A plane cascade test piece with cold air injection for realizing flow birefringence

Abstract

The present application belongs to the technical field of aero-engine impeller mechanical test, and provides a plane cascade test piece with cold air injection for realizing flow binary, which comprises a blade body, a cold air duct and a gas collection cavity. The blade body surface is provided with a plurality of cold air grooves extending along the blade height direction; the cold air duct is arranged inside the blade body, and the upper and lower ends thereof are respectively provided with an inlet; an array of film holes is formed on the pipe wall; and the gas collection cavity is formed by the cold air duct outer wall and the blade body inner wall. The cold air is introduced from the upper and lower inlets, flows into the gas collection cavity through the array of film holes, is mixed, and is uniformly sprayed out through the cold air grooves. The present application eliminates the velocity component and flow unevenness of the cold air in the blade height direction through the mixing effect of the gas collection cavity, combines the geometric configuration of the continuous cold air groove, simultaneously meets the requirements of plane cascade test on geometric and physical flow binary, and solves the technical problems of cold air local accumulation and non-binary flow in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of aero-engine turbomachinery testing technology, and relates to a test piece with a cold gas injection planar blade cascade that realizes flow duality. Background Technology

[0002] Blade design is fundamental to the development of aero-engine turbomachinery (such as compressors and turbines), directly impacting their aerodynamic efficiency. Planar blade cascade testing involves conducting airflow tests on a specific section (or a novel two-dimensional blade profile) of a turbine or compressor blade within a finite, planar blade array to determine the influence of different aerodynamic parameters on blade performance, thereby validating the design results. Due to its low cost, short development cycle, and high controllability, planar blade cascade testing has become an important tool for aerodynamic design and theoretical research in turbomachinery.

[0003] However, real blade cascades contain complex three-dimensional flow structures, including shock waves, boundary layer separation, endwall boundary layers, and secondary vortices. The core assumption of planar blade cascade experiments is that the flow should be strictly confined to a two-dimensional plane, meaning the flow state is consistent across all sections along the blade height, minimizing three-dimensional effects. To meet this "two-dimensionality" requirement, traditional test specimen designs often employ the following measures:

[0004] (1) Arrange 6 to 7 blade channels to form an approximately infinite blade cascade; (2) Increase the blade aspect ratio to keep the central region away from the influence of the endwall secondary flow; (3) Under high load conditions, the development of the boundary layer on the end wall is controlled by front-gate suction or venting.

[0005] The methods described above can basically meet the duality requirements in conventional planar blade cascades without cooled gas injection. However, modern high-performance aero-engine turbines generally employ active cooling technologies such as film cooling, and the introduction of cooled gas significantly alters the flow field structure, posing new challenges to the design of experimental components.

[0006] Currently, most planar blade cascades with cooling air injection adopt a "two-end air supply + discrete film cooling holes" scheme (such as...). Figure 1 (As shown). However, this approach has two fundamental problems: First, there is the geometric non-binary nature: the air film pores are discontinuously distributed along the leaf height direction, which disrupts the two-dimensional continuity; Second, the flow is non-binary: after the cold air is ejected, it interacts with the mainstream, inducing three-dimensional vortex structures such as kidney-shaped vortices (e.g., Figure 2 As shown, this violates the fluid duality assumption.

[0007] To improve geometric continuity, one approach is to replace the film cooling orifice with a cooling air slot extending along the blade height. While this geometrically satisfies the duality requirement, the cooling air must be introduced from the outside. Regardless of whether the air is supplied from one or both sides, there is a velocity component and pressure loss along the blade height within the air supply channel. This results in uneven cooling air flow and velocity along the blade height at the slot outlet, thus failing to achieve true flow duality. Summary of the Invention

[0008] To address the problem that existing test schemes for planar blade cascades with cooling gas injection cannot meet the requirements of flow duality in terms of both geometry and flow characteristics, this invention discloses a test piece for planar blade cascades with cooling gas injection that achieves flow duality. The test piece for planar blade cascades with cooling gas injection includes a blade body, a cooling gas duct, a cooling gas groove, and a gas collection chamber.

[0009] Specifically, the surface of the blade body is provided with multiple cooling air grooves extending along the blade height direction; the cooling air duct is disposed inside the blade body, with an upper inlet and a lower inlet at its upper and lower ends respectively, and the wall of the cooling air duct is provided with an array of air film holes; the air collection chamber is formed by the outer wall of the cooling air duct and the inner wall of the blade body. The cold air is introduced from the upper inlet and the lower inlet, flows out through the air film hole array and enters the air collection chamber. It is mixed in the air collection chamber to eliminate the velocity component along the blade height direction, and finally is injected into the main flow through multiple cold air slots to keep the cold air flow rate and aerodynamic parameters consistent at different blade height sections, so as to achieve flow duality.

[0010] Furthermore, the pressure and flow rate of the cold air introduced from the upper inlet and the lower inlet are configured to be consistent to form a vertically symmetrical flow field within the air collection chamber.

[0011] Furthermore, multiple cooling gas slots are distributed on the pressure and suction surfaces of the blade body and are located within the chordal range covered by the gas collection chamber. The chordal position and density of each cooling gas slot are configured according to the required aerodynamic performance so that the cooling gas ejected from different blade height sections can achieve flow duality.

[0012] Furthermore, the number of cooling air slots is 3 to 8.

[0013] Furthermore, the cooling air duct is disposed in the leading edge region of the blade body, with its front end located within 0% to 5% chord length downstream of the blade leading edge stagnation point, and its rear end not exceeding 25% chord length.

[0014] Furthermore, the cross-section of the cooling air duct is arc-shaped, and its outer wall profile matches the local profile of the leading edge of the blade, so that the air collecting chamber has a flow cross section that gradually expands from the leading edge to the trailing edge in the leading edge region.

[0015] Preferably, the axial projection length of the cooling air duct is 15% to 25% of the blade chord length, and its maximum thickness is located in the middle of the blade cascade, gradually thinning in the upstream and downstream direction.

[0016] Furthermore, the air film pore array is distributed in multiple rows and columns on the wall of the cold air duct; Define P as the center-to-center distance between adjacent film pores in the direction from the leading edge to the trailing edge. a The center-to-center distance between adjacent film pores along the leaf height direction is P. h In the region near the leading edge, P h ≤P a In the trailing edge region, P h >P a .

[0017] Furthermore, the air film pores in the air film pore array are uniformly distributed and satisfy the following parameter relationship: (a) The pore diameter D of the air film pores satisfies: 0.4 mm ≤ D ≤ 0.6 mm; (b) The center-to-center distance P between adjacent film pores in the direction from the leading edge to the trailing edge a Satisfy: 2.5D ≤ P a ≤ 3.5D; (c) Distance P between adjacent film pores along the leaf height direction h In the leading edge region, the following condition is satisfied: 5D ≤ P h ≤ 7D; (d) Distance P between adjacent film pores along the leaf height direction h In the trailing edge region, the following condition is satisfied: 7D ≤ P h ≤ 9D; (e) The wall thickness t of the air duct satisfies: 0.4 mm ≤ t ≤ 0.6 mm.

[0018] Furthermore, the thickness of the gas collecting cavity at any position is not less than 1 mm.

[0019] Compared with the prior art, the present invention has at least the following advantages: (1) A continuously extending cold air trough along the blade height direction is used for jetting, which meets the basic requirements of flow duality in the planar blade cascade test in terms of geometric configuration; (2) By using the mixing design in the gas collection chamber, the velocity component of the cold air in the blade height direction is effectively eliminated, so that the flow of cold air is strictly limited to the two-dimensional plane of the blade height section. (3) It avoids the accumulation or uneven distribution of cold air in local areas and achieves high uniformity of cold air flow and outflow state throughout the entire blade height range. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The existing planar blade cascade test specimen design with cooling air; Figure 2 It is a three-dimensional vortex structure downstream of the film air vent; Figure 3 The present invention provides a test specimen with a cooling gas injection planar blade cascade that realizes flow duality; Figure 4 A view of the film film aperture array on a planar blade cascade test specimen with cooling gas injection; Among them, 100 is the blade body; 200 is the air duct; 300 is the air duct; and 400 is the air collection chamber. Detailed Implementation

[0022] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0023] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features of the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] like Figure 3 and Figure 4 As shown, this embodiment of the invention discloses a planar blade cascade test piece with cooling gas injection that realizes flow duality. The test piece includes a blade body 100, a cooling gas duct 200, a cooling gas groove 300, and a gas collection chamber 400.

[0025] The blade body 100 has multiple cooling air grooves 300 extending along the blade height direction on its surface; a cooling air duct 200 is disposed inside the blade body 100, with an upper inlet and a lower inlet at its upper and lower ends, respectively, and an array of air film holes is formed on the duct wall of the cooling air duct 200; the air collecting chamber 400 is formed by the outer wall of the cooling air duct 200 and the inner wall of the blade body 100.

[0026] The cold air is introduced from the upper inlet and the lower inlet, flows out through the air film perforation array and enters the air collection chamber 400. It is mixed in the air collection chamber 400 to eliminate the velocity component along the blade height direction, and finally is injected into the main flow through multiple cold air slots 300. This can meet the duality requirements of the planar blade cascade test in terms of geometric configuration, so that the cold air flow rate and aerodynamic parameters at different blade height sections are kept consistent, and the flow duality is achieved.

[0027] The test specimen provided by this invention, by incorporating a dual-inlet cooling gas duct 200 and a gas collection chamber 400 inside the blade, ensures thorough mixing of the cooling gas before it enters the cooling gas duct 300, effectively eliminating velocity component and flow unevenness along the blade height direction, thus achieving physical flow duality. Simultaneously, the use of a cooling gas duct 300 extending along the blade height direction guarantees geometric duality. This design solves the problem in existing technologies where planar blade cascade tests with cooling gas injection cannot simultaneously achieve geometric and physical duality, providing a reliable technical means for verifying the aerodynamic performance of high-precision airfoils.

[0028] In one embodiment, the pressure and flow rate of the cold air introduced from the upper inlet and the lower inlet are configured to be consistent. On the one hand, this can reduce the speed of the cold air along the blade height under the same air supply flow rate. On the other hand, it can form a vertically symmetrical flow field in the air collection chamber 400, so that the cold air flows vertically symmetrically in the middle position of the blade, which is beneficial to ensuring the duality of flow.

[0029] In one embodiment, a plurality of cooling gas slots 300 are distributed on the pressure and suction surfaces of the blade body 100 and are located within the chordal range covered by the air collection chamber 400. The chordal position and density of each cooling gas slot 300 are configured according to the required aerodynamic performance so that the cooling gas ejected from different blade height sections can achieve flow duality. Preferably, the number of cooling gas slots 300 is 3 to 8.

[0030] In one embodiment, the cooling air duct 200 is disposed in the leading edge region of the blade body 100, with its front end located within 0% to 5% of the chord length downstream of the blade leading edge stagnation point and its rear end not exceeding 25% of the chord length.

[0031] In one embodiment, such as Figure 3 As shown, the cooling air duct 200 can be integrally formed with the blade body by 3D printing or precision casting, or fixed by interference fit and welding. Its cross-section is arc-shaped, and its outer wall contour matches the local profile of the leading edge of the blade, so that the air collection chamber 400 has a flow cross section that gradually expands from the leading edge to the trailing edge in the leading edge region.

[0032] Preferably, the axial projection length of the cooling air duct 200 is 15% to 25% of the blade chord length, and its maximum thickness is located in the middle of the blade cascade, gradually thinning in the upstream and downstream direction.

[0033] In one embodiment, the air film pore array is distributed in multiple rows and columns on the wall of the cold air duct 200. The air film pores can eliminate the velocity of the cold air along the blade height direction, so that the cold air enters the air collection chamber 400 along a two-dimensional plane.

[0034] In practice, the center-to-center distance between adjacent film pores in the direction from the leading edge to the trailing edge is defined as P. a The center-to-center distance between adjacent film pores along the leaf height direction is P. h In the region near the leading edge, P h ≤P a In the trailing edge region, P h >P a .

[0035] In one embodiment, the air film pores in the air film pore array are uniformly distributed and satisfy the following parameter relationship: (a) The pore diameter D of the air film pores satisfies: 0.4 mm ≤ D ≤ 0.6 mm; (b) The center-to-center distance P between adjacent film pores in the direction from the leading edge to the trailing edge a Satisfy: 2.5D ≤ P a ≤ 3.5D; (c) Distance P between adjacent film pores along the leaf height direction h In the leading edge region, the following condition is satisfied: 5D ≤ P h ≤ 7D; (d) Distance P between adjacent film pores along the leaf height direction h In the trailing edge region, the following condition is satisfied: 7D ≤ P h ≤ 9D; (e) The wall thickness t of the air duct 200 satisfies: 0.4 mm ≤ t ≤ 0.6 mm.

[0036] For example, the aperture D of the film cooling hole on the air duct 200 can be determined according to the blade size and actual machining capability. In this example, the aperture D of the film cooling hole can be 0.5 mm, and the guide holes are spaced axially (i.e., the center distance between adjacent film cooling holes in the direction from the leading edge to the trailing edge) P. a Set to 3D, leaf height direction spacing (i.e., the center distance P between adjacent film pores along the leaf height direction). h The setting is 7D, and the thickness of the air duct is 0.5mm.

[0037] In one embodiment, the thickness of the gas collecting cavity 400 at any position is not less than 1 mm.

[0038] During operation, two streams of cool air with identical pressure and flow rate enter the cool air duct 200 through the upper and lower inlets, respectively, and then flow into the air collection chamber 400 through the film cooling perforation array. Within the air collection chamber 400, the cool air from both ends is thoroughly mixed, eliminating the original velocity gradient along the blade height and creating a uniform pressure field. Finally, the uniform cool air is ejected through the cool air duct 300, interacting with the mainstream. Because the ejected cool air has consistent parameters along the blade height, the flow duality of the entire flow field is ensured, meeting the requirements of high-precision planar cascade experiments.

[0039] Compared with the prior art, the present invention has at least the following advantages: (1) A continuously extending cold air trough along the blade height direction is used for jetting, which meets the basic requirements of flow duality in the planar blade cascade test in terms of geometric configuration; (2) By using the mixing design in the gas collection chamber, the velocity component of the cold air in the blade height direction is effectively eliminated, so that the flow of cold air is strictly limited to the two-dimensional plane of the blade height section. (3) It avoids the accumulation or uneven distribution of cold air in local areas and achieves high uniformity of cold air flow and outflow state throughout the entire blade height range.

[0040] Obviously, those skilled in the art should understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Various modifications and variations of the embodiments of the present invention are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A test specimen with a cooling gas injection planar blade cascade realizing flow duality, characterized in that, include: The blade body (100) has a plurality of cooling air grooves (300) extending along the blade height direction on its surface. A cooling air duct (200) is disposed inside the blade body (100), with an upper inlet and a lower inlet at its upper and lower ends, respectively, and an array of air film holes is formed on the wall of the cooling air duct (200). The air collection chamber (400) is formed by the outer wall of the cold air duct (200) and the inner wall of the blade body (100); The cold air is introduced from the upper inlet and the lower inlet respectively, flows out through the air film hole array and enters the air collection chamber (400). It is mixed in the air collection chamber (400) to eliminate the velocity component along the blade height direction, and finally is injected into the main flow through multiple cold air slots (300) so that the cold air flow rate and aerodynamic parameters at different blade height sections are kept consistent, and the flow duality is realized. The pressure and flow rate of the cold air introduced from the upper inlet and the lower inlet are configured to be consistent to form a vertically symmetrical flow field within the air collection chamber (400); The air film pore array is distributed in multiple rows and columns on the wall of the cold air duct (200), and the center distance between adjacent air film pores in the direction from the leading edge to the trailing edge is defined as P. a The center-to-center distance between adjacent air film pores along the leaf height direction is P. h In the region near the leading edge, P h ≤P a In the trailing edge region, P h >P a ; The air film pores in the air film pore array are uniformly distributed and satisfy the following parameter relationship: (a) The pore diameter D of the air film pores satisfies: 0.4 mm ≤ D ≤ 0.6 mm; (b) The center-to-center distance P between adjacent film pores in the direction from the leading edge to the trailing edge a Satisfy: 2.5D ≤ P a ≤ 3.5D; (c) Distance P between adjacent film pores along the leaf height direction h In the leading edge region, the following condition is satisfied: 5D ≤ P h ≤ 7D; (d) Distance P between adjacent film pores along the leaf height direction h In the trailing edge region, the following condition is satisfied: 7D ≤ P h ≤ 9D; (e) The wall thickness t of the air duct (200) satisfies: 0.4 mm ≤ t ≤ 0.6 mm.

2. The experimental specimen with a cooling gas injection planar blade cascade realizing flow duality according to claim 1, characterized in that, Multiple cooling gas slots (300) are distributed on the pressure surface and suction surface of the blade body (100) and are located within the chordal range covered by the gas collection chamber (400). The chordal position and density of each cooling gas slot (300) are configured according to the required aerodynamic performance so that the cooling gas ejected from different blade height sections can achieve flow duality.

3. The experimental specimen with a cooling gas injection planar blade cascade realizing flow duality according to claim 1 or 2, characterized in that, The number of the cold air ducts (300) is 3 to 8.

4. The experimental specimen with a cooling gas injection planar blade cascade realizing flow duality according to claim 1, characterized in that, The cooling air duct (200) is located in the leading edge region of the blade body (100), with its front end located within 0% to 5% of the chord length downstream of the blade leading edge stagnation point, and its rear end located no more than 25% of the chord length.

5. The experimental specimen with a cooling gas injection planar blade cascade realizing flow duality according to claim 4, characterized in that, The cross-section of the cooling air duct (200) is arc-shaped, and its outer wall profile matches the local profile of the leading edge of the blade, so that the air collecting chamber (400) has a flow cross section that gradually expands from the leading edge to the trailing edge in the leading edge region.

6. The experimental specimen with a cooling gas injection planar blade cascade realizing flow duality according to claim 5, characterized in that, The axial projection length of the cooling air duct (200) is 15% to 25% of the blade chord length, and its maximum thickness is located in the middle of the blade cascade, gradually thinning in the upstream and downstream direction.

7. The experimental specimen with a cooling gas injection planar blade cascade realizing flow duality according to claim 1, characterized in that, The thickness of the gas collecting chamber (400) at any position is not less than 1 mm.

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