Slotted blade with wide-range self-adaptability

Abstract

The invention discloses a slotted blade with wide-area self-adaptability, which belongs to the technical field of fluid machinery and comprises a blade main body, a jet flow seam, an air entraining port, a jet flow port and a variable-rigidity flexible valve. The jet flow seam penetrates through the blade body, an air entraining opening and a jet flow opening are formed in the two ends of the jet flow seam respectively, the air entraining opening is located in the pressure face side of the blade body, the jet flow opening is located in the suction face side of the blade body, and the variable-rigidity flexible valves are located in the jet flow seam and installed on the two side wall faces of the jet flow seam. The variable-rigidity flexible valve is installed in the jet flow seam and can be opened or closed in a self-adaptive mode according to the working condition of the blade. The variable-stiffness flexible valve is made of metamaterials and has the variable-stiffness characteristic, and the adaptability of the blade is further improved. According to the invention, self-adaptive adjustment can be realized in a relatively wide working range, the flow loss is reduced, and the operation efficiency of the device is ensured.

Description

Technical Field

[0001] The present invention relates to a slotted blade with wide-range adaptability, belonging to the technical field of fluid machinery. Background Art

[0002] In various axial compressors targeted at applications such as aero gas turbine engines, obtaining a higher pressure ratio for a single-stage compressor has been the long-term development direction in the field of compressors. When attempting to increase the load of a single-stage compressor significantly beyond the current level, the compressor pressure ratio and efficiency will drop sharply or even lead to compressor stall due to the occurrence of flow separation on the blade back. Therefore, various flow control technologies that can suppress or even eliminate flow separation have attracted the attention of researchers at home and abroad.

[0003] Based on the existing work in the field of flow control at home and abroad, the related technologies mainly fall into two categories: (1) Passive flow control technologies, such as slotted blades, tandem blades, trip wires, vortex generators, etc. (2) Active flow control technologies, such as suction compressors, synthetic jets, acoustic excitation, plasma excitation, traveling wave wall control, etc.

[0004] To meet the needs of future higher-load compressor blade designs, these technologies have significant deficiencies from the perspective of practical engineering applications. The characteristic of active flow control technologies is that they require external energy input. Their advantage is that the flow control parameters can be adjusted according to the operating conditions, but they usually have complex structures, require external gas sources or power supplies, and require many auxiliary devices, so they are difficult to implement in practical engineering applications. The characteristic of passive flow control technologies is that they do not require external energy input. They have the advantages of simple structure, easy implementation, long service life, etc., but their main disadvantage is that the flow control parameters cannot be adjusted according to the operating conditions. For example, Figure 1 shows the comparison of loss coefficients between slotted blades and seamless blades at different angles of attack. It can be seen that in the case of small angles of attack, the seamless blade has better performance; while in the case of large angles of attack, the slotted blade has better performance. The above analysis requires that passive control has stronger adaptability to variable operating conditions.

[0005] Therefore, it is imperative to seek a new technology that combines the strong engineering applicability of passive flow control technologies and the strong operating condition adaptability of active flow control technologies. Summary of the Invention

[0006] The object of the present invention is to overcome the deficiencies in the prior art and provide a slotted blade with wide-range self-adaptability, which can adaptively close or open the jet without introducing an external gas source or power source, so as to not only have a good inhibitory effect on the flow separation on the suction surface of the blade under large angle of attack conditions, but also reduce the flow loss inside the device when there is no separation at small angles of attack, thereby solving the problem in the prior art that seamless and slotted blades are suitable for different working conditions.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions: In a first aspect, the present invention provides a slotted blade with wide-range self-adaptability, including: a blade body, a jet slot, an air intake port, a jet port, and a variable stiffness flexible valve. The jet slot penetrates through the blade body, and its two ends are respectively an air intake port and a jet port. The air intake port is located on the pressure surface side of the blade body, and the jet port is located on the suction surface side of the blade body. The variable stiffness flexible valve is located in the jet slot and is installed on the two side walls of the jet slot. When the angle of attack of the blade body is greater than a set threshold, the variable stiffness flexible valve is in an open state, and a jet is generated at the jet port to inhibit the flow separation on the suction surface. When the angle of attack of the blade body is less than the set threshold, the variable stiffness flexible valve is in a closed state, and no jet is generated at the jet port.

[0008] Further, the number of the jet slots N ≥1, and the jet slots are arranged at different positions in the chord direction of the blade, and at most N jets can be generated simultaneously.

[0009] Further, the variable stiffness flexible valve is a cantilever structure installed on both sides of the jet slot.

[0010] Further, the number of variable stiffness flexible valves in each jet slot M ≥1.

[0011] Further, the variable stiffness flexible valve is installed in the jet slot in the forward or reverse direction.

[0012] Further, when the variable stiffness flexible valve is installed in the forward direction, the variable stiffness flexible valve opens when the pressure difference △ P between the air intake port and the jet port is greater than the set threshold and closes when it is less than the set threshold. When the variable stiffness flexible valve is installed in the reverse direction, the variable stiffness flexible valve opens when △ P is less than the set threshold and closes when it is greater than the set threshold.

[0013] Further, the variable stiffness flexible valve is made of a metamaterial with variable stiffness characteristics.

[0014] Furthermore, the variable-stiffness flexible valve uses a porous metamaterial. When the ambient pressure around the variable-stiffness flexible valve becomes higher, the porosity of the material decreases, resulting in a higher stiffness. When the ambient pressure around the variable-stiffness flexible valve becomes lower, the porosity of the material increases, resulting in a lower stiffness.

[0015] Furthermore, the variable-stiffness flexible valves near the leading edge of the blade are installed forward, and the variable-stiffness flexible valves near the trailing edge of the blade are installed backward.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The present invention provides a slotted blade with wide-range adaptability, which can automatically close and open single or multiple jets under different working conditions only relying on its own structure. Thus, it can adaptively open the jets at a large angle of attack to suppress the flow separation on the suction surface of the blade, and close the jet slots at a small angle of attack to reduce the flow loss inside the device. It does not require external energy sources such as air sources or power sources and external auxiliary devices, so it has the advantages of relatively simple structure, strong adaptability, and strong engineering practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 shows the relationship between the loss coefficients of seamless and slotted blades and the angle of attack; Figure 2 is a typical compressor pressure ratio - flow characteristic diagram; Figure 3 is a schematic diagram of a wide-range adaptive slotted blade at a large angle of attack (valve open); Figure 4 is a schematic diagram of a wide-range adaptive slotted blade at a small angle of attack (valve closed); Figure 5 is a schematic diagram of a variable-stiffness flexible valve made of porous material (undeformed state).

[0018] 1. Blade body; 2. Jet slot; 3. Air intake port; 4. Jet port; 5. Variable-stiffness flexible valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0021] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0022] Example 1, as Figure 1 shown, when the angle of attack is small, the loss coefficient of the seamless blade is low; while when the angle of attack is large, the loss coefficient of the slotted blade is low. Therefore, for the slotted blade, we hope that the slot automatically closes at a small angle of attack and automatically opens at a large angle of attack, thereby enhancing the self - adaptability of the blade.

[0023] As Figure 2 shown, according to the characteristic diagram of the compressor, enhancing the self - adaptability should start from two aspects. On the one hand, it is to enhance its self - adaptability to variable angles of attack (distance from the surge boundary), and on the other hand, it is to enhance its self - adaptability to variable speeds.

[0024] As Figure 3 shown, this embodiment introduces a slotted blade with wide - range self - adaptability, including: blade body 1, jet slot 2, air - intake port 3, jet port 4, variable - stiffness flexible valve 5. Among them, the jet slot 2 penetrates through the blade body 1, and its two ends are respectively the air - intake port 3 and the jet port 4. The air - intake port 3 is located on the pressure - side of the blade body 1, the jet port 4 is located on the suction - side of the blade body 1, and the variable - stiffness flexible valve 5 is located inside the jet slot 2 and installed on its two side walls. As Figure 3As shown, when the blade body 1 is in the large angle of attack condition, the variable stiffness flexible valve 5 is in the open state, and a jet flow is generated at the jet orifice 4 to suppress the flow separation on the suction surface. As Figure 4 shown, when the blade body 1 is in the small angle of attack condition, the variable stiffness flexible valve 5 is in the closed state, and no jet flow is generated at the jet orifice 4. Therefore, the blade can adaptively generate or close the jet flow within a wide working range, reduce the flow loss, and ensure the operation efficiency of the device.

[0025] The number of the jet slots 2 N ≥1, and they are arranged at different positions in the chord direction of the blade, and at most N jets can be generated simultaneously ( Figure 3 in the embodiment N =2).

[0026] The variable stiffness flexible valve 5 is a cantilever structure installed on both sides of the jet slot 2, and the number of valves in each jet slot 2 M ≥1 ( Figure 3 in the embodiment M =2).

[0027] The variable stiffness flexible valve 5 can be installed in the jet slot 2 in the forward or reverse direction. When installed in the forward direction, the variable stiffness flexible valve 5 opens when the pressure difference △ P between the air intake port 3 and the jet orifice 4 is large (as Figure 3 shown), and closes when it is small (as Figure 4 shown); when installed in the reverse direction, the variable stiffness flexible valve 5 opens when △ P is small (as Figure 3 shown), and closes when it is large (as Figure 4 shown). In addition, the variable stiffness flexible valves in different jet slots do not need to be opened or closed synchronously. This characteristic can enhance the adaptability of the blade to the variable angle of attack (i.e., Figure 2 the adaptability in the direction of the change of the angle of attack).

[0028] As Figure 5 shown, the variable stiffness flexible valve 5 is made of metamaterial, such as porous material, so as to have the variable stiffness characteristic. When the ambient pressure around the variable stiffness flexible valve 5 is high (i.e., Figure 2 in the direction of increasing Mach number or increasing rotational speed), the porosity of the material decreases, so as to have a higher stiffness; while when the ambient pressure around it is low, the porosity of the material increases, so as to have a lower stiffness (i.e., Figure 2 in the direction of decreasing Mach number or decreasing rotational speed). This characteristic can enhance the adaptability of the blade to the variable Mach number or variable rotational speed (i.e., Figure 2 the adaptability in the direction of the change of Mach number or rotational speed).

[0029] For the forward and reverse installation of the variable-stiffness flexible valve 5, it is characterized in that the variable-stiffness flexible valve 5 usually close to the leading edge is installed forward, while the variable-stiffness flexible valve 5 close to the trailing edge is installed reversely (as Figure 3 and Figure 4 shown).

[0030] Next, a preferred embodiment is used to illustrate the content involved in the above embodiments.

[0031] As Figure 3 shown, for a typical stator blade of a large diffuser low-speed compressor, its chord length is 100 mm and the maximum thickness is 10 mm. The number of jet slots N = 2, and the number of valves in each jet slot M = 2. The two jet slots are respectively arranged at the positions near the leading edge and near the trailing edge. The valves in the jet slot near the leading edge are arranged forward, and the valves in the jet slot near the trailing edge are arranged reversely. As Figure 1 and Figure 2 shown, at the design rotational speed, when the angle of attack α < 16°, the valves in the two jet slots are both in the closed state, and no jet flow is generated in the two jet slots; when the angle of attack α > 16°, due to the increase in the angle of attack, the blade is in the forward-loaded state. The pressure on both sides of the valve in the jet slot near the leading edge increases, while the pressure on both sides of the valve in the jet slot near the trailing edge decreases. Therefore, the valves in the two jet slots open simultaneously, generating two jets, which can effectively suppress the flow separation on the suction surface of the blade and maintain low flow losses. The variable-stiffness flexible valve is made of a porous material, and its porosity is 0.1 at the design rotational speed. As Figure 2 shown, when the rotational speed decreases, both the ambient pressure and the pressure difference around the variable-stiffness flexible valve decrease. The decrease in the pressure difference makes the valve with a fixed stiffness unable to open in the state of a large angle of attack, but the decrease in the ambient pressure increases the porosity (> 0.1) and decreases the stiffness of the variable-stiffness flexible valve, so that it can open within a certain range and effectively control the flow. Therefore, compared with the conventional slotted blades and the slotted blades with valves of fixed stiffness, this scheme has a wider range of self-adaptability.

[0032] This embodiment provides a slotted blade for realizing wide-range self-adaptability, which can automatically close and open the jet slots under different working conditions only by its own structure, so that it can adaptively open the jet at a large angle of attack at different rotational speeds to suppress the flow separation on the suction surface of the blade, and close the jet slots at a small angle of attack to reduce the internal flow losses. It does not require external energy sources such as air sources or power sources and external auxiliary devices, so it has the advantages of relatively simple structure, strong self-adaptability, and strong engineering practicability.

[0033] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A slotted blade with wide-range adaptability, characterized in that: include: A blade body (1), a jet slit (2), an air inlet (3), a jet outlet (4), and a variable stiffness flexible valve (5); the jet slit (2) penetrates the blade body (1), and its two ends are the air inlet (3) and the jet outlet (4), respectively; the air inlet (3) is located on the pressure side of the blade body (1), and the jet outlet (4) is located on the suction side of the blade body (1); the variable stiffness flexible valve (5) is located in the jet slit (2) and is mounted on the two side walls of the jet slit (2); when the angle of attack of the blade body (1) is greater than a set threshold, the variable stiffness flexible valve (5) is in an open state, and a jet is generated at the jet outlet (4) to suppress flow separation on the suction side; when the angle of attack of the blade body (1) is less than the set threshold, the variable stiffness flexible valve (5) is in a closed state, and no jet is generated at the jet outlet (4).

2. The slotted blade with wide-range adaptability according to claim 1, characterized in that: The number of the jet slits (2) N ≥1, the jet slots (2) are arranged at different positions in the chord direction of the blade, and can simultaneously generate at most N A jet of fluid.

3. The slotted blade with wide-range adaptability according to claim 1, characterized in that: The variable stiffness flexible valve (5) is a cantilever structure installed on both sides of the jet slit (2).

4. The slotted blade with wide-range adaptability according to claim 3, characterized in that: Number of variable stiffness flexible valves in each jet slit (2) M ≥1.

5. The slotted blade with wide-range adaptability according to claim 1, characterized in that: The variable stiffness flexible valve (5) is installed in the jet slit (2) in a forward or reverse direction.

6. The slotted blade with wide-range adaptability according to claim 1, characterized in that: When the variable stiffness flexible valve (5) is installed in the forward direction, the variable stiffness flexible valve (5) has a pressure difference △ between the air inlet (3) and the jet outlet (4). P When the pressure is greater than a set threshold, the valve opens; when the pressure is less than a set threshold, the valve closes. When the variable stiffness flexible valve (5) is installed in reverse, the variable stiffness flexible valve (5) is in the range of △ P It is turned on when it is less than the set threshold and turned off when it is greater than the set threshold.

7. The slotted blade with wide-range adaptability according to claim 1, characterized in that: The variable stiffness flexible valve (5) is made of a metamaterial with variable stiffness characteristics.

8. The slotted blade with wide-range adaptability according to claim 7, characterized in that: The variable stiffness flexible valve (5) adopts a porous metamaterial. When the pressure of the environment around the variable stiffness flexible valve (5) increases, the porosity of the material decreases, thereby having a higher stiffness; when the pressure of the environment around the variable stiffness flexible valve (5) decreases, the porosity of the material increases, thereby having a lower stiffness.

9. The slotted blade with wide-range adaptability according to claim 1, characterized in that: The variable stiffness flexible valve (5) close to the leading edge of the blade is installed in a forward direction, and the variable stiffness flexible valve (5) close to the trailing edge of the blade is installed in a reverse direction.

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