Blade structure with adjustable blade top clearance of gas turbine

Abstract

The invention relates to a blade structure with an adjustable blade top gap of a gas turbine, and aims to effectively control and manage leakage flow in the blade top gap and reduce the efficiency loss of the gas turbine. The blade structure mainly comprises a blade tip groove chamber, a shape memory alloy thin layer and a blade tip winglet. The blade tip groove chambers are arranged into double rows of discrete fan-shaped groove chambers in the circumferential direction of the blade top, and a shape memory alloy thin layer is integrated at the bottom. On one hand, the fan-shaped groove chamber structure can enable airflow to form a resident vortex to reduce the flow loss near the blade tip, and on the other hand, the shape memory alloy thin layer dynamically compensates the heating expansion amount of the blade and the casing when the turbomachinery operates, so that the blade top gap is actively regulated and controlled to be maintained at the set optimal value. And the blade tip winglets are asymmetrically arranged to improve airflow distribution, so that vortexes and unstable airflow in a blade tip area are reduced. The innovative structure provides an effective solution for the flow control problem of the blade tip clearance of the gas turbine, and is beneficial to improving the overall efficiency and performance of the gas turbine.

Description

Technical Field

[0001] The present invention discloses a blade structure with adjustable tip clearance for a gas turbine, which relates to the technical field of passive flow control of turbomachinery. Background Art

[0002] The tip clearance can reduce the direct contact between the blade and the casing, thereby avoiding damage and performance degradation caused by friction during the operation of the turbomachinery. However, the existence of the tip clearance will cause leakage flow when the fluid passes through the blade. This leakage flow will increase the load and flow loss near the tip, reduce the efficiency of the turbomachinery, and further affect the performance and stability of the turbomachinery. Therefore, how to effectively control and manage the leakage flow in the tip clearance has become a key technical challenge in the design and operation of turbomachinery. In the face of this problem, the current control methods for the clearance flow mainly include active control technologies that actively change the system structure or state based on external energy input and passive control technologies that rely on the system's own structure or materials to adapt to environmental changes. However, the active control technology has a complex implementation structure and high cost, while the passive control technology has a simple implementation structure and low cost but is limited by limited working conditions.

[0003] National invention patent CN201810214041.9 discloses a design method for a casing and a tip groove for passive control of clearance flow. In the axial-flow turbine rotor cascade, a curve of a bimodal Gaussian function in a finite domain is used as the profile of the blade mean camber line in the pitch direction, a continuous and smooth inner wall surface of the casing is constructed, and a corresponding surface groove is arranged at the top of the flat-top moving blade to achieve the control of the clearance leakage flow. However, it is difficult to manufacture the blade and the casing with the bimodal Gaussian function curve profile, and the blade is in a high-speed rotation state during operation, and cracks are likely to occur due to fatigue at the peak of the blade height. Summary of the Invention

[0004] In view of the deficiencies of the prior art in the above background art, the present invention proposes a blade structure with adjustable tip clearance for a gas turbine.

[0005] In order to solve the above technical problems, the present invention proposes a blade structure with adjustable tip clearance for a gas turbine, which mainly includes a tip groove chamber, a shape memory alloy thin layer, and a tip wing.

[0006] The tip groove chamber is arranged at the tip, located in the 2 / 3 chord length area in front of the tip, and two rows of discrete sector groove chambers are arranged circumferentially. The groove chambers are only distributed in the proximal wall area outside 20% of the tip radial height, and the middle of the tip to the inner diameter area remains a smooth surface without grooves. The shape memory alloy thin layer is arranged at the bottom of the tip groove chamber. The tip winglet is located in the edge area of the suction surface and the pressure surface of the tip, and the tip winglets are arranged asymmetrically along the tip chord. The top of the tip winglet is flush with the tip platform, and the bottom extends from the tip surface towards the root direction to the blade body surface. The top view projection of the tip groove chamber has a circumferential spread angle of 60°, the sector radius is 3% of the chord length (R = 0.03C, C is the blade chord length), the circumferential pitch is 0.5 times the width of the tip groove chamber, and the depth of the tip groove chamber can be adaptively adjusted within the range of 0.01C to 0.05C with temperature. The bottom of the tip groove chamber is integrated with a shape memory alloy thin layer, and the phase change inside the shape memory alloy thin layer caused by temperature change drives the dynamic change of the groove chamber depth, forming a temperature-sensitive adaptive tip flow channel structure. The function of the tip groove chamber is that when a part of the air flow enters the tip groove chamber, a stagnation vortex will be formed in the groove chamber, thereby enhancing the mixing of the air flow in the tip clearance, and further increasing the resistance of the leakage flow in the clearance and reducing the flow loss near the tip. The shape memory alloy thin layer uses a millisecond pulsed fiber laser to ensure the metallurgical bonding between the shape memory alloy and the groove chamber substrate. First, a 0.05 mm thick Au-18%Sn solder foil is pre-placed, and by using the interaction between the laser and the solder, a liquid transition layer is formed at the interface. With the assistance of ultrasonic vibration with a frequency of 20 kHz and an amplitude of 5 μm, the oxide film is broken and the spreading of the solder on the surface of the shape alloy is promoted. Then, double-beam laser offset welding is used. The main beam focuses on the solder layer, and the auxiliary beam preheats the substrate, reducing the temperature gradient by 40% and avoiding the attenuation of the phase change performance of the shape memory alloy. The function of the shape memory alloy thin layer is to dynamically compensate for the thermal expansion amount of the blade and the casing during the operation of the turbomachine, thereby realizing the active control of the tip clearance and maintaining the tip clearance at the set optimal value. The tip winglet is an airfoil structure with a bend, arranged asymmetrically, the top is flush with the tip platform, and the bottom extends towards the root direction to the blade body surface. The spanwise thickness of the tip winglet on the pressure surface side is 1 / 3 of the blade thickness, and the spanwise thickness of the tip winglet on the suction surface side is 1 / 6 of the blade thickness. The function of the tip winglet is to improve the air flow distribution by increasing the tip area, and further reduce the eddy current and unstable air flow in the tip area.

[0007] The beneficial effects of the present invention are as follows. By designing a blade that includes a tip groove chamber, a shape memory alloy thin layer, and a tip winglet, the influence of leakage flow caused by the tip clearance on the turbomachine is effectively reduced. The tip groove chamber increases the resistance of the leakage flow in the clearance, thereby reducing the flow loss near the tip. By integrating the shape memory alloy thin layer, the change amount of the tip clearance is adjusted according to the temperature change, so as to maintain the tip clearance at the set optimal value. By setting the tip winglet, the tip area is increased, the additional frictional resistance of the leakage flow is increased, and the movement trajectory of the leakage vortex core is changed, ultimately improving the overall efficiency and stability of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Attached Figure 1 is the structural diagram of the blade of the present invention

[0009] Attached Figure 2 is the spanwise schematic diagram of the blade structure of the present invention

[0010] Attached Figure 3 is the a-a cross-sectional view of the blade structure of the present invention

[0011] In the figure: 1 is the tip groove chamber, 2 is the tip winglet, 3 is the suction surface, 4 is the pressure surface, 5 is the shape memory alloy thin layer, 21 is the tip winglet on the pressure surface side, and 22 is the tip winglet on the suction surface side. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] The following further describes the specific implementation method of the present invention in conjunction with the drawings:

[0013] To solve the above technical problems, the blade structure of the present invention mainly includes a tip groove chamber (1), a shape memory alloy thin layer (5), and a tip winglet (2). Combining Figures 1 to 3As shown, in this embodiment, the tip slot chamber (1) is arranged at the tip, located in the 2 / 3 chord length area in front of the tip, and two rows of discrete sector slot chambers are arranged circumferentially. The slot chambers are only distributed in the proximal wall area outside 20% of the tip radial height, and the area from the middle of the tip to the inner diameter remains a smooth surface without slots. The shape memory alloy thin layer (5) is arranged at the bottom of the tip slot chamber (1). The tip winglet (2) is located in the edge area between the suction surface (3) and the pressure surface (4) of the tip, and the tip winglet (2) is arranged asymmetrically along the tip chord. The top of the tip winglet (2) is flush with the tip platform, and the bottom extends from the tip surface towards the blade root to the blade body surface. The top view projection of the tip slot chamber (1) has a circumferential spread angle of 60°, the sector radius is 3% of the chord length, the circumferential pitch is 0.5 times the width of the tip slot chamber, and the depth of the tip slot chamber (1) can be adaptively adjusted within the range of 0.01C to 0.05C with temperature. The shape memory alloy thin layer (5) is integrated at the bottom of the tip slot chamber (1). The shape memory alloy thin layer (5) uses a millisecond pulsed fiber laser to ensure a metallurgical bond between the shape memory alloy and the substrate of the tip slot chamber (1). First, a Au-18%Sn solder foil with a thickness of 0.05 mm is pre-placed, and by using the interaction between the laser and the solder, a liquid transition layer is formed at the interface. With the assistance of ultrasonic vibration with a frequency of 20 kHz and an amplitude of 5 μm, the oxide film is broken and the spreading of the solder on the surface of the shape alloy is promoted. Then, double-beam laser offset welding is used. The main beam focuses on the solder layer, and the auxiliary beam preheats the substrate, reducing the temperature gradient by 40% and avoiding the attenuation of the phase change performance of the shape memory alloy. The tip winglet (2) is an airfoil structure with a bend, arranged asymmetrically, with the top flush with the tip platform and the bottom extending towards the blade root to the blade body surface. The spanwise thickness of the tip winglet (21) on the pressure surface side is 1 / 3 of the blade thickness, and the spanwise thickness of the tip winglet (22) on the suction surface side is 1 / 6 of the blade thickness.

Claims

1. A blade structure with adjustable tip clearance of a gas turbine mainly includes a tip groove chamber, a shape memory alloy thin layer and a tip winglet; it is characterized in that: The tip slot chamber is arranged at the tip, located in the 2 / 3 chord length area in front of the tip, and two rows of discrete sector slot chambers are arranged circumferentially; the slot chambers are only distributed in the proximal wall area 20% outside the radial height of the tip, and the middle of the tip to the inner diameter area remains a smooth surface without slots; the shape memory alloy thin layer is arranged at the bottom of the tip slot chamber; the tip winglet is located in the edge area of the suction surface and pressure surface of the tip, and the tip winglets are arranged asymmetrically along the tip chord; the top of the tip winglet is flush with the tip platform, and the bottom extends from the tip surface towards the root direction to the blade body surface; the top view projection of the tip slot chamber has a circumferential spread angle of 60°, the sector radius is 3% of the chord length (R = 0.03C, C is the blade chord length), the circumferential pitch is 0.5 times the width of the tip slot chamber, and the depth of the tip slot chamber can be adaptively adjusted within the range of 0.01C to 0.05C with temperature; the bottom of the tip slot chamber is integrated with a shape memory alloy thin layer, and the phase change inside the shape memory alloy thin layer driven by temperature change drives the dynamic change of the slot chamber depth, forming a temperature-sensitive adaptive tip flow channel structure; the function of the tip slot chamber is that when a part of the air flow enters the tip slot chamber, a stagnation vortex will be formed in the slot chamber, thereby enhancing the mixing of the air flow in the tip clearance, and further increasing the resistance of the leakage flow in the clearance and reducing the flow loss near the tip; the shape memory alloy thin layer uses a millisecond pulsed fiber laser to ensure the metallurgical bonding between the shape memory alloy and the slot chamber substrate; first, a 0.05 mm thick Au-18%Sn solder foil is pre-placed, and the interaction between the laser and the solder is used to form a liquid transition layer at the interface; with the assistance of ultrasonic vibration with a frequency of 20 kHz and an amplitude of 5 μm, the oxide film is broken and the spreading of the solder on the surface of the shape alloy is promoted; then double-beam laser offset welding is used, the main beam focuses on the solder layer, and the auxiliary beam preheats the substrate to reduce the temperature gradient by 40% and avoid the attenuation of the phase change performance of the shape memory alloy; the function of the shape memory alloy thin layer is to actively control the tip clearance by dynamically compensating the thermal expansion amount of the blade and the casing during the operation of the turbomachine, so that the tip clearance is maintained at the set optimal value; the tip winglet is an airfoil structure with a bend, arranged asymmetrically, the top is flush with the tip platform, and the bottom extends towards the root direction to the blade body surface; On the pressure side, the spanwise thickness of the tip winglet is 1 / 3 of the blade thickness, and on the suction side, the spanwise thickness of the tip winglet is 1 / 6 of the blade thickness; the function of the tip winglet is to improve the air flow distribution by increasing the tip area, and further reduce the eddy current and unstable air flow in the tip area.

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