90% blade height sections, there is local separation at the outlet of the axial diffuser 5, and the local separation basically disappears before entering the exhaust volute 6, as shown in FIGS. 15-17. The outlet flow angle α6 of the axial inducer 5 is extracted, that is, α6=91.4°, and the average Mach number Ma 6c =0.19. Through calculation, the related parameters and the flow state in the first performance judgment parameter can satisfy the preset judgment condition. If any parameter does not satisfy the preset judgment condition, the iteration calculation needs to return to step two until all satisfy.

[0138] Steps two to four are the application of the joint design method of the present application. The design method can realize that the efficiency loss of the blade diffuser 3a and the axial inducer 5 is small, at the same time, the design of the axial diffuser ensures that the flow angle of the flow entering the exhaust volute is basically unchanged under various working conditions, which has strong adaptability and reduces the volute loss under various working conditions.

[0139] Step five: exhaust volute design. In the embodiment of the present application, the exhaust volute 6 is a volute structure with equal through-flow cross sections in the circumferential direction, an outlet flange is arranged at the radial direction of the volute, the axial length of the volute matches the diameter of the flange, and the structure is compact and simple. The design can well adapt to the flow field of the axial diffuser outlet, the gas flow angle entering the exhaust volute 6 is controlled within 5°, and the tangential velocity Vt satisfies: Vt<5m / s. Because the tangential velocity is small, the gas flow in the exhaust volute 6 is basically uniform except for the vicinity of the outlet flange. The equal cross-section volute structure can adapt to the actual situation of the flow distribution. As shown in FIGS. 18 and 19, there is no obvious separation zone in any cross section of the exhaust volute 6, and the main separation zone appears on one side of the flange and disappears soon. The efficiency loss at the design point of the volute is less than 2.5%, and the loss in the high-efficiency zone is less than 4%.

[0140] In the embodiment of the present application, the polytropic efficiency of the first model stage from the impeller inlet to the exhaust volute outlet is 0.839, and the applicable high-efficiency flow range is 80%-120% of the design point. The adjustable inlet guide vane is used for adjustment, and the opening degree of the guide vane is controlled within -70-+20°. The application range of the first model stage is widened to 30%-135% of the design point. The first model stage can be popularized to the modeling design of LNG low-temperature marine compressor products with a flow coefficient of 0.06≤φ≤0.175.

[0141] Embodiment 2

[0142] The design input parameters of the second model stage of the LNG low-temperature marine centrifugal compressor include: design Mach number Ma 2u =1.1, energy coefficient τ=0.748, and design flow coefficient φ=0.045. The structure design of the main flow passage components is carried out according to the following steps, which specifically include:

[0143] Step one: impeller design. The impeller 2 is selected as a three-dimensional impeller, and long and short blades are used. The load is concentrated in the middle and rear parts of the impeller, so that the model stage has very high efficiency and a wide operating range. As shown in FIG. 21, according to the computational fluid dynamics (CFD) modeling, detailed analysis of the internal flow of the impeller can be provided, including pressure distribution and flow separation. The static pressure distribution of the impeller 2 at the design point operating condition is obtained, and the position with the largest static pressure difference is determined to be at 75%-90% of the blade length. As shown in FIGS. 22-24, there is no large-area flow separation in the middle of the flow passage of the impeller at 10%, 50%, and 90% of the blade height cross sections. The polytropic efficiency can reach 91.5%, the extracted gas flow angle β2=20.1°, and the outlet Mach number Ma 2c =0.668.

[0144] Step two: adjustable blade diffuser design. The meridian of the hub side and the shaft disc side of the adjustable blade diffuser 3b is composed of a straight line and is perpendicular to the axial direction. The ratio of the inlet width b3 of the adjustable blade diffuser 3b to the outlet width b2 of the impeller 2 satisfies: b3 / b2=0.97, the ratio of the inlet diameter D3 of the adjustable blade diffuser 3b to the diameter D2 of the impeller 2 satisfies: D3 / D2=1.2, the inlet installation angle of the adjustable blade diffuser 3b matches the outlet flow angle of the impeller 2, so that the outlet flow of the impeller 2 can smoothly enter the adjustable blade diffuser 3b. The ratio of the outlet width b4 of the adjustable blade diffuser 3b to the inlet width b3 satisfies: b4 / b3=1, the ratio of the outlet diameter D4 of the adjustable blade diffuser 3b to the diameter D2 of the impeller 2 satisfies: D4 / D2=1.93, and the number of blades Z=11. The inlet installation angle α3A of the adjustable blade diffuser 3b and the flow angle of the outlet flow of the impeller 2 are less than 5 degrees, the outlet installation angle α4A of the adjustable blade diffuser 3b and the inlet installation angle α3A satisfy: α4A=α3A+20°, the adjustment center of the adjustable blade diffuser 3b is located at 35% of the blade midline, the inlet diameter D3 and the diameter D2 of the impeller 2 satisfy: 1.11≤D3 / D2≤1.28 when the adjustment angle is adjusted, and the blade installation angle satisfies: 5°≤α3A≤30°. This design can suppress the flow separation of the diffuser in the meridian plane, as shown in FIG. 20. In the 10%, 50%, and 90% height sections, there is no large-area flow separation in the middle of the diffuser flow passage, and the main separation occurs after 60% of the diffuser blade length and the position, as shown in FIGS. 25-27. From the structural point of view, the adjustable blade diffuser 3b adopts a wedge-shaped diffuser, and low-speed separation occurs in the outlet part of the diffuser. The average flow angle α4 of the outlet section of the adjustable blade diffuser 3b is extracted, the average Mach number Ma 4c =0.291, and after adjusting the adjustable diffuser angle, the average value of the inlet flow angle changes by about 0-6°, and the average value of the outlet flow angle changes by about 0-18°. According to the calculation, the related parameters and flow states in the second performance judgment parameter can satisfy the preset judgment condition of the second model stage. If any parameter does not meet the requirement, the structure needs to be changed and the iteration calculation is performed until all the requirements are met. This design ensures that the flow velocity is not too high, thereby reducing the loss of the subsequent stator member. Compared with the inlet guide vane, the adjustable blade diffuser has small pressure loss and wide efficient operation range.

[0145] Step three: bend design. In the embodiment of the present application, the bend 4 is tangent to the straight line segment at the outlet of the blade diffuser 3b, enters the horizontal straight line segment after a 90° circular arc turning, and b5 / b4≈2.2. The CFD analysis result shows that under the design Mach number and design flow coefficient working condition, there is separation on the hub side of the meridian bend 4, and the separation area accounts for about 30% of the meridian bend flow passage, as shown in FIG. 19. This separation only occurs on the hub side of the bend, and does not cause obvious efficiency loss after entering the volute.

[0146] Step four: exhaust volute design. In the embodiment of the present application, the exhaust volute 6 is a volute structure with equal through-flow cross sections in the circumferential direction, an outlet flange is arranged at the radial direction of the volute, the axial length of the volute matches the diameter of the flange, ensuring compact and simple structure. This design can match the flow field of the outlet, the gas flow angle α6=51° and the tangential velocity to peripheral velocity ratio vt / u2=0.129 under the design Mach number and design flow coefficient of the gas flow entering the volute, as shown in FIGS. 28-29, there is no obvious separation zone in any cross section in the volute, and the main separation zone appears on one side of the flange. The efficiency loss of the volute is less than 3% under the design Mach number and design flow coefficient, and the efficiency loss is 4% at the highest Mach number efficiency.

[0147] In the embodiment of the present application, the model stage efficiency from the inlet of the impeller 2 to the outlet of the exhaust volute 6 is higher than 78% when the Mach number Mu=0.9-1.2, and the adjustment range is relatively wide. The performance curve of the adjustable blade diffuser 3b at the initial angle shows a regularity that the performance curve moves in the direction of increasing flow as the machine Mach number of the model stage increases. When the diffuser is adjusted within ±0-5°, the regularity is consistent with the initial angle, and when the diffuser is adjusted within ±5-10°, the performance curve range is wider for smaller machine Mach numbers.

[0148] The polytropic efficiency of the second model stage from the inlet of the impeller to the outlet of the exhaust volute is 0.80, the high-efficiency flow range that can be applied is 70%-115% of the design point, the adjustable blade diffuser is adjusted, and the opening is controlled within-10° to +10°, the application range of the second model stage is widened to 40%-145% of the design point. The second model stage can adapt to the inlet temperature deviation of different working conditions from-100-30℃ in the fixed-speed operation, at this time, the design Mach number Mu=0.9-1.2 of the second model stage, and the high-efficiency flow range can still guarantee 40%-135% of the design point. The second model stage can be extended to the modeling design of LNG low-temperature marine compressor products with a flow coefficient φ<0.06.

[0149] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for aerodynamic design of a cryogenic compressor, the method comprising: obtaining design input parameters of a centrifugal compressor, the design input parameters comprising a design flow coefficient, a design Mach number and an energy head coefficient; in response to the design flow coefficient being greater than or equal to 0.06 and less than or equal to 0.175, determining a model stage of the centrifugal compressor as a first model stage, the flow passage components of the first model stage comprising an adjustable inlet guide vane, an impeller, a fixed vane diffuser, a bend, an axial diffuser and a discharge volute; in response to the design flow coefficient being less than 0.06, determining the model stage of the centrifugal compressor as a second model stage, the flow passage components of the second model stage comprising an impeller, an adjustable vane diffuser, a bend and a discharge volute; determining design parameters of the flow passage components of the centrifugal compressor according to the design input parameters and the model stage of the centrifugal compressor.

2. The aerodynamic design method of claim 1, wherein, the machine Mach number of the first model stage being greater than or equal to 0.9 and less than or equal to 1.1, and the energy head coefficient of the first model stage being greater than or equal to 0.7 and less than or equal to 0.

8.

3. The aerodynamic design method of claim 2, wherein, the determining design parameters of the flow passage components of the centrifugal compressor according to the design input parameters and the model stage of the centrifugal compressor; comprising determining structural design parameters and aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters comprising an outlet flow angle of the impeller and an outlet cross-sectional average Mach number of the impeller; determining structural design parameters of the fixed vane diffuser and the axial diffuser according to the structural design parameters and the aerodynamic parameters of the impeller.

4. The aerodynamic design method of claim 3, wherein, the determining structural design parameters and aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters comprising an outlet flow angle of the impeller and an outlet cross-sectional average Mach number of the impeller; comprising: the determining structural design parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor; determining a location of maximum static pressure difference of the impeller at a design point operating condition and a flow state of gas in a flow passage of the impeller according to the structural design parameters of the impeller; in response to the location of maximum static pressure difference being located within a range of 50%-100% blade length and the flow state of gas in the flow passage being free of flow separation, obtaining the aerodynamic parameters of the impeller; otherwise, returning to the previous step and readjusting the structural design parameters of the impeller.

5. The aerodynamic design method of claim 3, wherein, the determining structural design parameters of the fixed vane diffuser and the axial diffuser according to the structural design parameters and the aerodynamic parameters of the impeller; comprising: determining initial design parameters of the fixed vane diffuser and the axial diffuser according to the structural design parameters and the aerodynamic parameters of the impeller; determining first performance judgment parameters and a flow state of gas according to the initial design parameters of the fixed vane diffuser and the axial diffuser; the first performance judgment parameters comprising an outlet flow angle of the fixed vane diffuser, an outlet cross-sectional average Mach number of the fixed vane diffuser, an inlet flow angle of the axial diffuser and an inlet cross-sectional average Mach number of the axial diffuser; determining the initial design parameters as the structural design parameters of the fixed-blade diffuser and the axial guide vane, otherwise, readjusting the initial design parameters of the fixed-blade diffuser and the axial guide vane and re-determining the design performance determination parameters; wherein the preset determination condition comprises one or more of the following: at the design Mach number design point, the outlet flow angle distribution of the fixed-blade diffuser is uniform, and the average value of the outlet flow angle is greater than or equal to 34° and less than or equal to 39°, the average Mach number of the outlet section of the fixed-blade diffuser is greater than or equal to 0.31 and less than or equal to 0.38, and the gas flow in the flow passage between the outlet of the fixed-blade diffuser and the inlet of the axial guide vane is not separated; in the design Mach number efficient region, the outlet flow angle distribution of the fixed-blade diffuser is uniform, and the average value of the outlet flow angle is greater than or equal to 32° and less than or equal to 45°, the average Mach number of the outlet section of the fixed-blade diffuser is greater than or equal to 0.28 and less than or equal to 0.52, and the gas separation in the meridian plane of the small flow region occurs on the shaft disc side; at the design Mach number design point, the inlet flow angle distribution of the axial diffuser is uniform, and the average value of the inlet flow angle is greater than or equal to 34° and less than or equal to 39°, the average Mach number of the inlet section of the axial diffuser is greater than or equal to 0.24 and less than or equal to 0.31, the blade installation angle of the axial diffuser exceeds 90°, the gas appears local separation in the range of 30% to 70% of the blade height and the separation area disappears before entering the exhaust volute; in the design Mach number efficient region, the inlet flow angle distribution of the axial diffuser is uniform, and the average value of the inlet flow angle is greater than or equal to 32° and less than or equal to 40°, the average Mach number of the inlet section of the axial diffuser is greater than or equal to 0.22 and less than or equal to 0.44; the design Mach number efficient region refers to a flow range in which the polytropic efficiency of the first model stage from the inlet of the impeller to the outlet of the exhaust volute is greater than or equal to 70% at the design Mach number.

6. The aerodynamic design method of claim 5, wherein, The first performance determination parameters further comprise: the outlet flow angle of the impeller, the outlet section average Mach number of the impeller, the inlet flow angle of the exhaust volute, and the inlet section average Mach number of the exhaust volute; and wherein the preset determination condition further comprises one or more of the following: in the design Mach number efficient region, the outlet flow angle distribution of the impeller is uniform, and the average value of the outlet flow angle of the impeller is greater than or equal to 20° and less than or equal to 32°, the outlet section average Mach number of the impeller is greater than or equal to 0.67 and less than or equal to 0.74; in the design Mach number efficient region, the gas flow in the meridian flow passage at the bend is not separated; in the design Mach number efficient region, the gas flow in the meridian flow passage at the bend is not separated; In the design Mach number efficient region, the inlet flow angle distribution of the exhaust volute is uniform, and the average value of the inlet flow angle of the exhaust volute is greater than or equal to 87° and less than or equal to 93°, the average Mach number of the inlet section of the exhaust volute is greater than or equal to 0.15 and less than or equal to 0.

28.

7. Aerodynamic design method according to claim 5 or 6, wherein, The blade of the fixed blade diffuser is a full height wedge-shaped blade, wherein, The ratio of the inlet diameter D3 of the fixed blade diffuser to the diameter D2 of the impeller satisfies: 1.15≤D3 / D2≤1.25; The ratio of the outlet diameter D4 of the fixed blade diffuser to the diameter D2 of the impeller satisfies: 1.60≤D4 / D2≤1.70; The ratio of the inlet width b3 of the fixed blade diffuser to the outlet width b2 of the impeller satisfies: 0.85≤b3 / b2≤1; The ratio of the outlet width b4 of the fixed blade diffuser to the inlet width b3 of the fixed blade diffuser satisfies: b4 / b3=1; The number of blades of the fixed blade diffuser is greater than or equal to 7 and less than or equal to 13; and the number of blades of the fixed blade diffuser is less than the number of blades of the impeller; The inlet installation angle of the fixed blade diffuser is greater than the outlet flow angle of the impeller, and the difference between the two is greater than or equal to 12° and less than or equal to 15°.

8. The aerodynamic design method of claim 5 or 6, wherein, The ratio of the inlet width b5 of the axial guide vane to the outlet width b4 of the fixed blade diffuser satisfies: 0.75≤b5 / b4≤0.8; The ratio of the blade length L of the axial guide vane to the diameter D2 of the impeller satisfies: 0.2≤L / D2≤0.25; The ratio of the center diameter D5 of the axial guide vane to the diameter D2 of the impeller satisfies: 1.85≤D5 / D2≤1.90; The ratio of the inlet relative position L5 of the axial guide vane to the diameter of the impeller satisfies: 0.2≤L5 / D2≤0.25; The outlet installation angle of the axial guide vane is greater than or equal to 100° and less than or equal to 110°, and the inlet installation angle of the axial guide vane is substantially consistent with the outlet installation angle of the fixed blade diffuser; The number of blades of the axial guide vane is greater than or equal to 33 and less than or equal to 53.

9. The aerodynamic design method of any one of claims 1-6, wherein, The polytropic efficiency of the first model stage from the inlet of the impeller to the outlet of the exhaust volute at the design Mach number and the design flow coefficient is greater than or equal to 0.83 and less than or equal to 0.85, and the efficient flow range applicable to the first model stage is 80%-115% of the design point.

10. The aerodynamic design method of any one of claims 1-6, wherein, The guide vane opening of the adjustable inlet guide vane is -70° to +20°, and the efficient flow range applicable to the first model stage is 40%-120% of the design point.

11. The aerodynamic design method of claim 1, wherein, The machine Mach number of the second model stage is greater than or equal to 0.9 and less than or equal to 1.2, and the energy head coefficient of the second model stage is greater than or equal to 0.7 and less than or equal to 0.

8.

12. The aerodynamic design method of claim 11, wherein, The design parameters of the flow components of the centrifugal compressor are determined according to the design input parameters and the model stages of the centrifugal compressor; including determining structural design parameters and aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters including an outlet flow angle of the impeller and an outlet Mach number of the impeller; determining structural design parameters of the variable-blade diffuser according to the structural design parameters and the aerodynamic parameters of the impeller.

13. The aerodynamic design method of claim 12, wherein, The determining structural design parameters and aerodynamic parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor, the aerodynamic parameters including an outlet flow angle of the impeller and an outlet Mach number of the impeller, comprises: determining structural design parameters of the impeller according to the design input parameters and the model stage of the centrifugal compressor; determining a position of maximum static pressure difference of the impeller at the design point and a flow state of gas in a flow passage of the impeller according to the structural design parameters of the impeller; in response to the position of maximum static pressure difference being located in a range of 50%-100% of blade length and gas not appearing flow separation in the flow passage, obtaining the aerodynamic parameters of the impeller; otherwise, returning to the previous step and readjusting the structural design parameters of the impeller.

14. The aerodynamic design method of claim 13, wherein, The determining structural design parameters of the variable-blade diffuser according to the structural design parameters and the aerodynamic parameters of the impeller comprises: determining initial design parameters of the variable-blade diffuser according to the structural design parameters and the aerodynamic parameters of the impeller, the initial design parameters of the variable-blade diffuser including an initial installation angle and an angle adjustment range; determining second performance judgment parameters at different angles and performance curves of the second model stage at different angles according to the initial design parameters of the variable-blade diffuser, the second performance judgment parameters including an inlet flow angle, an inlet cross-sectional average Mach number, an outlet flow angle and an outlet cross-sectional average Mach number of the variable-blade diffuser; in response to the second performance judgment parameters and the performance curves satisfying a preset judgment condition, determining the initial design parameters as the structural design parameters of the variable-blade diffuser; otherwise, readjusting the initial design parameters of the variable-blade diffuser and redetermining the second performance judgment parameters; wherein the preset judgment condition comprises one or more of the following: in an initial angle design Mach number efficient zone, an average value of the inlet flow angle of the variable-blade diffuser is greater than or equal to 15° and less than or equal to 30°, and an outlet cross-sectional average Mach number of the variable-blade diffuser is greater than or equal to 0.58 and less than or equal to 0.80; in the initial angle design Mach number efficient zone, an average value of the outlet flow angle of the variable-blade diffuser is greater than or equal to 45° and less than or equal to 55°, and the outlet cross-sectional average Mach number of the variable-blade diffuser is greater than or equal to 0.16 and less than or equal to 0.35; in a regulation angle design Mach number, a variation amplitude of an average value of the inlet flow angle of the variable-blade diffuser compared with an average value of the inlet flow angle at the initial angle is less than 10°, and a variation amplitude of an average value of the outlet flow angle of the variable-blade diffuser compared with an average value of the outlet flow angle at the initial angle is less than 20°.

15. The aerodynamic design method of claim 14, wherein, the second performance determining parameter further comprises: a flow separation area ratio of the gas in the meridian flow passage at the bend, an inlet flow angle of the exhaust volute, and a ratio of the tangential velocity of the gas at the inlet of the exhaust volute to the blade peripheral velocity; and wherein the preset determining condition further comprises one or more of: in the design Mach number efficient region, the flow separation area ratio of the gas in the meridian flow passage at the bend is less than 50%, and the separation area is concentrated on the shroud side; in the design Mach number efficient region, the inlet flow angle of the exhaust volute is uniformly distributed, and the average value of the inlet flow angle is greater than or equal to 45° and less than or equal to 60°, and the ratio of the tangential velocity of the gas at the inlet of the exhaust volute to the blade peripheral velocity is less than 0.

155.

16. The aerodynamic design method of claim 14 or 15, wherein, the blades of the adjustable blade diffuser are full height wedge-shaped blades; a ratio of an initial angle inlet diameter D3 of the adjustable blade diffuser to a diameter D2 of the impeller satisfies: 1.15≤D3 / D2≤1.25; a ratio of an initial angle outlet diameter D4 of the adjustable blade diffuser to the diameter D2 of the impeller satisfies: 1.90≤D4 / D2≤1.95; a ratio of an initial angle inlet width b3 of the adjustable blade diffuser to an outlet width b2 of the impeller satisfies: 0.93≤b3 / b2≤1; a ratio of an initial angle outlet width to the inlet width of the adjustable blade diffuser is 1; an initial angle blade number of the adjustable blade diffuser is greater than or equal to 7 and less than or equal to 13, and the initial angle blade number of the adjustable blade diffuser is less than a blade number of the impeller; an initial installation angle of an inlet of the adjustable blade diffuser is less than or equal to an outlet flow angle of the impeller, and a difference between the two is greater than or equal to 0 and less than or equal to 5°; an initial installation angle of an outlet of the adjustable blade diffuser is greater than the initial installation angle of the inlet of the adjustable blade diffuser, and a difference between the two is greater than or equal to 15° and less than or equal to 25°, and an angle adjustment range is ±10° of the initial installation angle; an adjustment center of the adjustable blade diffuser is located at 30%-40% of a blade midline of the adjustable blade diffuser, and after adjustment of an angle, a ratio of an inlet diameter D3 of the adjustable blade diffuser to the diameter D2 of the impeller satisfies: D3 / D2≥1.1, and the initial installation angle of the inlet of the adjustable blade diffuser is greater than or equal to 5°.

17. The aerodynamic design method of any one of claims 11-15, wherein, two ends of the bend in the second model stage are connected to the adjustable blade diffuser and the exhaust volute, outlet flow of the adjustable blade diffuser enters the exhaust volute after a 90° turn of the outlet flow through the bend, an arc inlet of the bend is tangent to the shroud and the hub of a straight line segment of the outlet of the adjustable blade diffuser, and a ratio of an inlet width b5 of the bend to an initial angle outlet width b4 of the adjustable blade diffuser satisfies: 0.8≤b5 / b4≤2.

5.

18. The aerodynamic design method of any one of claims 11-15, wherein, the second model stage has a polytropic efficiency at design Mach number, design flow coefficient greater than or equal to 0.79 and less than or equal to 0.82, and an efficient flow range of 80-115% of the design point from the inlet of the impeller to the outlet of the exhaust volute.

19. The aerodynamic design method of claim 18, wherein, the adjustable vane diffuser is controlled between -10° and +10°, and the second model stage has an efficient flow range of 40-135% of the design point.

20. The aerodynamic design method of any one of claims 1-6, 11-15, wherein, the exhaust volute is an equal cross-section volute with equal cross-sections in the circumferential direction. the adjustable vane diffuser is controlled between -10° and +10°, and the second model stage has an efficient flow range of 40-135% of the design point. the exhaust volute is an equal cross-section volute with equal cross-sections in the circumferential direction.

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