Axial flow compressor-diffuser coupling design method and ultra-compact diffuser

Abstract

The invention relates to the technical field of aero-engine design, in particular to an axial flow compressor-diffuser coupling design method and an ultra-compact coupling structure.The axial flow compressor-diffuser coupling design method comprises the steps that flow channels corresponding to a rotor and a stator of an original compressor are expanded to obtain a target compressor; performing expansion processing on the original diffuser to obtain a target diffuser; and an ultra-compact coupling structure of the axial flow compressor-diffuser is obtained. According to the axial flow compressor-diffuser, the expansion degree of an airflow channel of the compressor is increased, so that the airflow circulation area is increased, the actual axial length of the target diffuser is remarkably shortened while the speed reduction and diffusion performance of the diffuser is guaranteed, and then the coupling structure of the axial flow compressor-diffuser is more compact; and meanwhile, the adaptive capacity and the matching relation of the diffuser to the air flow at the outlet of the air compressor are optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine design, and particularly relates to an axial compressor-diffuser coupling design method and an ultra-tight coupling structure. Background Art

[0002] An aero-engine is a systematic project. Driven by the requirements of higher thrust-to-weight ratio and lower fuel consumption rate for advanced aero-engines, the structural layout of each component of the engine is more compact, the design requirements are significantly improved, and its research and development urgently need to shift from the traditional design method of single and separated design of each component to a systematic design method that emphasizes multi-component coupling, integration, and matching. The axial compressor and the main combustion chamber are key core components in an aero-engine that are adjacent in space and through which the air flow passes sequentially. Among them, as the main structure for organizing and distributing the air flow in the main combustion chamber, the diffuser directly receives the complex air flow at the outlet of the axial compressor and provides the harsh intake environment required by the combustion chamber flame tube, and supports the safe and stable operation of the combustion chamber under all operating conditions of the engine with high diffusing capacity and extremely small flow losses. Therefore, the diffusing capacity and flow losses of the diffuser are directly related to the performance levels of the compressor, the combustion chamber, and even the entire aero-engine.

[0003] With the increase in the pressure ratio and load level of the axial compressor, the coupling and matching problem between the diffuser and its upstream axial compressor becomes more prominent: as Figure 8 shown, the design of the high-load axial compressor causes the flow path of the compressor to contract sharply along the way, the outlet area is small, and the blade size of the outlet stage is small. All these lead to the continuous increase in the distortion degree and velocity magnitude of the air flow at the compressor outlet, and the characteristics of strong shear, strong three-dimensional, and strong adverse pressure gradient in the diffuser internal flow are more prominent, resulting in large flow losses in the diffuser component and poor diffusing effect, and it is difficult to shorten the axial length of the diffuser, thus bringing severe challenges to the design of advanced diffusers with the characteristics of compactness, high efficiency, and low resistance.

[0004] Therefore, it is necessary to provide an axial compressor-diffuser coupling design method and an ultra-compact coupling structure to solve the above problems. Summary of the Invention

[0005] The present invention provides an axial compressor-diffuser coupling design method and an ultra-compact coupling structure to solve the problem that it is difficult to shorten the axial length of the existing diffuser, which brings severe challenges to the design of diffusers with the characteristics of compactness, high efficiency, and low resistance.

[0006] An axial compressor-diffuser coupling design method of the present invention adopts the following technical solutions, including: Performing expansion processing on the flow paths corresponding to the rotor and stator of the original compressor according to a preset expansion angle range to obtain an expanded target compressor; Adopt the method of controlling variables, and design the optimal upper wall expansion angle and the optimal lower wall expansion angle according to the preset upper wall expansion angle range and the preset lower wall expansion angle range. According to the optimal upper wall expansion angle and the optimal lower wall expansion angle, perform expansion processing on the original diffuser to obtain the target diffuser; Perform a smooth transition on the flow path surface at the connection between the inlet of the target diffuser and the trailing edge of the last-stage stator of the target compressor to form a coupled structure of the axial compressor - diffuser; Among them, the structure between the flow path cross-section of the front end face of the rotor of the target compressor in the coupled structure and the outlet cross-section of the target diffuser is used as the virtual diffuser; and the expansion ratio of the virtual diffuser is the same as that of the original diffuser.

[0007] Preferably, the steps for designing the optimal upper wall expansion angle and the optimal lower wall expansion angle of the diffuser are as follows: Adopt the method of controlling variables, and select parameter combinations composed of the upper wall expansion angle and the lower wall expansion angle within the preset upper wall expansion angle range and the preset lower wall expansion angle range; Obtain the coupled static pressure recovery coefficient after the diffuser and the target compressor are coupled for each parameter combination; Take the parameter combination with the maximum coupled static pressure recovery coefficient as the optimal parameter combination, that is, obtain the optimal upper wall expansion angle and the optimal lower wall expansion angle.

[0008] Preferably, when the expansion ratio of the virtual diffuser is the same as that of the original diffuser, the relationship satisfied between the optimal upper wall expansion angle, the optimal lower wall expansion angle and the expansion ratio of the original diffuser is:

[0009] In the formula, represents the outer radius of the inlet flow path of the virtual diffuser; represents the inner radius of the inlet flow path of the virtual diffuser; represents the optimal lower wall expansion angle of the target diffuser; represents the optimal upper wall expansion angle of the target diffuser; represents the axial length of the target diffuser; represents the inlet cross-sectional area of the original diffuser; represents the outlet cross-sectional area of the original diffuser; represents the expansion ratio of the original diffuser.

[0010] Preferably, the preset upper wall expansion angle range is: 0° - 15°; the preset lower wall expansion angle range is: 0° - 15°.

[0011] Preferably, the trailing edge of the stator of the target compressor adopts a "C"-type swept structure, and the tip sweep angle and the root sweep angle of the stator of the "C"-type swept structure are equal, and the angle ranges corresponding to the tip sweep angle and the root sweep angle are both 0° to 15°.

[0012] Preferably, according to the preset expansion angle range, the steps of expanding the flow channels corresponding to the rotor and the stator of the original compressor are as follows: Design the rotor casing flow channel expansion angle according to the preset rotor casing flow channel expansion angle range; design the rotor hub flow channel expansion angle according to the preset rotor hub flow channel expansion angle range of the compressor; Design the stator casing flow channel expansion angle according to the preset stator casing flow channel expansion angle range of the compressor; design the stator hub flow channel expansion angle according to the preset stator hub flow channel expansion angle range of the compressor; Expand the rotor flow channel of the original compressor based on the designed rotor hub flow channel expansion angle and the designed rotor casing flow channel expansion angle; expand the stator flow channel of the original compressor based on the designed stator hub flow channel expansion angle and the designed stator casing flow channel expansion angle.

[0013] Preferably, the rotor casing flow channel expansion angle range, the rotor casing hub expansion angle range, the stator casing flow channel expansion angle range, and the stator hub flow channel expansion angle range are all: 0° to 5°.

[0014] Preferably, the flow channel profile in the target diffuser is any one of an arc, a straight line, a polynomial curve, a Bezier curve, a B-spline curve, and a NURBS curve, or a combination of any two line profiles.

[0015] An ultra-compact coupling structure for axial compressor-diffuser coupling design adopts the following technical solution, and designs the ultra-compact coupling structure according to an axial compressor-diffuser coupling design method of the present invention.

[0016] The beneficial effects of the present invention are: 1. By expanding the rotor flow path and stator flow path of the original compressor, the air flow path of the subsequent stages of the compressor near the diffuser is expanded to increase the air flow area, enabling the air flow to decelerate and diffuse in advance in the compressor, thereby reducing the air flow velocity at the compressor outlet. At the same time, the control variable method is used to optimize the expansion angles corresponding to the upper and lower walls of the original diffuser, so that a virtual diffuser is formed between the outlet of the optimized target diffuser and the flow port at the front end face of the rotor of the expanded target compressor. The entire air flow starts to decelerate from the inlet of the virtual diffuser and completes deceleration until the outlet of the virtual diffuser. That is, the entire structure is equivalent to advancing the inlet of the diffuser, and the expansion ratio of the virtual diffuser is the same as that of the original diffuser. While ensuring the deceleration and diffusion performance of the diffuser, the axial length of the actual target diffuser is significantly shortened, and thus the coupled structure of the axial compressor - diffuser is made more compact.

[0017] 2. Design the stator of the target compressor into a "C"-shaped swept structure, which realizes the optimization of the stator blades of the compressor, improves the flow field structure at the compressor outlet, optimizes the adaptability and matching relationship of the target diffuser to the air flow at the compressor outlet, and thus significantly shortens the axial length of the diffuser while enhancing the deceleration and diffusion performance of the diffuser. Brief Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a flowchart of a method for coupling design of an axial compressor - diffuser of the present invention; Figure 2 It is a three-dimensional structure diagram of a super-compact coupled structure designed by using a method for coupling design of an axial compressor - diffuser of the present invention; Figure 3 It is a meridional plane structure diagram of a super-compact coupled structure designed by using a method for coupling design of an axial compressor - diffuser of the present invention; Figure 4 It is a schematic diagram of the rotor of the subsequent stages of the compressor in a super-compact coupled structure designed by using a method for coupling design of an axial compressor - diffuser of the present invention; Figure 5 It is a schematic diagram of the stator of the subsequent stages of the compressor in a super-compact coupled structure designed by using a method for coupling design of an axial compressor - diffuser of the present invention; Figure 6Comparison diagram of the axial distribution curves of the flow channel areas perpendicular to the axial section in the target diffuser of the compressor-diffuser of the traditional technology and the ultra-compact coupling structure of the present invention; Figure 7 Comparison diagram of the axial distribution curves of the average velocities of each air flow surface perpendicular to the axial section in the target diffuser of the compressor-diffuser of the traditional technology and the ultra-compact coupling structure of the present invention; Figure 8 Three-dimensional structure schematic diagram of the compressor-diffuser structure of the traditional technology; Figure 9 Meridional plane schematic diagram of the compressor-diffuser structure of the traditional technology.

[0020] In the figure: 1. Rotor; 2. Stator; 3. Rotor casing flow channel; 4. Rotor hub flow channel; 5. Stator casing flow channel; 6. Stator hub flow channel; 7. Diffuser upper wall surface; 8. Diffuser lower wall surface. Specific embodiments

[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Such as Figure 8As shown, the existing high-load axial flow compressor design causes the compressor flow passage to contract sharply along the way, with a small outlet area and small blade sizes at the outlet stage. All these lead to a continuous increase in the distortion degree and velocity magnitude of the airflow at the compressor outlet, making the strong shear, strong three-dimensional, and strong adverse pressure gradient characteristics of the internal flow in the diffuser more prominent. As a result, the flow loss in the diffuser component is large and the diffusing effect is not good, and it is difficult to shorten the axial length of the diffuser, thus posing a severe challenge to the design of an advanced diffuser with the characteristics of compactness, high efficiency, and low resistance. However, for a long time, the design division interface between the axial flow compressor and the diffuser of the main combustion chamber is clear, and designers often ignore the inherent flow correlation characteristics of the axial flow compressor - diffuser, resulting in a large research gap in the relevant component matching relationships and matching designs. There is also a large room for improvement in the aerodynamic performance and structural compactness of the components under the split design. On the one hand, traditional multi-stage axial flow compressors usually adopt a design of contracting the airflow channel to maintain a relatively high airflow velocity, while their downstream diffusers usually require a design of expanding the airflow channel to achieve airflow deceleration and diffusion. If the working objectives and matching relationships of the axial flow compressor and the diffuser of the main combustion chamber can be considered overall, a design concept of reducing the degree of contraction of the airflow channel in the later stages of the compressor close to the diffuser can be adopted to increase the airflow passage area, enabling the airflow to decelerate and diffuse in advance in the compressor, improving the anti-separation ability of the diffuser and achieving design compactness. On the other hand, most traditional diffuser designs are based on the assumption of a uniform incoming flow at the diffuser inlet, that is, the distortion phenomena of pressure, velocity, and airflow angle that actually exist at the outlet of the axial flow compressor are not considered. However, there is a large deviation between the split and isolated diffuser design without considering the influence of the upstream compressor and the actual flow conditions, so there are natural defects. Considering the high correlation between the diffuser flow field structure and loss characteristics and the compressor flow characteristics, reasonable optimization design of the compressor blades can specifically improve the flow field structure at the compressor outlet, optimize the adaptability and matching relationship of the diffuser to the airflow at the compressor outlet, and achieve an improvement in the performance level of the diffuser.

[0023] Based on the above analysis, this invention proposes an embodiment of a coupling design method for an axial flow compressor - diffuser from the aspects of decelerating and diffusing in advance in the axial flow compressor and optimizing the three-dimensional shape of the blades, as Figure 1 shown, including: S1. Expand the flow passages corresponding to the rotor and stator of the original compressor to obtain a target compressor; Specifically, expand the flow passages corresponding to the rotor and stator of the original compressor according to a preset expansion angle range to obtain the expanded target compressor.

[0024] Exemplarily, in a specific embodiment, the steps of expanding the rotor and stator of the original compressor according to a preset expansion angle range are as follows: Design the expansion angle of the rotor casing flow passage according to the preset expansion angle range of the rotor casing flow passage; design the expansion angle of the rotor hub flow passage according to the preset expansion angle range of the rotor hub flow passage of the compressor; design the expansion angle of the stator casing flow passage according to the preset expansion angle range of the stator casing flow passage of the compressor; design the expansion angle of the stator hub flow passage according to the preset expansion angle range of the stator hub flow passage of the compressor; expand the rotor flow passage of the original compressor based on the designed expansion angle of the rotor hub flow passage and the designed expansion angle of the rotor casing flow passage; expand the stator flow passage of the original compressor based on the designed expansion angle of the stator hub flow passage and the designed expansion angle of the stator casing flow passage, and then the target compressor after the expansion process can be obtained.

[0025] Among them, the expansion angle range of the rotor casing flow passage, the expansion angle range of the rotor casing hub, the expansion angle range of the stator casing flow passage, and the expansion angle range of the stator hub flow passage are all: 0° to 5°, and 5° is taken in this embodiment.

[0026] Exemplarily, in a specific embodiment, in order to improve the flow field structure at the compressor outlet and optimize the adaptability and matching relationship between the target diffuser and the air flow at the compressor outlet, the trailing edge of the stator of the target compressor in this embodiment adopts a "C"-type swept structure, and the tip sweep angle of the stator with the "C"-type swept structure is equal to the root sweep angle, and the angle range corresponding to the tip sweep angle and the root sweep angle is 0° to 15°, and 10° is taken in this embodiment. S2. Expand the original diffuser to obtain the target diffuser; Specifically, the control variable method is adopted, and the optimal upper wall surface expansion angle and the optimal lower wall surface expansion angle are designed according to the preset upper wall surface expansion angle range and the preset lower wall surface expansion angle range, and the original diffuser is expanded according to the optimal upper wall surface expansion angle and the optimal lower wall surface expansion angle to obtain the target diffuser.

[0027] Exemplarily, in a specific embodiment, the steps of designing the optimal upper wall surface expansion angle and the optimal lower wall surface expansion angle are as follows: Adopt the control variable method, select parameter combinations composed of the upper wall surface expansion angle and the lower wall surface expansion angle within the preset upper wall surface expansion angle range and the preset lower wall surface expansion angle range; obtain the coupling static pressure recovery coefficient after the coupling of the diffuser and the target compressor for each parameter combination; take the parameter combination with the largest coupling static pressure recovery coefficient as the optimal parameter combination, that is, obtain the optimal upper wall surface expansion angle and the optimal lower wall surface expansion angle. Among them, the expression of the coupling static pressure recovery coefficient is:

[0028] In the formula, Denote the static pressure at the inlet of the stator of the target compressor; Denote the static pressure at the outlet of the target diffuser, Denote the total pressure at the inlet of the stator of the target compressor.

[0029] Exemplarily, in a specific embodiment, the flow path profile in the target diffuser is any one of an arc, a straight line, a polynomial curve, a Bezier curve, a B-spline curve, and a NURBS curve, or a combination of any two of these line types. In this embodiment, the flow path profile in the diffuser is designed as a combination of an arc section and a straight line section. Specifically, the inlet section of the diffuser is an arc section, the outlet section is a straight line section, and the arc section is tangent to the straight line section.

[0030] S3. Obtain the ultra-compact coupling structure of the axial compressor-diffuser; Specifically, smooth the flow path surface at the connection between the inlet of the target diffuser and the trailing edge of the last-stage stator of the target compressor to form the ultra-compact coupling structure of the axial compressor-diffuser. Among them, the structure between the flow path cross-section of the front end face of the rotor of the target compressor in the ultra-compact coupling structure and the outlet cross-section of the target diffuser is used as the virtual diffuser; and the expansion ratio of the virtual diffuser is the same as that of the original diffuser.

[0031] Among them, when the expansion ratio of the virtual diffuser is the same as that of the original diffuser, the relational expressions satisfied between the optimal upper wall expansion angle, the optimal lower wall expansion angle and the expansion ratio of the original diffuser are:

[0032] In the formula, Denote the outer radius of the inlet flow path of the virtual diffuser; Denote the inner radius of the inlet flow path of the virtual diffuser; Denote the optimal lower wall expansion angle of the target diffuser; Denote the optimal upper wall expansion angle of the target diffuser; Denote the axial length of the target diffuser; as Figure 9 shown, Denote the inlet cross-sectional area of the original diffuser; Denote the outlet cross-sectional area of the original diffuser; Denote the expansion ratio of the original diffuser.

[0033] An ultra-compact coupling structure for the coupling design of an axial compressor-diffuser, comprising: designing the ultra-compact coupling structure according to an axial compressor-diffuser coupling design method of the present invention, and the designed ultra-compact coupling structure is as Figure 2 shown.

[0034] The following combines the attached Figure 2 to the attached Figure 8Specific description of this embodiment: The present invention adopts the design concept of reducing the contraction degree of the air flow passage for the later stages of the compressor and the compound sweep design for the blade profile. First, Figure 8 The rotor and stator passage profiles of the original compressor shown are expanded. Taking the axial direction as the reference, Figure 8 On the basis of the original compressor shown, the rotor casing flow passage and the stator casing flow passage, the rotor hub flow passage and the stator hub flow passage are respectively expanded by a certain angle to form Figure 2 The rotor casing flow passage 3 and the stator casing flow passage 5, the rotor hub flow passage 4 and the stator hub flow passage 6 shown, and ensure smooth transition of the flow passage profile; thus Figure 8 The chord lengths of the rotor and stator of the original compressor shown are increased to obtain Figure 2 The rotor 1 and stator 2 of the target compressor shown, and the trailing edge of the stator 2 is designed as a "C"-type swept structure to improve the flow field structure at the compressor outlet, optimize the adaptability and matching relationship of the target diffuser to the outlet air flow of the target compressor. On the one hand, increasing the air flow passage expansion angle of the compressor increases the actual flow area of the air flow in the later stages of the compressor, that is, deceleration and pressurization are carried out from the flow port at the front end face of the rotor of the target compressor, that is, early deceleration and pressurization are realized, the air flow velocity at the compressor outlet / diffuser inlet is reduced, the anti-separation ability of the diffuser is improved and the design compactness is realized; on the other hand, the compound sweep design of the blade profile of the stator 2 improves the flow field distortion at the compressor outlet, thus significantly improving the flow field structure in the downstream diffuser and the matching relationship between the later stages of the compressor and the diffuser, realizing the reduction of the total pressure loss of the diffuser and the improvement of the static pressure recovery ability. Compared with the coupling structure of the traditional axial flow compressor and diffuser, the ultra-compact coupling structure proposed by the present invention based on the optimized matching design of the axial flow compressor has the advantages of more compact structure, lower total pressure loss and higher static pressure recovery ability.

[0035] As Figure 3 shown, the main structural schematic diagram of the meridian plane of the ultra-compact coupling structure based on the axial flow compressor-diffuser coupling design of this example, as Figure 3As shown by the black dashed line. The rotor flow passage and stator flow passage of the subsequent stage of the ultra-compact coupling structure are significantly less contracted compared to the traditional flow passage, and locally reach an expanding degree. The deceleration and pressure increase of the air flow occur earlier in the subsequent stage of the compressor, the actual flow area of the air flow increases, the air flow velocity at the outlet of the target compressor / inlet of the target diffuser decreases, and the anti-separation ability of the air flow in the target diffuser is enhanced. The range of the expansion ratio of the optional target diffuser also increases accordingly, thereby significantly shortening the axial length of the target diffuser. The three-dimensional backward sweep design of the stator blade profile of the subsequent stage of the ultra-compact diffuser can change the radial distribution of the air flow parameters at the outlet of the compressor, improve the flow field distortion at the outlet of the target compressor, and thus significantly improve the flow field structure in the downstream target diffuser and the matching relationship between the subsequent stage of the target compressor and the diffuser, achieving a reduction in the total pressure loss of the target diffuser and an improvement in the static pressure recovery ability. Among them, the profile lines of the outlet flow passage of the target compressor and the inlet flow passage of the target diffuser of the ultra-compact coupling structure are tangent to ensure a smooth transition of the flow passage and reduce the aerodynamic loss.

[0036] Combined with Figure 3 and Figure 4 , the geometric parameters of the target diffuser of the ultra-compact coupling structure are defined as follows: the upper wall expansion angle θ of the target diffuser, defined as the angle between the line connecting the outlet and inlet of the upper wall of the diffuser and the rotation axis, and the range of the target upper wall expansion angle is 0° < θ < 15°; the lower wall expansion angle η of the target diffuser, defined as the angle between the line connecting the outlet and inlet of the lower wall of the target diffuser and the rotation axis, and the range of the lower wall expansion angle of the target diffuser is 0° < η < 15°; the inlet cross-sectional area A 1 and the outlet cross-sectional area A 2 of the original diffuser, and the expansion ratio A 2 / A 1 of the original diffuser remain unchanged before and after the modification of the compressor and diffuser. Then, using the control variable method and according to the preset range of the upper wall expansion angle and the preset range of the lower wall expansion angle, the optimal upper wall expansion angle of the target diffuser is and the optimal lower wall expansion angle is . Then, when the expansion ratio of the virtual diffuser is the same as that of the original diffuser, the relationship satisfied among the optimal upper wall expansion angle, the optimal lower wall expansion angle, and the expansion ratio of the original diffuser is:

[0037] In the formula, represents the outer radius of the inlet flow passage of the virtual diffuser; represents the inner radius of the inlet flow passage of the virtual diffuser; represents the optimal lower wall expansion angle of the target diffuser; Denote the optimal upper wall expansion angle of the target diffuser; Denote the axial length of the target diffuser; Denote the inlet cross-sectional area of the original diffuser; Denote the outlet cross-sectional area of the original diffuser; Denote the expansion ratio of the original diffuser.

[0038] It should be noted that the control variable method is used to select the optimal upper wall expansion angle as and the optimal lower wall expansion angle as The purpose is to significantly shorten the axial length on the premise of ensuring the reduction of total pressure loss and the improvement of static pressure recovery ability of the diffuser.

[0039] Therefore, on the premise of ensuring that the expansion ratio and axial length of the diffuser remain unchanged, the meridian flow passage corresponding to the inlet of the target diffuser and the stator trailing edge of the target compressor is smoothly transitioned, as Figure 3 shown, the connection between the upper wall 7 of the target diffuser and the stator casing flow passage 5 of the target compressor is smoothly transitioned, and the connection between the lower wall 8 of the target diffuser and the stator hub flow passage 6 of the target compressor is smoothly transitioned to avoid geometric mutations.

[0040] As Figure 4 shown, the rotor in the target compressor with a super-compact coupling structure is represented by a black dotted line, and the expansion angle of the rotor casing flow passage is α , that is, the expansion angle of the rotor casing flow passage is defined as the angle between the rotor casing flow passage and the rotation axis, and the range of the expansion angle of the rotor casing flow passage is 0° < α < 5°; the expansion angle of the rotor hub flow passage is β , the expansion angle of the rotor hub flow passage is the angle between the rotor hub flow passage and the rotation axis, and its range is 0° < β < 5°. The axial chord length of the rotor in the target compressor with a super-compact coupling structure can increase by 10% - 50% with the expansion of the rotor casing flow passage and the hub flow passage. The outlet air flow velocity of the compressor rotor designed with the concept of increasing the expansion degree of the air flow passage decreases, realizing air flow deceleration and pressurization. At the same load level, the air flow passage pressurization replaces part of the blade turning pressurization. The rotor blade with a longer axial chord length and a smaller bend angle in the optimized matching design can effectively reduce the aerodynamic load of the rotor blade, thereby reducing the tip leakage flow and the end region secondary flow loss, improving the matching relationship between the compressor and the diffuser, and further enhancing the performance level of the compressor and the diffuser.

[0041] As Figure 5 shown, the stator in the target compressor with a super-compact coupling structure is represented by a black dotted line, and the expansion angle of the stator casing flow passage is δ , that is, the expansion angle of the stator casing flow passage is defined as the angle between the stator casing flow passage and the rotation axis, and the range of the expansion angle of the stator casing flow passage is 0° <δ < 5°; the stator hub flow passage divergence angle is ε , that is, the stator hub flow passage divergence angle is the angle between the stator hub flow passage and the rotating shaft, and its range is 0° < ε < 5°. The stator of the target compressor of the ultra-compact diffuser adopts a "C"-type swept three-dimensional shape design, and the tip sweep angle is the same as the root sweep angle, which is γ . The tip sweep angle is defined as the angle between the line connecting the trailing edge point of the stator tip and the trailing edge point of the blade center relative to the radial direction, and the root sweep angle is defined as the angle between the line connecting the trailing edge point of the stator root and the trailing edge point of the blade center relative to the radial direction. The range of the tip sweep angle is 0° < γ < 15°. Adopting a "C"-type swept shape design for the stator blades can suppress the flow separation in the end region, greatly increase the stable operating margin of the compressor and the diffuser, and can improve the flow field distortion at the compressor outlet, thereby significantly improving the flow field structure in the downstream diffuser and the matching relationship between the subsequent stages of the compressor and the diffuser, achieving a reduction in the total pressure loss of the diffuser and an improvement in the static pressure recovery ability.

[0042] Such as Figure 6 shown, Figure 6 The black solid line shown is the curve of the flow passage area perpendicular to the axial section along the axial direction of the subsequent stage of the traditional compressor and the target diffuser of the present invention, Figure 6 The black dashed line shown is the curve of the flow passage area perpendicular to the axial section along the axial direction of the target diffuser of the ultra-compact coupling structure based on the axial compressor-diffuser coupled design. It can be seen from Figure 6 that the target diffuser of the coupling structure of the present invention has an increased area compared to the traditional flow passage area. The ratio of the flow passage areas at the inlet and outlet sections of the subsequent stage of the target compressor of the coupling structure is less than 1, and the axial length of the target diffuser is shortened by a mm compared to the original diffuser.

[0043] Such as Figure 7 shown, Figure 7 The black solid line in is the curve of the average velocity of the airflow surface perpendicular to the axial section along the axial direction of the subsequent stage of the traditional compressor and the diffuser, Figure 7 The black dashed line in is the curve of the average velocity of the airflow surface perpendicular to the axial section along the axial direction of the subsequent stage of the target compressor and the target diffuser of the ultra-compact coupling structure based on the axial compressor-diffuser coupled design. It can be seen from Figure 7 that the average velocity of the airflow surface perpendicular to the axial section of the compressor designed by the present invention is lower than that of the traditional compressor, and on the premise that the axial length of the diffuser of the ultra-compact coupling structure is shortened by a mm, the average velocity of the airflow surface at the outlet of the compressor of the ultra-compact coupling structure can be reduced to a lower level.

[0044] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for designing an axial compressor-diffuser coupling, characterized in that: include: According to a preset expansion angle range, the flow passages corresponding to the rotor and the stator of the original compressor are expanded to obtain an expanded target compressor; Using the control variable method, and according to the preset upper wall expansion angle range and the preset lower wall expansion angle range, the optimal upper wall expansion angle and the optimal lower wall expansion angle are designed, and according to the optimal upper wall expansion angle and the optimal lower wall expansion angle, the original diffuser is expanded to obtain the target diffuser; The flow passage surface at the connection between the inlet of the target diffuser and the trailing edge of the last-stage stator of the target compressor is smoothly transitioned to form an ultra-compact coupling structure of the axial flow compressor-diffuser; The structure between the flow passage section of the rotor front end face of the target compressor of the ultra-compact coupling structure and the outlet section of the target diffuser is used as a virtual diffuser; and the expansion ratio of the virtual diffuser is the same as the expansion ratio of the original diffuser.

2. The axial flow compressor-diffuser coupling design method according to claim 1, characterized in that: The steps for designing the optimal upper wall expansion angle and the optimal lower wall expansion angle of the diffuser are: A control variable method is adopted to select a parameter combination consisting of an upper wall expansion angle and a lower wall expansion angle in a preset upper wall expansion angle range and a preset lower wall expansion angle range; Obtain the coupled static pressure recovery coefficient after the diffuser and the target compressor are coupled under each parameter combination; The parameter combination when the coupled static pressure recovery coefficient is the largest is taken as the optimal parameter combination, that is, the optimal upper wall expansion angle and the optimal lower wall expansion angle are obtained.

3. The axial flow compressor-diffuser coupling design method according to claim 1, characterized in that: When the expansion ratio of the virtual diffuser is the same as that of the original diffuser, the relationship between the optimal upper wall expansion angle, the optimal lower wall expansion angle and the expansion ratio of the original diffuser is: In the formula, represents the outer radius of the inlet flow channel of the virtual diffuser; represents the inner radius of the inlet flow channel of the virtual diffuser; represents the optimal lower wall expansion angle of the target diffuser; represents the optimal upper wall expansion angle of the target diffuser; represents the axial length of the target diffuser; represents the inlet cross-sectional area of ​​the original diffuser; represents the exit cross-sectional area of ​​the original diffuser; Represents the expansion ratio of the original diffuser.

4. The axial flow compressor-diffuser coupling design method according to claim 1, characterized in that: The preset upper wall expansion angle range is: 0°~15°; the preset lower wall expansion angle range is: 0°~15°.

5. The axial flow compressor-diffuser coupling design method according to claim 1, characterized in that: The stator trailing edge of the target compressor adopts a "C" type swept structure, and the tip sweep angle of the stator of the "C" type swept structure is equal to the root sweep angle.

6. The axial flow compressor-diffuser coupling design method according to claim 5, characterized in that: The angle ranges corresponding to the tip sweep angle and the root sweep angle are both 0°~15°.

7. The axial flow compressor-diffuser coupling design method according to claim 1, characterized in that: According to the preset expansion angle range, the steps of expanding the flow passages corresponding to the rotor and stator of the original compressor are as follows: According to the preset range of expansion angles of the rotor case flow passage, the expansion angle of the rotor case flow passage is designed; according to the preset range of expansion angles of the compressor rotor hub flow passage, the expansion angle of the rotor hub flow passage is designed; According to the preset expansion angle range of the compressor stator case flow passage, the expansion angle of the stator case flow passage is designed; according to the preset expansion angle range of the compressor stator hub flow passage, the expansion angle of the stator hub flow passage is designed; The rotor flow passage of the original compressor is expanded based on the designed rotor hub flow passage expansion angle and the designed rotor case flow passage expansion angle; the stator flow passage of the original compressor is expanded based on the designed stator hub flow passage expansion angle and the designed stator case flow passage expansion angle.

8. The axial flow compressor-diffuser coupling design method according to claim 7, characterized in that: The expansion angle range of the rotor case flow passage, the expansion angle range of the rotor case hub, the expansion angle range of the stator case flow passage and the expansion angle range of the stator hub flow passage are all: 0°~5°.

9. The axial flow compressor-diffuser coupling design method according to claim 1, characterized in that: The flow channel profile in the target diffuser is any one of an arc, a straight line, a polynomial curve, a Bezier curve, a B-spline curve, and a NURBS curve, or a combination of any two of the line types.

10. An ultra-compact coupling structure of an axial flow compressor-diffuser, characterized in that: An ultra-compact coupling structure is designed according to the axial compressor-diffuser coupling design method according to any one of claims 1 to 9.

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