Suction type cascade test device and method

Abstract

The invention discloses a suction type cascade test device and method, and the device comprises a cascade (1) and at least one suction cavity (2), the cascade (1) comprises a blade (11) and at least one grid plate (12), the blade (11) is connected to the grid plate (12), the suction cavity (2) is provided with a tapered cavity structure, one end of the suction cavity (2) is in fluid communication with the grid plate (12), and airflow passing through the blade (11) can be sucked into the suction cavity (2). The axial speed density ratio of the cascade (1) is effectively controlled, the deviation between test measurement data and a true value is reduced, and the accuracy of a test result is improved; and meanwhile, by arranging the suction cavity (2), the flowability of gas in the cascade (1) is improved, and the problem of non-uniform flow among a plurality of blades (11) is avoided, so that the periodicity in a channel of the cascade (1) is ensured, and test measurement data is more reasonable.

Description

Technical Field

[0001] The present invention relates to the field of plane blade cascade test devices, and in particular to a suction blade cascade test device and method. Background Art

[0002] During compressor design, flat cascade tests can verify the aerodynamic performance of characteristic cross-section blades, providing an important reference for blade geometry and flow design. During compressor flat cascade tests, the endwall boundary layer is prone to separation due to the strong adverse pressure gradient within the cascade passage. The lateral pressure gradient drives the fluid in the endwall boundary layer from the pressure side toward the suction side, causing the lower-energy boundary layer fluid to accumulate in the corner region formed by the suction side and the endwall. Under the influence of the adverse pressure gradient, the fluid accumulated in the corner region begins to flow back, a phenomenon known as corner separation. The presence of flow structures such as boundary layer separation and corner separation causes flow blockage near the endwall within the cascade passage, resulting in a reduction in the effective flow area at the cascade outlet and an excessively high axial velocity density ratio (AVDR). Consequently, parameters such as the loss coefficient, outlet flow angle, and blade surface pressure distribution measured during flat cascade tests deviate significantly from their true values ​​under two-dimensional flow fields, failing to reflect the two-dimensional characteristics of the blade.

[0003] In current cascade test devices, suction is usually used to remove low-energy fluid in the proximal wall area to eliminate the impact of AVDR deviation, thereby controlling the AVDR within the target range. Suction grooves are machined on the cascade plate of the cascade test piece, and the cascade plate suction grooves are covered by a suction cavity on the outer wall of the cascade plate. The suction cavity is connected to a vacuum pump, thereby achieving the purpose of removing low-energy fluid in the proximal wall area.

[0004] For the air bleed system located on the outer wall of the cascade, the bleed device commonly used in existing technical solutions is prone to backflow and blockage within the rectangular suction cavity, affecting the flow of the suctioned gas. This leads to uneven suction flow within different cascade channels, disrupting channel periodicity and failing to guarantee suction performance. In addition, the flow rates between multiple suction pipes may be unequal, increasing suction unevenness.

[0005] Patent document CN109162952B discloses an adsorption compressor cascade experimental device located within a cascade wind tunnel. Long and short suction rods are each connected to an external suction device, and a suction flow rate for the external suction device connected to the long suction rod is set. The suction flow rate for the external suction device connected to the short suction rod is set as needed to draw air from the suction surface of the blade. Through layered suction, the suction airflow from the end wall is drawn from a first-layer suction cavity, while the suction airflow from the blade suction surface is drawn from a second-layer suction cavity. The two airflows are completely separated, achieving the different requirements of boundary layer suction under different operating conditions by separately controlling the suction flow rates of the end wall and blade suction surface. However, this solution fails to address the problem in existing technical solutions where the flow within the suction cavity is prone to separation and blockage, which in turn affects the periodicity and suction effect within the cascade channel.

[0006] Patent document CN110186688B discloses a curved tail plate of a transonic flat blade turbine test bench with a hole-and-slot structure for suction, which is composed of an inner curved tail plate and a hole-shaped or slot-shaped hollow structure on the tail plate, wherein the inner curved tail plate includes a straight line segment and a quadratic curve segment as two geometric structures, and the tail plate is provided with a hole-shaped or slot-shaped hollow structure; under high Mach number and large negative angle of attack test conditions, the use of the tail plate curved surface and the hole-shaped or slot-shaped hollow structure on the tail plate can avoid the over-expansion of the wake when it leaves the tail plate and enters the suction channel, but does not solve the problem in the prior art that the flow in the suction cavity is prone to separation and blockage, which in turn affects the periodicity and suction effect in the blade channel.

[0007] In summary, the above two existing patents have not solved the problem in the existing technical solutions that the flow in the suction cavity is prone to separation, blockage, etc., which in turn affects the periodicity and suction effect in the blade channel. Summary of the Invention

[0008] Based on the above technical problems, the present invention proposes a suction blade test device and method to solve the problem that the flow in the suction cavity is prone to separation and blockage in the existing technical solutions, which in turn affects the periodicity and suction effect in the blade channel.

[0009] To achieve the above-mentioned object, the present invention provides a suction-type cascade test device.

[0010] A suction cascade test device includes a cascade and at least one suction chamber, wherein the cascade includes blades and at least one grating plate, wherein the blades are connected to the grating plate, and the suction chamber has a tapered chamber structure, wherein one end of the suction chamber is fluidically connected to the grating plate, and airflow passing through the blades can be sucked into the suction chamber.

[0011] Furthermore, the end of the suction chamber with a larger opening is connected to the grid plate.

[0012] Furthermore, the suction chamber includes a first connection port and a second connection port, the first connection port is connected to an external suction device; the second connection port is directly or indirectly connected to the grid plate.

[0013] Furthermore, the ratio of the cross-sectional area of ​​the first connecting port to the cross-sectional area of ​​the second connecting port is 0.2-0.5.

[0014] Furthermore, a through air flow channel is formed between the first connecting port and the second connecting port.

[0015] Furthermore, in the suction chamber, the midpoint of the line connecting the center of the first connecting port and the center of the first connecting port, and a plane parallel to the first connecting port is a middle cross-section, and the relationship between the equivalent diameter d of the middle cross-section, the equivalent diameter d1 of the first connecting port, and the equivalent diameter d2 of the second connecting port satisfies the following formula:

[0016]

[0017] The control coefficient k is in the range of -0.1-0.2.

[0018] Furthermore, the blades are embedded in the grid plate.

[0019] Furthermore, the grid plate includes a plurality of suction parts, and each of the suction parts is arranged corresponding to one of the blades.

[0020] Furthermore, the suction portion includes a plurality of suction grooves, and the suction grooves penetrate through two opposite surfaces of the grid plate.

[0021] Furthermore, the plurality of suction grooves in one suction portion are all parallel to the chord of the blade.

[0022] Furthermore, the plurality of suction grooves in one suction portion are arranged at equal intervals.

[0023] Furthermore, in one of the suction parts, the arrangement positions of the suction grooves are arranged in increasing distance from the blades, and the lengths of the suction grooves are arranged in decreasing inverse proportion to the distances between the suction grooves and the blades, as expressed by:

[0024] L=L0-nd,

[0025] Wherein L is the length of the suction groove, L0 is the chord length of the blade, n is the length coefficient, the range of n is 0.3-0.4, and d is the distance between the suction groove and the blade.

[0026] Furthermore, the angle formed by the blade and any side of the grid plate is 15°-60°.

[0027] Furthermore, the plurality of blades are arranged parallel to each other.

[0028] Furthermore, it includes a flat base connected to the blade grid and the suction chamber.

[0029] Furthermore, the flat base comprises a plurality of through holes (31), and the plurality of through holes (31) are all passed through two opposite surfaces of the flat base.

[0030] Furthermore, the chord length of the blade is 20 mm-100 mm.

[0031] Furthermore, the distance between the plurality of blades is 0.4 to 1.25 times the chord length of the blade.

[0032] To achieve the above object, the present invention further provides a suction cascade test method using the above suction cascade test device.

[0033] A suction cascade test method, comprising:

[0034] S1: adjusting the speed and pressure of the airflow passing through the blade according to test requirements;

[0035] S2: adjusting the suction pressure of the external suction device connected to the suction chamber to 3 kPa-101 kPa according to the axial velocity density ratio of the airflow passing through the blade;

[0036] S3: Obtaining the operating parameters of the blade through measurement.

[0037] Furthermore, the step S3 further includes:

[0038] The operating parameters of the blade include loss coefficient, outlet airflow angle and / or blade surface pressure.

[0039] Based on the above technical solution, the present invention has at least the following beneficial effects:

[0040] 1. The present invention proposes a suction-type cascade test device and method. By providing a suction chamber on the outside of the cascade, the axial velocity-density ratio of the cascade is effectively controlled, which helps reduce the deviation between the test measurement data and the true value and improves the accuracy of the test results. At the same time, the provision of the suction chamber improves the fluidity of the gas inside the cascade, avoiding the problem of uneven flow between multiple blades, thereby ensuring the periodicity within the cascade channel and making the test measurement data more reasonable.

[0041] 2. The present invention proposes a suction blade test device and method. By optimizing the shape and design of the suction slots, the problem of uneven flow between multiple suction pipes is avoided, so that the periodicity within the blade channel can be well maintained. On this basis, key parameters such as the loss coefficient, outlet airflow angle, and blade surface pressure show a good agreement with the numerical simulation results, which means that the test data can truly reflect the aerodynamic performance of the blade profile, providing an accurate and comprehensive reference basis for compressor design, and helping to improve the overall performance and reliability of the compressor.

[0042] 3. The present invention proposes a suction-type blade cascade test device and method. The suction chamber adopts a transition section structural design and a single-sided suction chamber is provided with a unique suction passage. This not only optimizes the suction effect, but also more efficiently sucks out the low-energy fluid in the proximal wall area of ​​the blade cascade channel, thereby significantly improving the flow field quality and ensuring the reliability of the test results. At the same time, the circular threaded opening design at the outlet of the suction chamber greatly facilitates the installation of the suction pipeline, simplifies the installation process, improves the practicality of the device, and enables researchers to perform test operations more conveniently, further improving the test efficiency and convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0044] Figure 1 A three-dimensional structural diagram of a suction cascade test device according to one embodiment is shown;

[0045] Figure 2 A top view of a suction cascade test apparatus according to one embodiment is shown;

[0046] Figure 3 A detailed schematic diagram of the suction portion of an embodiment is shown.

[0047] The above drawings include the following reference numerals:

[0048] 1. Blade cascade; 2. Suction chamber; 3. Flat base;

[0049] 11. Blade; 12. Grid;

[0050] 21. First connection port; 22. Second connection port;

[0051] 31. Through hole;

[0052] 121. Suction portion; 1211. Suction groove. DETAILED DESCRIPTION

[0053] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0054] The present invention is described in further detail below with reference to specific embodiments. These embodiments are not to be construed as limiting the scope of protection claimed by the present invention. The term "including" when used indicates the presence of a feature, but does not exclude the presence or addition of one or more other features; the terms "lateral", "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for ease of description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be construed as limiting the present invention; in addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance.

[0055] In this description, it should be noted that, unless otherwise specified or limited, the terms "installed," "connected," and "connected" should be understood broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to direct connections, indirect connections through an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention. Furthermore, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0056] Example

[0057] The present invention proposes a suction blade test device, such as Figure 1 As shown in the figure, it includes a cascade 1 and at least one suction chamber 2, the cascade 1 includes blades 11 and at least one grating 12, the blades 11 are connected to the grating 12, the suction chamber 2 has a tapered chamber structure, one end of the suction chamber 2 is fluidically connected to the grating 12, and the airflow passing through the blades 11 can be sucked into the suction chamber 2.

[0058] Furthermore, the suction chamber 2 is connected to an external suction device through the first connection port 21 and is connected to the flat base 3 through the second connection port 22. In other embodiments, the suction chamber 2 can be directly connected to the grid plate 12 to suck the gas flowing through the inside of the blade 1.

[0059] Furthermore, the flat base includes a through hole 31 , and the gas inside the cascade 1 is sucked into the suction chamber 2 through the suction groove 1211 and the through hole 31 by an external suction device.

[0060] Further, if Figure 1The first connecting port 21 of the suction chamber 2 shown in the figure is a circular structure, and the second connecting port 22 is a rectangular structure. In other embodiments, the second connecting port 22 may be rectangular or elliptical and cover all the suction grooves 1211 of the grid plate 12 .

[0061] Furthermore, the ratio of the cross-sectional area A1 of the first connecting port 21 of the suction chamber 2 to the cross-sectional area A2 of the second connecting port 22 is 0.4. In this embodiment, the equivalent diameter of the middle section is calculated as follows:

[0062]

[0063] Where d is the equivalent diameter of the middle section, A is the area of ​​the middle section, and the equivalent diameter expression when the second connection port 22 is rectangular is:

[0064]

[0065] Where d2 is the equivalent diameter of the second connecting port 22, a is the length of the second connecting port 22, b is the width of the second connecting port 22, and the relationship between the equivalent diameter d of the middle section, the equivalent diameter d1 of the first connecting port 21, and the equivalent diameter d2 of the second connecting port 22 satisfies the following formula:

[0066]

[0067] Furthermore, the equivalent diameter d1 of the first connecting port 21 is in the range of 65 mm to 95 mm, the equivalent diameter d2 of the second connecting port 22 is in the range of 100 mm to 150 mm, and the equivalent diameter d of the middle section is in the range of 88 mm to 128 mm.

[0068] In this embodiment, the control coefficient k is selected as 0.1. In other embodiments, k can also be set to 0.5, 0.15, etc. The equivalent diameter d1 of the first connecting port 21 is selected as 95 mm, the equivalent diameter d2 of the second connecting port 22 is selected as 150 mm, and the equivalent diameter d of the middle section is selected as 128 mm.

[0069] Table 1 Control coefficient performance table of a specific embodiment of the present invention

[0070]

[0071]

[0072] Table 1 shows a control coefficient performance table of a specific embodiment of the present invention. According to the different control coefficients k in Table 1, the flow rate ratio of the suction chamber 2 is controlled. According to the data, preferably, the equivalent diameter d1 of the first connecting port 21 is 95 mm, the equivalent diameter d2 of the second connecting port 22 is 150 mm, and the equivalent diameter d of the middle section is 128 mm.

[0073] Further, if Figure 1 As shown in FIG, eight blades 11 are arranged inside the cascade 1. The blades 11 are embedded in the cascade plate 12. The blades 11 are arranged parallel to each other. The distance between each blade 11 is 40 mm. The angle formed by the blade 11 and the edge of the cascade 1 is 45°.

[0074] Further, combined with Figure 2 and Figure 3 , wherein each blade 11 corresponds to a group of suction parts 121 , and all the suction grooves 1211 in each group of suction parts 121 are parallel to the chord of the blade 11 . In this embodiment, each group of suction parts 121 has 6 suction grooves 1211 .

[0075] Furthermore, the relationship between the blade 11 and the suction groove 1211 is as follows:

[0076] L=L0-nd,

[0077] Wherein, L is the length of the suction groove 1211 , L0 is the chord length of the blade 11 , d is the distance between the suction groove 1211 and the blade 11 , and the chord length L0 of the blade 11 ranges from 20 mm to 100 mm.

[0078] In this embodiment, the chord length L0 of the blade 11 is 30 mm, the distance between the blades 11 is 1 times the chord length L0, that is, 30 mm, the distance d between the suction grooves 1211 is 5 mm, the length coefficient n is 0.4, and the lengths of the suction grooves 1211 are 28 mm, 26 mm, 24 mm, 22 mm, 20 mm and 18 mm respectively. In other embodiments, the chord length L0 of the blade 11 can be 20 mm, 50 mm or a length within other ranges, and the length coefficient can also be 0.3 or 0.35, etc.

[0079] To achieve the above object, the present invention further provides a suction cascade test method, using the suction cascade test device described above, comprising the following steps:

[0080] S1: adjusting the speed and pressure of the airflow passing through the blade 11 according to test requirements;

[0081] S2: adjusting the suction pressure of the external suction device connected to the suction chamber 2 to 3 kPa-101 kPa according to the axial velocity density ratio of the airflow passing through the blade 11;

[0082] Specifically, in this embodiment, the pressure of the external suction device is adjusted to 50kPa. In other embodiments, the pressure of the external suction device can be adjusted within the range of 3kPa-101kPa to 3kPa, 15kPa, 40kPa, 80kPa or 101kPa, etc., according to experimental requirements.

[0083] S3: Obtaining the operating parameters of the blade 11 through measurement.

[0084] Furthermore, the step S3 further includes:

[0085] The operating parameters of the blade 11 include a loss coefficient, an outlet airflow angle and / or a surface pressure of the blade 11 .

[0086] Furthermore, the axial velocity of the fluid between the blades 11 and the density of the fluid are collected to calculate the axial velocity density ratio, which is expressed as follows:

[0087]

[0088] Where AVDR is the axial velocity density ratio, V2 is the fluid axial velocity of the airflow outlet section, ρ2 is the fluid density of the airflow outlet section, V1 is the fluid axial velocity of the airflow inlet section, and ρ1 is the fluid density of the airflow inlet section.

[0089] In summary, it can be seen from the above description that the above embodiments of the present invention achieve the following technical effects:

[0090] 1. The present invention proposes a suction-type cascade test device and method. By providing a suction chamber on the outside of the cascade, the axial velocity-density ratio of the cascade is effectively controlled, which helps reduce the deviation between the test measurement data and the true value and improves the accuracy of the test results. At the same time, the provision of the suction chamber improves the fluidity of the gas inside the cascade, avoiding the problem of uneven flow between multiple blades, thereby ensuring the periodicity within the cascade channel and making the test measurement data more reasonable.

[0091] 2. The present invention proposes a suction blade test device and method. By optimizing the shape and design of the suction slots, the problem of uneven flow between multiple suction pipes is avoided, so that the periodicity within the blade channel can be well maintained. On this basis, key parameters such as the loss coefficient, outlet airflow angle, and blade surface pressure show a good agreement with the numerical simulation results, which means that the test data can truly reflect the aerodynamic performance of the blade profile, providing an accurate and comprehensive reference basis for compressor design, and helping to improve the overall performance and reliability of the compressor.

[0092] 3. The present invention proposes a suction-type blade cascade test device and method. The suction chamber adopts a transition section structural design and a single-sided suction chamber is provided with a unique suction passage. This not only optimizes the suction effect, but also more efficiently sucks out the low-energy fluid in the proximal wall area of ​​the blade cascade channel, thereby significantly improving the flow field quality and ensuring the reliability of the test results. At the same time, the circular threaded opening design at the outlet of the suction chamber greatly facilitates the installation of the suction pipeline, simplifies the installation process, improves the practicality of the device, and enables researchers to perform test operations more conveniently, further improving the test efficiency and convenience.

[0093] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

[0094] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0095] It should be noted that, in the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

Claims

1. A suction cascade test device, characterized in that: The invention comprises a blade cascade (1) and at least one suction chamber (2), wherein the blade cascade (1) comprises blades (11) and at least one grid plate (12), wherein the blades (11) are connected to the grid plate (12), and the suction chamber (2) has a tapered chamber structure, wherein one end of the suction chamber (2) is fluidically connected to the grid plate (12), and an airflow passing through the blades (11) can be sucked into the suction chamber (2).

2. The device according to claim 1, characterized in that The end of the suction chamber (2) with a larger opening is connected to the grid plate (12).

3. The device according to claim 2, characterized in that The suction chamber (2) comprises a first connecting port (21) and a second connecting port (22), The first connection port (21) is connected to an external suction device; The second connection port (22) is directly or indirectly connected to the grid plate (12).

4. The device according to claim 3, characterized in that The ratio of the cross-sectional area of ​​the first connecting port (21) to the cross-sectional area of ​​the second connecting port (22) is 0.2-0.

5.

5. The device according to claim 3, characterized in that: A through air flow channel is formed between the first connecting port (21) and the second connecting port (22).

6. The device according to claim 3, characterized in that In the suction chamber (2), the center of the first connecting port (21) and the midpoint of the line connecting the center of the first connecting port (21), and the plane parallel to the first connecting port (21) are the middle section, and the relationship between the equivalent diameter d of the middle section and the equivalent diameter d1 of the first connecting port (21) and the equivalent diameter d2 of the second connecting port (22) satisfies the following formula: The control coefficient k is in the range of -0.1-0.

2.

7. The device according to claim 1, characterized in that The blades (11) are embedded in the grid plate (12).

8. The device according to claim 1, characterized in that The grid plate (12) includes a plurality of suction portions (121), Each of the suction portions (121) is provided corresponding to one of the blades (11).

9. The device according to claim 8, characterized in that The suction portion (121) includes a plurality of suction grooves (1211) The suction groove (1211) passes through two opposite surfaces of the grid plate (12).

10. The device according to claim 9, characterized in that: The plurality of suction grooves (1211) in one suction portion (121) are all parallel to the chord of the blade (11).

11. The device according to claim 10, characterized in that The plurality of suction grooves (1211) in one suction portion (121) are arranged at equal intervals.

12. The device according to claim 9, characterized in that In one of the suction portions (121), the arrangement positions of the suction grooves (1211) are arranged such that the distance from the blades (11) increases, and the length of the suction grooves (1211) decreases in inverse proportion to the distance between the suction grooves (1211) and the blades, as expressed by: L=L0-nd, Wherein L is the length of the suction groove (1211), L0 is the chord length of the blade (11), n ​​is the length coefficient, the range of n is 0.3-0.4, and d is the distance between the suction groove (1211) and the blade (11).

13. The device according to claim 1, characterized in that The angle formed by the blade (11) and any side of the grid plate (12) is 15°-60°.

14. The device according to claim 1, characterized in that The plurality of blades (11) are arranged parallel to each other.

15. The device according to claim 1, characterized in that comprising a flat base (3), The flat plate base (3) is connected to the blade grid (1) and the suction chamber (2).

16. The device according to claim 15, characterized in that The flat base (3) includes a plurality of through holes (31), The plurality of through holes (31) are all passed through two opposite surfaces of the flat plate base (3).

17. The device according to claim 1, characterized in that The chord length of the blade (11) is 20 mm to 100 mm.

18. The device according to claim 1, characterized in that The distance between the plurality of blades (11) is 0.4 to 1.25 times the chord length of the blade (11).

19. A test method using the suction cascade test device according to any one of claims 1 to 18, characterized in that: include: S1: adjusting the speed and pressure of the airflow passing through the blade (11) according to test requirements; S2: adjusting the suction pressure of the external suction device connected to the suction chamber (2) to 3 kPa-101 kPa according to the axial velocity density ratio of the airflow passing through the blade (11); S3: Obtaining the operating parameters of the blade (11) by measurement.

20. The method according to claim 19, characterized in that The step S3 further includes: The operating parameters of the blade (11) include loss coefficient, outlet airflow angle and / or blade surface pressure.

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